Showing 1–50 of 235 results for author: Amado, J

Planet-induced Periodic Modulation of Stellar Activity in GJ~436: Insights into a Warm Neptune's Magnetic Field

Authors: D. Revilla, P. J. Amado, R. Luque, P. Schöfer, A. Binnenfeld, J. A. Caballero, Artie P. Hatzes, G. W. Henry, S. Jeffers, S. Kaur, A. F. Lanza, E. Pallé, L. Peña-Moñino, M. Pérez-Torres, A. Quirrenbach, A. Reiners, I. Ribas, D. Viganò, S. Zucker

Abstract: Interactions between stellar and planetary magnetic fields are expected to produce observable radio and optical signals modulated by their orbital periods, but direct detections remain elusive. We analyze 17 years of spectroscopic data of the GJ 436 system. This M2.5 V star hosts a transiting Neptune-sized planet in a close-in, inclined orbit. The data shows repeated enhancements of the stellar ch… ▽ More Interactions between stellar and planetary magnetic fields are expected to produce observable radio and optical signals modulated by their orbital periods, but direct detections remain elusive. We analyze 17 years of spectroscopic data of the GJ 436 system. This M2.5 V star hosts a transiting Neptune-sized planet in a close-in, inclined orbit. The data shows repeated enhancements of the stellar chromospheric activity at approximately the same phase of its 8-year activity cycle modulated by a combination of the planet's orbital period and the stellar rotation. We interpret this modulation as star-planet interaction. We propose a new geometrical model to interpret these signals, then, estimate the power of the interaction and, from models, estimate the magnetic field of GJ 436 b to be between 6 and 110G. This finding opens new pathways to detect star-planet interactions and to investigate planetary magnetic fields and their implications on atmospheric retention and detectability. △ Less

Submitted 9 April, 2026; v1 submitted 8 April, 2026; originally announced April 2026.

Comments: 48 pages, 19 figures, 2 tables. Sent to journal on 16/12/2024

The Vera C. Rubin Observatory Data Preview 1

Authors: Vera C Rubin Observatory Team, Tatiana Acero Cuellar, Emily Acosta, Christina L Adair, Prakruth Adari, Jennifer K Adelman McCarthy, Anastasia Alexov, Russ Allbery, Robyn Allsman, Yusra AlSayyad, Jhonatan Amado, Nathan Amouroux, Pierre Antilogus, Alexis Aracena Alcayaga, Gonzalo Aravena Rojas, Claudio H Araya Cortes, Eric Aubourg, Tim S Axelrod, John Banovetz, Carlos Barria, Amanda E Bauer, Brian J Bauman, Ellen Bechtol, Keith Bechtol, Andrew C Becker , et al. (303 additional authors not shown)

Abstract: We present Rubin Data Preview 1 DP1, the first data from the NSF DOE Vera C Rubin Observatory, comprising raw and calibrated single epoch images, coadds, difference images, detection catalogs, and ancillary data products. DP1 is based on 1792 optical near infrared exposures acquired over 48 distinct nights by the Rubin Commissioning Camera LSSTComCam on the Simonyi Survey Telescope at the Summit F… ▽ More We present Rubin Data Preview 1 DP1, the first data from the NSF DOE Vera C Rubin Observatory, comprising raw and calibrated single epoch images, coadds, difference images, detection catalogs, and ancillary data products. DP1 is based on 1792 optical near infrared exposures acquired over 48 distinct nights by the Rubin Commissioning Camera LSSTComCam on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón Chile in late 2024. DP1 covers $\sim$15 deg$^2$ distributed across seven roughly equal-sized non-contiguous fields, each independently observed in six broad photometric bands $ugrizy$. The median FWHM of the point spread function across all bands is approximately 1.14 arcseconds, with the sharpest images reaching about 0.58 arcseconds. The 5$σ$ point source depths for coadded images in the deepest field the Extended Chandra Deep Field South are $u$ = 24.55, $g$ = 26.18, $r$ = 25.96, $i$ = 25.71, $z$ = 25.07, $y$ = 23.1. Other fields are no more than 2.2 magnitudes shallower in any band where they have nonzero coverage. DP1 contains approximately 2.3 million distinct astrophysical objects, of which 1.6 million are extended in at least one band in coadds and 431 solar system objects of which 93 are new discoveries. DP1 is approximately 3.5 TB in size and is available to Rubin data rights holders via the Rubin Science Platform a cloud based environment for the analysis of petascale astronomical data. While small compared to future LSST releases its high quality and diversity of data support a broad range of early science investigations ahead of full operations in 2026. △ Less

Submitted 24 March, 2026; originally announced March 2026.

Comments: 59 pages, 41 figures

Report number: RTN-095.lsst.io

Towards a Comprehensive Understanding of Planetary Systems through Population-Level, Large-Scale Surveys

Authors: Francisco J. Pozuelos, Pedro J. Amado, Jesús Aceituno, Marina Centenera-Merino, Stefan Cikota, Javier Flores, Julius Göhring, Sergio León-Saval, Kalaga Madhav, Giuseppe Morello, Abani Nayak, Jose L. Ortiz, David Pérez-Medialdea, María Isabel Ruiz-López, Miguel A. Sánchez-Carrasco, Alejandro Sánchez-López

Abstract: Over the past three decades, exoplanet research has delivered an extensive census of planets spanning a wide range of masses, sizes, and orbital configurations. Despite this progress, the physical interpretation of these populations remains severely limited, as precise constraints on planetary masses, interior structures, and atmospheres are available only for a small, highly selected subset of ta… ▽ More Over the past three decades, exoplanet research has delivered an extensive census of planets spanning a wide range of masses, sizes, and orbital configurations. Despite this progress, the physical interpretation of these populations remains severely limited, as precise constraints on planetary masses, interior structures, and atmospheres are available only for a small, highly selected subset of targets. As a result, most known exoplanets remain physically ambiguous, preventing the construction of robust population-level trends and limiting our understanding of planet formation, evolution, and habitability. In the coming decades, missions such as PLATO, Earth 2.0, and the Nancy Grace Roman Space Telescope will dramatically expand the number of exoplanets detected. However, without a corresponding capability to characterise planetary masses and atmospheres at scale, these discoveries will remain largely detection-driven. Current and planned facilities, including JWST and ELT-class instruments, excel at detailed studies of individual systems but are intrinsically unsuited for large, homogeneous surveys. This white paper identifies population-level physical characterisation as a fundamental science challenge for the 2040s and motivates the need for a new observational paradigm. We outline how photonics-enabled, modular telescope architectures can deliver the survey speed, stability, and scalability required to jointly probe planetary interiors and atmospheres across statistically meaningful samples, thereby enabling a comprehensive and physically grounded understanding of planetary systems. △ Less

Submitted 26 January, 2026; originally announced January 2026.

Comments: White paper submitted to the ESO Call for White Papers on Future Science Questions (2040s)

Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts

Authors: E. Poultourtzidis, G. Lacedelli, E. Pallé, I. Carleo, C. Magliano, S. Geraldía-González, J. A. Caballero, G. Morello, J. Orell-Miquel, H. M. Tabernero, F. Murgas, G. Covone, F. J. Pozuelos, P. J. Amado, V. J. S. Béjar, S. Chairetas, C. Cifuentes, D. R. Ciardi, K. A. Collins, I. J. M. Crossfield, E. Esparza-Borges, G. Fernández-Rodríguez, A. Fukui, Y. Hayashi, A. P. Hatzes , et al. (27 additional authors not shown)

Abstract: We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM~J0902+7138), TOI-4529 (G~2--21), and TOI-5388 (Wolf~346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of $4.65$, $5.88$, and $2.59$ days, and they orbit early-M dwarfs (M2.0V, M1.5V, and M3.0V,… ▽ More We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM~J0902+7138), TOI-4529 (G~2--21), and TOI-5388 (Wolf~346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of $4.65$, $5.88$, and $2.59$ days, and they orbit early-M dwarfs (M2.0V, M1.5V, and M3.0V, respectively). We were able to precisely determine the radius of all three planets with a precision of $< 7\, \%$, the mass of TOI-1243 b with a precision of $19\, \%$, and upper mass limits for TOI-4529 b and TOI-5388 b. The radius of TOI-1243 b is $2.33\pm0.12\, {R_{\oplus}}$, its mass is $7.7 \pm 1.5\,{M_{\oplus}}$, and the mean density is $0.61 \pm 0.15 \, {ρ_\oplus}$. The radius of TOI-4529 b is $1.77 ^{+0.09}_{-0.08} \, {R_{\oplus}}$, the $3 σ$ upper mass limit is $4.9 \, {M_{\oplus}}$, and the $3 σ$ upper density limit is $0.88\, {ρ_\oplus}$. The third planet, TOI-5388 b, is Earth-sized with a radius of $0.99 ^{+0.07}_{-0.06} \, {R_{\oplus}}$, a $3 σ$ upper mass limit of $2.2 \, {M_{\oplus}}$, and a $3 σ$ upper density limit of $2.2\, {ρ_\oplus}$. While TOI-5388 b is most probably rocky, given its Earth-like radius, TOI-1243 b and TOI-4529 b are located in a highly degenerate region in the mass-radius space. TOI-4529 b appears to lean toward a water-world composition. TOI-1243 b has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample. △ Less

Submitted 12 January, 2026; originally announced January 2026.

Comments: 21 pages, 15 figures. Accepted for publication in A&A

Elemental abundance pattern and temperature inversion on the dayside of HAT-P-70b observed with CARMENES and PEPSI

Authors: B. Guo, F. Yan, Th. Henning, L. Nortmann, M. Stangret, D. Cont, E. Pallé, D. Shulyak, K. G. Strassmeier, I. Ilyin, F. Lesjak, A. Reiners, S. Liu, K. Molaverdikhani, G. Scandariato, E. Keles, J. A. Caballero, P. J. Amado, A. Quirrenbach, I. Ribas, S. Góngora, A. P. Hatzes, M. López-Puertas, D. Montes, K. Poppenhaeger , et al. (3 additional authors not shown)

Abstract: Ground-based high-resolution spectroscopy has identified various chemical species in the atmospheres of ultra-hot Jupiters, including neutral and ionized metals, providing key insights into planet formation through refractory element abundances. We observed the dayside thermal emission spectrum of the UHJ HAT-P-70b using the high-resolution spectrographs CARMENES and PEPSI. Through cross-correlati… ▽ More Ground-based high-resolution spectroscopy has identified various chemical species in the atmospheres of ultra-hot Jupiters, including neutral and ionized metals, providing key insights into planet formation through refractory element abundances. We observed the dayside thermal emission spectrum of the UHJ HAT-P-70b using the high-resolution spectrographs CARMENES and PEPSI. Through cross-correlation analysis, we detect emission signals of Al i, AlH, Ca ii, Cr i, Fe i, Fe ii, Mg i, Mn i, and Ti i, marking the first detection of Al i and AlH in an exoplanetary atmosphere. Tentative signals of C i, Ca i, Na i, NaH, and Ni i are also identified. These detections enable atmospheric retrievals to constrain the thermal profile and elemental abundances of the planet's dayside hemisphere. The retrieved temperature-pressure profile reveals a strong thermal inversion. The chemical free retrieval yields a metallicity of [Fe/H] = 0.38(+0.74/-1.11), while the chemical equilibrium retrieval gives [Fe/H] = 0.23(+1.08/-0.98), both consistent with solar metallicity. We also tentatively find an enhanced abundance of Ni, possibly due to the accretion of Ni-rich planetesimals during formation. On the other hand, elements with condensation temperatures above 1400 K (e.g., Ca, Ti, and V) appear slightly depleted, which may be caused by nightside cold trapping. However, Al, with the highest condensation temperature at 1653K, displays a solar like abundance, which might reflect the formation-related enrichment of Al. Our retrieval indicates extremely high volume mixing ratios of metal ions (Fe ii and Ca ii), which are significantly inconsistent with predictions from chemical equilibrium models. This disequilibrium suggests that the atmosphere is likely undergoing significant hydrodynamic escaping, which enhances the atmospheric density at high altitudes where the ionic lines are formed. △ Less

Submitted 24 December, 2025; originally announced December 2025.

Comments: 18 pages, 15 figures. Accepted for publication in A&A

TOI-7166 b: A Habitable Zone mini-Neptune planet around a nearby low-mass star

Authors: Khalid Barkaoui, Francisco J. Pozuelos, Benjamin V. Rackham, Adam J. Burgasser, Amaury H. M. J. Triaud, Miquel Serra-Ricart, Mathilde Timmermans, Selçuk. Yalçınkaya, Abderahmane Soubkiou, Keivan G. Stassun, Karen A. Collins, Pedro J. Amado, Özgur Baştürk, Artem Burdanov, Yasmin T. Davis, Julien de Wit, Brice-Olivier Demory, Sarah Deveny, Georgina Dransfield, Elsa Ducrot, Michaël Gillon, Yilen Gómez Maqueo Chew, Matthew J. Hooton, Keith Horne, Steve B. Howell , et al. (19 additional authors not shown)

Abstract: We present the discovery and validation of TOI-7166b, a 2.01+/-0.05R_Earth planet orbiting a nearby low-mass star. We validated the planet by combining TESS and multi-color high-precision photometric observations from ground-based telescopes, together with spectroscopic data, high-contrast imaging, archival images, and statistical arguments. The host star is an M4-type dwarf at a distance of ~35 p… ▽ More We present the discovery and validation of TOI-7166b, a 2.01+/-0.05R_Earth planet orbiting a nearby low-mass star. We validated the planet by combining TESS and multi-color high-precision photometric observations from ground-based telescopes, together with spectroscopic data, high-contrast imaging, archival images, and statistical arguments. The host star is an M4-type dwarf at a distance of ~35 pc from the Sun. It has a mass and a radius of Ms=0.190+/-0.004M_Sun and Rs=0.222+/-0.005R_Sun, respectively. TOI-7166b has an orbital period of 12.9 days, which places it close to the inner edge of the Habitable Zone of its host star, receiving an insolation flux of Sp=1.07+/-0.08S_Earth and an equilibrium temperature of Teq=249+/-5K (assuming a null Bond albedo). The brightness of the host star makes TOI-7166 a suitable target for radial velocity follow-up to measure the planetary mass and bulk density. Moreover, the physical parameters of the system including the infrared brightness (Kmag = 10.6) of the star and the planet-to-star radius ratio (0.0823+/-0.0012) make TOI-7166b an exquisite target for transmission spectroscopic observations with the JWST, to constrain the exoplanet atmospheric compositions. △ Less

Submitted 7 December, 2025; originally announced December 2025.

Comments: 13 Figures and 4 Tables. Published in MNRAS

Journal ref: Monthly Notices of the Royal Astronomical Society, 2025, Volume 544, Issue 2, pp. 2637-2652, 16 pp

Revisiting the atmosphere of HAT-P-70b with CARMENES high-resolution transmission spectroscopy

Authors: Tianjun Gan, Jaume Orell-Miquel, Fei Yan, Lisa Nortmann, Jorge Sanz-Forcada, Enric Pallé, Shude Mao, Pedro J. Amado, José A. Caballero, Stefan Cikota, David Cont, Artie P. Hatzes, Thomas Henning, Fabio Lesjak, Manuel López-Puertas, David Montes, Juan Carlos Morales, Alberto Peláez-Torres, Andreas Quirrenbach, Ansgar Reiners, Ignasi Ribas, Andreas Schweitzer

Abstract: Owing to hot and inflated envelopes that facilitate atmospheric studies, ultra-hot Jupiters (UHJs) have attracted much attention. Significant progress has been achieved, from enlarging the sample size to broadening the studies to encompass diverse stellar types and ages. Here, we present a transmission spectroscopy study of HAT-P-70b, an UHJ orbiting a young A-type star, through high-resolution ob… ▽ More Owing to hot and inflated envelopes that facilitate atmospheric studies, ultra-hot Jupiters (UHJs) have attracted much attention. Significant progress has been achieved, from enlarging the sample size to broadening the studies to encompass diverse stellar types and ages. Here, we present a transmission spectroscopy study of HAT-P-70b, an UHJ orbiting a young A-type star, through high-resolution observations with CARMENES at the 3.5m Calar Alto telescope. By using the line-by-line technique, we confirm the previous detections of Ha, Na I, and Ca II, report a new tentative detection of K I, and impose an upper limit on the He triplet absorption. Through cross-correlation analysis, we identify the Ca II and Fe I absorptions, both blue-shifted by approximately 5 km/s, indicating a day-to-night side atmospheric wind. Additionally, we find a new tentative detection of K I. We do not see any significant atmospheric molecular signal in the near-infrared data. Putting HAT-P-70b in the context of UHJs from the literature, it turns out that (1) Ha absorption is more common on gas giants orbiting stars younger than 1 Gyr, with a relative detection probability of $P_{\rm Age<1\,Gyr}({\rm Ha})/P_{\rm Age\geq1\,Gyr}({\rm Ha})\sim 3$; (2) any UHJ is likely to exhibit Fe I absorption if it has Ca II. △ Less

Submitted 7 December, 2025; originally announced December 2025.

Comments: 19 pages, 11 figures, 3 tables, accepted for publication in AJ

Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES$^+$ observations

Authors: A. Peláez-Torres, A. Sánchez-López, L. Nortmann, M. López-Puertas, E. González-Álvarez, H. M. Tabernero, C. Jiang, D. Revilla, G. Morello, J. Orell-Miquel, E. Pallé, P. J. Amado, J. A. Caballero, I. Ribas, A. Reiners, A. Quirrenbach, D. Cont, S. Dreizler, A. Fernández-Martín, A. P. Hatzes, Th. Henning, F. Lesjak, D. Montes, A. Schweizer, T. Trifonov , et al. (1 additional authors not shown)

Abstract: We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES$^+$ so as to provide the most constrained results possible at high resolution. We removed telluric and stellar signals from the data using SysRem and potential planetary signals were investigated using the cross-corre… ▽ More We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES$^+$ so as to provide the most constrained results possible at high resolution. We removed telluric and stellar signals from the data using SysRem and potential planetary signals were investigated using the cross-correlation technique. Following standard procedures for undetected species, we performed injection recovery tests and Bayesian retrievals to place constraints on the detectability of the main near-infrared absorbers. In addition, we simulated ELT/ANDES observations by computing end-to-end in silico datasets with EXoPLORE. No molecular signals were detected in the atmosphere of GJ 436 b, which is consistent with previous studies. Combined CARMENES-CRIRES$^+$ injection-recovery and Bayesian retrieval analyses show that the atmosphere is likely covered by high-altitude clouds ($\sim$ $1$ mbar) at low and intermediate metallicities or, alternatively, is very metal-rich ($\gtrsim$ $900\times$ solar), which would suppress spectral features without invoking clouds. Simulations of ELT/ANDES observations suggest a boost by nearly an order of magnitude to the upper limit in the photon-limited regime, reaching $0.1$ mbar at $10$-$300\times$ solar metallicities. The joint analysis of all useful transit observations from CARMENES and CRIRES$^+$ provides the most stringent constraints to date on the atmospheric properties of GJ 436 b. Complementary CCF-based and retrieval approaches consistently indicate that the atmosphere is either cloudy or highly metal enriched. Any weak near-infrared absorption lines, if present, are likely to be below current detection limits. However, according to our simulations, these features may be revealed with ELT/ANDES even in single-transit observations. △ Less

Submitted 3 December, 2025; originally announced December 2025.

Journal ref: A&A 705, A256 (2026)

Upper limits on atmospheric abundances of KELT-11b and WASP-69b from a retrieval approach

Authors: F. Lesjak, L. Nortmann, D. Cont, P. J. Amado, M. Azzaro, J. A. Caballero, S. Czesla, A. Hatzes, Th. Henning, M. López-Puertas, K. Molaverdikhani, D. Montes, J. Orell-Miquel, E. Pallé, A. Peláez-Torres, A. Quirrenbach, A. Reiners, I. Ribas, A. Sánchez-López, A. Schweitzer, F. Yan

Abstract: WASP-69b and KELT-11b are two low-density hot Jupiters, which are expected to show strong atmospheric features in their transmission spectra. Such features offer valuable insights into the chemical composition, thermal structure, and cloud properties of exoplanet atmospheres. High-resolution spectroscopic observations can be used to study the line-forming regions in exoplanet atmospheres and poten… ▽ More WASP-69b and KELT-11b are two low-density hot Jupiters, which are expected to show strong atmospheric features in their transmission spectra. Such features offer valuable insights into the chemical composition, thermal structure, and cloud properties of exoplanet atmospheres. High-resolution spectroscopic observations can be used to study the line-forming regions in exoplanet atmospheres and potentially detect signals despite the presence of clouds. We aimed to detect various molecular species and constrain the chemical abundances and cloud deck pressures using high-resolution spectroscopy. We observed multiple transits of these planets with CARMENES and applied the cross-correlation method to detect atmospheric signatures. Further, we used an injection-recovery approach and retrievals to place constraints on the atmospheric properties. We detected a tentative H$_2$O signal for KELT-11b but not for WASP-69b, and searches for other molecules such as H$_2$S and CH$_4$ resulted in non-detections for both planets. By investigating the signal strength of injected synthetic models, we constrained which atmospheric abundances and cloud deck pressures are consistent with our cross-correlation results. In addition, we show that a retrieval-based approach leads to similar constraints of these parameters. △ Less

Submitted 7 November, 2025; originally announced November 2025.

Comments: Accepted for publication in Astronomy & Astrophysics, 18 pages, 17 figures

The CARMENES search for exoplanets around M dwarfs : Understanding the wavelength dependence of radial velocity measurements

Authors: S. V. Jeffers, J. R. Barnes, P. Schöfer, S. Reffert, V. J. S. Béjar, A. Quirrenbach, A. Reiners, Y. Shan, M. R. Zapatero Osorio, B. Fuhrmeister, P. J. Amado, J. A. Caballero, I. Ribas, C. Cardona Guillén, F. Del Sordo, M. Fernández, A. García-López, A. Guijarro, A. P. Hatzes, M. Lafarga, N. Lodieu, M. Kürster, K. Molaverdikhani, D. Montes, J. C. Morales

Abstract: Context. Current exoplanet surveys are focused on detecting small exoplanets orbiting in the liquid-water habitable zones of their host stars. Despite the recent significant advancements in instrumental developments, the current limitation in detecting these exoplanets is the intrinsic variability of the host star itself. Aims. Our aim is to use the full CARMENES guaranteed time observations (GTO)… ▽ More Context. Current exoplanet surveys are focused on detecting small exoplanets orbiting in the liquid-water habitable zones of their host stars. Despite the recent significant advancements in instrumental developments, the current limitation in detecting these exoplanets is the intrinsic variability of the host star itself. Aims. Our aim is to use the full CARMENES guaranteed time observations (GTO) data set spanning more than 8 years of observations of over 350 stars to investigate the wavelength dependence of high-precision radial velocities (RV), as stellar activity features should exhibit a wavelength dependence while the RV variation due to an orbiting planet will be wavelength independent. Methods. We use the chromatic index (CRX) to quantify the slope of the measured RVs as a function of logarithmic wavelength. We investigate the dependence of the CRX in the full CARMENES GTO sample on 24 stellar activity indices in the visible and near-infrared channels of the CARMENES spectrograph and each star's stellar parameters. We also present an updated convective turnover time scaling for the calculation of the stellar Rossby number for M dwarfs. Results. Our results show that approximately 17\% of GTO stars show a strong or a moderate correlation between CRX and RV. We can improve the measured RVs by a factor of up to nearly 4 in rms by subtracting the RV predicted by the CRX-RV correlation from the measured RVs. Mid M dwarfs with moderate rotational velocities, moderate CRX-gradients and quasi-stable activity features have the best rms improvement factors. Conclusions. We conclude that the CRX is a powerful diagnostic in mitigation of stellar activity and the search for low mass rocky planets. △ Less

Submitted 29 October, 2025; originally announced October 2025.

Comments: published in A&A

Journal ref: 2025A&A...696A..27J

The Atmospheric Composition of Sub-Neptune K2-18 b and Implications for its Formation

Authors: Gareb Fernández-Rodríguez, Giuseppe Morello, Jonathan C. Tan, Enric Pallé, Mark R. Swain, Efthymios Poultourtzidis, Alfredo Biagini, Quentin Changeat, Chengzi Jiang, Francisco J. Pozuelos, Pedro J. Amado

Abstract: Unlocking the atmospheres of sub-Neptunes is among JWST's major achievements, yet such observations demand complex analyses that strongly affect interpretations. We present an independent reanalysis of the original JWST transmission spectrum of K2-18 b, to assess the robustness of previously claimed detections, explore the parameter space, and implications for its formation. The observations were… ▽ More Unlocking the atmospheres of sub-Neptunes is among JWST's major achievements, yet such observations demand complex analyses that strongly affect interpretations. We present an independent reanalysis of the original JWST transmission spectrum of K2-18 b, to assess the robustness of previously claimed detections, explore the parameter space, and implications for its formation. The observations were reduced using a combination of public and customized pipelines producing a total of 12 different versions of the transmission spectrum by varying: spectral binning, limb-darkening, and a novel correction for the occulted stellar spot. We then performed atmospheric retrievals using TauREx 3, comparing models of varying complexity, robustly detecting CH$_4$ (3-4$σ$) across all configurations. The evidence for CO$_2$ is weaker and highly model-dependent. The tentative detection of dimethyl sulphide (DMS) vanishes in our most comprehensive retrieval models. We find that correcting the stellar spot in the NIRISS transit is a critical step, introducing a uniform offset that primarily drives the inference of a lower mean molecular weight atmosphere. Furthermore, the assumed complexity of the retrieval model itself introduces significant biases; including more molecules systematically increases the retrieved CH$_4$ abundance and atmospheric mean molecular weight, even for species without spectral features. The data are consistent with a hydrogen-rich atmosphere with an elevated O and an even more elevated C abundance, leading to a super-solar C/O. We show that the physical properties of the system planets K2-18 c, and K2-18 b are consistent with those expected by the in situ formation theory of Inside-Out Planet Formation (IOPF), interior to the carbon "soot" line, where an elevated C/O ratio of a primordial atmosphere is expected to be inherited from the protoplanetary disk. △ Less

Submitted 20 October, 2025; originally announced October 2025.

Comments: Comments welcome

A planetary system with a sub-Neptune planet in the habitable zone of TOI-2093

Authors: J. Sanz-Forcada, E. González-Álvarez, M. R. Zapatero Osorio, J. A. Caballero, V. J. S. Béjar, E. Herrero, C. Rodríguez-López, K. R. Sreenivas, L. Tal-Or, S. Vanaverbeke, A. P. Hatzes, R. Luque, E. Nagel, F. J. Pozuelos, D. Rapetti, A. Quirrenbach, P. J. Amado, M. Blazek, I. Carleo, D. Ciardi, C. Cifuentes, K. Collins, Th. Henning, D. W. Latham, J. Lillo-Box , et al. (11 additional authors not shown)

Abstract: Aims. We aim to confirm and measure the mass of the transiting planet candidate around the K5V star TOI-2093, previously announced by the Transiting Exoplanet Survey Satellite (TESS) project. Methods. We combined photometric data from 32 sectors between 2019 and 2024 with 86 radial velocity measurements obtained with the CARMENES spectrograph over a period of 2.4 years, along with a series of grou… ▽ More Aims. We aim to confirm and measure the mass of the transiting planet candidate around the K5V star TOI-2093, previously announced by the Transiting Exoplanet Survey Satellite (TESS) project. Methods. We combined photometric data from 32 sectors between 2019 and 2024 with 86 radial velocity measurements obtained with the CARMENES spectrograph over a period of 2.4 years, along with a series of ground-based, broadband photometric monitoring campaigns to characterize the host star and the transiting planet candidate, as well as to search for additional planets in the system. Our data indicate that TOI-2093 is a main-sequence star located at a distance of 83 pc, with solar metallicity, and a rotation period of 43.8 +- 1.8 d. Results. We have confirmed the planetary nature of the TESS transiting planet candidate, named TOI-2093 c, through the detection of its Keplerian signal in the spectroscopic data. We measured a planetary radius of 2.30 +- 0.12 Rearth, a Neptune-like mass of 15.8 +- 3.7 Mearth, and an orbital period of 53.81149 +- 0.00017 d. This makes TOI-2093 c the smallest exoplanet known in the habitable zone of a main-sequence FGK star. Given its size and relatively high density, TOI-2093 c belongs to a class of planets with no analog in the Solar System. In addition, the CARMENES data revealed the presence of a second planet candidate with a minimum mass of 10.6 +- 2.5 Mearth and an orbital period of 12.836 +- 0.021 d. This inner planet, which we designated TOI-2093 b, shows no detectable photometric transit in the TESS light curves. The orbital planes of the two planets are misaligned by more than 1.6 deg despite the near 4:1 mean-motion resonance of their orbital periods. △ Less

Submitted 30 September, 2025; originally announced October 2025.

Comments: Accepted by A&A. 12 pages, 7 figures, 5 tables in the main body (20 pages, 19 figures, 9 tables including appendices)

Improving radial velocity precision with CARMENES-PLUS:An upgrade of the near-infrared spectrograph cooling system

Authors: R. Varas, R. Calvo-Ortega, P. J. Amado, S. Becerril, H. Ruh, M. Azzaro, L. Hernandez, H. Magan-Madinabeitia, S. Reinhart, D. Maroto-Fernandez, J. Helmling, A. L. Huelmo, D. Benitez, J. F. Lopez, M. Pineda, J. A. Garcia, J. Garcia de la Fuente, J. Marin, F. Hernandez, J. Aceituno, J. A. Caballero, A. Kaminski, R. J. Mathar, A. Quirrenbach, A. Reiners , et al. (3 additional authors not shown)

Abstract: CARMENES is a dual-channel high-resolution spectrograph at the 3.5 m Calar Alto telescope designed to detect low-mass planets around late-type dwarfs by measuring their radial velocities (RVs). High thermal stability in both the visible (VIS) and near infrared channels is essential to achieve the precision required for these measurements. In particular, stabilising the NIR channel to the millikelv… ▽ More CARMENES is a dual-channel high-resolution spectrograph at the 3.5 m Calar Alto telescope designed to detect low-mass planets around late-type dwarfs by measuring their radial velocities (RVs). High thermal stability in both the visible (VIS) and near infrared channels is essential to achieve the precision required for these measurements. In particular, stabilising the NIR channel to the millikelvin level, which operates at cryogenic temperatures (140 K), poses significant engineering challenges.The CARMENES-PLUS project was initiated to improve the instruments intrinsic RV precision. In this article, we focus on the thermal stability improvements made to the NIR channels cooling system. The NIR cooling system was originally conceived to operate with a discontinuous flow of cryogenic nitrogen gas. As part of CARMENES-PLUS, this was upgraded to a continuous flow configuration. Additional changes included the installation of an automatic vacuum system, a proportional control valve, and a pressure regulation system. These upgrades were designed to reduce thermal fluctuations and enhance long-term stability. The implemented upgrades significantly improved the intrinsic RV precision of the NIR channel. We quantified this improvement using Fabry Perot calibration spectra, obtaining an intrinsic RV precision of 0.67 ms after the interventions, an improvement of nearly 2 ms . We also assessed the stability of the nightly zero points, finding a reduced scatter of 3.9 ms post upgrade, compared to 6.1 ms before. For a sample of slowly rotating stars (vsin i below 2 kms), the median scatter decreased from 8.8 ms to 6.7 ms after the upgrades. These results demonstrate that the thermal control upgrades introduced in CARMENES PLUS have enhanced the NIR channels RV performance, bringing it closer to the VIS channels stability and reinforcing CARMENES capabilities for exoplanet detection around M dwarfs. △ Less

Submitted 16 April, 2026; v1 submitted 22 September, 2025; originally announced September 2025.

Two warm Earth-sized exoplanets and an Earth-sized candidate in the M5V-M6V binary system TOI-2267

Authors: S. Zúñiga-Fernández, F. J. Pozuelos, M. Dévora-Pajares, N. Cuello, M. Greklek-McKeon, K. G. Stassun, V. Van Grootel, B. Rojas-Ayala, J. Korth, M. N. Günther, A. J. Burgasser, C. Hsu, B. V. Rackham, K. Barkaoui, M. Timmermans, C. Cadieux, R. Alonso, I. A. Strakhov, S. B. Howell, C. Littlefield, E. Furlan, P. J. Amado, J. M. Jenkins, J. D. Twicken, M. Sucerquia , et al. (41 additional authors not shown)

Abstract: We report two warm Earth-sized exoplanets orbiting the close binary TOI-2267 (M5+M6, separation ~8 au). Data from TESS and ground-based facilities confirm the planets, but we cannot determine which star they orbit. The planets have radii of 1.00+/-0.11 R_Earth (TOI-2267 b, P=2.28 d) and 1.14+/-0.13 R_Earth (TOI-2267 c, P=3.49 d) if around TOI-2267A, or 1.22+/-0.29 R_Earth and 1.36+/-0.33 R_Earth i… ▽ More We report two warm Earth-sized exoplanets orbiting the close binary TOI-2267 (M5+M6, separation ~8 au). Data from TESS and ground-based facilities confirm the planets, but we cannot determine which star they orbit. The planets have radii of 1.00+/-0.11 R_Earth (TOI-2267 b, P=2.28 d) and 1.14+/-0.13 R_Earth (TOI-2267 c, P=3.49 d) if around TOI-2267A, or 1.22+/-0.29 R_Earth and 1.36+/-0.33 R_Earth if around TOI-2267B. TESS also shows a candidate signal (TOI-2267.02, P=2.03 d, 0.95+/-0.12 or 1.13+/-0.30 R_Earth). Dynamical analysis shows all three cannot orbit one star; the most stable configuration has planets b and c (near a 3:2 resonance) orbiting one star and the candidate the other. This scenario would make TOI-2267 the most compact binary system known to host planets, with both components harbouring transiting worlds, offering a unique benchmark for studying planet formation and evolution in compact binary. △ Less

Submitted 8 September, 2025; v1 submitted 19 August, 2025; originally announced August 2025.

Comments: 18 pages article, 12 pages Appendix. Accepted for publication in A&A. Corresponding authors: S. Zúñiga-Fernández and F. J. Pozuelos

Journal ref: A&A 702, A85 (2025)

The CARMENES search for exoplanets around M dwarfs. Revisiting the GJ 317, GJ 463, and GJ 3512 systems and two newly discovered planets orbiting GJ 9773 and GJ 508.2

Authors: J. C. Morales, I. Ribas, S. Reffert, M. Perger, S. Dreizler, G. Anglada-Escudé, V. J. S. Béjar, E. Herrero, J. Kemmer, M. Kuzuhara, M. Lafarga, J. H. Livingston, F. Murgas, B. B. Ogunwale, L. Tal-Or, T. Trifonov, S. Vanaverbeke, P. J. Amado, A. Quirrenbach, A. Reiners, J. A. Caballero, J. F. Agüí Fernández, J. Banegas, P. Chaturvedi, S. Dufoer , et al. (11 additional authors not shown)

Abstract: Surveys for exoplanets indicate that the occurrence rate of gas giant planets orbiting late-type stars in orbits with periods shorter than 1000 days is lower than in the case of Sun-like stars. This is in agreement with planet formation models based on the core or pebble accretion paradigm. The CARMENES exoplanet survey has been conducting radial-velocity observations of several targets that show… ▽ More Surveys for exoplanets indicate that the occurrence rate of gas giant planets orbiting late-type stars in orbits with periods shorter than 1000 days is lower than in the case of Sun-like stars. This is in agreement with planet formation models based on the core or pebble accretion paradigm. The CARMENES exoplanet survey has been conducting radial-velocity observations of several targets that show long-period trends or modulations that are consistent with the presence of giant planets at large orbital separations. We present an analysis of five such systems that were monitored with the CARMENES spectrograph, as well as with the IRD spectrograph. In addition, we used archival data to improve the orbital parameters of the planetary systems. We improve the parameters of three previously known planets orbiting the M dwarfs GJ 317, GJ 463, and GJ 3512. We also determine the orbital parameters and minimum mass of the planet GJ 3512 c, for which only lower limits had been given previously. Furthermore, we present the discovery of two new giant planets orbiting the stars GJ 9733 and GJ 508.2, although for the second one only lower limits to the orbital properties can be determined. The new planet discoveries add to the short list of known giant planets orbiting M-dwarf stars with subsolar metallicity at long orbital periods above 2000 days. These results reveal that giant planets appear to form more frequently in wide orbits than in close-in orbits around low-mass and lower metallicity stars. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Comments: 32 pages (including appendix with radial velocity time series), 16 figures, 14 tables. Accepted for publication in A&A

The mass of the exo-Venus Gliese 12 b, as revealed by HARPS-N, ESPRESSO, and CARMENES

Authors: Daisy A. Turner, Yoshi Nike Emilia Eschen, Felipe Murgas, Annelies Mortier, Thomas G Wilson, Jorge Fernández Fernández, Nicole Gromek, Giuseppe Morello, Hugo M. Tabernero, Jo Ann Egger, Shreyas Vissapragada, José A. Caballero, Stefan Dreizler, Alix Violet Freckelton, Artie P. Hatzes, Ben Scott Lakeland, Evangelos Nagel, Luca Naponiello, Siegfried Vanaverbeke, Alexander Venner, María Rosa Zapatero Osorio, Pedro J. Amado, Víctor J. S. Béjar, Aldo Stefano Bonomo, Lars A. Buchhave , et al. (38 additional authors not shown)

Abstract: Small temperate planets are prime targets for exoplanet studies due to their possible similarities with the rocky planets in the Solar System. M dwarfs are promising hosts since the planetary signals are within our current detection capabilities. Gliese 12 b is a Venus-sized temperate planet orbiting a quiet M dwarf. We present here the first precise mass measurement of this small exoplanet. We pe… ▽ More Small temperate planets are prime targets for exoplanet studies due to their possible similarities with the rocky planets in the Solar System. M dwarfs are promising hosts since the planetary signals are within our current detection capabilities. Gliese 12 b is a Venus-sized temperate planet orbiting a quiet M dwarf. We present here the first precise mass measurement of this small exoplanet. We performed a detailed analysis using HARPS-N, ESPRESSO, and CARMENES radial velocities, along with new and archival \tess, \cheops, and MuSCAT2/3 photometry data. From fitting the available data, we find that the planet has a radius of $R_\mathrm{p} = 0.93\pm0.06 \,\mathrm{R_\oplus}$ and a mass of $M_\mathrm{p} = 0.95^{+0.29}_{-0.30} \,\mathrm{M_\oplus}$ (a $3.2σ$ measurement of the semi-amplitude $K=0.67\pm0.21\,\mathrm{m\,s^{-1}}$), and is on an orbit with a period of $12.761418^{+0.000060}_{-0.000055}\,\mathrm{d}$. A variety of techniques were utilised to attenuate stellar activity signals. Gliese 12 b has an equilibrium temperature of $T_\mathrm{eq}=317 \pm 8\,\mathrm{K}$, assuming an albedo of zero, and a density consistent with that of Earth and Venus ($ρ_\mathrm{p}=6.4\pm2.4\,\mathrm{g\,cm^{-3}}$). We find that Gliese 12 b has a predominantly rocky interior and simulations indicate that it is unlikely to have retained any of its primordial gaseous envelope. The bulk properties of Gliese 12 b place it in an extremely sparsely populated region of both mass--radius and density--$T_\mathrm{eq}$ parameter space, making it a prime target for follow-up observations, including Lyman-$α$ studies. △ Less

Submitted 3 October, 2025; v1 submitted 25 June, 2025; originally announced June 2025.

Comments: 25 pages, 14 figures; accepted for publication in MNRAS

A transiting giant planet in orbit around a 0.2-solar-mass host star

Authors: Edward M. Bryant, Andrés Jordán, Joel D. Hartman, Daniel Bayliss, Elyar Sedaghati, Khalid Barkaoui, Jamila Chouqar, Francisco J. Pozuelos, Daniel P. Thorngren, Mathilde Timmermans, Jose Manuel Almenara, Igor V. Chilingarian, Karen A. Collins, Tianjun Gan, Steve B. Howell, Norio Narita, Enric Palle, Benjamin V. Rackham, Amaury H. M. J. Triaud, Gaspar Á. Bakos, Rafael Brahm, Melissa J. Hobson, Vincent Van Eylen, Pedro J. Amado, Luc Arnold , et al. (34 additional authors not shown)

Abstract: Planet formation models suggest that the formation of giant planets is significantly harder around low-mass stars, due to the scaling of protoplanetary disc masses with stellar mass. The discovery of giant planets orbiting such low-mass stars thus imposes strong constraints on giant planet formation processes. Here, we report the discovery of a transiting giant planet orbiting a… ▽ More Planet formation models suggest that the formation of giant planets is significantly harder around low-mass stars, due to the scaling of protoplanetary disc masses with stellar mass. The discovery of giant planets orbiting such low-mass stars thus imposes strong constraints on giant planet formation processes. Here, we report the discovery of a transiting giant planet orbiting a $0.207 \pm 0.011 M_{\odot}$ star. The planet, TOI-6894 b, has a mass and radius of $M_P = 0.168 \pm 0.022 M_J (53.4 \pm 7.1 M_{\oplus})$ and $R_P = 0.855 \pm 0.022 R_J$, and likely includes $12 \pm 2 M_{\oplus}$ of metals. The discovery of TOI-6894 b highlights the need for a better understanding of giant planet formation mechanisms and the protoplanetary disc environments in which they occur. The extremely deep transits (17% depth) make TOI-6894 b one of the most accessible exoplanetary giants for atmospheric characterisation observations, which will be key for fully interpreting the formation history of this remarkable system and for the study of atmospheric methane chemistry. △ Less

Submitted 10 June, 2025; v1 submitted 9 June, 2025; originally announced June 2025.

Comments: Published in Nature Astronomy (https://www.nature.com/articles/s41550-025-02552-4)

Retrieving day- and nightside atmospheric properties of the ultra-hot Jupiter TOI-2109b. Detection of Fe and CO emission lines and evidence for inefficient heat transport

Authors: D. Cont, L. Nortmann, F. Lesjak, F. Yan, D. Shulyak, A. Lavail, M. Stangret, E. Pallé, P. J. Amado, J. A. Caballero, A. Hatzes, Th. Henning, N. Piskunov, A. Quirrenbach, A. Reiners, I. Ribas, J. F. Agüí Fernández, C. Akın, L. Boldt-Christmas, P. Chaturvedi, S. Czesla, A. Hahlin, K. Heng, O. Kochukhov, T. Marquart , et al. (10 additional authors not shown)

Abstract: The ultra-hot Jupiter (UHJ) TOI-2109b marks the lower edge of the equilibrium temperature gap between 3500 K and 4500 K, an unexplored thermal regime that separates KELT-9b, the hottest planet yet discovered, from all other currently known gas giants. To study the structure of TOI-2109b's atmosphere, we obtained high-resolution emission spectra of both the planetary day- and nightsides with CARMEN… ▽ More The ultra-hot Jupiter (UHJ) TOI-2109b marks the lower edge of the equilibrium temperature gap between 3500 K and 4500 K, an unexplored thermal regime that separates KELT-9b, the hottest planet yet discovered, from all other currently known gas giants. To study the structure of TOI-2109b's atmosphere, we obtained high-resolution emission spectra of both the planetary day- and nightsides with CARMENES and CRIRES$^+$. By applying the cross-correlation technique, we identified the emission signatures of Fe I and CO, as well as a thermal inversion layer in the dayside atmosphere; no significant H$_2$O signal was detected from the dayside. None of the analyzed species were detectable from the nightside atmosphere. We applied a Bayesian retrieval framework that combines high-resolution spectroscopy with photometric measurements to constrain the dayside atmospheric parameters and derive upper limits for the nightside hemisphere. The dayside thermal inversion extends from 3200 K to 4600 K, with an atmospheric metallicity consistent with that of the host star (0.36 dex). Only weak constraints could be placed on the C/O ratio ($>$ 0.15). The retrieved spectral line broadening is consistent with tidally locked rotation, indicating the absence of strong dynamical processes. An upper temperature limit of 2400 K and a maximum atmospheric temperature gradient of 700 K/log bar could be derived for the nightside. Comparison of the retrieved dayside T-p profile with theoretical models, the absence of strong atmospheric dynamics, and significant differences in the thermal constraints between the day- and nightside hemispheres suggest a limited heat transport efficiency across the planetary atmosphere. Overall, our results place TOI-2109b in a transitional regime between the UHJs below the thermal gap, which show both CO and H$_2$O emission lines, and KELT-9b, where molecular features are largely absent. △ Less

Submitted 22 April, 2025; originally announced April 2025.

Comments: Accepted for publication in A&A

The CARMENES search for exoplanets around M dwarfs. Cluster analysis of signals from spectral activity indicators to search for shared periods

Authors: J. Kemmer, M. Lafarga, B. Fuhrmeister, Y. Shan, P. Schöfer, S. V. Jeffers, J. A. Caballero, A. Quirrenbach, P. J. Amado, A. Reiners, I. Ribas, V. J. S. Béjar, F. Del Sordo, A. P. Hatzes, Th. Henning, I. Hermelo, A. Kaminski, D. Montes, J. C. Morales, S. Reffert

Abstract: A multitude of spectral activity indicators are routinely computed nowadays from the spectra generated as part of planet-hunting radial velocity surveys. Searching for shared periods among them can help to robustly identify astrophysical quantities of interest, such as the stellar rotation period. However, this identification can be complicated due to the fact that many different peaks occurring i… ▽ More A multitude of spectral activity indicators are routinely computed nowadays from the spectra generated as part of planet-hunting radial velocity surveys. Searching for shared periods among them can help to robustly identify astrophysical quantities of interest, such as the stellar rotation period. However, this identification can be complicated due to the fact that many different peaks occurring in the periodograms. This is especially true in the presence of aliasing and spurious signals caused by environmental influences affecting the instrument. Our goal is to test a clustering algorithm to find signals with the same periodicity, (i.e. with the stellar rotation period) in the periodograms of a large number of activity indicators. On this basis, we have looked to evaluate the correlations between activity indicators and fundamental stellar parameters. We used generalised Lomb-Scargle periodograms to find periodic signals in 24 activity indicators, spanning the VIS and NIR channels of the CARMENES spectrograph. Common periods were subsequently determined by a machine learning algorithm for density-based spatial clustering of applications with noise (DBSCAN). The clustering analysis of the signals apparent in the spectral activity indicators is a powerful tool for the detection of stellar rotation periods. It is straightforward to implement and can be easily automated, so that large data sets can be analysed. For a sample of 136 stars, we were able to recover the stellar rotation period in a total of 59 cases, including 3 with a previously unknown rotation period. In addition, we analysed spurious signals frequently occurring at the period of one year and its integer fractions, concluding that they are likely aliases of one underlying signal. Furthermore, we reproduced the results of several previous studies on the relationships between activity indicators and the stellar characteristics. △ Less

Submitted 11 April, 2025; originally announced April 2025.

Comments: 33 pages (16 pages main text), 14 figures, accepted for publication in Astronomy & Astrophysics

The CARMENES search for exoplanets around M dwarfs. Occurrence rates of Earth-like planets around very low-mass stars

Authors: A. Kaminski, S. Sabotta, J. Kemmer, P. Chaturvedi, R. Burn, J. C. Morales, J. A. Caballero, I. Ribas, A. Reiners, A. Quirrenbach, P. J. Amado, V. J. S. Béjar, S. Dreizler, E. W. Guenther, A. P. Hatzes, Th. Henning, M. Kürster, D. Montes, E. Nagel, E. Pallé, V. Pinter, S. Reffert, M. Schlecker, Y. Shan, T. Trifonov , et al. (2 additional authors not shown)

Abstract: Aims: Previous estimates of planet occurrence rates in the CARMENES survey indicated increased numbers of planets on short orbits for M dwarfs with masses below 0.34\,M$_\odot$. Here we focused on the lowest-mass stars in the survey, comprising 15 inactive targets with masses under 0.16\,M$_\odot$. Methods: To correct for detection biases, we determined detection sensitivity maps for individual… ▽ More Aims: Previous estimates of planet occurrence rates in the CARMENES survey indicated increased numbers of planets on short orbits for M dwarfs with masses below 0.34\,M$_\odot$. Here we focused on the lowest-mass stars in the survey, comprising 15 inactive targets with masses under 0.16\,M$_\odot$. Methods: To correct for detection biases, we determined detection sensitivity maps for individual targets and the entire sample. Using Monte Carlo simulations, we estimated planet occurrence rates for orbital periods of 1\,d to 100\,d and minimum masses from 0.5\,M$_\oplus$ to 10\,M$_\oplus$. Results: The radial velocity (RV) data from CARMENES reveal four new planets around three stars in our sample, namely G~268--110\,b, G~261--6\,b, and G~192--15\,b and c. All three b planets have minimum masses of 1.03--1.52\,M$_\oplus$ and orbital periods of 1.43--5.45\,d, while G~192--15\,c is a 14.3\,M$_\oplus$ planet on a wide, eccentric orbit with $P \approx 1218$\,d and $e \approx 0.68$. Our occurrence rates suggest considerable dependencies with respect to stellar masses. For planets below 3\,M$_\oplus$ we found rates consistent with one planet per star across all investigated periods, but the rates decrease almost by an order of magnitude for larger planet masses up to 10\,M$_\oplus$. Compared to previous studies, low-mass stars tend to harbor more planets with $P <10$\,d. We also demonstrate that synthetic planet populations based on the standard core accretion scenario predict slightly more massive planets on wider orbits than observed. Conclusions: Our findings confirm that planet occurrence rates vary with stellar masses even among M dwarfs, as we found more planets with lower masses and on shorter orbits in our subsample of very low-mass stars compared to more massive M dwarfs. Therefore, we emphasize the need for additional differentiation in future studies. △ Less

Submitted 8 April, 2025; v1 submitted 4 April, 2025; originally announced April 2025.

Comments: Number of pages: 25; number of figures: 23 (12 in main + 11 in appendix). Accepted in A&A; DOI (pending): 10.1051/0004-6361/202453381 (Volume 696, Article number A101)

Quasinormal modes of a Proca field in Schwarzschild-AdS$_5$ spacetime via the isomonodromy method

Authors: Julián Barragán Amado, Tiago V. Fernandes, David C. Lopes

Abstract: We consider Proca field perturbations in a five-dimensional Schwarzschild-anti-de Sitter (Schwarzschild-AdS$_{5}$) black hole geometry. Using the vector spherical harmonic (VSH) method, we show that the Proca field decomposes into scalar-type and vector-type components according to their tensorial behavior on the three-sphere. Two degrees of freedom of the field are described by scalar-type compon… ▽ More We consider Proca field perturbations in a five-dimensional Schwarzschild-anti-de Sitter (Schwarzschild-AdS$_{5}$) black hole geometry. Using the vector spherical harmonic (VSH) method, we show that the Proca field decomposes into scalar-type and vector-type components according to their tensorial behavior on the three-sphere. Two degrees of freedom of the field are described by scalar-type components, which are coupled due to the mass term, while the remaining two degrees of freedom are described by a vector-type component, which decouples completely. Motivated by the Frolov-Krtouš-Kubizňák-Santos (FKKS) ansatz in the limit of zero spin, we use a field transformation to decouple the scalar-type components at the expense of introducing a complex separation parameter $β$. This parameter can be determined analytically, and its values correspond to two distinct polarizations of the scalar-type sector: "electromagnetic" and "non-electromagnetic", denoted by $β_{+}$ and $β_{-}$, respectively. In the scalar-type sector, the radial differential equation for each polarization is a Fuchsian differential equation with five singularities, whereas in the vector-type sector, the radial equation has four singularities. By means of the isomonodromy method, we reformulate the boundary value problem in terms of the initial conditions of the Painlevé VI $τ$ function and, using a series expansion of the $τ$ function, we compute the scalar-type and vector-type quasinormal modes (QNMs) in the small horizon limit. Our results are in overall very good agreement with those obtained via the numerical integration method. This shows that the isomonodromy method is a reliable method to compute quasinormal modes in the small horizon limit with high accuracy. △ Less

Submitted 31 March, 2025; originally announced April 2025.

Comments: 29 pages, 8 figures

CARMENES as an Instrument for Exoplanet Research

Authors: José A. Caballero, Walter Seifert, Andreas Quirrenbach, Pedro J. Amado, Ignasi Ribas, Ansgar Reiners

Abstract: CARMENES stands for Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs. CARMENES took six years from a concept to the start of operations, and a couple more years of initial data collection until the first science publication, but now is revolutionising our knowledge on exoplanets and their stars in our immediate vicinity. Here we des… ▽ More CARMENES stands for Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs. CARMENES took six years from a concept to the start of operations, and a couple more years of initial data collection until the first science publication, but now is revolutionising our knowledge on exoplanets and their stars in our immediate vicinity. Here we describe what CARMENES is: (i) an ultra-stabilised two-channel spectrograph at an almost dedicated 3.5 m telescope in southern Spain that covers in high spectral resolution and without big gaps from 0.52 mum to 1.71 mum; (ii) a science project aimed at comprehensively searching for and studying planetary systems with nearby, bright, M-dwarf hosts, but that also investigates transiting planets around other stars; and (iii) the German-Spanish consortium that designed and built the instrument and that has operated it under guaranteed and legacy time observations. △ Less

Submitted 7 March, 2025; originally announced March 2025.

Comments: To be published in: Handbook of Exoplanets, 2nd edition, Hans Deeg and Juan Antonio Belmonte (eds. in chief), Springer International Publishing AG, part of Springer Nature. The corresponding images in full size can be downloaded at this link: https://carmenes.caha.es/ext/instrument/CARMENES_Handbook_Caballero_Figs.pdf (massive file)

TOI-2015b: a sub-Neptune in strong gravitational interaction with an outer non-transiting planet

Authors: K. Barkaoui, J. Korth, E. Gaidos, E. Agol, H. Parviainen, F. J. Pozuelos, E. Palle, N. Narita, S. Grimm, M. Brady, J. L. Bean, G. Morello, B. V. Rackham, A. J. Burgasser, V. Van Grootel, B. Rojas-Ayala, A. Seifahrt, E. Marfil, V. M. Passegger, M. Stalport, M. Gillon, K. A. Collins, A. Shporer, S. Giacalone, S. Yalçınkaya , et al. (97 additional authors not shown)

Abstract: TOI-2015 is a known exoplanetary system around an M4 dwarf star, consisting of a transiting sub-Neptune planet in a 3.35-day orbital period, TOI-2015b, accompanied by a non-transiting companion, TOI-2015c. High-precision RV measurements were taken with the MAROON-X spectrograph, and high-precision photometric data were collected several networks. We re-characterize the target star by combining opt… ▽ More TOI-2015 is a known exoplanetary system around an M4 dwarf star, consisting of a transiting sub-Neptune planet in a 3.35-day orbital period, TOI-2015b, accompanied by a non-transiting companion, TOI-2015c. High-precision RV measurements were taken with the MAROON-X spectrograph, and high-precision photometric data were collected several networks. We re-characterize the target star by combining optical spectr, Bayesian Model Averaging (BMA) and Spectral Energy Distribution (SED) analysis. The TOI-2015 host star is a K=10.3mag M4-type dwarf with a sub-solar metallicity of [Fe/H]=-0.31+/-0.16, and a Teff=3200K. Our photodynamical analysis of the system strongly favors the 5:3 mean motion resonance and in this scenario the planet b has an orbital period of 3.34days, a mass of Mp=9.02+/-0.34Me, a radius of Rp=3.309+/-0.012Re, resulting in a density of rhop= 1.40+/-0.06g/cm3, indicative of a Neptune like composition. Its transits exhibit large (>1hr) timing variations indicative of an outer perturber in the system. We performed a global analysis of the high-resolution RV measurements, the photometric data, and the TTVs, and inferred that TOI-2015 hosts a second planet, TOI-2015c, in a non-transiting configuration. TOI-2015c has an orbital period of Pc=5.583days and a mass of Mp=8.91+0.38-0.40Me. The dynamical configuration of TOI-2015b and TOI-2015c can be used to constrain the system's planetary formation and migration history. Based on the mass-radius composition models, TOI-2015b is a water-rich or rocky planet with a hydrogen-helium envelope. Moreover, TOI-2015b has a high transmission spectroscopic metric (TSM=149), making it a favorable target for future transmission spectroscopic observations with JWST to constrain the atmospheric composition of the planet. Such observations would also help to break the degeneracies in theoretical models of the planet's interior structure. △ Less

Submitted 10 February, 2025; originally announced February 2025.

Comments: The paper has been accepted for publication in Astronomy and Astrophysics

Connection between planetary He I $λ$10830 Å absorption and extreme-ultraviolet emission of planet-host stars

Authors: J. Sanz-Forcada, M. López-Puertas, M. Lampón, S. Czesla, L. Nortmann, J. A. Caballero, M. R. Zapatero Osorio, P. J. Amado, F. Murgas, J. Orell-Miquel, E. Pallé, A. Quirrenbach, A. Reiners, I. Ribas, A. Sánchez-López, E. Solano

Abstract: Context. The detection of the He I 10830 A triplet in exoplanet atmospheres has opened a new window for probing planetary properties, including atmospheric escape. Unlike Lyman alpha, the triplet is less affected by ISM absorption. Sufficient XUV stellar irradiation may trigger the formation of the He I triplet via photoionization and posterior recombination processes in the planet atmospheres. On… ▽ More Context. The detection of the He I 10830 A triplet in exoplanet atmospheres has opened a new window for probing planetary properties, including atmospheric escape. Unlike Lyman alpha, the triplet is less affected by ISM absorption. Sufficient XUV stellar irradiation may trigger the formation of the He I triplet via photoionization and posterior recombination processes in the planet atmospheres. Only a weak trend between stellar XUV and the planetary He I strength has been observed so far. Aims. We aim to confirm this mechanism for producing the He I absorption in exoplanetary atmospheres by examining a sample of planetary systems. Methods. We obtained homogeneous measurements of the planetary He I line EW and consistently computed the stellar XUV ionizing irradiation. We first derived new coronal models for the planet-host stars. We used updated data from the X-exoplanets database, archival X-ray spectra of M-type stars (including AU Mic and Proxima Cen), and new XMM-Newton X-ray data obtained for the CARMENES project. These data were complemented at longer wavelengths with publicly available HST, FUSE, and EUVE spectra. A total of 75 stars are carefully analyzed to obtain a new calibration between X-ray and EUV emission. Results. Two distinct relationships between stellar X-ray emission (5-100 A) and EUV_H (100-920 A) or EUV_He (100-504 A) radiation are obtained to scale the emission from late-type stellar coronae. A total of 48 systems with reported planetary He I 10830 A studies, exhibit a robust relationship between the planetary He I feature and the ionizing XUV_He received by the planet, corrected by stellar and planetary radii, and the planet's gravitational potential. Some outliers could be explained by a different atmospheric composition or the lack of planetary gaseous atmospheres. This relation may be used to predict the He I 10830 A absorption in exoplanet atmospheres. △ Less

Submitted 30 January, 2025; v1 submitted 7 January, 2025; originally announced January 2025.

Comments: Accepted by A&A. 12 pages, 5 figures in the main body (42 pages, 22 figures, 21 tables including appendices)

Journal ref: A&A, 693, A285 (2025)

CARMENES input catalogue of M dwarfs IX. Multiplicity from close spectroscopic binaries to ultra-wide systems

Authors: C. Cifuentes, J. A. Caballero, J. González-Payo, P. J. Amado, V. J. S. Béjar, A. J. Burgasser, M. Cortés-Contreras, N. Lodieu, D. Montes, A. Quirrenbach, A. Reiners, I. Ribas, J. Sanz-Forcada, W. Seifert, M. R. Zapatero Osorio

Abstract: Multiplicity studies greatly benefit from focusing on M dwarfs because they are often paired in a variety of configurations with both stellar and substellar objects, including exoplanets. We aim to address the observed multiplicity of M dwarfs by conducting a systematic analysis using the latest available astrophotometric data. For every star in a sample of 2214 M dwarfs from the CARMENES catalogu… ▽ More Multiplicity studies greatly benefit from focusing on M dwarfs because they are often paired in a variety of configurations with both stellar and substellar objects, including exoplanets. We aim to address the observed multiplicity of M dwarfs by conducting a systematic analysis using the latest available astrophotometric data. For every star in a sample of 2214 M dwarfs from the CARMENES catalogue, we investigated the existence of resolved and unresolved physical companions in the literature and in all-sky surveys, especially in Gaia DR3 data products. We covered a very wide range of separations, from known spectroscopic binaries in tight arrangements $\sim$0.01 au to remarkably separated ultra-wide pairs ($\sim$10$^5$ au). We identified 835 M dwarfs in 720 multiple systems, predominantly binaries. Thus, we propose 327 new binary candidates based on Gaia data. If these candidates are finally confirmed, we expect the multiplicity fraction of M dwarfs to be 40.3$^{+2.1}_{-2.0}$ %. When only considering the systems already identified, the multiplicity fraction is reduced to 27.8$^{+1.9}_{-1.8}$ %. This result is in line with most of the values published in the literature. We also identified M-dwarf multiple systems with FGK, white dwarf, ultra-cool dwarf, and exoplanet companions, as well as those in young stellar kinematic groups. We studied their physical separations, orbital periods, binding energies, and mass ratios. We argue that based on reliable astrometric data and spectroscopic investigations from the literature (even when considering detection biases), the multiplicity fraction of M dwarfs could still be significantly underestimated. This calls for further high-resolution follow-up studies to validate these findings. △ Less

Submitted 16 December, 2024; originally announced December 2024.

The CARMENES search for exoplanets around M dwarfs. The impact of rotation and magnetic fields on the radial velocity jitter in cool stars

Authors: H. L. Ruh, M. Zechmeister, A. Reiners, E. Nagel, Y. Shan, C. Cifuentes, S. V. Jeffers, L. Tal-Or, V. J. S. Béjar, P. J. Amado, J. A. Caballero, A. Quirrenbach, I. Ribas, J. Aceituno, A. P. Hatzes, Th. Henning, A. Kaminski, D. Montes, J. C. Morales, P. Schöfer, A. Schweitzer, R. Varas

Abstract: Radial velocity (RV) jitter represents an intrinsic limitation on the precision of Doppler searches for exoplanets that can originate from both instrumental and astrophysical sources. We aim to determine the RV jitter floor in M dwarfs and investigate the stellar properties that lead to RV jitter induced by stellar activity. We determined the RV jitter in 239 M dwarfs from the CARMENES survey that… ▽ More Radial velocity (RV) jitter represents an intrinsic limitation on the precision of Doppler searches for exoplanets that can originate from both instrumental and astrophysical sources. We aim to determine the RV jitter floor in M dwarfs and investigate the stellar properties that lead to RV jitter induced by stellar activity. We determined the RV jitter in 239 M dwarfs from the CARMENES survey that are predominantly of mid to late spectral type and solar metallicity. We also investigated the correlation between stellar rotation and magnetic fields with RV jitter. The median jitter in the CARMENES sample is 3.1 m/s, and it is 2.3 m/s for stars with an upper limit of 2 km/s on their projected rotation velocities. We provide a relation between the stellar equatorial rotation velocity and RV jitter in M dwarfs based on a subsample of 129 well-characterized CARMENES stars. RV jitter induced by stellar rotation dominates for stars with equatorial rotation velocities greater than 1 km/s. A jitter floor of 2 m/s dominates in stars with equatorial rotation velocities below 1 km/s. This jitter floor likely contains contributions from stellar jitter, instrumental jitter, and undetected companions. We study the impact of the average magnetic field and the distributions of magnetic filling factors on the RV jitter. We find a series of stars with excess RV jitter and distinctive distributions of magnetic filling factors. These stars are characterized by a dominant magnetic field component between 2-4 kG. An RV jitter floor can be distinguished from RV jitter induced by activity and rotation based on the stellar equatorial rotation velocity. RV jitter induced by activity and rotation primarily depends on the equatorial rotation velocity. This RV jitter is also related to the distribution of magnetic filling factors, and this emphasizes the role of the magnetic field in the generation of RV jitter. △ Less

Submitted 10 December, 2024; originally announced December 2024.

Journal ref: A&A, 692, A138 (2024)

Searching for star-planet interactions in GJ 486 at radio wavelengths with the uGMRT

Authors: L. Peña-Moñino, M. Pérez-Torres, D. Kansabanik, G. Blázquez-Calero, R. D. Kavanagh, J. F. Gómez, J. Moldón, A. Alberdi, P. J. Amado, G. Anglada, J. A. Caballero, A. Mohan, P. Leto, M. Narang, M. Osorio, D. Revilla, C. Trigilio

Abstract: We search for radio emission from star-planet interactions in the M-dwarf system GJ~486, which hosts an Earth-like planet. We observed the GJ~486 system with the upgraded Giant Metrewave Radio Telescope (uGMRT) from 550 to 750 MHz in nine different epochs, between October 2021 and February 2022, covering almost all orbital phases of GJ~486 b from different orbital cycles. We obtained radio images… ▽ More We search for radio emission from star-planet interactions in the M-dwarf system GJ~486, which hosts an Earth-like planet. We observed the GJ~486 system with the upgraded Giant Metrewave Radio Telescope (uGMRT) from 550 to 750 MHz in nine different epochs, between October 2021 and February 2022, covering almost all orbital phases of GJ~486 b from different orbital cycles. We obtained radio images and dynamic spectra of the total and circularly polarized intensity for each individual epoch We do not detect any quiescent radio emission in any epoch above 3$σ$. Similarly, we do not detect any bursty emission in our dynamic spectra. While we cannot completely rule out that the absence of a radio detection is due to time variability of the radio emission, or to the maximum electron-cyclotron maser emission being below our observing range, this seems unlikely. We discuss two possible scenarios: an intrinsic dim radio signal, or alternatively, that the anisotropic beamed emission pointed away from the observer. If the non-detection of radio emission from star-planet interaction in GJ~486 is due to an intrinsically dim signal, this implies that, independently of whether the planet is magnetized or not, the mass-loss rate is small (\dot{M}_\star $\lesssim$ 0.3 \dot{M}_\sun) and that, concomitantly, the efficiency of the conversion of Poynting flux into radio emission must be low ($β\lesssim 10^{-3}$). Free-free absorption effects are negligible, given the high value of the coronal temperature. Finally, if the anisotropic beaming pointed away from us, this would imply that GJ~486 has very low values of its magnetic obliquity and inclination. △ Less

Submitted 27 November, 2024; v1 submitted 26 November, 2024; originally announced November 2024.

Journal ref: A&A 693, A223 (2025)

CARMENES input catalogue of M dwarfs VIII. Kinematics in the solar neighbourhood

Authors: M. Cortés-Contreras, J. A. Caballero, D. Montes, C. Cardona-Guillén, V. J. S. Béjar, C. Cifuentes, H. M. Tabernero, M. R. Zapatero Osorio, P. J. Amado, S. V. Jeffers, M. Lafarga, N. Lodieu, A. Quirrenbach, A. Reiners, I. Ribas, P. Schöfer, A. Schweitzer, W. Seifert

Abstract: Aims. Our goals are to characterise the kinematic properties and to identify young and old stars among the M dwarfs of the CARMENES input catalogue. Methods. We compiled the spectral types, proper motions, distances, and radial velocities for 2187 M dwarfs. We used the public code SteParKin to derive their galactic space velocities and identify members in the different galactic populations. We als… ▽ More Aims. Our goals are to characterise the kinematic properties and to identify young and old stars among the M dwarfs of the CARMENES input catalogue. Methods. We compiled the spectral types, proper motions, distances, and radial velocities for 2187 M dwarfs. We used the public code SteParKin to derive their galactic space velocities and identify members in the different galactic populations. We also identified candidate members in young stellar kinematic groups, with ages ranging from 1 Ma to 800 Ma with SteParKin, LACEwING, and BANYAN Σ. We removed known close binaries and perform an analysis of kinematic, rotation, and activity indicators (rotational periods and projected velocities, Halpha, X-rays, and UV emission) for 1546 M dwarfs. We defined five rotation-activity-colour relations satisfied by young (τ <= 800 Ma) stars. Results. We identified 191 young M dwarf candidates (~12%), 113 of which are newly recognised in this work. In this young sample, there are 118 very active stars based on Hα emission, fast rotation, and X-ray and UV emission excess. Of them, 27 have also strong magnetic fields, 9 of which are likely younger than 50 Ma. Additionally, there are 87 potentially young stars and 99 stars with a dubious youth classification, which may increase the fraction of young stars to an astounding 24%. Only one star out of the 2187 exhibits kinematics typical of the old Galactic halo. Conclusions. A combined analysis of kinematic and rotation-activity properties provides a robust method for identifying young M dwarfs from archival data. However, more observational efforts are needed to ascertain the true nature of numerous young star candidates in the field and, perhaps more importantly, to precisely quantify their age. △ Less

Submitted 11 November, 2024; originally announced November 2024.

Hints of auroral and magnetospheric polarized radio emission from the scallop-shell star 2MASS J05082729$-$2101444

Authors: Simranpreet Kaur, Daniele Viganò, Víctor J. S. Béjar, Álvaro Sánchez Monge, Òscar Morata, Devojyoti Kansabanik, Josep Miquel Girart, Juan Carlos Morales, Guillem Anglada-Escudé, Felipe Murgas, Yutong Shan, Ekaterina Ilin, Miguel Pérez-Torres, María Rosa Zapatero Osorio, Pedro J. Amado, José A. Caballero, Fabio Del Sordo, Enric Palle, Andreas Quirrenbach, Ansgar Reiners, Ignasi Ribas

Abstract: Scallop-shell stars, a recently discovered class of young M dwarfs, show complex optical light curves that are characterized by periodic dips as well as other features that are stable over tens to hundreds of rotation cycles. The origin of these features is not well-understood. 2MASS J05082729$-$2101444 is a $\sim$25 Myr old scallop-shell star that was identified using TESS data; it has a photomet… ▽ More Scallop-shell stars, a recently discovered class of young M dwarfs, show complex optical light curves that are characterized by periodic dips as well as other features that are stable over tens to hundreds of rotation cycles. The origin of these features is not well-understood. 2MASS J05082729$-$2101444 is a $\sim$25 Myr old scallop-shell star that was identified using TESS data; it has a photometric period of 6.73h that has been attributed to rotation. Of the $\sim$50 recently confirmed scallop-shell stars, it is one of the few detected at radio frequencies between 1 and 8 GHz. We observed this rare system with the upgraded Giant Meterwave Radio Telescope at 575--720 MHz, covering 88% of the photometric period in each of the two observations scheduled almost a month apart in 2023. We detected $\sim$millijansky emission from the target in both epochs, with a significant circular polarization fraction: $|V/I|\sim$20--50%. The 3.5-min phase-folded light curves reveal unique variability in circular polarization, showing an $\sim$hour-long helicity reversal in both epochs, similar in amplitude, length, and (possibly) phase. These results suggest two emission components: The first is a persistent, moderately polarized component possibly ascribable to gyro-synchrotron emission driven by centrifugal breakout events. The second is a highly polarized, short burst-like component, likely due to an electron cyclotron maser (ECM), indicative of auroral emission and potentially responsible for the helicity reversal. To explain this, we discuss the different origins of the plasma responsible for the radio emission, including the possibility that the occulting material is acting as a plasma source. Future coordinated multifrequency radio and optical observations can further constrain the underlying scenario, as well as the magnetic geometry of the system, if we assume an ECM-like auroral emission. △ Less

Submitted 29 October, 2024; originally announced October 2024.

Comments: 9 pages, 5 figures, 1 table, Accepted for publication in Astronomy & Astrophysics Letters

Journal ref: A&A 691, L17 (2024)

The effect of resummation on retarded Green's function and greybody factor in $AdS$ black holes

Authors: Julián Barragán Amado, Shankhadeep Chakrabortty, Arpit Maurya

Abstract: We investigate the retarded Green's function and the greybody factor in asymptotically AdS black holes. Using the connection coefficients of the Heun equation, expressed in terms of the Nekrasov-Shatashvili (NS) free energy of an $SU(2)$ supersymmetric gauge theory with four fundamental hypermultiplets, we derive asymptotic expansions for both the retarded Green's function and the greybody factor… ▽ More We investigate the retarded Green's function and the greybody factor in asymptotically AdS black holes. Using the connection coefficients of the Heun equation, expressed in terms of the Nekrasov-Shatashvili (NS) free energy of an $SU(2)$ supersymmetric gauge theory with four fundamental hypermultiplets, we derive asymptotic expansions for both the retarded Green's function and the greybody factor in the small horizon limit. Furthermore, we compute the corrections to these asymptotic expansions resulting from the resummation procedure of the instanton part of the NS function. △ Less

Submitted 11 September, 2024; originally announced September 2024.

Comments: 37 pages, 5 figures

RedDots: Limits on habitable and undetected planets orbiting nearby stars GJ 832, GJ 674, and Ross 128

Authors: F. Liebing, S. V. Jeffers, P. Gorrini, C. A. Haswell, S. Dreizler, J. R. Barnes, C. Hartogh, V. Koseleva, F. Del Sordo, P. J. Amado, J. A. Caballero, M. J. López-González, N. Morales, A. Reiners, I. Ribas, A. Quirrenbach, E. Rodríguez, L. Tal-Or, Y. Tsapras

Abstract: Aims. Using HARPS spectroscopic data obtained by the RedDots campaign, as well as archival data from HARPS and CARMENES, supplemented with ASH2 and T90 photometry, we aim to search for additional planets around the three M dwarfs GJ 832, GJ 674, and Ross 128. We also aim to determine limits on possible undetected, habitable planets. We investigate (i) the reliability of the recovered orbital eccen… ▽ More Aims. Using HARPS spectroscopic data obtained by the RedDots campaign, as well as archival data from HARPS and CARMENES, supplemented with ASH2 and T90 photometry, we aim to search for additional planets around the three M dwarfs GJ 832, GJ 674, and Ross 128. We also aim to determine limits on possible undetected, habitable planets. We investigate (i) the reliability of the recovered orbital eccentricities and (ii) the reliability of Bayesian evidence as a diagnostic for selecting the best model. Methods. We employed Markov-chain Monte Carlo, nested sampling, and Gaussian process (GP) analyses to fit a total of 20 different models. We used the residuals to create grids for injection-recovery simulations to obtain detection limits on potentially undiscovered planets. Results. Our refined orbital elements for GJ 832 b, GJ 674 b, and Ross 128 b confirm (GJ 832, GJ 674) or increase (Ross 128) prior eccentricity determinations. No additional planets were found in any of the systems. The detection limits obtained for all three systems are between 30 and 50 cm/s for orbital periods in the range of 1 to 10 000 days. Using N-body simulations, we find that undiscovered secondary planets are unlikely (Ross 128) or incapable (GJ 674) of having caused the observed eccentricities of the known planets. We find that the eccentricity of GJ 832 b is not significantly different from zero. Conclusions. GJ 832 b, GJ 674 b, and Ross 128 b retain their status as hosting lonely and (for the latter two) eccentric planets. Finally, our results show that Bayesian evidence, when used in conjunction with GP, is not a robust diagnostic for selecting the best model in cases of low-activity stars. In such cases, we advise an inspection of the shapes of the posterior distributions and to ensure that relevant simulations are performed to assess the validity of the perceived best model. △ Less

Submitted 2 September, 2024; originally announced September 2024.

Comments: Abstract shortened to fit the character limit; 25 pages, 14 Figures, 6 Tables; Appendix available at Zenodo; Accepted for publication by A&A

The CARMENES search for exoplanets around M dwarfs: Magnesium and silicon abundances of K7-M5.5 stars

Authors: H. M. Tabernero, Y. Shan, J. A. Caballero, C. Duque-Arribas, D. Montes, J. I. González Hernández, M. R. Zapatero Osorio, A. Schweitzer, Th. Henning, M. Cortés-Contreras, A. Quirrenbach, P. J. Amado, A. Reiners, I. Ribas, G. Bergond, J. C. Morales

Abstract: We present the abundances of magnesium (Mg) and silicon (Si) for 314 dwarf stars with spectral types in the interval K7.0-M5.5 (Teff range ~4200-3050 K) observed with the CARMENES high-resolution spectrograph at the 3.5 m telescope at the Calar Alto Observatory. Our analysis employs the BT-Settl model atmospheres, the radiative transfer code Turbospectrum, and a state-of-the-art selection of atomi… ▽ More We present the abundances of magnesium (Mg) and silicon (Si) for 314 dwarf stars with spectral types in the interval K7.0-M5.5 (Teff range ~4200-3050 K) observed with the CARMENES high-resolution spectrograph at the 3.5 m telescope at the Calar Alto Observatory. Our analysis employs the BT-Settl model atmospheres, the radiative transfer code Turbospectrum, and a state-of-the-art selection of atomic and molecular data. These Mg and Si abundances are critical for understanding both the chemical evolution and assembly of the Milky Way and the formation and composition of rocky planets. Our chemical abundances show a line-to-line scatter at the level of 0.1 dex for all studied spectral types. The typical error bar of our chemical abundance measurements is +- 0.11 dex (Mg) and +- 0.16 dex (Si) for all spectral types based on the comparison of the results obtained for stellar components of multiple systems. The derived abundances are consistent with the galactic evolution trends and observed chemical abundance distribution of earlier FGK-type stars in the solar neighbourhood. Besides, our analysis provides compatible abundances for stars in multiple systems. In addition, we studied the abundances of different galactic stellar populations. In this paper, we also explore the relation of the Mg and Si abundances of stars with and without known planets. △ Less

Submitted 29 July, 2024; originally announced July 2024.

Comments: 11 Pages, 5 figures. Accepted for publication in A&A

Revisiting the dynamical masses of the transiting planets in the young AU Mic system: Potential AU Mic b inflation at $\sim$20 Myr

Authors: M. Mallorquín, V. J. S. Béjar, N. Lodieu, M. R. Zapatero Osorio, H. Yu, A. Suárez Mascareño, M. Damasso, J. Sanz-Forcada, I. Ribas, A. Reiners, A. Quirrenbach, P. J. Amado, J. A. Caballero, S. Aigrain, O. Barragán, S. Dreizler, A. Fernández-Martín, E. Goffo, Th. Henning, A. Kaminski, B. Klein, R. Luque, D. Montes, J. C. Morales, E. Nagel , et al. (4 additional authors not shown)

Abstract: Understanding planet formation is important in the context of the origin of planetary systems in general and of the Solar System in particular, as well as to predict the likelihood of finding Jupiter, Neptune, and Earth analogues around other stars. We aim to precisely determine the radii and dynamical masses of transiting planets orbiting the young M star AU Mic using public photometric and spect… ▽ More Understanding planet formation is important in the context of the origin of planetary systems in general and of the Solar System in particular, as well as to predict the likelihood of finding Jupiter, Neptune, and Earth analogues around other stars. We aim to precisely determine the radii and dynamical masses of transiting planets orbiting the young M star AU Mic using public photometric and spectroscopic datasets. We characterise the stellar activity and physical properties (radius, mass, density) of the transiting planets in the young AU Mic system through joint transit and radial velocity fits with Gaussian processes. We determine a radius of $R^{b}$= 4.79 +/- 0.29 R$_\oplus$, a mass of $M^{b}$= 9.0 +/- 2.7 M$_\oplus$, and a bulk density of $ρ^{b}$ = 0.49 +/- 0.16 g cm$^{-3}$ for the innermost transiting planet AU Mic b. For the second known transiting planet, AU Mic c, we infer a radius of $R^{c}$= 2.79 +/- 0.18 R$_\oplus$, a mass of $M^{c}$= 14.5 +/- 3.4 M$_\oplus$, and a bulk density of $ρ^{c}$ = 3.90 +/- 1.17 g cm$^{-3}$. According to theoretical models, AU Mic b may harbour an H2 envelope larger than 5\% by mass, with a fraction of rock and a fraction of water. AU Mic c could be made of rock and/or water and may have an H2 atmosphere comprising at most 5\% of its mass. AU Mic b has retained most of its atmosphere but might lose it over tens of millions of years due to the strong stellar radiation, while AU Mic c likely suffers much less photo-evaporation because it lies at a larger separation from its host. Using all the datasets in hand, we determine a 3$σ$ upper mass limit of $M^{[d]}\sin{i}$ = 8.6 M$_{\oplus}$ for the AU Mic 'd' TTV-candidate. In addition, we do not confirm the recently proposed existence of the planet candidate AU Mic 'e' with an orbital period of 33.4 days. △ Less

Submitted 23 July, 2024; originally announced July 2024.

Comments: Accepted in A&A. 28 pages, 15 figures

ANDES, the high resolution spectrograph for the ELT: science goals, project overview and future developments

Authors: A. Marconi, M. Abreu, V. Adibekyan, V. Alberti, S. Albrecht, J. Alcaniz, M. Aliverti, C. Allende Prieto, J. D. Alvarado Gómez, C. S. Alves, P. J. Amado, M. Amate, M. I. Andersen, S. Antoniucci, E. Artigau, C. Bailet, C. Baker, V. Baldini, A. Balestra, S. A. Barnes, F. Baron, S. C. C. Barros, S. M. Bauer, M. Beaulieu, O. Bellido-Tirado , et al. (264 additional authors not shown)

Abstract: The first generation of ELT instruments includes an optical-infrared high-resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of $\sim$100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 $μ$m with the goal of ex… ▽ More The first generation of ELT instruments includes an optical-infrared high-resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of $\sim$100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 $μ$m with the goal of extending it to 0.35-2.4 $μ$m with the addition of a U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allow ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases, there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states. △ Less

Submitted 19 July, 2024; originally announced July 2024.

Comments: SPIE astronomical telescope and instrumentation 2024, in press

The CARMENES search for exoplanets around M dwarfs. Revisiting the GJ 581 multi-planetary system with new Doppler measurements from CARMENES, HARPS, and HIRES

Authors: A. von Stauffenberg, T. Trifonov, A. Quirrenbach, S. Reffert, A. Kaminski, S. Dreizler, I. Ribas, A. Reiners, M. Kürster, J. D. Twicken, D. Rapetti, J. A. Caballero, P. J. Amado, V. J. S. Béjar, C. Cifuentes, S. Góngora, A. P. Hatzes, Th. Henning, D. Montes, J. C. Morales, A. Schweitzer

Abstract: GJ 581 is a nearby M dwarf known to host a packed multiple planet system with 2 super-Earths and a Neptune-mass planet. We present new orbital analyses of the system, utilizing recent RV data obtained from the CARMENES spectrograph combined with newly reprocessed archival data from the HARPS and HIRES spectrographs. Our aim was to analyze the post-discovery spectroscopic data of GJ 581, which were… ▽ More GJ 581 is a nearby M dwarf known to host a packed multiple planet system with 2 super-Earths and a Neptune-mass planet. We present new orbital analyses of the system, utilizing recent RV data obtained from the CARMENES spectrograph combined with newly reprocessed archival data from the HARPS and HIRES spectrographs. Our aim was to analyze the post-discovery spectroscopic data of GJ 581, which were obtained with CARMENES. In addition, we used publicly available HIRES and HARPS spectroscopic data to seek evidence of the known and disputed exoplanets in this system. We aimed to investigate the stellar activity of GJ 581 and update the planetary system's orbital parameters using state-of-the-art numerical models and techniques. We performed a periodogram analysis of the available precise CARMENES, HIRES, and HARPS RVs and of stellar activity indicators. We conducted detailed orbital analyses by testing various orbital configurations consistent with the RV data. We studied the posterior probability distribution of the parameters fit to the data and explored the long-term stability and overall orbital dynamics of the system. We refined the orbital parameters of the system using the most precise and complete set of Doppler data available. Consistent with the existing literature, we confirm that the system is unequivocally composed of only 3 planets detectable in the present data, dismissing the putative planet GJ 581 d as an artifact of stellar activity. Our N-body fit reveals that the system's inclination is i $=$ 47.0 deg, which implies that the planets could be up to 30% more massive than their previously reported minimum masses. Furthermore, we report that the system exhibits long-term stability, as indicated by the posterior probability distribution, characterized by secular dynamical interactions without the involvement of mean motion resonances. △ Less

Submitted 16 July, 2024; originally announced July 2024.

Comments: 21 pages, 8 Figures, 5 Tables, 1 Appendix, Accepted for publication in A&A (20th March 2024), Data available at the CDS

ANDES, the high-resolution spectrograph for the ELT: RIZ Spectrograph preliminary design

Authors: Bruno Chazelas, Yevgeniy Ivanisenko, Audrey Lanotte, Pablo Santos Diaz, Ludovic Genolet, Michael Sordet, Ian Hughes, Christophe Lovis, Tobias M. Schmidt, Manuel Amate, José Peñate Castro, Afrodisio Vega Moreno, Fabio Tenegi, Roberto Simoes, Jonay I. González Hernández, María Rosa Zapatero Osorio, Javier Piqueras, Tomás Belenguer Dávila, Rocío Calvo Ortega, Roberto Varas González, Luis Miguel González Fernández, Pedro J. Amado, Jonathan Kern, Frank Dionies, Svend-Marian Bauer , et al. (22 additional authors not shown)

Abstract: We present here the preliminary design of the RIZ module, one of the visible spectrographs of the ANDES instrument 1. It is a fiber-fed high-resolution, high-stability spectrograph. Its design follows the guidelines of successful predecessors such as HARPS and ESPRESSO. In this paper we present the status of the spectrograph at the preliminary design stage. The spectrograph will be a warm, vacuum-… ▽ More We present here the preliminary design of the RIZ module, one of the visible spectrographs of the ANDES instrument 1. It is a fiber-fed high-resolution, high-stability spectrograph. Its design follows the guidelines of successful predecessors such as HARPS and ESPRESSO. In this paper we present the status of the spectrograph at the preliminary design stage. The spectrograph will be a warm, vacuum-operated, thermally controlled and fiber-fed echelle spectrograph. Following the phase A design, the huge etendue of the telescope will be reformed in the instrument with a long slit made of smaller fibers. We discuss the system design of the spectrographs system. △ Less

Submitted 26 June, 2024; originally announced June 2024.

Comments: Paper submitted to the SPIE astronomical telescope and instrumentation 2024, conference title : Ground-based and Airborne Instrumentation for Astronomy X, paper reference number : 13096-171

Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3

Authors: Michaël Gillon, Peter P. Pedersen, Benjamin V. Rackham, Georgina Dransfield, Elsa Ducrot, Khalid Barkaoui, Artem Y. Burdanov, Urs Schroffenegger, Yilen Gómez Maqueo Chew, Susan M. Lederer, Roi Alonso, Adam J. Burgasser, Steve B. Howell, Norio Narita, Julien de Wit, Brice-Olivier Demory, Didier Queloz, Amaury H. M. J. Triaud, Laetitia Delrez, Emmanuël Jehin, Matthew J. Hooton, Lionel J. Garcia, Clàudia Jano Muñoz, Catriona A. Murray, Francisco J. Pozuelos , et al. (59 additional authors not shown)

Abstract: Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely unexplored, and only one of them, TRAPPIST-1, has so far been found to host a transiting planetary system. In this context, we present the SPECULOOS project's detection of an Earth-sized planet in a 17… ▽ More Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely unexplored, and only one of them, TRAPPIST-1, has so far been found to host a transiting planetary system. In this context, we present the SPECULOOS project's detection of an Earth-sized planet in a 17 h orbit around an ultracool dwarf of M6.5 spectral type located 16.8 pc away. The planet's high irradiation (16 times that of Earth) combined with the infrared luminosity and Jupiter-like size of its host star make it one of the most promising rocky exoplanet targets for detailed emission spectroscopy characterization with JWST. Indeed, our sensitivity study shows that just ten secondary eclipse observations with the Mid-InfraRed Instrument/Low-Resolution Spectrometer on board JWST should provide strong constraints on its atmospheric composition and/or surface mineralogy. △ Less

Submitted 2 June, 2024; originally announced June 2024.

Detection of Fe and Ti on the dayside of the ultrahot Jupiter MASCARA-1b with CARMENES

Authors: B. Guo, F. Yan, L. Nortmann, D. Cont, A. Reiners, E. Pallé, D. Shulyak, K. Molaverdikhani, Th. Henning, G. Chen, M. Stangret, S. Czesla, F. Lesjak, M. López-Puertas, I. Ribas, A. Quirrenbach, J. A. Caballero, P. J. Amado, M. Blazek, D. Montes, J. C. Morales, E. Nagel, M. R. Zapatero Osorio

Abstract: Ultrahot Jupiters are a type of gaseous exoplanet that orbit extremely close to their host star, resulting in significantly high equilibrium temperatures. In recent years, high-resolution emission spectroscopy has been broadly employed in observing the atmospheres of ultrahot Jupiters. We used the CARMENES spectrograph to observe the high-resolution spectra of the dayside hemisphere of MASCARA-1b… ▽ More Ultrahot Jupiters are a type of gaseous exoplanet that orbit extremely close to their host star, resulting in significantly high equilibrium temperatures. In recent years, high-resolution emission spectroscopy has been broadly employed in observing the atmospheres of ultrahot Jupiters. We used the CARMENES spectrograph to observe the high-resolution spectra of the dayside hemisphere of MASCARA-1b in both visible and near-infrared. Through cross-correlation analysis, we detected signals of \ion{Fe}{i} and \ion{Ti}{i}. Based on these detections, we conducted an atmospheric retrieval and discovered the presence of a strong inversion layer in the planet's atmosphere. The retrieved Ti and Fe abundances are broadly consistent with solar abundances. In particular, we obtained a relative abundance of [Ti/Fe] as $-1.0 \pm 0.8$ under the free retrieval and $-0.4^{+0.5}_{-0.8}$ under the chemical equilibrium retrieval, suggesting the absence of significant titanium depletion on this planet. Furthermore, we considered the influence of planetary rotation on spectral line profiles. The resulting equatorial rotation speed was determined to be $4.4^{+1.6}_{-2.0}\,\mathrm{km\,s^{-1}}$, which agrees with the rotation speed induced by tidal locking. △ Less

Submitted 29 April, 2024; originally announced April 2024.

Comments: 18 pages, 11 figures; accepted for publication in A&A

The MOPYS project: A survey of 70 planets in search of extended He I and H atmospheres. No evidence of enhanced evaporation in young planets

Authors: J. Orell-Miquel, F. Murgas, E. Pallé, M. Mallorquín, M. López-Puertas, M. Lampón, J. Sanz-Forcada, L. Nortmann, S. Czesla, E. Nagel, I. Ribas, M. Stangret, J. Livingston, E. Knudstrup, S. H. Albrecht, I. Carleo, J. Caballero, F. Dai, E. Esparza-Borges, A. Fukui, K. Heng, Th. Henning, T. Kagetani, F. Lesjak, J. P. de Leon , et al. (8 additional authors not shown)

Abstract: During the first Gyr of their life, exoplanet atmospheres suffer from different atmospheric escape phenomena that can strongly affect the shape and morphology of the exoplanet itself. These processes can be studied with Ly$α$, H$α$ and/or He I triplet observations. We present high-resolution spectroscopy observations from CARMENES and GIARPS checking for He I and H$α$ signals in 20 exoplanetary at… ▽ More During the first Gyr of their life, exoplanet atmospheres suffer from different atmospheric escape phenomena that can strongly affect the shape and morphology of the exoplanet itself. These processes can be studied with Ly$α$, H$α$ and/or He I triplet observations. We present high-resolution spectroscopy observations from CARMENES and GIARPS checking for He I and H$α$ signals in 20 exoplanetary atmospheres: V1298Tau c, K2-100b, HD63433b, HD63433c, HD73583b, HD73583c, K2-77b, TOI-2076b, TOI-2048b, HD235088b, TOI-1807b, TOI-1136d, TOI-1268b, TOI-1683b, TOI-2018b, MASCARA-2b, WASP-189b, TOI-2046b, TOI-1431b, and HAT-P-57b. We report two new high-resolution spectroscopy He I detections for TOI-1268b and TOI-2018b, and an H$α$ detection for TOI-1136d. The MOPYS (Measuring Out-flows in Planets orbiting Young Stars) project aims to understand the evaporating phenomena and test their predictions from the current observations. We compiled a list of 70 exoplanets with He I and/or H$α$ observations, from this work and the literature, and we considered the He I and H$α$ results as proxy for atmospheric escape. Our principal results are that 0.1-1Gyr-old planets do not exhibit more He I or H$α$ detections than older planets, and evaporation signals are more frequent for planets orbiting $\sim$1-3Gyr-old stars. We provide new constrains to the cosmic shoreline, the empirical division between rocky planets and planets with atmosphere, by using the evaporation detections and explore the capabilities of a new dimensionless parameter, $R_{\rm He}/R_{\rm Hill}$, to explain the He I triplet detections. Furthermore, we present a statistically significant upper boundary for the He I triplet detections in the $T_{\rm eq}$ vs $ρ_{\rm p}$ parameter space. Planets located above that boundary are unlikely to show He I absorption signals. △ Less

Submitted 22 July, 2024; v1 submitted 25 April, 2024; originally announced April 2024.

Comments: Accepted in A&A. 64 pages, many figures. Supplementary material in Zenodo

Journal ref: A&A 689, A179 (2024)

Peregrine: ML-based Malicious Traffic Detection for Terabit Networks

Authors: João Romeiras Amado, Francisco Pereira, David Pissarra, Salvatore Signorello, Miguel Correia, Fernando M. V. Ramos

Abstract: Malicious traffic detectors leveraging machine learning (ML), namely those incorporating deep learning techniques, exhibit impressive detection capabilities across multiple attacks. However, their effectiveness becomes compromised when deployed in networks handling Terabit-speed traffic. In practice, these systems require substantial traffic sampling to reconcile the high data plane packet rates w… ▽ More Malicious traffic detectors leveraging machine learning (ML), namely those incorporating deep learning techniques, exhibit impressive detection capabilities across multiple attacks. However, their effectiveness becomes compromised when deployed in networks handling Terabit-speed traffic. In practice, these systems require substantial traffic sampling to reconcile the high data plane packet rates with the comparatively slower processing speeds of ML detection. As sampling significantly reduces traffic observability, it fundamentally undermines their detection capability. We present Peregrine, an ML-based malicious traffic detector for Terabit networks. The key idea is to run the detection process partially in the network data plane. Specifically, we offload the detector's ML feature computation to a commodity switch. The Peregrine switch processes a diversity of features per-packet, at Tbps line rates - three orders of magnitude higher than the fastest detector - to feed the ML-based component in the control plane. Our offloading approach presents a distinct advantage. While, in practice, current systems sample raw traffic, in Peregrine sampling occurs after feature computation. This essential trait enables computing features over all traffic, significantly enhancing detection performance. The Peregrine detector is not only effective for Terabit networks, but it is also energy- and cost-efficient. Further, by shifting a compute-heavy component to the switch, it saves precious CPU cycles and improves detection throughput. △ Less

Submitted 27 March, 2024; originally announced March 2024.

TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization

Authors: E. Goffo, P. Chaturvedi, F. Murgas, G. Morello, J. Orell-Miquel, L. Acuña, L. Peña-Moñino, E. Pallé, A. P. Hatzes, S. Geraldía-González, F. J. Pozuelos, A. F. Lanza, D. Gandolfi, J. A. Caballero, M. Schlecker, M. Pérez-Torres, N. Lodieu, A. Schweitzer, C. Hellier, S. V. Jeffers, C. Duque-Arribas, C. Cifuentes, V. J. S. Béjar, M. Daspute, F. Dubois , et al. (25 additional authors not shown)

Abstract: We report the confirmation and mass determination of a mini-Neptune transiting the M3.5 V star TOI-4438 (G 182-34) every 7.44 days. A transit signal was detected with NASA's TESS space mission in the sectors 40, 52, and 53. In order to validate the planet TOI-4438 b and to determine the system properties, we combined TESS data with high-precision radial velocity measurements from the CARMENES spec… ▽ More We report the confirmation and mass determination of a mini-Neptune transiting the M3.5 V star TOI-4438 (G 182-34) every 7.44 days. A transit signal was detected with NASA's TESS space mission in the sectors 40, 52, and 53. In order to validate the planet TOI-4438 b and to determine the system properties, we combined TESS data with high-precision radial velocity measurements from the CARMENES spectrograph, spanning almost one year, and ground-based transit photometry. We found that TOI-4438 b has a radius of Rb = 2.52 +/- 0.13 R_Earth (5% precision), which together with a mass of Mb=5.4 +/- 1.1 M_Earth (20% precision), results in a bulk density of rho = 1.85+0.51-0.44 g cm-3 (28% precision), aligning the discovery with a volatile-rich planet. Our interior structure retrieval with a pure water envelope yields a minimum water mass fraction of 46% (1-sigma). TOI-4438 b is a volatile-rich mini-Neptune with likely H/He mixed with molecules, such as water, CO_2, and CH_4. The primary star has a J-band magnitude of 9.7, and the planet has a high transmission spectroscopy metric (TSM) of 136 +/- 13. Taking into account the relatively warm equilibrium temperature of T_eq = 435 +/- 15 K, and the low activity level of its host star, TOI-4438 b is one of the most promising mini-Neptunes around an M dwarf for transmission spectroscopy studies. △ Less

Submitted 14 March, 2024; originally announced March 2024.

Comments: Accepted for publication on Astronomy & Astrophysics

Teegarden's Star revisited: A nearby planetary system with at least three planets

Authors: S. Dreizler, R. Luque, I. Ribas, V. Koseleva, H. L. Ruh, E. Nagel, F. J. Pozuelos, M. Zechmeister, A. Reiners, J. A. Caballero, P. J. Amado, V. J. S. Béjar, J. L. Bean, M. Brady, C. Cifuentes, M. Gillon, A. P. Hatzes, Th. Henning, D. Kasper, D. Montes, J. C. Morales, C. A. Murray, E. Pallé, A. Quirrenbach, A. Seifahrt , et al. (4 additional authors not shown)

Abstract: The two known planets in the planetary system of Teegarden's Star are among the most Earth-like exoplanets currently known. Revisiting this nearby planetary system with two planets in the habitable zone aims at a more complete census of planets around very low-mass stars. A significant number of new radial velocity measurements from CARMENES, ESPRESSO, MAROON-X, and HPF, as well as photometry from… ▽ More The two known planets in the planetary system of Teegarden's Star are among the most Earth-like exoplanets currently known. Revisiting this nearby planetary system with two planets in the habitable zone aims at a more complete census of planets around very low-mass stars. A significant number of new radial velocity measurements from CARMENES, ESPRESSO, MAROON-X, and HPF, as well as photometry from TESS motivated a deeper search for additional planets. We confirm and refine the orbital parameters of the two know planets Teegarden's Star b and c. We also report the detection of a third planet d with an orbital period of 26.13+-0.04 d and a minimum mass of 0.82+-0.17 M_Earth. A signal at 96 d is attributed to the stellar rotation period. The interpretation of a signal at 172 d remains open. The TESS data exclude transiting short-period planets down to about half an Earth radius. We compare the planetary system architecture of very low-mass stars. In the currently known configuration, the planetary system of Teegarden's star is dynamically quite different from that of TRAPPIST-1, which is more compact, but dynamically similar to others such as GJ 1002. △ Less

Submitted 1 February, 2024; originally announced February 2024.

Comments: Astronomy & Astrophysics, accepted; 21 pages, 18 figures

Wolf 327b: A new member of the pack of ultra-short-period super-Earths around M dwarfs

Authors: F. Murgas, E. Pallé, J. Orell-Miquel, I. Carleo, L. Peña-Moñino, M. Pérez-Torres, C. N. Watkins, S. V. Jeffers, M. Azzaro, K. Barkaoui, A. A. Belinski, J. A. Caballero, D. Charbonneau, D. V. Cheryasov, D. R. Ciardi, K. A. Collins, M. Cortés-Contreras, J. de Leon, C. Duque-Arribas, G. Enoc, E. Esparza-Borges, A. Fukui, S. Geraldía-González, E. A. Gilbert, A. P. Hatzes , et al. (30 additional authors not shown)

Abstract: Planets with orbital periods shorter than 1 day are rare and have formation histories that are not completely understood. Small ($R_\mathrm{p} < 2\; R_\oplus$) ultra-short-period (USP) planets are highly irradiated, probably have rocky compositions with high bulk densities, and are often found in multi-planet systems. Additionally, USP planets found around small stars are excellent candidates for… ▽ More Planets with orbital periods shorter than 1 day are rare and have formation histories that are not completely understood. Small ($R_\mathrm{p} < 2\; R_\oplus$) ultra-short-period (USP) planets are highly irradiated, probably have rocky compositions with high bulk densities, and are often found in multi-planet systems. Additionally, USP planets found around small stars are excellent candidates for characterization using present-day instrumentation. Of the current full sample of approximately 5500 confirmed exoplanets, only 130 are USP planets and around 40 have mass and radius measurements. Wolf 327 (TOI-5747) is an M dwarf ($R_\star = 0.406 \pm 0.015 \; R_\odot$, $M_\star = 0.405 \pm 0.019 \; M_\odot$, $T_{\mathrm{eff}}=3542 \pm 70$ K, and $V = 13$ mag) located at a distance $d = 28.5$ pc. NASA's planet hunter satellite, TESS, detected transits in this star with a period of 0.573 d (13.7 h) and with a transit depth of 818 ppm. Ground-based follow-up photometry, high resolution imaging, and radial velocity (RV) measurements taken with the CARMENES spectrograph confirm the presence of this new USP planet. Wolf 327b is a super-Earth with a radius of $R_\mathrm{p} = 1.24 \pm 0.06 \; R_\oplus$ and a mass of $M_\mathrm{p} = 2.53 \pm 0.46 \; M_\oplus$, yielding a bulk density of $7.24 \pm 1.66 $\,g cm$^{-3}$ and thus suggesting a rocky composition. Owing to its close proximity to its host star ($a = 0.01$ au), Wolf 327b has an equilibrium temperature of $996 \pm 22$ K. This planet has a mass and radius similar to K2-229b, a planet with an inferred Mercury-like internal composition. Planet interior models suggest that Wolf 327b has a large iron core, a small rocky mantle, and a negligible (if any) H/He atmosphere. △ Less

Submitted 22 January, 2024; originally announced January 2024.

Comments: 26 pages, 19 figures. Accepted for publication in A&A

CARMENES input catalog of M dwarfs: VII. New rotation periods for the survey stars and their correlations with stellar activity

Authors: Yutong Shan, Daniel Revilla, Sebastian L. Skrzypinski, Stefan Dreizler, Victor J. S. Bejar, Jose A. Caballero, Carlos Cardona Guillen, Carlos Cifuentes, Birgit Fuhrmeister, Ansgar Reiners, Siegfried Vanaverbeke, Ignasi Ribas, Andreas Quirrenbach, Pedro J. Amado, Francisco J. Aceituno, Victor Casanova, Miriam Cortes-Contreras, Franky Dubois, Paula Gorrini, Thomas Henning, Enrique Herrero, Sandra V. Jeffers, Jonas Kemmer, Sairam Lalitha, Nicolas Lodieu , et al. (18 additional authors not shown)

Abstract: Abridged: We measured photometric and spectroscopic $P_{\rm rot}$ for a large sample of nearby bright M dwarfs with spectral types from M0 to M9, as part of our continual effort to fully characterize the Guaranteed Time Observation programme stars of the CARMENES survey. We determine $P_{\rm rot}$ for 129 stars. Combined with the literature, we tabulate $P_{\rm rot}$ for 261 stars, or 75% of our s… ▽ More Abridged: We measured photometric and spectroscopic $P_{\rm rot}$ for a large sample of nearby bright M dwarfs with spectral types from M0 to M9, as part of our continual effort to fully characterize the Guaranteed Time Observation programme stars of the CARMENES survey. We determine $P_{\rm rot}$ for 129 stars. Combined with the literature, we tabulate $P_{\rm rot}$ for 261 stars, or 75% of our sample. We evaluate the plausibility of all periods available for this sample by comparing them with activity signatures and checking for consistency between multiple measurements. We find that 166 of these stars have independent evidence that confirmed their $P_{\rm rot}$. There are inconsistencies in 27 periods, which we classify as debated. A further 68 periods are identified as provisional detections that could benefit from independent verification. We provide an empirical relation for the $P_{\rm rot}$ uncertainty as a function of the $P_{\rm rot}$ value, based on the dispersion of the measurements. We show that published formal errors seem to be often underestimated for periods $\gtrsim 10$ d. We highlight the importance of independent verification on $P_{\rm rot}$ measurements, especially for inactive M dwarfs. We examine rotation-activity relations with emission in X-rays, H$α$, Ca II H & K, and surface magnetic field strengths. We find overall agreement with previous works, as well as tentative differences in the partially versus fully convective subsamples. We show $P_{\rm rot}$ as a function of stellar mass, age, and galactic kinematics. With the notable exception of three transiting planet systems and TZ Ari, all known planet hosts in this sample have $P_{\rm rot} \gtrsim 15$ d. This indicates that important limitations need to be overcome before the radial velocity technique can be routinely used to detect and study planets around young and active stars. △ Less

Submitted 17 January, 2024; originally announced January 2024.

Comments: Accepted for publication in A&A

The elusive atmosphere of WASP-12 b / High-resolution transmission spectroscopy with CARMENES

Authors: S. Czesla, M. Lampón, D. Cont, F. Lesjak, J. Orell-Miquel, J. Sanz-Forcada, E. Nagel, L. Nortmann, K. Molaverdikhani, M. López-Puertas, F. Yan, A. Quirrenbach, J. A. Caballero, E. Pallé, J. Aceituno, P. J. Amado, Th. Henning, S. Khalafinejad, D. Montes, A. Reiners, I. Ribas, A. Schweitzer

Abstract: To date, the hot Jupiter WASP-12 b has been the only planet with confirmed orbital decay. The late F-type host star has been hypothesized to be surrounded by a large structure of circumstellar material evaporated from the planet. We obtained two high-resolution spectral transit time series with CARMENES and extensively searched for absorption signals by the atomic species Na, H, Ca, and He using t… ▽ More To date, the hot Jupiter WASP-12 b has been the only planet with confirmed orbital decay. The late F-type host star has been hypothesized to be surrounded by a large structure of circumstellar material evaporated from the planet. We obtained two high-resolution spectral transit time series with CARMENES and extensively searched for absorption signals by the atomic species Na, H, Ca, and He using transmission spectroscopy, thereby covering the He I triplet with high resolution for the first time. We apply SYSREM for atomic line transmission spectroscopy, introduce the technique of signal protection to improve the results for individual absorption lines, and compare the outcomes to those of established methods. No transmission signals were detected and the most stringent upper limits as of yet were derived for the individual indicators. Nonetheless, we found variation in the stellar Halpha and He I lines, the origin of which remains uncertain but is unlikely to be activity. To constrain the enigmatic activity state of WASP-12, we analyzed XMM-Newton X-ray data and found the star to be moderately active at most. We deduced an upper limit for the X-ray luminosity and the irradiating X-ray and extreme ultraviolet (XUV) flux of WASP-12 b. Based on the XUV flux upper limit and the lack of the He I signal, our hydrodynamic models slightly favor a moderately irradiated planet with a thermospheric temperature of <= 12,000 K, and a conservative upper limit of <= 4e12 g/s on the mass-loss rate. Our study does not provide evidence for an extended planetary atmosphere or absorption by circumstellar material close to the planetary orbit. △ Less

Submitted 4 January, 2024; originally announced January 2024.

Comments: Accepted for publication in A&A

A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067

Authors: R. Luque, H. P. Osborn, A. Leleu, E. Pallé, A. Bonfanti, O. Barragán, T. G. Wilson, C. Broeg, A. Collier Cameron, M. Lendl, P. F. L. Maxted, Y. Alibert, D. Gandolfi, J. -B. Delisle, M. J. Hooton, J. A. Egger, G. Nowak, M. Lafarga, D. Rapetti, J. D. Twicken, J. C. Morales, I. Carleo, J. Orell-Miquel, V. Adibekyan, R. Alonso , et al. (127 additional authors not shown)

Abstract: Planets with radii between that of the Earth and Neptune (hereafter referred to as sub-Neptunes) are found in close-in orbits around more than half of all Sun-like stars. Yet, their composition, formation, and evolution remain poorly understood. The study of multi-planetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial con… ▽ More Planets with radii between that of the Earth and Neptune (hereafter referred to as sub-Neptunes) are found in close-in orbits around more than half of all Sun-like stars. Yet, their composition, formation, and evolution remain poorly understood. The study of multi-planetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here, we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94 to 2.85 Re. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres. △ Less

Submitted 29 November, 2023; originally announced November 2023.

Comments: Published in Nature on November 30, 2023. Supplementary Information can be found in the online version of the paper in the journal

Journal ref: Nature 623, 932-937 (2023)

The discovery space of ELT-ANDES. Stars and stellar populations

Authors: Ian U. Roederer, Julián D. Alvarado-Gómez, Carlos Allende Prieto, Vardan Adibekyan, David Aguado, Pedro J. Amado, Eliana M. Amazo-Gómez, Martina Baratella, Sydney A. Barnes, Thomas Bensby, Lionel Bigot, Andrea Chiavassa, Armando Domiciano de Souza, Camilla Juul Hansen, Silva P. Järvinen, Andreas J. Korn, Sara Lucatello, Laura Magrini, Roberto Maiolino, Paolo Di Marcantonio, Alessandro Marconi, José R. De Medeiros, Alessio Mucciarelli, Nicolas Nardetto, Livia Origlia , et al. (9 additional authors not shown)

Abstract: The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is the optical and near-infrared high-resolution echelle spectrograph envisioned for the European Extremely Large Telescope (ELT). We present a selection of science cases, supported by new calculations and simulations, where ANDES could enable major advances in the fields of stars and stellar populations. We focus on three key areas, inclu… ▽ More The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is the optical and near-infrared high-resolution echelle spectrograph envisioned for the European Extremely Large Telescope (ELT). We present a selection of science cases, supported by new calculations and simulations, where ANDES could enable major advances in the fields of stars and stellar populations. We focus on three key areas, including the physics of stellar atmospheres, structure, and evolution; stars of the Milky Way, Local Group, and beyond; and the star-planet connection. The key features of ANDES are its wide wavelength coverage at high spectral resolution and its access to the large collecting area of the ELT. These features position ANDES to address the most compelling and potentially transformative science questions in stellar astrophysics of the decades ahead, including questions which cannot be anticipated today. △ Less

Submitted 27 November, 2023; originally announced November 2023.

Comments: 46 pages, 8 figures; submitted to Experimental Astronomy on behalf of the ANDES Science Team

The CARMENES search for exoplanets around M dwarfs. Telluric absorption corrected high S/N optical and near-infrared template spectra of 382 M dwarf stars

Authors: E. Nagel, S. Czesla, A. Kaminski, M. Zechmeister, L. Tal-Or, J. H. M. M. Schmitt, A. Reiners, A. Quirrenbach, A. García López, J. A. Caballero, I. Ribas, P. J. Amado, V. J. S. Béjar, M. Cortés-Contreras, S. Dreizler, A. P. Hatzes, Th. Henning, S. V. Jeffers, M. Kürster, M. Lafarga, M. López-Puertas, D. Montes, J. C. Morales, S. Pedraz, A. Schweitzer

Abstract: Light from celestial objects interacts with the molecules of the Earth's atmosphere, resulting in the production of telluric absorption lines in ground-based spectral data. Correcting for these lines, which strongly affect red and infrared wavelengths, is often needed in a wide variety of scientific applications. Here, we present the template division telluric modeling (TDTM) technique, a method f… ▽ More Light from celestial objects interacts with the molecules of the Earth's atmosphere, resulting in the production of telluric absorption lines in ground-based spectral data. Correcting for these lines, which strongly affect red and infrared wavelengths, is often needed in a wide variety of scientific applications. Here, we present the template division telluric modeling (TDTM) technique, a method for accurately removing telluric absorption lines in stars that exhibit numerous intrinsic features. Based on the Earth's barycentric motion throughout the year, our approach is suited for disentangling telluric and stellar spectral components. By fitting a synthetic transmission model, telluric-free spectra are derived. We demonstrate the performance of the TDTM technique in correcting telluric contamination using a high-resolution optical spectral time series of the feature-rich M3.0 dwarf star Wolf 294 that was obtained with the CARMENES spectrograph. We apply the TDTM approach to the CARMENES survey sample, which consists of 382 targets encompassing 22357 optical and 20314 near-infrared spectra, to correct for telluric absorption. The corrected spectra are coadded to construct template spectra for each of our targets. This library of telluric-free, high signal-to-noise ratio, high-resolution (R>80000) templates comprises the most comprehensive collection of spectral M-dwarf data available to date, both in terms of quantity and quality, and is available at the project website (http://carmenes.cab.inta-csic.es). △ Less

Submitted 23 October, 2023; originally announced October 2023.

Comments: 31 pages, 24 figures, 3 tables, accepted for publication by A&A

Journal ref: A&A 680, A73 (2023)

TOI-1801 b: A temperate mini-Neptune around a young M0.5 dwarf

Authors: M. Mallorquín, E. Goffo, E. Pallé, N. Lodieu, V. J. S. Béjar, H. Isaacson, M. R. Zapatero Osorio, S. Dreizler, S. Stock, R. Luque, F. Murgas, L. Peña, J. Sanz-Forcada, G. Morello, D. R. Ciardi, E. Furlan, K. A. Collins, E. Herrero, S. Vanaverbeke, P. Plavchan, N. Narita, A. Schweitzer, M. Pérez-Torres, A. Quirrenbach, J. Kemmer , et al. (57 additional authors not shown)

Abstract: We report the discovery, mass, and radius determination of TOI-1801 b, a temperate mini-Neptune around a young M dwarf. TOI-1801 b was observed in TESS sectors 22 and 49, and the alert that this was a TESS planet candidate with a period of 21.3 days went out in April 2020. However, ground-based follow-up observations, including seeing-limited photometry in and outside transit together with precise… ▽ More We report the discovery, mass, and radius determination of TOI-1801 b, a temperate mini-Neptune around a young M dwarf. TOI-1801 b was observed in TESS sectors 22 and 49, and the alert that this was a TESS planet candidate with a period of 21.3 days went out in April 2020. However, ground-based follow-up observations, including seeing-limited photometry in and outside transit together with precise radial velocity (RV) measurements with CARMENES and HIRES revealed that the true period of the planet is 10.6 days. These observations also allowed us to retrieve a mass of 5.74 $\pm$ 1.46 $M_\oplus$, which together with a radius of 2.08 $\pm$ 0.12 $R_\oplus$, means that TOI-1801 b is most probably composed of water and rock, with an upper limit of 2\% by mass of H$_{2}$ in its atmosphere. The stellar rotation period of 16 days is readily detectable in our RV time series and in the ground-based photometry. We derived a likely age of 600--800 Myr for the parent star TOI-1801, which means that TOI-1801 b is the least massive young mini-Neptune with precise mass and radius determinations. Our results suggest that if TOI-1801 b had a larger atmosphere in the past, it must have been removed by some evolutionary mechanism on timescales shorter than 1 Gyr. △ Less

Submitted 24 October, 2023; v1 submitted 16 October, 2023; originally announced October 2023.

Comments: Accepted in A&A. 29 pages, 21 figures

Journal ref: A&A 680, A76 (2023)

Planetary companions orbiting the M dwarfs GJ 724 and GJ 3988. A CARMENES and IRD collaboration

Authors: P. Gorrini, J. Kemmer, S. Dreizler, R. Burn, T. Hirano, F. J. Pozuelos, M. Kuzuhara, J. A. Caballero, P. J. Amado, H. Harakawa, T. Kudo, A. Quirrenbach, A. Reiners, I. Ribas, V. J. S. Béjar, P. Chaturvedi, C. Cifuentes, D. Galadí-Enríquez, A. P. Hatzes, A. Kaminski, T. Kotani, M. Kürster, J. H. Livingston, M. J. López González, D. Montes , et al. (14 additional authors not shown)

Abstract: We report the discovery of two exoplanets around the M dwarfs GJ 724 and GJ 3988 using the radial velocity (RV) method. We obtained a total of 153 3.5 m Calar Alto/CARMENES spectra for both targets and measured their RVs and activity indicators. We also added archival ESO/HARPS data for GJ 724 and infrared RV measurements from Subaru/IRD for GJ 3988. We searched for periodic and stable signals to… ▽ More We report the discovery of two exoplanets around the M dwarfs GJ 724 and GJ 3988 using the radial velocity (RV) method. We obtained a total of 153 3.5 m Calar Alto/CARMENES spectra for both targets and measured their RVs and activity indicators. We also added archival ESO/HARPS data for GJ 724 and infrared RV measurements from Subaru/IRD for GJ 3988. We searched for periodic and stable signals to subsequently construct Keplerian models, considering different numbers of planets, and we selected the best models based on their Bayesian evidence. Gaussian process (GP) regression was included in some models to account for activity signals. For both systems, the best model corresponds to one single planet. The minimum masses are $10.75^{+0.96}_{-0.87}$ and $3.69^{+0.42}_{-0.41}$ Earth-masses for GJ 724 b and GJ 3988 b, respectively. Both planets have short periods (P < 10 d) and, therefore, they orbit their star closely (a < 0.05 au). GJ 724 b has an eccentric orbit (e = $0.577^{+0.055}_{-0.052}$), whereas the orbit of GJ 3988 b is circular. The high eccentricity of GJ 724 b makes it the most eccentric single exoplanet (to this date) around an M dwarf. Thus, we suggest a further analysis to understand its configuration in the context of planetary formation and architecture. In contrast, GJ 3988 b is an example of a common type of planet around mid-M dwarfs. △ Less

Submitted 9 October, 2023; originally announced October 2023.

Comments: A&A in press

Journal ref: A&A 680, A28 (2023)