Showing 1–50 of 212 results for author: Desert, J

Phase-dependent chemistry of WASP-43 b revealed with a suite of one-, two-, and three-dimensional models

Authors: Robin Baeyens, Julianne I. Moses, Jasmina Blecic, Elspeth K. H. Lee, Lucas Teinturier, Shang-Min Tsai, Jeehyun Yang, Jingxuan Yang, Ludmila Carone, Renyu Hu, Sven Kiefer, Anjali A. A. Piette, Taylor J. Bell, Nicolas Crouzet, Ian Dobbs-Dixon, Christiane Helling, Nicolas Iro, Dominic Samra, Olivia Venot, Jean-Michel Désert

Abstract: Our goal is to investigate the chemistry of the hot Jupiter WASP-43 b in detail using theoretical models, considering the constraints of the James Webb Space Telescope MIRI phase curve. With a suite of pseudo-two-dimensional and three-dimensional photochemical models, we simulate the composition of WASP-43 b in various configurations, and compare them with atmospheric retrieval models. We confirm… ▽ More Our goal is to investigate the chemistry of the hot Jupiter WASP-43 b in detail using theoretical models, considering the constraints of the James Webb Space Telescope MIRI phase curve. With a suite of pseudo-two-dimensional and three-dimensional photochemical models, we simulate the composition of WASP-43 b in various configurations, and compare them with atmospheric retrieval models. We confirm that disequilibrium chemistry in our theoretical models reduces the methane concentration on the planet night side for wind jet speeds > 500 m/s. Varying the metallicity in the models induces large changes in the CO$_2$ and SO$_2$ concentrations, with SO$_2$ producing mid-infrared absorption features in synthetic emission spectra of the night side at atmospheric metallicities > 10x solar. Our models provide evidence for pole-to-equator circulation enhancing the CH$_4$, NH$_3$, and HCN abundances, which is nonetheless insufficient for detectable spectral features. Finally, we show that H$_2$O, CO, and CO$_2$ are robustly modeled, but species affected by photochemistry are more sensitive to model-specific assumptions and pathways. We conclude that horizontal quenching is the prime mechanism that explains the non-detection of methane in the MIRI phase-curve of WASP-43 b. This mechanism requires only moderate wind speeds and is operative at various thermal structures and atmospheric metallicities. Furthermore, coupled carbon-sulfur chemistry leads to an additional decrease in methane compared to previous models in the literature that did not contain sulfur chemistry. We do not favor a high metallicity as it would have led to observable SO$_2$ features in the MIRI spectra. Our study shows that phase-dependent photochemistry models are essential tools in the interpretation of hot-Jupiter phase curves, but benchmarking is needed to improve the accuracy of photochemical models in the future. △ Less

Submitted 9 July, 2026; originally announced July 2026.

Comments: 25 pages, 18 figures, accepted for publication in A&A

CHEOPS observations of V1298 Tau: updated planetary densities and implications on the early evolution of the young system

Authors: Hinna Shivkumar, Sérgio Gomes, Jean-Michel Désert, John Livingston, John Lopez, Vatsal Panwar, James Sikora, Saugata Barat, Pierre F. L. Maxted, Thomas G. Wilson, Antonija Oklopčić, Silvia Toonen

Abstract: The young (10-30 Myr) multi-planet system V1298 Tau presents a unique opportunity to probe the early formation and evolution of young systems. We present new CHEOPS observations of the three innermost planets, yielding high-precision planetary radii ($\sim$5-11 $R_\oplus$ ) and improving the radius ratios (Rp/Rs) by 30-71% compared to previous multiple TESS observations. Combined with refined peri… ▽ More The young (10-30 Myr) multi-planet system V1298 Tau presents a unique opportunity to probe the early formation and evolution of young systems. We present new CHEOPS observations of the three innermost planets, yielding high-precision planetary radii ($\sim$5-11 $R_\oplus$ ) and improving the radius ratios (Rp/Rs) by 30-71% compared to previous multiple TESS observations. Combined with refined period and mass determinations from transit-timing variation (TTV) measurements, we derive revised bulk densities (0.06-0.23 g/cm$^3$) for these planets. We find that the innermost planet c is denser compared to the outermost planet at the 3.4-$σ$ level, while the bulk densities of the three outermost planets are consistent within the reported uncertainties. These bulk densities suggest differing envelope mass fraction across the system, indicating differential atmospheric evolution in the young system. We further assess the early dynamical state of the V1298 Tau system and find that within the range of simulations performed we find no evidence for present-day mean-motion resonance trapping. As an independent diagnostic, we compute the forced eccentricities and low Normalized Angular Momentum Deficit (NAMD) exhibited by the system. Our simulations suggest that no past dynamical excitation is required to explain the present orbital architecture. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Comments: 10 pages, 5 figures. Accepted for publication in MNRAS on 30 June 2026

Photochemical Production of CS2 in Temperate-to-Warm Gas Giant Exoplanet Atmospheres

Authors: Jeehyun Yang, Vighnesh Nagpal, Michael Zhang, Qiao Xue, Eliza M. -R. Kempton, Jacob L. Bean, Michael R. Line, Jonathan J. Fortney, Peter Gao, Matthew C. Nixon, Caroline Piaulet-Ghorayeb, Kevin B. Stevenson, Madison Brady, Joost P. Wardenier, Luis Welbanks, Jean-Michel Désert, Guangwei Fu, Vivien Parmentier

Abstract: Sulfur chemistry has emerged as an important probe of exoplanet atmospheres in the JWST era, although observational constraints have thus far been largely limited to SO2 and H2S in warm and hot exoplanets. Recent JWST observations have revealed CS2 in several cooler gas-giant exoplanets, yielding a new tracer of sulfur chemistry. However, the detailed chemical pathways responsible for the formatio… ▽ More Sulfur chemistry has emerged as an important probe of exoplanet atmospheres in the JWST era, although observational constraints have thus far been largely limited to SO2 and H2S in warm and hot exoplanets. Recent JWST observations have revealed CS2 in several cooler gas-giant exoplanets, yielding a new tracer of sulfur chemistry. However, the detailed chemical pathways responsible for the formation of CS2 remain poorly understood. Here, we use TOI-6894 b, a temperate gas giant with evidence for CS2, as a test case for one-dimensional photochemical kinetic-transport modeling and sensitivity analyses of CS2 chemistry. We show that CS2 is produced through coupled thermochemical and photochemical processes involving CH4 and H2S as the primary carbon and sulfur reservoirs, with S2 photolysis driving disequilibrium sulfur chemistry. Our models provide a self-consistent explanation for the observed CS2 feature in TOI-6894 b. Extending our analysis to gas giant exoplanets spanning a wide range of Teq, we find that CS2 abundance peaks in temperate to warm atmospheres (Teq ~ 500 - 700 K), and declines toward both lower and higher temperatures. This temperature dependence provides a unified framework for interpreting current CS2 observations, accounting for reported detections in temperate to warm planets and the lack of detections in colder and hotter giant exoplanets. Our results establish CS2 as a complementary probe of sulfur inventories and atmospheric metallicity in cool gas giant exoplanets △ Less

Submitted 22 June, 2026; originally announced June 2026.

Comments: 15 pages, 5 figures, Companion paper to Zhang et al. (2026), submitted concurrently to ApJL

C, N, O, S, and photochemistry in a temperate giant planet orbiting a late M dwarf

Authors: Michael Zhang, Qiao Xue, Jeehyun Yang, Vighnesh Nagpal, Michael R. Line, Guangwei Fu, Matthew C. Nixon, Jacob L. Bean, Peter Gao, Eliza M. -R. Kempton, Luis Welbanks, Edward M. Bryant, Daniel Bayliss, Madison Brady, Jean-Michel Désert, Vincent Van Eylen, Jonathan J. Fortney, Andrés Jordán, Vivien Parmentier, Caroline Piaulet-Ghorayeb, Elyar Sedaghati, Kevin B. Stevenson, Amaury H. M. J. Triaud

Abstract: We report the JWST NIRSpec/PRISM transit spectrum of TOI-6894b, an exceptional 420 K sub-Saturn that is the only known giant planet transiting a late M dwarf. Remarkably, both the light curve and the transit spectrum exhibit almost no stellar contamination. The spectrum is dominated by prominent absorption features from CH$_4$ and the photochemical product CS$_2$. For the first time in a transit s… ▽ More We report the JWST NIRSpec/PRISM transit spectrum of TOI-6894b, an exceptional 420 K sub-Saturn that is the only known giant planet transiting a late M dwarf. Remarkably, both the light curve and the transit spectrum exhibit almost no stellar contamination. The spectrum is dominated by prominent absorption features from CH$_4$ and the photochemical product CS$_2$. For the first time in a transit spectrum, NH$_3$ is visually evident, while subtler features from H$_2$O, and CO$_2$ can also be seen. We significantly improve upon state-of-the-art photochemical reaction networks, and use our new network to run radiative-convective photochemical models at different metallicities. These models show that the spectrum--in particular the size of the NH$_3$ and CO$_2$ features relative to the CH$_4$ and H$_2$O features--is most consistent with a metallicity of 3--10$\times$ solar. Using a semi-free retrieval framework that perturbs the self-consistent model's abundance and temperature profiles to fit the data, we find that the planet's C/O, N/O, and S/O ratios are broadly consistent with solar values. A grid retrieval on 1D radiative-convective photochemical equilibrium (RCPE) models reveals a similar result: $[M/H]=0.46 \pm 0.08$ and C/O=$0.69 \pm 0.06$. The planet's atmospheric metallicity, abundance ratios, and bulk metal fraction are all strikingly similar to that of Jupiter, Saturn, and other gas giant exoplanets, despite orbiting a very low-mass star. △ Less

Submitted 25 June, 2026; v1 submitted 22 June, 2026; originally announced June 2026.

Comments: Updating with far more realistic error inflation scheme in semi-free retrievals, which has the side benefit of greatly shrinking N/O, C/N, S/N, M/H posteriors

Magnetic field strengths of hot giant exoplanets consistent with Solar System values

Authors: Julia V. Seidel, Vivien Parmentier, Bibiana Prinoth, Thea Hood, Nishil Mehta, Valentin De Lia, Konstantin Batygin, Tristan Guillot, Ragnar Van den Broeck, Hayley Beltz, Brian Thorsbro, Florian Debras, Daniel D. B. Koll, Thaddeus D. Komacek, Emily Rauscher, Lorenzo Pino, Matteo Brogi, Joost P. Wardenier, Jacob L. Bean, Björn Benneke, Jean-Michel L. B. Désert, Pablo Drake, Siddharth Gandhi, Mark Hammond, David Kasper , et al. (7 additional authors not shown)

Abstract: Magnetic fields are ubiquitous in the universe. They play a key role in shaping the activity of stars, the habitability of rocky planets, and the long-term retention of planetary atmospheres. Theoretical scaling laws are largely constrained by the limited set of stars and Solar System planets, leading to a wide range of possible values for hot giant planets outside of the Solar System from fractio… ▽ More Magnetic fields are ubiquitous in the universe. They play a key role in shaping the activity of stars, the habitability of rocky planets, and the long-term retention of planetary atmospheres. Theoretical scaling laws are largely constrained by the limited set of stars and Solar System planets, leading to a wide range of possible values for hot giant planets outside of the Solar System from fractions of the Jovian field to orders of magnitude larger. Ultra-hot Jupiters, with their highly ionised atmospheres, provide a new avenue to probe magnetic effects, as their atmospheric circulation could be directly sensitive to atmospheric magnetic field strength. Using high-spectral resolution observations targeting the iron lines of ultra-hot Jupiters we measure the Doppler shift and thus the wind speed of seven transiting ultra-hot Jupiters. We find a clear decrease of wind speed with increasing planetary temperature, a trend inconsistent with purely hydrodynamic mechanisms but naturally reproduced by magnetic drag. From this relation we estimate the possible strength of magnetic fields of hot giant planets to at most a few gauss - comparable to the Jovian equatorial field. Our results support the idea that magnetic fields affect the atmospheric circulation of ultra-hot Jupiters and could provide a crucial benchmark for scaling laws used to predict magnetic fields in exoplanets, from hot Jupiters to rocky Earths with additional implications for future direct observations. △ Less

Submitted 21 June, 2026; originally announced June 2026.

Comments: Preprint version of the article accepted under the same title in Nature Astronomy. Please find the accepted manuscript at https://www.nature.com/articles/s41550-026-02870-1 , with the DOI 10.1038/s41550-026-02870-1. Submitted 30th Sept 2025, accepted 16th April, 2026. 17 pages, 9 figures

KRONOS II: Solar-like Umbra and Penumbra Properties on the Young Sun V1298~Tau

Authors: Matthew M. Murphy, Adina D. Feinstein, Meir E. Schochet, Benjamin V. Rackham, Luis Welbanks, Darryl Z. Seligman, Girish M. Duvvuri, Eva-Maria Ahrer, John H. Livingston, Saugata Barat, Jean-Michel Désert, Rafael Luque, Catriona Murray, Matthew C. Nixon, Sydney Petz, Michael Radica, Hinna Shivkumar

Abstract: Transiting exoplanets provide a unique laboratory for studying stellar surface heterogeneities via starspot or facular occultations. When observed at multiple wavelengths, this configuration enables spectroscopic characterization of spot thermal contrasts, distributions, and morphology. In this work, we leverage JWST NIRISS/SOSS transit observations of the 20--30 Myr planets V1298 Tau bcd to study… ▽ More Transiting exoplanets provide a unique laboratory for studying stellar surface heterogeneities via starspot or facular occultations. When observed at multiple wavelengths, this configuration enables spectroscopic characterization of spot thermal contrasts, distributions, and morphology. In this work, we leverage JWST NIRISS/SOSS transit observations of the 20--30 Myr planets V1298 Tau bcd to study the surface properties of their solar analog host star V1298~Tau. We identify 14 starspot crossing events across two visits. We derive $0.8-2.8μ$m starspot contrast spectra and demonstrate the contrasts can only be explained when accounting for the umbral and penumbral components of the starspots, robust to which stellar model grid is assumed. The spot temperatures are broadly consistent between visits, suggesting that V1298~Tau ($T_\mathrm{phot}=4880\pm20$ K) has starspots with $T_{\mathrm{umbra}}$ = 3265--3436 K umbrae and $T_{\mathrm{penumbra}}$ = 4388--4659 K penumbrae, and are $\sim$30% umbrae by area. The differences between these spot components and the stellar photosphere are consistent with sunspots. Additionally, the relation between the spot contrast and the ratio of umbral to penumbral area is similar to that of the Sun. Combining these JWST observations with long baseline multi-band photometry from the Las Cumbres Observatory, we also estimated the global unocculted spot distribution, revealing at least 5 additional large unocculted active regions. All together, these measurements suggest that while the total spot coverage evolves in time, the relative temperatures of surface heterogeneities on Sun-like stars may be consistent throughout their lifetimes. Furthermore, these results demonstrate that JWST exoplanet transit observations can be useful for starspot substructure characterization. △ Less

Submitted 15 June, 2026; originally announced June 2026.

Comments: Submitted to the Astrophysical Journal. Comments are welcome. 24 pages, 12 figures

Horizontal transport as a source of disequilibrium chemistry on the nightside of a hot exoplanet

Authors: Vivien Parmentier, Kevin B. Stevenson, Luis Welbanks, Jake Taylor, Everett Schlawin, Louis-Philippe Coulombe, Yao Tang, Mike Line, Hinna Shivkumar, Xianyu Tan, Jacob L. Bean, Jean-Michel Désert, Jonathan J. Fortney, Peter Gao, Mark Hammond, Eliza M. -R. Kempton, Thaddeus D. Komacek, Megan Weiner Mansfield

Abstract: Hot Jupiters have temperature gradients of several hundreds of degrees between their permanent day and nightsides. In equilibrium, the primary carbon reservoir is expected to transition from CO on the dayside to CH4 on the nightside. Theory predicts that the atmospheric circulation, characterised by km/s winds, can advect chemical species from the dayside to the nightside faster than the time need… ▽ More Hot Jupiters have temperature gradients of several hundreds of degrees between their permanent day and nightsides. In equilibrium, the primary carbon reservoir is expected to transition from CO on the dayside to CH4 on the nightside. Theory predicts that the atmospheric circulation, characterised by km/s winds, can advect chemical species from the dayside to the nightside faster than the time needed for the CO-to-CH4 chemical reaction to reach equilibrium. However direct evidence of this process has, so far, remained elusive, partly because it is often degenerate with other processes, such as vertical mixing or non-stellar elemental abundances. Here, we present observational evidence for such day-to-night transport of chemical species by observing both the dayside and the nightside of the hot Jupiter NGTS-10A b with the JWST/NIRSpec instrument. We constrain the presence of H2O and CO with similar abundances on both the dayside and nightside. Our observations are compatible with a solar-composition atmosphere at chemical equilibrium on the dayside, but indicative of disequilibrium chemistry for the nightside as it is significantly depleted in CH4 compared to equilibrium chemistry predictions. We further show that the lack of CH4 on the planet's nightside cannot be attributed to non-solar elemental abundances or to vertical mixing mechanisms and must therefore be due to horizontal chemical quenching. Our study shows the fundamental role atmospheric transport plays in shaping the distribution of chemical species on exoplanet atmospheres. △ Less

Submitted 6 May, 2026; originally announced May 2026.

Comments: Preprint version, accepted version in Nature Astronomy available here https://www.nature.com/articles/s41550-026-02845-2

Journal ref: Nat Astron (2026)

Confirmation of Fe I on MASCARA-5 b's Dayside Observed With EXPRES

Authors: James T. Sikora, Joe Llama, Rachael M. Roettenbacher, Elisabeth M. Brann, Jean-Michel Désert, Alex S. Polanski, Malena Rice, Lily Zhao

Abstract: MASCARA-5~b/TOI-1431~b is an ultra-hot Jupiter \citep[$P_{\rm orb}=2.650237\pm0.000003\,{\rm d}$, $T_{\rm eq}=2370\pm70\,{\rm K}$, $M_{\rm p}=3.12\pm0.18\,M_{\rm Jup}$, $R_{\rm p}=1.49\pm0.05\,R_{\rm Jup}$;][]{addison2021} orbiting a bright Am star ($V=8.0\,{\rm mag}$). Recent time-series observations obtained with PEPSI@LBT during the planet's post-eclipse phases have revealed Fe~{\sc i} emission… ▽ More MASCARA-5~b/TOI-1431~b is an ultra-hot Jupiter \citep[$P_{\rm orb}=2.650237\pm0.000003\,{\rm d}$, $T_{\rm eq}=2370\pm70\,{\rm K}$, $M_{\rm p}=3.12\pm0.18\,M_{\rm Jup}$, $R_{\rm p}=1.49\pm0.05\,R_{\rm Jup}$;][]{addison2021} orbiting a bright Am star ($V=8.0\,{\rm mag}$). Recent time-series observations obtained with PEPSI@LBT during the planet's post-eclipse phases have revealed Fe~{\sc i} emission lines indicative of a thermally inverted atmosphere. These observations demonstrate that MASCARA-5~b is well-suited to atmospheric characterization via emission spectroscopy, thereby motivating further follow-up observations covering additional orbital phases to constrain the planet's atmospheric chemistry, thermal structure, and dynamics. Here we present pre-eclipse time-series observations obtained with the high-resolution optical spectrograph EXPRES@LDT. Our analysis confirms the previous detection of gas-phase Fe~{\sc i} on MASCARA-5~b's dayside (with a $5.5σ$ significance obtained from two nights of observations) and the fact that the thermal profile is inverted with lower and upper temperatures $\sim2000\,{\rm K}$ and $\sim4500\,{\rm K}$, respectively. A search for Fe~{\sc ii} and Cr~{\sc i} did not yield any plausible detections. We also find that the pre-eclipse signal exhibits a non-negligible blueshift of $-3.2\pm1.4\,{\rm km/s}$ potentially caused by winds. △ Less

Submitted 30 April, 2026; originally announced May 2026.

Comments: 15 pages, 11 figures; accepted for publication in AJ

Assessment of PLATO Science Performance

Authors: Juan Cabrera, Heike Rauer, Reza Samadi, Valerio Nascimbeni, Anko Boerner, Denis Grießbach, Carsten Paproth, Martin Pertenaıs, Sami-M. Niemi, Szilard Csizmadia, Asier Abreu, Conny Aerts, Suzanne Aigrain, Matthias Ammler-von Eiff, Beatriz Aparicio del Moral, Thierry Appourchaux, David J. Armstrong, Ann Baeke, Gabor G. Balazs, Kevin Belkacem, Aaron Birch, Paz Bluhm, Tobias Boenke, Fabrice Boquet, Sam Bowling , et al. (99 additional authors not shown)

Abstract: The PLATO mission is scheduled for launch early 2027. In this paper we present an overview of the performance drivers for the mission at the time where all flight models of the cameras have been tested and integrated on the optical bench. The PLATO consortium needs an estimate of the planet detection yield to dimension the ground-based radial velocity follow-up resources. We provide updated estima… ▽ More The PLATO mission is scheduled for launch early 2027. In this paper we present an overview of the performance drivers for the mission at the time where all flight models of the cameras have been tested and integrated on the optical bench. The PLATO consortium needs an estimate of the planet detection yield to dimension the ground-based radial velocity follow-up resources. We provide updated estimates on the yield of planet detections that can be expected from the mission under certain assumptions. As of today, large uncertainties remain on the planet occurrence rates, especially for small planets in long-period orbits, and on our ability to detect these planets in the presence of stellar variability and instrumental noise. To partially overcome these limitations, we compare results using different planet occurrence rates, detectability rates, and we include an estimate on the expected contribution of stellar variability to the noise budget. The final detection yield of PLATO will provide constraints to planet occurrence rates which in turn will help constraining planet formation models. △ Less

Submitted 6 April, 2026; originally announced April 2026.

Comments: submitted to the special issue on PLATO in Experimental Astronomy

The Third Option: Color Phase Curves to Characterize the Atmospheres of Temperate Rocky Exoplanets

Authors: Drake Deming, Andrew Lincowski, Laura Kreidberg, Miles Currie, Jean-Michel Desert, Guangwei Fu, Jacob Lustig-Yaeger, Victoria Meadows, Ignas Snellen

Abstract: Detecting and characterizing the atmospheres of rocky exoplanets has proven to be challenging for JWST. Transit spectroscopy of the TRAPPIST-1 planets has been impacted by the effects of spots and faculae on the host star. Secondary eclipses have detected hot rocks, but evidence for atmospheres has been difficult to obtain. However, there is a third option that we call color phase curves. This met… ▽ More Detecting and characterizing the atmospheres of rocky exoplanets has proven to be challenging for JWST. Transit spectroscopy of the TRAPPIST-1 planets has been impacted by the effects of spots and faculae on the host star. Secondary eclipses have detected hot rocks, but evidence for atmospheres has been difficult to obtain. However, there is a third option that we call color phase curves. This method will apply to synchronously rotating non-transiting planets as well as transiting planets. A color phase curve uses photometry at a long-IR wavelength near the peak of the planetary thermal emission (e.g., 21 microns) divided by photometry at a shorter wavelength where the star dominates more strongly (e.g., 12 microns). We avoid wavelengths having potentially strong molecular absorption (e.g., 15 microns) to minimize degeneracies in the color phase curve, and we aim to detect and characterize the planetary atmosphere via its longitudinal heat transfer. The ratio of two wavelengths observed nearly simultaneously is designed to isolate thermal emission from the planet, discriminate against the star, and largely cancel instrumental systematic effects. Moreover, we show that invoking mass-radius relations, and using self-consistent physical models, will permit the longitudinal heat transfer to be measured independent of the orbital inclination. Radial velocity surveys are detecting many new exoplanets, including temperate rocky worlds with Earth-like masses. Most of those planets will not transit, but color phase curves have the potential to detect and characterize their atmospheres. △ Less

Submitted 28 January, 2026; originally announced January 2026.

Comments: 14 pages, 6 figures, submission to The Open Journal of Astrophysics

A young progenitor for the most common planetary systems in the Galaxy

Authors: John H. Livingston, Erik A. Petigura, Trevor J. David, Kento Masuda, James Owen, David Nesvorný, Konstantin Batygin, Jerome de Leon, Mayuko Mori, Kai Ikuta, Akihiko Fukui, Noriharu Watanabe, Jaume Orell Miquel, Felipe Murgas, Hannu Parviainen, Judith Korth, Florence Libotte, Néstor Abreu García, Pedro Pablo Meni Gallardo, Norio Narita, Enric Pallé, Motohide Tamura, Atsunori Yonehara, Andrew Ridden-Harper, Allyson Bieryla , et al. (17 additional authors not shown)

Abstract: The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii). The planets form a chain of ne… ▽ More The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii). The planets form a chain of near-resonances that result in transit-timing variations of several hours. Here we present a multi-year campaign to characterize this system with transit-timing variations, a method insensitive to the intense magnetic activity of the star. Through targeted observations, we first resolved the previously unknown orbital period of the outermost planet. The full 9-year baseline from these and archival data then enabled robust determination of the masses and orbital parameters for all four planets. We find the planets have low, sub-Neptune masses and nearly circular orbits, implying a dynamically tranquil history. Their low masses and large radii indicate that the inner planets underwent a period of rapid cooling immediately after dispersal of the protoplanetary disk. Still, they are much less dense than mature planets of comparable size. We predict the planets will contract to 1.5-4.0 Earth radii and join the population of super-Earths and sub-Neptunes that nature produces in abundance. △ Less

Submitted 15 January, 2026; originally announced January 2026.

Comments: 45 pages, 11 figures, 6 tables

Journal ref: Nature 649, 310-314 (2026)

Large-scale time-series spectroscopy for stellar ages

Authors: David Gruner, Sydney A. Barnes, Ansgar Reiners, Klaus G. Strassmeier, Cristina Chiappini, Jörg Weingrill, Michael Weber, Ilya Ilyin, Thomas Granzer, Özgün Adebali, Jean-Michel Désert, Marica Valentini, Dario Fritzewski, Paolo Ventura, Alfio Bonanno, Jose-Dias do Nascimento, Jorge Melendez, Santosh Joshi, Yong-Cheol Kim

Abstract: To date, Galactic Astronomy has largely concerned itself with astrophysical processes, and with the locations, space motions and compositions of objects. Consider, for example, the elucidation of the components of the Galaxy over the past decades, its mapping as enabled by Gaia and its predecessors, the photometric and spectroscopic characterization of innumerable astrophysical objects in various… ▽ More To date, Galactic Astronomy has largely concerned itself with astrophysical processes, and with the locations, space motions and compositions of objects. Consider, for example, the elucidation of the components of the Galaxy over the past decades, its mapping as enabled by Gaia and its predecessors, the photometric and spectroscopic characterization of innumerable astrophysical objects in various wavelength ranges, both from the ground and from space, and the expanding discovery and characterization of exoplanets; all focused on the current, static Galaxy. This White Paper proposes a dedicated program to derive stellar ages from time-series spectroscopy to hasten the transformation of this static conception into a dynamical one with age-labeled objects and events. △ Less

Submitted 15 January, 2026; originally announced January 2026.

Comments: White Paper submitted to ESO for the "Expanding Horizons: Transforming Astronomy in the 2040s" Call

Horizontal and vertical exoplanet thermal structure from a JWST spectroscopic eclipse map

Authors: Ryan C. Challener, Megan Weiner Mansfield, Patricio E. Cubillos, Anjali A. A. Piette, Louis-Philippe Coulombe, Hayley Beltz, Jasmina Blecic, Emily Rauscher, Jacob L. Bean, Björn Benneke, Eliza M. -R. Kempton, Joseph Harrington, Thaddeus D. Komacek, Vivien Parmentier, S. L. Casewell, Nicolas Iro, Luigi Mancini, Matthew C. Nixon, Michael Radica, Maria E. Steinrueck, Luis Welbanks, Natalie M. Batalha, Claudio Caceres, Ian J. M. Crossfield, Nicolas Crouzet , et al. (11 additional authors not shown)

Abstract: Highly-irradiated giant exoplanets known as "ultra-hot Jupiters" are anticipated to exhibit large variations of atmospheric temperature and chemistry as a function of longitude, latitude, and altitude. Previous observations have hinted at these variations, but the existing data have been fundamentally restricted to probing hemisphere-integrated spectra, thereby providing only coarse information on… ▽ More Highly-irradiated giant exoplanets known as "ultra-hot Jupiters" are anticipated to exhibit large variations of atmospheric temperature and chemistry as a function of longitude, latitude, and altitude. Previous observations have hinted at these variations, but the existing data have been fundamentally restricted to probing hemisphere-integrated spectra, thereby providing only coarse information on atmospheric gradients. Here we present a spectroscopic eclipse map of an extrasolar planet, resolving the atmosphere in multiple dimensions simultaneously. We analyze a secondary eclipse of the ultra-hot Jupiter WASP-18b observed with the NIRISS instrument on JWST. The mapping reveals weaker longitudinal temperature gradients than were predicted by theoretical models, indicating the importance of hydrogen dissociation and/or nightside clouds in shaping global thermal emission. Additionally, we identify two thermally distinct regions of the planet's atmosphere: a "hotspot" surrounding the substellar point and a "ring" near the dayside limbs. The hotspot region shows a strongly inverted thermal structure due to the presence of optical absorbers and a water abundance marginally lower than the hemispheric average, in accordance with theoretical predictions. The ring region shows colder temperatures and poorly constrained chemical abundances. Similar future analyses will reveal three-dimensional thermal, chemical, and dynamical properties of a broad range of exoplanet atmospheres. △ Less

Submitted 28 October, 2025; originally announced October 2025.

Comments: Published in Nature Astronomy. First two authors contributed equally

Testing the performance of cross-correlation techniques to search for molecular features in JWST NIRSpec G395H observations of transiting exoplanets

Authors: Emma Esparza-Borges, Mercedes López-Morales, Enric Pallé, Vladimir Makhnev, Iouli Gordon, Robert Hargreaves, James Kirk, Claudio Cáceres, Ian J. M. Crossfield, Nicolas Crouzet, Leen Decin, Jean-Michel Désert, Laura Flagg, Antonio García Muñoz, Joseph Harrington, Karan Molaverdikhani, Giuseppe Morello, Nikolay Nikolov, Arif Solmaz, Benjamin V. Rackham, Seth Redfield

Abstract: Cross-correlations techniques offer an alternative method to search for molecular species in JWST observations of exoplanet atmospheres. In a previous article, we applied cross-correlation functions for the first time to JWST NIRSpec/G395H observations of exoplanet atmospheres, resulting in a detection of CO in the transmission spectrum of WASP-39b and a tentative detection of CO isotopologues. He… ▽ More Cross-correlations techniques offer an alternative method to search for molecular species in JWST observations of exoplanet atmospheres. In a previous article, we applied cross-correlation functions for the first time to JWST NIRSpec/G395H observations of exoplanet atmospheres, resulting in a detection of CO in the transmission spectrum of WASP-39b and a tentative detection of CO isotopologues. Here we present an improved version of our cross-correlation technique and an investigation into how efficient the technique is when searching for other molecules in JWST NIRSpec/G395H data. Our search results in the detection of more molecules via cross-correlations in the atmosphere of WASP-39b, including $\rm H_{2}O$ and $\rm CO_{2}$, and confirms the CO detection. This result proves that cross-correlations are a robust and computationally cheap alternative method to search for molecular species in transmission spectra observed with JWST. We also searched for other molecules ($\rm CH_{4}$, $\rm NH_{3}$, $\rm SO_{2}$, $\rm N_{2}O$, $\rm H_{2}S$, $\rm PH_{3}$, $\rm O_{3}$ and $\rm C_{2}H_{2}$) that were not detected, for which we provide the definition of their cross-correlation baselines for future searches of those molecules in other targets. We find that that the cross-correlation search of each molecule is more efficient over limited wavelength regions of the spectrum, where the signal for that molecule dominates over other molecules, than over broad wavelength ranges. In general we also find that Gaussian normalization is the most efficient normalization mode for the generation of the molecular templates. △ Less

Submitted 29 September, 2025; originally announced September 2025.

Comments: Accepted for publication in Monthly Notices of the Royal Astronomical Society

A carbon-rich atmosphere on a windy pulsar planet

Authors: Michael Zhang, Maya Beleznay, Timothy D. Brandt, Roger W. Romani, Peter Gao, Hayley Beltz, Matthew Bailes, Matthew C. Nixon, Jacob L. Bean, Thaddeus D. Komacek, Brandon P. Coy, Guangwei Fu, Rafael Luque, Daniel J. Reardon, Emma Carli, Ryan M. Shannon, Jonathan J. Fortney, Anjali A. A. Piette, M. Coleman Miller, Jean-Michel Desert

Abstract: A handful of enigmatic Jupiter-mass objects have been discovered orbiting pulsars. One such object, PSR\,J2322-2650b, uniquely resembles a hot Jupiter exoplanet due to its minimum density of 1.8 g/cm^3 and its ~1900 K equilibrium temperature. We use JWST to observe PSR J2322-2650b's emission spectrum across an entire orbit. In stark contrast to every known exoplanet orbiting a main-sequence star,… ▽ More A handful of enigmatic Jupiter-mass objects have been discovered orbiting pulsars. One such object, PSR\,J2322-2650b, uniquely resembles a hot Jupiter exoplanet due to its minimum density of 1.8 g/cm^3 and its ~1900 K equilibrium temperature. We use JWST to observe PSR J2322-2650b's emission spectrum across an entire orbit. In stark contrast to every known exoplanet orbiting a main-sequence star, we find an atmosphere rich in molecular carbon (C3, C2) with strong westward winds. Our observations open up new exoplanetary chemical (ultra-high C/O and C/N ratios of >100 and >10,000, respectively) and dynamical regimes (ultra-fast rotation with external irradiation) to observational study. The extreme carbon enrichment poses a severe challenge to the current understanding of ``black widow'' companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores. △ Less

Submitted 15 December, 2025; v1 submitted 4 September, 2025; originally announced September 2025.

Comments: Final version accepted by ApJL

A metal-poor atmosphere with a hot interior for a young sub-Neptune progenitor: JWST/NIRSpec transmission spectrum of V1298 Tau b

Authors: Saugata Barat, Jean-Michel Désert, Sagnick Mukherjee, Jayesh M. Goyal, Qiao Xue, Yui Kawashima, Allona Vazan, William Misener, Hilke E. Schlichting, Jonathan J. Fortney, Jacob L. Bean, Swaroop Avarsekar, Gregory W. Henry, Robin Baeyens, Michael R. Line, John H. Livingston, Trevor David, Erik A. Petigura, James T. Sikora, Hinna Shivkumar, Adina D. Feinstein, Antonija Oklopčić

Abstract: We present the JWST/NIRSpec G395H transmission spectrum of the young (10 - 20 Myr old) transiting planet V1298 Tau b (9.85+/-0.35 Re, Teq=670K). Combined HST and JWST observations reveal a haze free, H/He dominated atmosphere with a large scale height (~1500km), allowing detection of CO2 (35 sigma), H2O (30 sigma), CO (10 sigma), CH4 (6 sigma), SO2 (4 sigma) and OCS (3.5 sigma). Our observations p… ▽ More We present the JWST/NIRSpec G395H transmission spectrum of the young (10 - 20 Myr old) transiting planet V1298 Tau b (9.85+/-0.35 Re, Teq=670K). Combined HST and JWST observations reveal a haze free, H/He dominated atmosphere with a large scale height (~1500km), allowing detection of CO2 (35 sigma), H2O (30 sigma), CO (10 sigma), CH4 (6 sigma), SO2 (4 sigma) and OCS (3.5 sigma). Our observations probe several scale heights (~4.4 in the CO2 4.3 microns and ~3 in the 2.7 micron water band). The planet's mass, inferred from atmospheric scale height using free retrieval and grid modelling is 12+/-1 and 15+/-1.7Me respectively which is significantly lower than previous radial velocity estimates and confirm it as a 'gas-dwarf' sub-Neptune progenitor. We find an atmospheric super-solar metallicity (logZ=0.6^+0.4_-0.6 x solar) and a sub-solar C/O ratio (0.22^+0.06_-0.05). The atmospheric metallicity is low compared to matured sub-Neptunes by an order of magnitude. The CH4 abundance ([CH4]=-6.2^+0.3_-0.5) is ~7 sigma lower than equilibrium chemistry prediction. To adjust for the low methane abundance, the self-consistent grids favour a high internal temperature (~500K) and vertical mixing (Kzz ~10^7-10^8 cm2/s). These internal temperatures are inconsistent with predictions from evolutionary models, which expect ~100 - 200K at the current system age. We estimate a gas-to-core mass fraction between 0.1 - 8 %, with a core mass of 11 - 12 Me, consistent with in-situ gas dwarf formation. A deep atmospheric metallicity gradient may explain both the high internal temperature and low observable metallicity. Over time, mass loss from such an atmosphere could enhance its metallicity, potentially reconciling V1298 Tau b with mature sub-Neptunes. △ Less

Submitted 23 July, 2025; v1 submitted 7 July, 2025; originally announced July 2025.

Comments: Accepted for publication in AJ, minor typos corrected

The Roasting Marshmallows Program with IGRINS on Gemini South III: Seeing deeper into the metal depleted atmosphere of a gas-giant on the cusp of the hot to ultra-hot Jupiter transition

Authors: Vatsal Panwar, Matteo Brogi, Krishna Kanumalla, Michael R. Line, Siddharth Gandhi, Peter C. B. Smith, Jacob L. Bean, Lorenzo Pino, Arjun B. Savel, Joost P. Wardenier, Heather Cegla, Hayley Beltz, Megan Weiner Mansfield, Jorge A. Sanchez, Jean-Michel Désert, Luis Welbanks, Viven Parmentier, Changwoo Kye, Jonathan J. Fortney, Tomás de Azevedo Silva

Abstract: Ultra-hot Jupiters are a class of gas-giant exoplanets that show a peculiar combination of thermochemical properties in the form of molecular dissociation, atomic ionization, and inverted thermal structures. Atmospheric characterization of gas giants lying in the transitional regime between hot and ultra-hot Jupiters can help in understanding the physical mechanisms that cause the fundamental tran… ▽ More Ultra-hot Jupiters are a class of gas-giant exoplanets that show a peculiar combination of thermochemical properties in the form of molecular dissociation, atomic ionization, and inverted thermal structures. Atmospheric characterization of gas giants lying in the transitional regime between hot and ultra-hot Jupiters can help in understanding the physical mechanisms that cause the fundamental transition in atmospheres between the two classes of hot gas giants. Using Doppler spectroscopy with IGRINS on Gemini South (1.4 to 2.5 $μ$m), we present the day-side high-resolution spectrum of WASP-122b (T$_{\mathrm{day}}$=2258$ \pm$ 54 K), a gas-giant situated at this transition. We detect the signal from H$_{2}$O, based on which we find that WASP-122b has a significantly metal-depleted atmosphere with metallicity log$_{10}$[Z$_{\mathrm{P}}$/Z$_{\odot}$] = $-$1.48$\pm$0.25 dex (0.033$_{-0.016}^{+0.018}$ $\times$ solar), and solar/sub-solar C/O ratio = 0.36$\pm$0.22 (3$σ$ upper limit 0.82). Drastically low atmospheric metallicity pushes the contribution function to higher pressures, resulting in the planetary spectral lines to originate from a narrow region around 1 bar where the thermal profile is non-inverted. This is inconsistent with solar composition radiative convective equilibrium (RCTE) which predicts an inverted atmosphere with spectral lines in emission. The sub-solar metallicity and solar/sub-solar C/O ratio is inconsistent with expectations from core-accretion. We find the planetary signal to be significantly shifted in K$_{\mathrm{P}}$ and V$_{\mathrm{sys}}$, which is in tension with the predictions from global circulation models and require further investigation. Our results highlight the detailed information content of high-resolution spectroscopy data and their ability to constrain complex atmospheric thermal structures and compositions of exoplanets. △ Less

Submitted 9 July, 2025; originally announced July 2025.

Comments: 28 pages, 22 figures, Accepted for publication in MNRAS

Time Resolved Absorption of Six Chemical Species With MAROON-X Points to Strong Drag in the Ultra Hot Jupiter TOI-1518 b

Authors: A. Simonnin, V. Parmentier, J. P. Wardenier, G. Chauvin, A. Chiavassa, M. N'Diaye, X. Tan, N. Heidari, B. Prinoth J. Bean, G. Hébrard, M. Line, D. Kitzmann, D. Kasper, S. Pelletier, J. V. Seidel, A. Seifhart, B. Benneke, X. Bonfils, M. Brogi, J-M. Désert, S. Gandhi, M. Hammond, E. K. H. Lee, C. Moutou, P. Palma-Bifani , et al. (5 additional authors not shown)

Abstract: Wind dynamics play a pivotal role in governing transport processes within planetary atmospheres, influencing atmospheric chemistry, cloud formation, and the overall energy budget. Understanding the strength and patterns of winds is crucial for comprehensive insights into the physics of ultra-hot Jupiter atmospheres. This study focuses on unraveling the wind dynamics and the chemical composition in… ▽ More Wind dynamics play a pivotal role in governing transport processes within planetary atmospheres, influencing atmospheric chemistry, cloud formation, and the overall energy budget. Understanding the strength and patterns of winds is crucial for comprehensive insights into the physics of ultra-hot Jupiter atmospheres. This study focuses on unraveling the wind dynamics and the chemical composition in the atmosphere of the ultra-hot Jupiter TOI-1518 b. Two transit observations using the high-resolution (Rλ = 85 000), optical (spectral coverage between 490 and 920 nm) spectrograph MAROON-X were obtained and analyzed to explore the chemical composition and wind dynamics using the cross-correlation techniques, global circulating models, and atmospheric retrieval. We report the detection of 14 species in the atmosphere of TOI-1518 b through cross-correlation analysis. Additionally, we measure the time-varying cross-correlation trails for 6 different species, compare them with predictions from General Circulation Models (GCM) and conclude that a strong drag is present in TOI-1518b's atmosphere. We find that the trails are species-dependent. Fe+ favors a stronger drag than Fe, which we interpret as a sign of magnetic effects being responsible for the observed strong drag. Furthermore, we show that Ca+ probes layers above the Roche lobe, leading to a qualitatively different trail than the other species. Finally, we use a retrieval analysis to characterize the abundance of the different species detected. That analysis is refined thanks to the updated planetary mass we derived from the radial-velocity detection using SOPHIE data. We measure an abundance of iron corresponding to 0.07 to 1.62 solar enrichment. The retrievals appear to be biased for the other elements, probably due to the different Kp/Vsys shifts between iron and the other elements, which we demonstrate in the case of VO. △ Less

Submitted 25 April, 2025; v1 submitted 2 December, 2024; originally announced December 2024.

Comments: 25 pages, 27 figures, accepted for publication in A&A

Journal ref: A&A 698, A314 (2025)

The Roasting Marshmallows Program with IGRINS on Gemini South II -- WASP-121 b has super-stellar C/O and refractory-to-volatile ratios

Authors: Peter C. B. Smith, Jorge A. Sanchez, Michael R. Line, Emily Rauscher, Megan Weiner Mansfield, Eliza M. -R. Kempton, Arjun Savel, Joost P. Wardenier, Lorenzo Pino, Jacob L. Bean, Hayley Beltz, Vatsal Panwar, Matteo Brogi, Isaac Malsky, Jonathan Fortney, Jean-Michel Desert, Stefan Pelletier, Vivien Parmentier, Krishna Kanumalla, Luis Welbanks, Michael Meyer, John Monnier

Abstract: A primary goal of exoplanet science is to measure the atmospheric composition of gas giants in order to infer their formation and migration histories. Common diagnostics for planet formation are the atmospheric metallicity ([M/H]) and the carbon-to-oxygen (C/O) ratio as measured through transit or emission spectroscopy. The C/O ratio in particular can be used to approximately place a planet's init… ▽ More A primary goal of exoplanet science is to measure the atmospheric composition of gas giants in order to infer their formation and migration histories. Common diagnostics for planet formation are the atmospheric metallicity ([M/H]) and the carbon-to-oxygen (C/O) ratio as measured through transit or emission spectroscopy. The C/O ratio in particular can be used to approximately place a planet's initial formation radius from the stellar host, but a given C/O ratio may not be unique to formation location. This degeneracy can be broken by combining measurements of both the C/O ratio and the atmospheric refractory-to-volatile ratio. We report the measurement of both quantities for the atmosphere of the canonical ultra hot Jupiter WASP-121 b using the high resolution (R=45,000) IGRINS instrument on Gemini South. Probing the planet's direct thermal emission in both pre- and post-secondary eclipse orbital phases, we infer that WASP-121 b has a significantly super-stellar C/O ratio of 0.70$^{+0.07}_{-0.10}$ and a moderately super-stellar refractory-to-volatile ratio at 3.83$^{+3.62}_{-1.67} \times$ stellar. This combination is most consistent with formation between the soot line and H$_2$O snow line, but we cannot rule out formation between the H$_2$O and CO snow lines or beyond the CO snow line. We also measure velocity offsets between H$_2$O, CO, and OH, potentially an effect of chemical inhomogeneity on the planet day side. This study highlights the ability to measure both C/O and refractory-to-volatile ratios via high resolution spectroscopy in the near-infrared H and K bands. △ Less

Submitted 23 October, 2024; originally announced October 2024.

Comments: 21 pages, 15 figures, accepted to AJ

Spectroscopically resolved partial phase curve of the rapid heating and cooling of the highly-eccentric Hot Jupiter HAT-P-2b with WFC3

Authors: Bob Jacobs, Jean-Michel Désert, Nikole Lewis, Ryan C. Challener, L. C. Mayorga, Zoë de Beurs, Vivien Parmentier, Kevin B. Stevenson, Julien de Wit, Saugata Barat, Jonathan Fortney, Tiffany Kataria, Michael Line

Abstract: The extreme environments of transiting close-in exoplanets in highly-eccentric orbits are ideal for testing exo-climate physics. Spectroscopically resolved phase curves not only allow for the characterization of their thermal response to irradiation changes but also unveil phase-dependent atmospheric chemistry and dynamics. We observed a partial phase curve of the highly-eccentric close-in giant p… ▽ More The extreme environments of transiting close-in exoplanets in highly-eccentric orbits are ideal for testing exo-climate physics. Spectroscopically resolved phase curves not only allow for the characterization of their thermal response to irradiation changes but also unveil phase-dependent atmospheric chemistry and dynamics. We observed a partial phase curve of the highly-eccentric close-in giant planet HAT-P-2b ($e=0.51,M=9M_{\rm{Jup}}$) with the Wide Field Camera 3 aboard the Hubble Space Telescope. Using these data, we updated the planet's orbital parameters and radius, and retrieved high-frequency pulsations consistent with the planet-induced pulsations reported in Spitzer data. We found that the peak in planetary flux occurred at $6.7\pm0.6$ hr after periastron, with a heating and cooling timescales of $9.0^{+3.5}_{-2.1}$ hr, and $3.6^{+0.7}_{-0.6}$ hr, respectively. We compare the light-curve to various 1-dimensional and 3-dimensional forward models, varying the planet's chemical composition. The strong contrast in flux increase and decrease timescales before and after periapse indicates an opacity term that emerges during the planet's heating phase, potentially due to more H$^{-}$ than expected from chemical equilibrium models. The phase-resolved spectra are largely featureless, that we interpret as indicative an inhomogeneous dayside. However, we identified an anomalously high flux in the spectroscopic bin coinciding with the hydrogen Paschen $β$ line and that is likely connected to the planet's orbit. We interpret this as due to shock heating of the upper atmosphere given the short timescale involved, or evidence for other star-planet interactions. △ Less

Submitted 14 October, 2024; originally announced October 2024.

Comments: In review in AJ

Report number: AAS55880R1

A Comprehensive Analysis Spitzer 4.5 $μ$m Phase Curve of Hot Jupiters

Authors: Lisa Dang, Taylor J. Bell, Ying, Shu, Nicolas B. Cowan, Jacob L. Bean, Drake Deming, Eliza M. -R. Kempton, Megan Weiner Mansfield, Emily Rauscher, Vivien Parmentier, Kevin B. Stevenson, Mark Swain, Laura Kreidberg, Tiffany Kataria, Jean-Michel Désert, Robert Zellem, Jonathan J. Fortney, Nikole K. Lewis, Michael Line, Caroline Morley, Adam Showman

Abstract: Although exoplanetary science was not initially projected to be a substantial part of the Spitzer mission, its exoplanet observations set the stage for current and future surveys with JWST and Ariel. We present a comprehensive reduction and analysis of Spitzer's 4.5 micron phase curves of 29 hot Jupiters on low-eccentricity orbits. The analysis, performed with the Spitzer Phase Curve Analysis (SPC… ▽ More Although exoplanetary science was not initially projected to be a substantial part of the Spitzer mission, its exoplanet observations set the stage for current and future surveys with JWST and Ariel. We present a comprehensive reduction and analysis of Spitzer's 4.5 micron phase curves of 29 hot Jupiters on low-eccentricity orbits. The analysis, performed with the Spitzer Phase Curve Analysis (SPCA) pipeline, confirms that BLISS mapping is the best detrending scheme for most, but not all, observations. Visual inspection remains necessary to ensure consistency across detrending methods due to the diversity of phase curve data and systematics. Regardless of the model selection scheme - whether using the lowest-BIC or a uniform detrending approach - we observe the same trends, or lack thereof. We explore phase curve trends as a function of irradiation temperature, orbital period, planetary radius, mass, and stellar effective temperature. We discuss the trends that are robustly detected and provide potential explanations for those that are not observed. While it is almost tautological that planets receiving greater instellation are hotter, we are still far from confirming dynamical theories of heat transport in hot Jupiter atmospheres due to the sample's diversity. Even among planets with similar temperatures, other factors like rotation and metallicity vary significantly. Larger, curated sample sizes and higher-fidelity phase curve measurements from JWST and Ariel are needed to firmly establish the parameters governing day-night heat transport on synchronously rotating planets. △ Less

Submitted 23 August, 2024; originally announced August 2024.

Comments: 16 pages, 6 figures, submitted to AAS journal

First Comparative Exoplanetology Within a Transiting Multi-planet System: Comparing the atmospheres of V1298 Tau b and c

Authors: Saugata Barat, Jean-Michel Désert, Jayesh M. Goyal, Allona Vazan, Yui Kawashima, Jonathan J. Fortney, Jacob L. Bean, Michael R. Line, Vatsal Panwar, Bob Jacobs, Hinna Shivkumar, James Sikora, Robin Baeyens, Antonija Oklopcić, Trevor J. David, John H. Livingston

Abstract: The V1298 Tau system (20-30Myr), is a benchmark young multi-planet system that provides the opportunity to perform comparative exoplanetology between planets orbiting the same star right after their formation. We present the first atmospheric comparison between two planets in the same transiting system: V1298 Tau b and V1298 Tau c. We derive constraints on the mass of planet b and c (<20M… ▽ More The V1298 Tau system (20-30Myr), is a benchmark young multi-planet system that provides the opportunity to perform comparative exoplanetology between planets orbiting the same star right after their formation. We present the first atmospheric comparison between two planets in the same transiting system: V1298 Tau b and V1298 Tau c. We derive constraints on the mass of planet b and c (<20M$_\oplus$ at 3$σ$ confidence level and $17_{-6}^{+13} M_{\oplus}$ respectively) and atmospheric metallicity (logZ/Z$_\odot$=-2.04$_{-0.59}^{0.69}$, -0.16$_{-0.94}^{1.15}$ respectively) from atmospheric retrievals. The V1298 Tau planets, are likely to be similar in terms of mass at the current age, implying that both planets are potential sub-Neptune/super-Earth progenitors. However, planet c is expected to lose a higher fraction of its mass compared to planet b given its close proximity to the host star. Alternatively, the observed spectrum of planet c can be explained by atmospheric hazes, which is in contrast to planet b where efficient haze formation can be ruled out. Higher haze formation efficiency in planet c could be due to differences in atmospheric composition, temperature and higher UV flux incident compared to planet b. △ Less

Submitted 6 November, 2024; v1 submitted 20 July, 2024; originally announced July 2024.

Comments: Accepted for publication in Astronomy and Astrophysics

Journal ref: A&A 692, A198 (2024)

A Benchmark JWST Near-Infrared Spectrum for the Exoplanet WASP-39b

Authors: A. L. Carter, E. M. May, N. Espinoza, L. Welbanks, E. Ahrer, L. Alderson, R. Brahm, A. D. Feinstein, D. Grant, M. Line, G. Morello, R. O'Steen, M. Radica, Z. Rustamkulov, K. B. Stevenson, J. D. Turner, M. K. Alam, D. R. Anderson, N. M. Batalha, M. P. Battley, D. Bayliss, J. L. Bean, B. Benneke, Z. K. Berta-Thompson, J. Brande , et al. (55 additional authors not shown)

Abstract: Observing exoplanets through transmission spectroscopy supplies detailed information on their atmospheric composition, physics, and chemistry. Prior to JWST, these observations were limited to a narrow wavelength range across the near-ultraviolet to near-infrared, alongside broadband photometry at longer wavelengths. To understand more complex properties of exoplanet atmospheres, improved waveleng… ▽ More Observing exoplanets through transmission spectroscopy supplies detailed information on their atmospheric composition, physics, and chemistry. Prior to JWST, these observations were limited to a narrow wavelength range across the near-ultraviolet to near-infrared, alongside broadband photometry at longer wavelengths. To understand more complex properties of exoplanet atmospheres, improved wavelength coverage and resolution are necessary to robustly quantify the influence of a broader range of absorbing molecular species. Here we present a combined analysis of JWST transmission spectroscopy across four different instrumental modes spanning 0.5-5.2 micron using Early Release Science observations of the Saturn-mass exoplanet WASP-39b. Our uniform analysis constrains the orbital and stellar parameters within sub-percent precision, including matching the precision obtained by the most precise asteroseismology measurements of stellar density to-date, and further confirms the presence of Na, K, H$_2$O, CO, CO$_2$, and SO$_2$ atmospheric absorbers. Through this process, we also improve the agreement between the transmission spectra of all modes, except for the NIRSpec PRISM, which is affected by partial saturation of the detector. This work provides strong evidence that uniform light curve analysis is an important aspect to ensuring reliability when comparing the high-precision transmission spectra provided by JWST. △ Less

Submitted 18 July, 2024; originally announced July 2024.

Comments: 34 pages, 11 figures, 3 tables. Nat Astron (2024)

Colorado Ultraviolet Transit Experiment Near-Ultraviolet Transmission Spectroscopy of the Ultra-hot Jupiter KELT-9b

Authors: Arika Egan, Kevin France, Aickara Gopinathan Sreejith, Luca Fossati, Tommi Koskinen, Brian Fleming, Nicholas Nell, Ambily Suresh, P. Wilson Cauley, Jean-Michele Desert, Pascal Petit, Aline A. Vidotto

Abstract: We present new near-ultraviolet (NUV, $λ$ = 2479 $-$ 3306 $Å$) transmission spectroscopy of KELT-9b, the hottest known exoplanet, obtained with the Colorado Ultraviolet Transit Experiment ($CUTE$) CubeSat. Two transits were observed on September 28th and September 29th 2022, referred to as Visits 1 and 2 respectively. Using a combined transit and systematics model for each visit, the best-fit broa… ▽ More We present new near-ultraviolet (NUV, $λ$ = 2479 $-$ 3306 $Å$) transmission spectroscopy of KELT-9b, the hottest known exoplanet, obtained with the Colorado Ultraviolet Transit Experiment ($CUTE$) CubeSat. Two transits were observed on September 28th and September 29th 2022, referred to as Visits 1 and 2 respectively. Using a combined transit and systematics model for each visit, the best-fit broadband NUV light curves are R$_{\text{p}}$/R$_{\star}$ $=$ 0.136$_{0.0146}^{0.0125}$ for Visit 1 and R$_{\text{p}}$/R$_{\star}$ $=$ 0.111$_{0.0190}^{0.0162}$ for Visit 2, appearing an average of 1.54$\times$ larger in the NUV than at optical wavelengths. While the systematics between the two visits vary considerably, the two broadband NUV light curves are consistent with each other. A transmission spectrum with 25 $Å$ bins suggests a general trend of excess absorption in the NUV, consistent with expectations for ultra-hot Jupiters. Although we see an extended atmosphere in the NUV, the reduced data lack the sensitivity to probe individual spectral lines. △ Less

Submitted 18 July, 2024; originally announced July 2024.

Seasonal Changes in the Atmosphere of HD 80606b Observed with JWST's NIRSpec/G395H

Authors: James T. Sikora, Jason F. Rowe, Jared Splinter, Saugata Barat, Lisa Dang, Nicolas B. Cowan, Thomas Barclay, Knicole D. Colón, Jean-Michel Désert, Stephen R. Kane, Joe Llama, Hinna Shivkumar, Keivan G. Stassun, Elisa V. Quintana

Abstract: High-eccentricity gas giant planets serve as unique laboratories for studying the thermal and chemical properties of H/He-dominated atmospheres. One of the most extreme cases is HD 80606b -- a hot Jupiter orbiting a sun-like star with an eccentricity of $0.93$ -- which experiences an increase in incident flux of nearly three orders of magnitude as the star-planet separation decreases from… ▽ More High-eccentricity gas giant planets serve as unique laboratories for studying the thermal and chemical properties of H/He-dominated atmospheres. One of the most extreme cases is HD 80606b -- a hot Jupiter orbiting a sun-like star with an eccentricity of $0.93$ -- which experiences an increase in incident flux of nearly three orders of magnitude as the star-planet separation decreases from $0.88\,{\rm AU}$ at apoastron to $0.03\,{\rm AU}$ at periastron. We observed the planet's periastron passage using \emph{JWST}'s NIRSpec/G395H instrument ($2.8-5.2\,{\rm μm}$) during a $21\,{\rm hr}$ window centered on the eclipse. We find that, as the planet passes through periastron, its emission spectrum transitions from a featureless blackbody to one in which CO, CH$_4$, and H$_2$O absorption features are visible. We detect CH$_4$ during post-periapse phases at $4.1-10.7σ$ depending on the phase and on whether a flux offset is included to account for NRS1 detector systematics. Following periapse, H$_2$O and CO are also detected at $4.2-5.5σ$ and $3.7-4.4σ$, respectively. Furthermore, we rule out the presence of a strong temperature inversion near the IR photosphere based on the lack of obvious emission features throughout the observing window. General circulation models had predicted an inversion during periapse passage. Our study demonstrates the feasibility of studying hot Jupiter atmospheres using partial phase curves obtained with NIRSpec/G395H. △ Less

Submitted 25 July, 2025; v1 submitted 17 July, 2024; originally announced July 2024.

Comments: 26 pages, 18 figures, 2 tables. Accepted by The Astronomical Journal

Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b

Authors: Diana Powell, Adina D. Feinstein, Elspeth K. H. Lee, Michael Zhang, Shang-Min Tsai, Jake Taylor, James Kirk, Taylor Bell, Joanna K. Barstow, Peter Gao, Jacob L. Bean, Jasmina Blecic, Katy L. Chubb, Ian J. M. Crossfield, Sean Jordan, Daniel Kitzmann, Sarah E. Moran, Giuseppe Morello, Julianne I. Moses, Luis Welbanks, Jeehyun Yang, Xi Zhang, Eva-Maria Ahrer, Aaron Bello-Arufe, Jonathan Brande , et al. (48 additional authors not shown)

Abstract: The recent inference of sulphur dioxide (SO$_2$) in the atmosphere of the hot ($\sim$1100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations suggests that photochemistry is a key process in high temperature exoplanet atmospheres. This is due to the low ($<$1 ppb) abundance of SO$_2$ under thermochemical equilibrium, compared to that produced from the photochemistry of H$_2$O a… ▽ More The recent inference of sulphur dioxide (SO$_2$) in the atmosphere of the hot ($\sim$1100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations suggests that photochemistry is a key process in high temperature exoplanet atmospheres. This is due to the low ($<$1 ppb) abundance of SO$_2$ under thermochemical equilibrium, compared to that produced from the photochemistry of H$_2$O and H$_2$S (1-10 ppm). However, the SO$_2$ inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 $μ$m, and therefore the detection of other SO$_2$ absorption bands at different wavelengths is needed to better constrain the SO$_2$ abundance. Here we report the detection of SO$_2$ spectral features at 7.7 and 8.5 $μ$m in the 5-12 $μ$m transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS). Our observations suggest an abundance of SO$_2$ of 0.5-25 ppm (1$σ$ range), consistent with previous findings. In addition to SO$_2$, we find broad water vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 $μ$m. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy element content (metallicity) for WASP-39b of $\sim$7.1-8.0 $\times$ solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range. △ Less

Submitted 10 July, 2024; originally announced July 2024.

Comments: Published in Nature

Journal ref: Nature 626, 979-983 (2024)

Phase-resolving the absorption signatures of water and carbon monoxide in the atmosphere of the ultra-hot Jupiter WASP-121b with GEMINI-S/IGRINS

Authors: Joost P. Wardenier, Vivien Parmentier, Michael R. Line, Megan Weiner Mansfield, Xianyu Tan, Shang-Min Tsai, Jacob L. Bean, Jayne L. Birkby, Matteo Brogi, Jean-Michel Désert, Siddharth Gandhi, Elspeth K. H. Lee, Colette I. Levens, Lorenzo Pino, Peter C. B. Smith

Abstract: Ultra-hot Jupiters are among the best targets for atmospheric characterization at high spectral resolution. Resolving their transmission spectra as a function of orbital phase offers a unique window into the 3D nature of these objects. In this work, we present three transits of the ultra-hot Jupiter WASP-121b observed with Gemini-S/IGRINS. For the first time, we measure the phase-dependent absorpt… ▽ More Ultra-hot Jupiters are among the best targets for atmospheric characterization at high spectral resolution. Resolving their transmission spectra as a function of orbital phase offers a unique window into the 3D nature of these objects. In this work, we present three transits of the ultra-hot Jupiter WASP-121b observed with Gemini-S/IGRINS. For the first time, we measure the phase-dependent absorption signals of CO and H$_{\text{2}}$O in the atmosphere of an exoplanet, and we find that they are different. While the blueshift of CO increases during the transit, the absorption lines of H$_{\text{2}}$O become less blueshifted with phase, and even show a redshift in the second half of the transit. These measurements reveal the distinct spatial distributions of both molecules across the atmospheres of ultra-hot Jupiters. Also, we find that the H$_{\text{2}}$O signal is absent in the first quarter of the transit, potentially hinting at cloud formation on the evening terminator of WASP-121b. To further interpret the absorption trails of CO and H$_{\text{2}}$O, as well as the Doppler shifts of Fe previously measured with VLT/ESPRESSO, we compare the data to simulated transits of WASP-121b. To this end, we post-processes the outputs of global circulation models with a 3D Monte-Carlo radiative transfer code. Our analysis shows that the atmosphere of WASP-121b is subject to atmospheric drag, as previously suggested by small hotspot offsets inferred from phase-curve observations. Our study highlights the importance of phase-resolved spectroscopy in unravelling the complex atmospheric structure of ultra-hot Jupiters and sets the stage for further investigations into their chemistry and dynamics. △ Less

Submitted 18 July, 2024; v1 submitted 13 June, 2024; originally announced June 2024.

Comments: 24 pages, 16 figures, accepted for publication in PASP

The PLATO Mission

Authors: Heike Rauer, Conny Aerts, Juan Cabrera, Magali Deleuil, Anders Erikson, Laurent Gizon, Mariejo Goupil, Ana Heras, Jose Lorenzo-Alvarez, Filippo Marliani, César Martin-Garcia, J. Miguel Mas-Hesse, Laurence O'Rourke, Hugh Osborn, Isabella Pagano, Giampaolo Piotto, Don Pollacco, Roberto Ragazzoni, Gavin Ramsay, Stéphane Udry, Thierry Appourchaux, Willy Benz, Alexis Brandeker, Manuel Güdel, Eduardo Janot-Pacheco , et al. (820 additional authors not shown)

Abstract: PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observati… ▽ More PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5 %, 10 %, 10 % for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile at the beginning of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases. △ Less

Submitted 18 November, 2024; v1 submitted 8 June, 2024; originally announced June 2024.

Two-Dimensional Eclipse Mapping of the Hot Jupiter WASP-43b with JWST MIRI/LRS

Authors: Mark Hammond, Taylor J. Bell, Ryan C. Challener, Neil T. Lewis, Megan Weiner Mansfield, Isaac Malsky, Emily Rauscher, Jacob L. Bean, Ludmila Carone, João M. Mendonça, Lucas Teinturier, Xianyu Tan, Nicolas Crouzet, Laura Kreidberg, Giuseppe Morello, Vivien Parmentier, Jasmina Blecic, Jean-Michel Désert, Christiane Helling, Pierre-Olivier Lagage, Karan Molaverdikhani, Matthew C. Nixon, Benjamin V. Rackham, Jingxuan Yang

Abstract: We present eclipse maps of the two-dimensional thermal emission from the dayside of the hot Jupiter WASP-43b, derived from an observation of a phase curve with the JWST MIRI/LRS instrument. The observed eclipse shapes deviate significantly from those expected for a planet emitting uniformly over its surface. We fit a map to this deviation, constructed from spherical harmonics up to order… ▽ More We present eclipse maps of the two-dimensional thermal emission from the dayside of the hot Jupiter WASP-43b, derived from an observation of a phase curve with the JWST MIRI/LRS instrument. The observed eclipse shapes deviate significantly from those expected for a planet emitting uniformly over its surface. We fit a map to this deviation, constructed from spherical harmonics up to order $\ell_{\rm max}=2$, alongside the planetary, orbital, stellar, and systematic parameters. This yields a map with a meridionally-averaged eastward hot-spot shift of $(7.75 \pm 0.36)^{\circ}$, with no significant degeneracy between the map and the additional parameters. We show the latitudinal and longitudinal contributions of the day-side emission structure to the eclipse shape, finding a latitudinal signal of $\sim$200 ppm and a longitudinal signal of $\sim$250 ppm. To investigate the sensitivity of the map to the method, we fix the non-mapping parameters and derive an "eigenmap" fitted with an optimised number of orthogonal phase curves, which yields a similar map to the $\ell_{\rm max}=2$ map. We also fit a map up to $\ell_{\rm max}=3$, which shows a smaller hot-spot shift, with a larger uncertainty. These maps are similar to those produced by atmospheric simulations. We conclude that there is a significant mapping signal which constrains the spherical harmonic components of our model up to $\ell_{\rm max}=2$. Alternative mapping models may derive different structures with smaller-scale features; we suggest that further observations of WASP-43b and other planets will drive the development of more robust methods and more accurate maps. △ Less

Submitted 25 April, 2024; originally announced April 2024.

Comments: Accepted for publication in The Astronomical Journal

Impact of Electron Precipitation on Brown Dwarf Atmospheres and the Missing Auroral H$_{3}^{+}$ Emission

Authors: J. Sebastian Pineda, Gregg Hallinan, Jean Michel Desert, Leon K. Harding

Abstract: Recent observations have demonstrated that very-low mass stars and brown dwarfs are capable of sustaining strong magnetic fields despite their cool and neutral atmospheres. These kG field strengths are inferred based on strong highly circularly polarized GHz radio emission, a consequence of the electron cyclotron maser instability. Crucially, these observations imply the existence of energetic non… ▽ More Recent observations have demonstrated that very-low mass stars and brown dwarfs are capable of sustaining strong magnetic fields despite their cool and neutral atmospheres. These kG field strengths are inferred based on strong highly circularly polarized GHz radio emission, a consequence of the electron cyclotron maser instability. Crucially, these observations imply the existence of energetic non-thermal electron populations, associated with strong current systems, as are found in the auroral regions of the magnetized planets of the Solar System. Intense auroral electron precipitation will lead to electron collisions with the H$_{2}$ gas that should ultimately generate the ion H$_{3}^{+}$. With this motivation, we targeted a sample of ultracool dwarfs, known to exhibit signatures associated with aurorae, in search of the K-band emission features of H$_{3}^{+}$ using the Keck telescopes on Mauna Kea. From our sample of 9 objects, we found no clear indication of H$_{3}^{+}$ emission features in our low-medium resolution spectra (R$\sim$3600). We also modeled the impact of an auroral electron beam on a brown dwarf atmosphere, determining the depth at which energetic beams deposit their energy and drive particle impact ionization. We find that the H$_{3}^{+}$ non-detections can be explained by electron beams of typical energies $\gtrsim$2-10~keV, which penetrate deeply enough that any H$_{3}^{+}$ produced is chemically destroyed before radiating energy through its infrared transitions. Strong electron beams could further explain the lack of UV detections, and suggest that most or nearly all of the precipitating auroral energy must ultimately emerge as thermal emissions deep in brown dwarf atmospheres. △ Less

Submitted 13 March, 2024; originally announced March 2024.

Comments: accepted to ApJ

Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b

Authors: Taylor J. Bell, Nicolas Crouzet, Patricio E. Cubillos, Laura Kreidberg, Anjali A. A. Piette, Michael T. Roman, Joanna K. Barstow, Jasmina Blecic, Ludmila Carone, Louis-Philippe Coulombe, Elsa Ducrot, Mark Hammond, João M. Mendonça, Julianne I. Moses, Vivien Parmentier, Kevin B. Stevenson, Lucas Teinturier, Michael Zhang, Natalie M. Batalha, Jacob L. Bean, Björn Benneke, Benjamin Charnay, Katy L. Chubb, Brice-Olivier Demory, Peter Gao , et al. (58 additional authors not shown)

Abstract: Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5… ▽ More Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5-12 $μ$m with JWST's Mid-Infrared Instrument (MIRI). The spectra reveal a large day-night temperature contrast (with average brightness temperatures of 1524$\pm$35 and 863$\pm$23 Kelvin, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase curve shape and emission spectra strongly suggest the presence of nightside clouds which become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2$σ$ upper limit of 1-6 parts per million, depending on model assumptions). △ Less

Submitted 23 January, 2024; originally announced January 2024.

Comments: 61 pages, 13 figures, 4 tables. This preprint has been submitted to and accepted in principle for publication in Nature Astronomy without significant changes

The metal-poor atmosphere of a Neptune/Sub-Neptune planet progenitor

Authors: Saugata Barat, Jean-Michel Désert, Allona Vazan, Robin Baeyens, Michael R. Line, Jonathan J. Fortney, Trevor J. David, John H. Livingston, Bob Jacobs, Vatsal Panwar, Hinna Shivkumar, Kamen O. Todorov, Lorenzo Pino, Georgia Mraz, Erik A. Petigura

Abstract: Young transiting exoplanets offer a unique opportunity to characterize the atmospheres of fresh and evolving products of planet formation. We present the transmission spectrum of V1298 Tau b; a 23 Myr old warm Jovian sized planet orbiting a pre-main sequence star. We detect a primordial atmosphere with an exceptionally large atmospheric scale height and a water vapour absorption at 5$σ$ level of s… ▽ More Young transiting exoplanets offer a unique opportunity to characterize the atmospheres of fresh and evolving products of planet formation. We present the transmission spectrum of V1298 Tau b; a 23 Myr old warm Jovian sized planet orbiting a pre-main sequence star. We detect a primordial atmosphere with an exceptionally large atmospheric scale height and a water vapour absorption at 5$σ$ level of significance. We estimate a mass and density upper limit (24$\pm$5$M_{\oplus}$, 0.12gm/$cm^{3}$ respectively). V1298 Tau b is one of the lowest density planets discovered till date. We retrieve a low atmospheric metallicity (logZ=$-0.1^{+0.66}_{-0.72}$ solar), consistent with solar/sub-solar values. Our findings challenge the expected mass-metallicity from core-accretion theory. Our observations can be explained by in-situ formation via pebble accretion together with ongoing evolutionary mechanisms. We do not detect methane, which hints towards a hotter than expected interior from just the formation entropy of this planet. Our observations suggest that V1298 Tau b is likely to evolve into a Neptune/sub-Neptune type of planet. △ Less

Submitted 28 December, 2023; originally announced December 2023.

Comments: 37 pages, Submitted Nature Astronomy

A Combined Ground-based and JWST Atmospheric Retrieval Analysis: Both IGRINS and NIRSpec Agree The Atmosphere of WASP-77A b is Metal-Poor

Authors: Peter Smith, Michael Line, Jacob Bean, Matteo Brogi, Prune August, Luis Welbanks, Jean-Michel Desert, Jonathan Lunine, Jorge Sanchez, Megan Mansfield, Lorenzo Pino, Emily Rauscher, Eliza Kempton, Joseph Zalesky, Martin Fowler

Abstract: Ground-based, high-resolution and space-based, low-resolution spectroscopy are the two main avenues through which transiting exoplanet atmospheres are studied. Both methods provide unique strengths and shortcomings, and combining the two can be a powerful probe into an exoplanet's atmosphere. Within a joint atmospheric retrieval framework, we combined JWST NIRSpec/G395H secondary eclipse spectra a… ▽ More Ground-based, high-resolution and space-based, low-resolution spectroscopy are the two main avenues through which transiting exoplanet atmospheres are studied. Both methods provide unique strengths and shortcomings, and combining the two can be a powerful probe into an exoplanet's atmosphere. Within a joint atmospheric retrieval framework, we combined JWST NIRSpec/G395H secondary eclipse spectra and Gemini South/IGRINS pre- and post-eclipse thermal eclipse observations of the hot Jupiter WASP-77A b. Our inferences from the IGRINS and NIRSpec data sets are consistent with each other, and combining the two allows us to measure the gas abundances of H$_2$O and CO as well as the vertical thermal structure with higher precision than either data set provided individually. We confirm WASP-77A b's subsolar metallicty ([(C+O)/H]=-0.61$^{+0.10}_{-0.09}$) and solar C/O ratio (C/O = 0.57$^{+0.06}_{-0.06}$). The two types of data are complementary, and our abundance inferences are mostly driven by the IGRINS data while inference of the thermal structure is driven by the NIRSpec data. Our ability to draw inferences from the post-eclipse IGRINS data is highly sensitive to the number of singular values removed in the detrending process, potentially due to high and variable humidity. We also search for signatures for atmospheric dynamics in the IGRINS data and find that propagated ephemeris error can manifest as both an orbital eccentricity or a strong equatorial jet. Neither are detected when using more up-to-date ephemerides. However, we find moderate evidence of thermal inhomogeneity and measure a cooler nightside that presents itself in the later phases after secondary eclipse. △ Less

Submitted 20 December, 2023; originally announced December 2023.

Comments: Accepted to AJ. 31 pages, 19 figures

Retrieving planet formation parameters of WASP-77Ab using SimAb

Authors: N. Khorshid, M. Min, J. M. Désert

Abstract: The atmospheric compositions of planets offer a unique view into their respective formation processes. State-of-the-art observatories and techniques are finally able to provide high-precision data on atmospheric composition that can be used to constrain planet formation. In this context, we focus on the formation of WASP-77Ab based on previous observations of its atmosphere, which have provided pr… ▽ More The atmospheric compositions of planets offer a unique view into their respective formation processes. State-of-the-art observatories and techniques are finally able to provide high-precision data on atmospheric composition that can be used to constrain planet formation. In this context, we focus on the formation of WASP-77Ab based on previous observations of its atmosphere, which have provided precise C/O and metallicity measurements. We use the SimAb planet formation simulation to model the formation of WASP-77Ab. We assume two compositions for the disk WASP-77Ab was formed within: one of a solar composition and one that represents the composition of WASP-77A. In addition, we considered two different scenarios regarding the migration of the planet and we study the possible planet formation paths that reproduce the composition of WASP-77Ab. This work shows that the planet is expected to have formed in a disk where not many planetesimals could be accreted. Moreover, we demonstrate that the most likely migration scenario is disk-free migration, whereby the planet initiates its Type II migration within the CO ice line and ends it beyond the water ice line. △ Less

Submitted 27 November, 2023; originally announced November 2023.

Comments: 10 pages, 9 figures

Journal ref: volum number:675 Year: 2023 Pages:A95

Photodissociation and induced chemical asymmetries on ultra-hot gas giants. A case study of HCN on WASP-76 b

Authors: Robin Baeyens, Jean-Michel Désert, Annemieke Petrignani, Ludmila Carone, Aaron David Schneider

Abstract: Recent observations have resulted in the detection of chemical gradients on ultra-hot gas giants. Notwithstanding their high temperature, chemical reactions in ultra-hot atmospheres may occur in disequilibrium, due to vigorous day-night circulation and intense UV radiation from their stellar hosts. The goal of this work is to explore whether photochemistry is affecting the composition of ultra-hot… ▽ More Recent observations have resulted in the detection of chemical gradients on ultra-hot gas giants. Notwithstanding their high temperature, chemical reactions in ultra-hot atmospheres may occur in disequilibrium, due to vigorous day-night circulation and intense UV radiation from their stellar hosts. The goal of this work is to explore whether photochemistry is affecting the composition of ultra-hot giant planets, and if it can introduce horizontal chemical gradients. In particular, we focus on hydrogen cyanide (HCN) on WASP-76 b, as it is a photochemically active molecule with a reported detection on only one side of this planet. We use a pseudo-2D chemical kinetics code to model the chemical composition of WASP-76 b along its equator. Our approach improves on chemical equilibrium models by computing vertical mixing, horizontal advection, and photochemistry. We find that production of HCN is initiated through thermal and photochemical dissociation of CO and N$_2$ on the day side of WASP-76 b. The resulting radicals are subsequently transported to the night side via the equatorial jet stream, where they recombine into different molecules. This process results in an HCN gradient with a maximal abundance on the planet's morning limb. We verified that photochemical dissociation is a necessary condition for this mechanism, as thermal dissociation alone proves insufficient. Other species produced via night-side disequilibrium chemistry are SO$_2$ and S$_2$. Our model acts as a proof of concept for chemical gradients on ultra-hot exoplanets. We demonstrate that even ultra-hot planets can exhibit disequilibrium chemistry and recommend that future studies do not neglect photochemistry in their analyses of ultra-hot planets. △ Less

Submitted 11 March, 2024; v1 submitted 1 September, 2023; originally announced September 2023.

Comments: 19 pages, 12 figures, accepted for publication in A&A

Journal ref: A&A 686, A24 (2024)

A Non-Detection of Iron in the First High-Resolution Emission Study of the Lava Planet 55 Cnc e

Authors: Kaitlin C. Rasmussen, Miles H. Currie, Celeste Hagee, Christiaan van Buchem, Matej Malik, Arjun B. Savel, Matteo Brogi, Emily Rauscher, Victoria Meadows, Megan Mansfield, Eliza M. R. Kempton, Jean-Michel Desert, Joost P. Wardenier, Lorenzo Pino, Michael Line, Vivien Parmentier, Andreas Seifahrt, David Kasper, Madison Brady, Jacob L. Bean

Abstract: Close-in lava planets represent an extreme example of terrestrial worlds, but their high temperatures may allow us to probe a diversity of crustal compositions. The brightest and most well-studied of these objects is 55 Cancri e, a nearby super-Earth with a remarkably short 17-hour orbit. However, despite numerous studies, debate remains about the existence and composition of its atmosphere. We pr… ▽ More Close-in lava planets represent an extreme example of terrestrial worlds, but their high temperatures may allow us to probe a diversity of crustal compositions. The brightest and most well-studied of these objects is 55 Cancri e, a nearby super-Earth with a remarkably short 17-hour orbit. However, despite numerous studies, debate remains about the existence and composition of its atmosphere. We present upper limits on the atmospheric pressure of 55 Cnc e derived from high-resolution time-series spectra taken with Gemini-N/MAROON-X. Our results are consistent with current crustal evaporation models for this planet which predict a thin $\sim$ 100 mbar atmosphere. We conclude that, if a mineral atmosphere is present on 55 Cnc e, the atmospheric pressure is below 100 mbar. △ Less

Submitted 5 September, 2023; v1 submitted 20 August, 2023; originally announced August 2023.

Comments: Accepted to the AJ. 7 pages, 5 figures

CUTE reveals escaping metals in the upper atmosphere of the ultra-hot Jupiter WASP-189b

Authors: A. G. Sreejith, Kevin France, Luca Fossati, Tommi T. Koskinen, Arika Egan, P. Wilson Cauley, Patricio. E. Cubillos, S. Ambily, Chenliang Huang, 5 Panayotis Lavvas, Brian T. Fleming, Jean-Michel Desert, Nicholas Nell, Pascal Petit, Aline Vidotto

Abstract: Ultraviolet observations of Ultra-hot Jupiters (UHJs), exoplanets with temperatures over 2000\,K, provide us with an opportunity to investigate if and how atmospheric escape shapes their upper atmosphere. Near-ultraviolet transit spectroscopy offers a unique tool to study this process owing to the presence of strong metal lines and a bright photospheric continuum as the light source against which… ▽ More Ultraviolet observations of Ultra-hot Jupiters (UHJs), exoplanets with temperatures over 2000\,K, provide us with an opportunity to investigate if and how atmospheric escape shapes their upper atmosphere. Near-ultraviolet transit spectroscopy offers a unique tool to study this process owing to the presence of strong metal lines and a bright photospheric continuum as the light source against which the absorbing gas is observed. WASP-189b is one of the hottest planets discovered to date, with a day-side temperature of about 3400\,K orbiting a bright A-type star. We present the first near-ultraviolet observations of WASP-189b, acquired with the Colorado Ultraviolet Transit Experiment ($CUTE$). $CUTE$ is a 6U NASA-funded ultraviolet spectroscopy mission, dedicated to monitoring short-period transiting planets. WASP-189b was one of the $CUTE$ early science targets and was observed during three consecutive transits in March 2022. We present an analysis of the $CUTE$ observations and results demonstrating near-ultraviolet (2500--3300~Å) broadband transit depth ($1.08^{+0.08}_{-0.08}\%$) of about twice the visual transit depth indicating that the planet has an extended, hot upper atmosphere with a temperature of about 15000\,K and a moderate mass loss rate of about \SI{4e8}{\kg\per\second}. We observe absorption by Mg{\sc ii} lines ($R_p/R_s$ of $0.212^{+0.038}_{-0.061}$) beyond the Roche lobe at $>$4$σ$ significance in the transmission spectrum at a resolution of 10~Å, while at lower resolution (100~Å), we observe a quasi-continuous absorption signal consistent with a "forest" of low-ionization metal absorption dominated by Fe{\sc ii}. The results suggest an upper atmospheric temperature ($\sim15000$\,K), higher than that predicted by current state-of-the-art hydrodynamic models. △ Less

Submitted 10 August, 2023; originally announced August 2023.

Comments: Accepted for publication in The Astrophysical Journal Letters

Probing reflection from aerosols with the near-infrared dayside spectrum of WASP-80b

Authors: Bob Jacobs, Jean-Michel Désert, Peter Gao, Caroline V. Morley, Jacob Arcangeli, Saugata Barat, Mark S. Marley, Julianne I. Moses, Jonathan J. Fortney, Jacob L. Bean, Kevin B. Stevenson, Vatsal Panwar

Abstract: The presence of aerosols is intimately linked to the global energy budget and the composition of a planet's atmospheres. Their ability to reflect incoming light prevents energy from being deposited into the atmosphere, and they shape spectra of exoplanets. We observed five near-infrared secondary eclipses of WASP-80b with the Wide Field Camera 3 (WFC3) aboard the \textit{Hubble Space Telescope} to… ▽ More The presence of aerosols is intimately linked to the global energy budget and the composition of a planet's atmospheres. Their ability to reflect incoming light prevents energy from being deposited into the atmosphere, and they shape spectra of exoplanets. We observed five near-infrared secondary eclipses of WASP-80b with the Wide Field Camera 3 (WFC3) aboard the \textit{Hubble Space Telescope} to provide constraints on the presence and properties of atmospheric aerosols. We detect a broadband eclipse depth of $34\pm10$\,ppm for WASP-80b. We detect a higher planetary flux than expected from thermal emission alone at $1.6σ$, which hints toward the presence of reflecting aerosols on this planet's dayside, indicating a geometric albedo of $A_g<0.33$ at 3$σ$. We paired the WFC3 data with Spitzer data and explored multiple atmospheric models with and without aerosols to interpret this spectrum. Albeit consistent with a clear dayside atmosphere, we found a slight preference for near-solar metallicities and for dayside clouds over hazes. We exclude soot haze formation rates higher than $10^{-10.7}$ g cm$^{-2}$s$^{-1}$ and tholin formation rates higher than $10^{-12.0}$ g cm$^{-2}$s$^{-1}$ at $3σ$. We applied the same atmospheric models to a previously published WFC3/Spitzer transmission spectrum for this planet and found weak haze formation. A single soot haze formation rate best fits both the dayside and the transmission spectra simultaneously. However, we emphasize that no models provide satisfactory fits in terms of the chi-square of both spectra simultaneously, indicating longitudinal dissimilarity in the atmosphere's aerosol composition. △ Less

Submitted 26 October, 2023; v1 submitted 26 July, 2023; originally announced July 2023.

Comments: Published in ApJ Letters (20 Oct 2023)

Journal ref: ApJL 2023 Volume 956, Number 2, page L43

Detection of carbon monoxide's 4.6 micron fundamental band structure in WASP-39b's atmosphere with JWST NIRSpec G395H

Authors: David Grant, Joshua D. Lothringer, Hannah R. Wakeford, Munazza K. Alam, Lili Alderson, Jacob L. Bean, Björn Benneke, Jean-Michel Désert, Tansu Daylan, Laura Flagg, Renyu Hu, Julie Inglis, James Kirk, Laura Kreidberg, Mercedes López-Morales, Luigi Mancini, Thomas Mikal-Evans, Karan Molaverdikhani, Enric Palle, Benjamin V. Rackham, Seth Redfield, Kevin B. Stevenson, Jeff Valenti, Nicole L. Wallack, Keshav Aggarwal , et al. (6 additional authors not shown)

Abstract: Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres, and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad double-branched structure composed of many individual absorption lines from 4.3 to 5.1 $\mathrmμ$m, which can now be spectrosco… ▽ More Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres, and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad double-branched structure composed of many individual absorption lines from 4.3 to 5.1 $\mathrmμ$m, which can now be spectroscopically measured with JWST. Here we present a technique for detecting the rotational sub-band structure of CO at medium resolution with the NIRSpec G395H instrument. We use a single transit observation of the hot Jupiter WASP-39b from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program at the native resolution of the instrument ($R \,{\sim} 2700$) to resolve the CO absorption structure. We robustly detect absorption by CO, with an increase in transit depth of 264 $\pm$ 68 ppm, in agreement with the predicted CO contribution from the best-fit model at low resolution. This detection confirms our theoretical expectations that CO is the dominant carbon-bearing molecule in WASP-39b's atmosphere, and further supports the conclusions of low C/O and super-solar metallicities presented in the JTEC ERS papers for WASP-39b. △ Less

Submitted 24 April, 2023; originally announced April 2023.

Comments: 11 pages, 5 figures, accepted for publication in ApJL

Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X

Authors: James Sikora, Jason Rowe, Saugata Barat, Jacob L. Bean, Madison Brady, Jean-Michel Désert, Adina D. Feinstein, Emily A. Gilbert, Gregory Henry, David Kasper, Déreck-Alexandre Lizotte, Michael R. B. Matesic, Vatsal Panwar, Andreas Seifahrt, Hinna Shivkumar, Gudmundur Stefánsson, Julian Stürmer

Abstract: The early K-type T-Tauri star, V1298 Tau ($V=10\,{\rm mag}$, ${\rm age}\approx20-30\,{\rm Myr}$) hosts four transiting planets with radii ranging from $4.9-9.6\,R_\oplus$. The three inner planets have orbital periods of $\approx8-24\,{\rm d}$ while the outer planet's period is poorly constrained by single transits observed with \emph{K2} and \emph{TESS}. Planets b, c, and d are proto-sub-Neptunes… ▽ More The early K-type T-Tauri star, V1298 Tau ($V=10\,{\rm mag}$, ${\rm age}\approx20-30\,{\rm Myr}$) hosts four transiting planets with radii ranging from $4.9-9.6\,R_\oplus$. The three inner planets have orbital periods of $\approx8-24\,{\rm d}$ while the outer planet's period is poorly constrained by single transits observed with \emph{K2} and \emph{TESS}. Planets b, c, and d are proto-sub-Neptunes that may be undergoing significant mass loss. Depending on the stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. Here we present results of a joint transit and radial velocity (RV) modelling analysis, which includes recently obtained \emph{TESS} photometry and MAROON-X RV measurements. Assuming circular orbits, we obtain a low-significance ($\approx2σ$) RV detection of planet c implying a mass of $19.8_{-8.9}^{+9.3}\,M_\oplus$ and a conservative $2σ$ upper limit of $<39\,M_\oplus$. For planets b and d, we derive $2σ$ upper limits of $M_{\rm b}<159\,M_\oplus$ and $M_{\rm d}<41\,M_\oplus$. For planet e, plausible discrete periods of $P_{\rm e}>55.4\,{\rm d}$ are ruled out at a $3σ$ level while seven solutions with $43.3<P_{\rm e}/{\rm d}<55.4$ are consistent with the most probable $46.768131\pm000076\,{\rm d}$ solution within $3σ$. Adopting the most probable solution yields a $2.6σ$ RV detection with mass a of $0.66\pm0.26\,M_{\rm Jup}$. Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets and that planet c is consistent with having a water-rich core with a substantial ($\sim5\%$ by mass) H$_2$ envelope. △ Less

Submitted 3 April, 2023; originally announced April 2023.

Comments: 18 pages, 13 figures, accepted for publication in AJ

A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b

Authors: Louis-Philippe Coulombe, Björn Benneke, Ryan Challener, Anjali A. A. Piette, Lindsey S. Wiser, Megan Mansfield, Ryan J. MacDonald, Hayley Beltz, Adina D. Feinstein, Michael Radica, Arjun B. Savel, Leonardo A. Dos Santos, Jacob L. Bean, Vivien Parmentier, Ian Wong, Emily Rauscher, Thaddeus D. Komacek, Eliza M. -R. Kempton, Xianyu Tan, Mark Hammond, Neil T. Lewis, Michael R. Line, Elspeth K. H. Lee, Hinna Shivkumar, Ian J. M. Crossfield , et al. (51 additional authors not shown)

Abstract: Close-in giant exoplanets with temperatures greater than 2,000 K (''ultra-hot Jupiters'') have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from the Hubble and Spitzer Space Telescopes. However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information conten… ▽ More Close-in giant exoplanets with temperatures greater than 2,000 K (''ultra-hot Jupiters'') have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from the Hubble and Spitzer Space Telescopes. However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information content of the data resulted in high sensitivity to the varying assumptions made in the treatment of instrument systematics and the atmospheric retrieval analysis. Here we present a dayside thermal emission spectrum of the ultra-hot Jupiter WASP-18b obtained with the NIRISS instrument on JWST. The data span 0.85 to 2.85 $μ$m in wavelength at an average resolving power of 400 and exhibit minimal systematics. The spectrum shows three water emission features (at $>$6$σ$ confidence) and evidence for optical opacity, possibly due to H$^-$, TiO, and VO (combined significance of 3.8$σ$). Models that fit the data require a thermal inversion, molecular dissociation as predicted by chemical equilibrium, a solar heavy element abundance (''metallicity'', M/H = 1.03$_{-0.51}^{+1.11}$ $\times$ solar), and a carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside brightness temperature map, which shows a peak in temperature near the sub-stellar point that decreases steeply and symmetrically with longitude toward the terminators. △ Less

Submitted 20 January, 2023; v1 submitted 19 January, 2023; originally announced January 2023.

Comments: JWST ERS bright star observations. Uploaded to inform JWST Cycle 2 proposals. Manuscript under review. 50 pages, 14 figures, 2 tables

The Colorado Ultraviolet Transit Experiment (CUTE) Mission Overview

Authors: Kevin France, Brian Fleming, Arika Egan, Jean-Michel Desert, Luca Fossati, Tommi T. Koskinen, Nicholas Nell, Pascal Petit, Aline A. Vidotto, Matthew Beasley, Nicholas DeCicco, Aickara Gopinathan Sreejith, Ambily Suresh, Jared Baumert, P. Wilson Cauley, Carolina Villarreal DAngelo, Keri Hoadley, Robert Kane, Richard Kohnert, Julian Lambert, Stefan Ulrich

Abstract: Atmospheric escape is a fundamental process that affects the structure, composition, and evolution of many planets. The signatures of escape are detectable on close-in, gaseous exoplanets orbiting bright stars, owing to the high levels of extreme-ultraviolet irradiation from their parent stars. The Colorado Ultraviolet Transit Experiment (CUTE) is a CubeSat mission designed to take advantage of th… ▽ More Atmospheric escape is a fundamental process that affects the structure, composition, and evolution of many planets. The signatures of escape are detectable on close-in, gaseous exoplanets orbiting bright stars, owing to the high levels of extreme-ultraviolet irradiation from their parent stars. The Colorado Ultraviolet Transit Experiment (CUTE) is a CubeSat mission designed to take advantage of the near-ultraviolet stellar brightness distribution to conduct a survey of the extended atmospheres of nearby close-in planets. The CUTE payload is a magnifying NUV (2479~--~3306 Ang) spectrograph fed by a rectangular Cassegrain telescope (206mm x 84mm); the spectrogram is recorded on a back-illuminated, UV-enhanced CCD. The science payload is integrated into a 6U Blue Canyon Technology XB1 bus. CUTE was launched into a polar, low-Earth orbit on 27 September 2021 and has been conducting this transit spectroscopy survey following an on-orbit commissioning period. This paper presents the mission motivation, development path, and demonstrates the potential for small satellites to conduct this type of science by presenting initial on-orbit science observations. The primary science mission is being conducted in 2022~--~2023, with a publicly available data archive coming on line in 2023. △ Less

Submitted 5 January, 2023; originally announced January 2023.

Comments: 12 pages, 5 figures, AJ - accepted

Early Release Science of the exoplanet WASP-39b with JWST NIRISS

Authors: Adina D. Feinstein, Michael Radica, Luis Welbanks, Catriona Anne Murray, Kazumasa Ohno, Louis-Philippe Coulombe, Néstor Espinoza, Jacob L. Bean, Johanna K. Teske, Björn Benneke, Michael R. Line, Zafar Rustamkulov, Arianna Saba, Angelos Tsiaras, Joanna K. Barstow, Jonathan J. Fortney, Peter Gao, Heather A. Knutson, Ryan J. MacDonald, Thomas Mikal-Evans, Benjamin V. Rackham, Jake Taylor, Vivien Parmentier, Natalie M. Batalha, Zachory K. Berta-Thompson , et al. (64 additional authors not shown)

Abstract: Transmission spectroscopy provides insight into the atmospheric properties and consequently the formation history, physics, and chemistry of transiting exoplanets. However, obtaining precise inferences of atmospheric properties from transmission spectra requires simultaneously measuring the strength and shape of multiple spectral absorption features from a wide range of chemical species. This has… ▽ More Transmission spectroscopy provides insight into the atmospheric properties and consequently the formation history, physics, and chemistry of transiting exoplanets. However, obtaining precise inferences of atmospheric properties from transmission spectra requires simultaneously measuring the strength and shape of multiple spectral absorption features from a wide range of chemical species. This has been challenging given the precision and wavelength coverage of previous observatories. Here, we present the transmission spectrum of the Saturn-mass exoplanet WASP-39b obtained using the SOSS mode of the NIRISS instrument on the JWST. This spectrum spans $0.6 - 2.8 μ$m in wavelength and reveals multiple water absorption bands, the potassium resonance doublet, as well as signatures of clouds. The precision and broad wavelength coverage of NIRISS-SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favoring a heavy element enhancement ("metallicity") of $\sim 10 - 30 \times$ the solar value, a sub-solar carbon-to-oxygen (C/O) ratio, and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are best explained by wavelength-dependent, non-gray clouds with inhomogeneous coverage of the planet's terminator. △ Less

Submitted 18 November, 2022; originally announced November 2022.

Comments: 48 pages, 12 figures, 2 tables. Under review at Nature

Photochemically-produced SO$_2$ in the atmosphere of WASP-39b

Authors: Shang-Min Tsai, Elspeth K. H. Lee, Diana Powell, Peter Gao, Xi Zhang, Julianne Moses, Eric Hébrard, Olivia Venot, Vivien Parmentier, Sean Jordan, Renyu Hu, Munazza K. Alam, Lili Alderson, Natalie M. Batalha, Jacob L. Bean, Björn Benneke, Carver J. Bierson, Ryan P. Brady, Ludmila Carone, Aarynn L. Carter, Katy L. Chubb, Julie Inglis, Jérémy Leconte, Mercedes Lopez-Morales, Yamila Miguel , et al. (60 additional authors not shown)

Abstract: Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability. However, no unambiguous photochemical products have been detected in exoplanet atmospheres to date. Recent observations from the JWST Transiting Exoplanet Early Release Science Program found a spectral absorption feature at 4.05 $μ$m arising from SO$_2$ in the atmosphere of WA… ▽ More Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability. However, no unambiguous photochemical products have been detected in exoplanet atmospheres to date. Recent observations from the JWST Transiting Exoplanet Early Release Science Program found a spectral absorption feature at 4.05 $μ$m arising from SO$_2$ in the atmosphere of WASP-39b. WASP-39b is a 1.27-Jupiter-radii, Saturn-mass (0.28 M$_J$) gas giant exoplanet orbiting a Sun-like star with an equilibrium temperature of $\sim$1100 K. The most plausible way of generating SO$_2$ in such an atmosphere is through photochemical processes. Here we show that the SO$_2$ distribution computed by a suite of photochemical models robustly explains the 4.05 $μ$m spectral feature identified by JWST transmission observations with NIRSpec PRISM (2.7$σ$) and G395H (4.5$σ$). SO$_2$ is produced by successive oxidation of sulphur radicals freed when hydrogen sulphide (H$_2$S) is destroyed. The sensitivity of the SO$_2$ feature to the enrichment of the atmosphere by heavy elements (metallicity) suggests that it can be used as a tracer of atmospheric properties, with WASP-39b exhibiting an inferred metallicity of $\sim$10$\times$ solar. We further point out that SO$_2$ also shows observable features at ultraviolet and thermal infrared wavelengths not available from the existing observations. △ Less

Submitted 24 March, 2023; v1 submitted 18 November, 2022; originally announced November 2022.

Comments: 39 pages, 14 figures, accepted to be published in Nature

Early Release Science of the exoplanet WASP-39b with JWST NIRCam

Authors: Eva-Maria Ahrer, Kevin B. Stevenson, Megan Mansfield, Sarah E. Moran, Jonathan Brande, Giuseppe Morello, Catriona A. Murray, Nikolay K. Nikolov, Dominique J. M. Petit dit de la Roche, Everett Schlawin, Peter J. Wheatley, Sebastian Zieba, Natasha E. Batalha, Mario Damiano, Jayesh M Goyal, Monika Lendl, Joshua D. Lothringer, Sagnick Mukherjee, Kazumasa Ohno, Natalie M. Batalha, Matthew P. Battley, Jacob L. Bean, Thomas G. Beatty, Björn Benneke, Zachory K. Berta-Thompson , et al. (74 additional authors not shown)

Abstract: Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength covera… ▽ More Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution, and high precision that, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0 - 4.0 $μ$m, exhibit minimal systematics, and reveal well-defined molecular absorption features in the planet's spectrum. Specifically, we detect gaseous H$_2$O in the atmosphere and place an upper limit on the abundance of CH$_4$. The otherwise prominent CO$_2$ feature at 2.8 $μ$m is largely masked by H$_2$O. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1-100$\times$ solar (i.e., an enrichment of elements heavier than helium relative to the Sun) and a sub-stellar carbon-to-oxygen (C/O) ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation or disequilibrium processes in the upper atmosphere. △ Less

Submitted 18 November, 2022; originally announced November 2022.

Comments: 35 pages, 13 figures, 3 tables, Nature, accepted

Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H

Authors: Lili Alderson, Hannah R. Wakeford, Munazza K. Alam, Natasha E. Batalha, Joshua D. Lothringer, Jea Adams Redai, Saugata Barat, Jonathan Brande, Mario Damiano, Tansu Daylan, Néstor Espinoza, Laura Flagg, Jayesh M. Goyal, David Grant, Renyu Hu, Julie Inglis, Elspeth K. H. Lee, Thomas Mikal-Evans, Lakeisha Ramos-Rosado, Pierre-Alexis Roy, Nicole L. Wallack, Natalie M. Batalha, Jacob L. Bean, Björn Benneke, Zachory K. Berta-Thompson , et al. (67 additional authors not shown)

Abstract: Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based and high-resolution ground-based facilities. Here we report the m… ▽ More Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based and high-resolution ground-based facilities. Here we report the medium-resolution (R$\sim$600) transmission spectrum of an exoplanet atmosphere between 3-5 $μ$m covering multiple absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST NIRSpec G395H. Our observations achieve 1.46x photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO$_2$ (28.5$σ$) and H$_2$O (21.5$σ$), and identify SO$_2$ as the source of absorption at 4.1 $μ$m (4.8$σ$). Best-fit atmospheric models range between 3 and 10x solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO$_2$, underscore the importance of characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec G395H as an excellent mode for time series observations over this critical wavelength range. △ Less

Submitted 18 November, 2022; originally announced November 2022.

Comments: 44 pages, 11 figures, 3 tables. Resubmitted after revision to Nature

Early Release Science of the exoplanet WASP-39b with JWST NIRSpec PRISM

Authors: Z. Rustamkulov, D. K. Sing, S. Mukherjee, E. M. May, J. Kirk, E. Schlawin, M. R. Line, C. Piaulet, A. L. Carter, N. E. Batalha, J. M. Goyal, M. López-Morales, J. D. Lothringer, R. J. MacDonald, S. E. Moran, K. B. Stevenson, H. R. Wakeford, N. Espinoza, J. L. Bean, N. M. Batalha, B. Benneke, Z. K. Berta-Thompson, I. J. M. Crossfield, P. Gao, L. Kreidberg , et al. (69 additional authors not shown)

Abstract: Transmission spectroscopy of exoplanets has revealed signatures of water vapor, aerosols, and alkali metals in a few dozen exoplanet atmospheres. However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations' relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species… ▽ More Transmission spectroscopy of exoplanets has revealed signatures of water vapor, aerosols, and alkali metals in a few dozen exoplanet atmospheres. However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations' relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species$-$in particular the primary carbon-bearing molecules. Here we report a broad-wavelength 0.5-5.5 $μ$m atmospheric transmission spectrum of WASP-39 b, a 1200 K, roughly Saturn-mass, Jupiter-radius exoplanet, measured with JWST NIRSpec's PRISM mode as part of the JWST Transiting Exoplanet Community Early Release Science Team program. We robustly detect multiple chemical species at high significance, including Na (19$σ$), H$_2$O (33$σ$), CO$_2$ (28$σ$), and CO (7$σ$). The non-detection of CH$_4$, combined with a strong CO$_2$ feature, favours atmospheric models with a super-solar atmospheric metallicity. An unanticipated absorption feature at 4$μ$m is best explained by SO$_2$ (2.7$σ$), which could be a tracer of atmospheric photochemistry. These observations demonstrate JWST's sensitivity to a rich diversity of exoplanet compositions and chemical processes. △ Less

Submitted 18 November, 2022; originally announced November 2022.

Comments: 41 pages, 4 main figures, 10 extended data figures, 4 tables. Under review in Nature

A strong H- opacity signal in the near-infrared emission spectrum of the ultra-hot Jupiter KELT-9b

Authors: Bob Jacobs, Jean-Michel Désert, Lorenzo Pino, Michael R. Line, Jacob L. Bean, Niloofar Khorshid, Everett Schlawin, Jacob Arcangeli, Saugata Barat, H. Jens Hoeijmakers, Thaddeus D. Komacek, Megan Mansfield, Vivien Parmentier, Daniel Thorngren

Abstract: We present the analysis of a spectroscopic secondary eclipse of the hottest transiting exoplanet detected to date, KELT-9b, obtained with the Wide Field Camera 3 aboard the Hubble Space Telescope. We complement these data with literature information on stellar pulsations and Spitzer/Infrared Array Camera and Transiting Exoplanet Survey Satellite eclipse depths of this target to obtain a broadban… ▽ More We present the analysis of a spectroscopic secondary eclipse of the hottest transiting exoplanet detected to date, KELT-9b, obtained with the Wide Field Camera 3 aboard the Hubble Space Telescope. We complement these data with literature information on stellar pulsations and Spitzer/Infrared Array Camera and Transiting Exoplanet Survey Satellite eclipse depths of this target to obtain a broadband thermal emission spectrum. Our extracted spectrum exhibits a clear turnoff at 1.4$μ$m. This points to H$^{-}$ bound-free opacities shaping the spectrum. To interpret the spectrum, we perform grid retrievals of self-consistent 1D equilibrium chemistry forward models, varying the composition and energy budget. The model with solar metallicity and C/O ratio provides a poor fit because the H$^{-}$ signal is stronger than expected, requiring an excess of electrons. This pushes our retrievals toward high atmospheric metallicities ($[M/H]=1.98^{+0.19}_{-0.21}$) and a C/O ratio that is subsolar by 2.4$σ$. We question the viability of forming such a high-metallicity planet, and therefore provide other scenarios to increase the electron density in this atmosphere. We also look at an alternative model in which we quench TiO and VO. This fit results in an atmosphere with a slightly subsolar metallicity and subsolar C/O ratio ($[M/H]=-0.22^{+0.17}_{-0.13}$, log(C/O)$=-0.34^{+0.19}_{-0.34}$). However, the required TiO abundances are disputed by recent high-resolution measurements of the same planet. △ Less

Submitted 18 November, 2022; originally announced November 2022.

Comments: 8 pages, 4 figures, Accepted for publication in A&A letters

Journal ref: A&A 668, L1 (2022)

The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultra Hot Jupiter WASP-18 b

Authors: Matteo Brogi, Vanessa Emeka-Okafor, Michael R. Line, Siddharth Gandhi, Lorenzo Pino, Eliza M. -R. Kempton, Emily Rauscher, Vivien Parmentier, Jacob L. Bean, Gregory N. Mace, Nicolas B. Cowan, Evgenya Shkolnik, Joost P. Wardenier, Megan Mansfield, Luis Welbanks, Peter Smith, Jonathan J. Fortney, Jayne L. Birkby, Joseph A. Zalesky, Lisa Dang, Jennifer Patience, Jean-Michel Désert

Abstract: We present high-resolution dayside thermal emission observations of the exoplanet WASP-18b using IGRINS on Gemini South. We remove stellar and telluric signatures using standard algorithms, and we extract the planet signal via cross correlation with model spectra. We detect the atmosphere of WASP-18b at a signal-to-noise ratio (SNR) of 5.9 using a full chemistry model, measure H2O (SNR=3.3), CO (S… ▽ More We present high-resolution dayside thermal emission observations of the exoplanet WASP-18b using IGRINS on Gemini South. We remove stellar and telluric signatures using standard algorithms, and we extract the planet signal via cross correlation with model spectra. We detect the atmosphere of WASP-18b at a signal-to-noise ratio (SNR) of 5.9 using a full chemistry model, measure H2O (SNR=3.3), CO (SNR=4.0), and OH (SNR=4.8) individually, and confirm previous claims of a thermal inversion layer. The three species are confidently detected (>4$σ$) with a Bayesian inference framework, which we also use to retrieve abundance, temperature, and velocity information. For this ultra-hot Jupiter (UHJ), thermal dissociation processes likely play an important role. Retrieving abundances constant with altitude and allowing the temperature-pressure profile to freely adjust results in a moderately super-stellar carbon to oxygen ratio (C/O=0.75^{+0.14}_{-0.17}) and metallicity ([M/H]=1.03^{+0.65}_{-1.01}). Accounting for undetectable oxygen produced by thermal dissociation leads to C/O=0.45^{+0.08}_{-0.10} and [M/H]=1.17^{+0.66}_{-1.01}. A retrieval that assumes radiative-convective-thermochemical-equilibrium and naturally accounts for thermal dissociation constrains C/O<0.34 (2$σ$) and [M/H]=0.48^{+0.33}_{-0.29}, in line with the chemistry of the parent star. Looking at the velocity information, we see a tantalising signature of different Doppler shifts at the level of a few km/s for different molecules, which might probe dynamics as a function of altitude and location on the planet disk. Our results demonstrate that ground-based, high-resolution spectroscopy at infrared wavelengths can provide meaningful constraints on the compositions and climate of highly irradiated planets. This work also elucidates potential pitfalls with commonly employed retrieval assumptions when applied to UHJ spectra. △ Less

Submitted 30 September, 2022; originally announced September 2022.

Comments: 27 pages, 18 figures, submitted to AAS Journals. Community feedback welcome

The GAPS Programme at TNG. XLI. The climate of KELT-9b revealed with a new approach to high spectral resolution phase curves

Authors: L. Pino, M. Brogi, J. M. Désert, V. Nascimbeni, A. S. Bonomo, E. Rauscher, M. Basilicata, K. Biazzo, A. Bignamini, F. Borsa, R. Claudi, E. Covino, M. P. Di Mauro, G. Guilluy, A. Maggio, L. Malavolta, G. Micela, E. Molinari, M. Molinaro, M. Montalto, D. Nardiello, M. Pedani, G. Piotto, E. Poretti, M. Rainer , et al. (3 additional authors not shown)

Abstract: [Abridged] We present a novel method to study the thermal emission of exoplanets as a function of orbital phase at very high spectral resolution, and apply it to investigate the climate of the ultra-hot Jupiter KELT-9b. We combine 3 nights of HARPS-N and 2 nights of CARMENES optical spectra, covering orbital phases between quadratures (0.25 < phi < 0.75), when the planet shows its day-side hemisph… ▽ More [Abridged] We present a novel method to study the thermal emission of exoplanets as a function of orbital phase at very high spectral resolution, and apply it to investigate the climate of the ultra-hot Jupiter KELT-9b. We combine 3 nights of HARPS-N and 2 nights of CARMENES optical spectra, covering orbital phases between quadratures (0.25 < phi < 0.75), when the planet shows its day-side hemisphere with different geometries. We co-add the signal of thousands of FeI lines through cross-correlation, which we map to a likelihood function. We investigate the phase-dependence of: (i) the line depths of FeI, and (ii) their Doppler shifts, by introducing a new method that exploits the very high spectral resolution of our observations. We confirm a previous detection of FeI emission and demonstrate a combined precision of 0.5 km s-1 on the orbital properties of KELT-9b. By studying the phase-resolved Doppler shift of FeI lines, we detect an anomaly in the planet's orbital radial velocity well-fitted with a slightly eccentric orbit (e = 0.016$\pm$0.003, w = 150$^{+13\circ}_{-11},~5σ$ preference). However, we argue that such anomaly can be explained by a day-night wind of a few km s-1 blowing neutral iron gas. Additionally, we find that the FeI emission line depths are symmetric around the substellar point within 10 deg ($2σ$). We show that these results are qualitatively compatible with predictions from general circulation models for ultra-hot Jupiter planets. Very high-resolution spectroscopy phase curves have the sensitivity to reveal a phase dependence in both the line depths and their Doppler shifts throughout the orbit. They are highly complementary to space-based phase curves obtained with HST and JWST, and open a new window into the still poorly understood climate and atmospheric structure of the hottest planets known. △ Less

Submitted 23 September, 2022; originally announced September 2022.

Comments: Recommended for publication on A&A after referee report, awaiting acceptance. 25 pages, 19 figures, 3 tables

Journal ref: A&A 668, A176 (2022)