Showing 1–50 of 335 results for author: Zhang, K

The Brown-dwarf Desert Persists as a Mass-ratio Desert around Low-mass Stars

Authors: Keming Zhang

Abstract: Sun-like stars are known to host a paucity of brown dwarf companions at close separations. Direct imaging surveys of intermediate-mass stars have suggested that the brown dwarf desert may be fundamentally a feature in the mass ratio. Microlensing surveys provide a unique opportunity to investigate the nature of this desert around low mass stars, as microlensing hosts have typical masses of 0.05-0.… ▽ More Sun-like stars are known to host a paucity of brown dwarf companions at close separations. Direct imaging surveys of intermediate-mass stars have suggested that the brown dwarf desert may be fundamentally a feature in the mass ratio. Microlensing surveys provide a unique opportunity to investigate the nature of this desert around low mass stars, as microlensing hosts have typical masses of 0.05-0.8 $M_\odot$. Here, we perform a statistical analysis of homogeneously selected binary-lens microlensing events in the literature, and identify a companion mass-ratio desert at $0.02\lesssim q\lesssim0.05$ and projected separations around 1-5 au. We derive a statistically significant truncation to the giant-planet mass-ratio distribution at $q\simeq0.02$, above which the occurrence rate density drops by approximately an order of magnitude. Due to the possibility that the small number of detected companions in this desert orbit white dwarfs, this mass-ratio desert may be closer to being completely dry around main-sequence stars. Below this desert, we derive a giant-planet ($q>4\times10^{-4}$) occurrence rate density of $5.8\pm0.8$% per decade of projected separation. Our analysis furthers the hypothesis that the brown dwarf desert is fundamentally a feature in the mass ratio, separating distinct populations of planetary and non-planetary companions that are likely formed via core accretion and gravitational instability, respectively. The persistence of this desert across stellar types suggests that both gas-giant planets and sub-stellar companions form in a scale-invariant fashion, with planets growing to a maximum of approximately 2% their host masses. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Comments: Accepted to ApJ Letters. 11 pages, 3 figures. Comments welcome

Journal ref: ApJL 995 L55 (2025)

Stability of Neutron-Dark Matter Mixed Stars and Hybrid Stars

Authors: Xiao-Ding Zhou, Tian-Shun Chen, Si-Man Wu, Kilar Zhang

Abstract: Concerning the stability of two-fluid star models, we prove the rigorous equivalence of two independent determining methods for mixed stars, after a brief review of the hybrid star case. Our derivations apply to general multi-fluid cases, and here we take dark matter admixed neutron star models for example, demonstrating a stability boundary distinct from the single-fluid case. Stable configuratio… ▽ More Concerning the stability of two-fluid star models, we prove the rigorous equivalence of two independent determining methods for mixed stars, after a brief review of the hybrid star case. Our derivations apply to general multi-fluid cases, and here we take dark matter admixed neutron star models for example, demonstrating a stability boundary distinct from the single-fluid case. Stable configurations form a surface in the three-dimensional parameter space of (either) central pressure, mass, and radius, which yields a group containing stable mixed stars. This group includes twin stars with identical masses and radii but different interior structures. These results can help interpret compact star observations and constrain dark matter properties through astrophysics. △ Less

Submitted 1 December, 2025; originally announced December 2025.

Comments: 23 pages, 10 figures, 1 table

Equivalence of Stability Criteria for Multi-Fluid Stars

Authors: Tian-Shun Chen, Xiao-Ding Zhou, Kilar Zhang

Abstract: We present a rigorous proof establishing the mathematical equivalence between two independent criteria for the marginal stability of multi-fluid relativistic stars: the dynamical criterion based on the vanishing of the fundamental radial pulsation mode's eigenfrequency, and the static criterion derived from the geometric alignment of mass and particle number gradients in the parameter space. Lever… ▽ More We present a rigorous proof establishing the mathematical equivalence between two independent criteria for the marginal stability of multi-fluid relativistic stars: the dynamical criterion based on the vanishing of the fundamental radial pulsation mode's eigenfrequency, and the static criterion derived from the geometric alignment of mass and particle number gradients in the parameter space. Leveraging this equivalence, we introduce a powerful and computationally efficient framework as an upgraded version of the critical curve method, to systematically map the stability boundaries for multi-fluid mixed stars across the entire parameter space of central pressures. Our analysis, applied to a variety of nuclear and dark matter equations of state, reveals the existence of stable region in the observable mass-radius diagram. By resolving degeneracies with 3-dimensional Mass-Radius-Pressure diagrams, we provide a complete topological view of the ensemble. This work supplies a robust theoretical foundation for interpreting multi-messenger astronomical observations and constraining the properties of dark matter. △ Less

Submitted 1 December, 2025; originally announced December 2025.

Comments: 8 pages, 5 figures

Investigating the Impacts of AGN Activities on Dwarf Galaxies with FAST HI Observations

Authors: Hong-Ying Chen, Chao-Wei Tsai, Pei Zuo, Niankun Yu, Jialai Wang, Kai Zhang, Guodong Li, Yogesh Chandola, Zheng Zheng, Jingwen Wu, Di Li, Lulu Bao

Abstract: We present the results of Hi line observations towards 26 Active Galactic Nuclei (AGN)-hosting and one star-forming dwarf galaxies (Mstar < 10^9.5 Msun) with the 19-beam spectral line receiver of FAST at 1.4 GHz. Our FAST observed targets are combined with other AGN-hosting dwarf galaxies covered in the ALFALFA footprint to form a more comprehensive sample. Utilizing the information from optical s… ▽ More We present the results of Hi line observations towards 26 Active Galactic Nuclei (AGN)-hosting and one star-forming dwarf galaxies (Mstar < 10^9.5 Msun) with the 19-beam spectral line receiver of FAST at 1.4 GHz. Our FAST observed targets are combined with other AGN-hosting dwarf galaxies covered in the ALFALFA footprint to form a more comprehensive sample. Utilizing the information from optical surveys, we further divide them into isolated and accompanied subsamples by their vicinity of nearby massive galaxies. We compare the Hi gas abundance and star-forming rate (SFR) between the subsamples to assess the role of internal and external processes that may regulate the gas content in dwarf galaxies. As a result, we find that AGN are more commonly identified in accompanied dwarf galaxies than in their isolated counterparts. Meanwhile, AGN-hosting dwarf galaxies have slightly but significant lower Hi mass fraction relatively to the non-AGN control sample in accompanied dwarf galaxies. On the other hand, we find a decreasing SFR in AGN-hosting dwarf galaxies towards denser environments, as well as an extremely low incidence of quenched isolated dwarfs within both AGN and non-AGN subsamples. These results indicate that although these AGN could potentially regulate the gas reservoir of dwarf galaxies, environmental effects are likely the dominant quenching mechanism in the low-mass universe. △ Less

Submitted 28 November, 2025; originally announced November 2025.

Comments: 24 pages, 6 figures

Journal ref: Monthly Notices of the Royal Astronomical Society, Volume 544, Issue 3, pp. 2713-2736 (2025)

A Submillimeter Survey of CS Excitation in Protoplanetary Disks: Evidence of X-ray-Driven Sulfur Chemistry

Authors: Charles J. Law, Romane Le Gal, Karin I. Öberg, Ke Zhang, Yuri Aikawa, Sean M. Andrews, Jaehan Bae, Alice S. Booth, Gianni Cataldi, L. Ilsedore Cleeves, Feng Long, François Ménard, Chunhua Qi, Richard Teague, David J. Wilner

Abstract: The sulfur chemistry in protoplanetary disks influences the properties of nascent planets, including potential habitability. Although the inventory of sulfur molecules in disks has gradually increased over the last decade, CS is still the most commonly-observed sulfur-bearing species and it is expected to be the dominant gas-phase sulfur carrier beyond the water snowline. Despite this, few dedicat… ▽ More The sulfur chemistry in protoplanetary disks influences the properties of nascent planets, including potential habitability. Although the inventory of sulfur molecules in disks has gradually increased over the last decade, CS is still the most commonly-observed sulfur-bearing species and it is expected to be the dominant gas-phase sulfur carrier beyond the water snowline. Despite this, few dedicated multi-line observations exist, and thus the typical disk CS chemistry is not well constrained. Moreover, it is unclear how that chemistry - and in turn, the bulk volatile sulfur reservoir - varies with stellar and disk properties. Here, we present the largest survey of CS to date, combining both new and archival observations from ALMA, SMA, and NOEMA of 12 planet-forming disks, covering a range of stellar spectral types and dust morphologies. Using these data, we derived disk-integrated CS gas excitation conditions in each source. Overall, CS chemistry appears similar across our sample with rotational temperatures of ${\approx}$10-40 K and column densities between 10$^{12}$-10$^{13}$ cm$^{-2}$. CS column densities do not show strong trends with most source properties, which broadly suggests that CS chemistry is not highly sensitive to disk structure or stellar characteristics. We do, however, identify a positive correlation between stellar X-ray luminosity and CS column density, which indicates that the dominant CS formation pathway is likely via ion-neutral reactions in the upper disk layers, where X-ray-enhanced S$^+$ and C$^+$ drive abundant CS production. Thus, using CS as a tracer of gas-phase sulfur abundance requires a nuanced approach that accounts for its emitting region and dependence on X-ray luminosity. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 24 pages, 12 figures, accepted for publication in ApJ

Searching for Exoplanets Born Outside the Milky Way: VOYAGERS Survey Design

Authors: Robert Aloisi, Andrew Vanderburg, Melinda Soares-Furtado, Phillip Cargile, Ke Zhang, Lina Necib, David W. Latham, Sam Quinn, Emily Pass, Anne Dattilo, Giacomo Mantovan, Francesco Amadori, Mariona Badenas-Agusti, Perry Berlind, Francesco Borsa, Walter Boschin, Lorenzo Cabona, Michael L. Calkins, Hans J. Deeg, Xavier Dumusque, Gilbert A. Esquerdo, Yoshi Nike Emilia Eschen, S. Filomeno, S. Geraldía-González, Natalia Guerrero , et al. (22 additional authors not shown)

Abstract: Observations over the past few decades have found that planets are common around nearby stars in our Galaxy, but little is known about planets that formed outside the Milky Way. We describe the design and early implementation of a survey to test whether planets also exist orbiting the remnant stars of ancient dwarf galaxies that merged with the Milky Way, and if so, how they differ from their Milk… ▽ More Observations over the past few decades have found that planets are common around nearby stars in our Galaxy, but little is known about planets that formed outside the Milky Way. We describe the design and early implementation of a survey to test whether planets also exist orbiting the remnant stars of ancient dwarf galaxies that merged with the Milky Way, and if so, how they differ from their Milky Way counterparts. VOYAGERS (Views Of Yore - Ancient Gaia-enceladus Exoplanet Revealing Survey) is a radial velocity (RV) search using precision spectrographs to discover exoplanets orbiting very low metallicity ($-2.8 < [\mathrm{Fe/H}] \leq -0.8$) stars born in the dwarf galaxy Enceladus, which merged with the Milky Way galaxy about 10 Gyr ago. A sample of 22 candidates have been screened from a catalog of Gaia-Enceladus-Sausage (GES) members using a combination of stellar properties and reconnaissance observations from the TRES spectrograph. Precision RV measurements have been initiated using the NEID, HARPS-N, and CARMENES spectrographs. We plan to focus most upcoming observations on 10 main sequence targets. Data collection is well underway, with 778 observations on 22 candidates (385 of which are 10 focus targets), but far from complete. This survey is designed to be sensitive to sub-Neptune mass planets with periods up to hundreds of days. We note that the RV analysis gives mass multiplied by $\sin (inclination)$ or the minimum mass for exoplanets. The expected survey yield is three planets, assuming that occurrence rates are similar to those in the Milky Way and taking into account the degeneracy with inclination in our yield models. Our survey is designed to detect at least one exoplanet if occurrence rates are similar to known Milky Way exoplanets or, if no exoplanets are discovered, to rule out a Milky Way-like planet population in GES with 95% confidence level. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 19 pages, 3 tables, 10 figures, accepted to PASP

High CO/H2 ratios supports an exocometary origin for a CO-rich debris disk

Authors: Kevin D. Smith, Luca Matrà, Ke Zhang, Aoife Brennan, Merdith Hughes, Christine Chen, Isa Rebollido, David Wilner, Aki Roberge, Seth Redfield, Antonio Hales, Karin Öberg

Abstract: Over 20 exocometary belts host detectable circumstellar gas, mostly in the form of CO. Two competing theories for its origin have emerged, positing the gas to be primordial or secondary. Primordial gas survives from the belt's parent protoplanetary disk and is therefore H$_2$-rich. Secondary gas is outgassed \textit{in-situ} by exocomets and is relatively H$_2$-poor. Discriminating between these s… ▽ More Over 20 exocometary belts host detectable circumstellar gas, mostly in the form of CO. Two competing theories for its origin have emerged, positing the gas to be primordial or secondary. Primordial gas survives from the belt's parent protoplanetary disk and is therefore H$_2$-rich. Secondary gas is outgassed \textit{in-situ} by exocomets and is relatively H$_2$-poor. Discriminating between these scenarios has not been possible for belts hosting unexpectedly large quantities of CO. We aim to break this gas origin dichotomy \textit{via} direct measurement of H$_2$ column densities in two edge-on CO-rich exocometary belts around $\sim$15 Myr-old A-type stars, constraining the $\frac{\text{CO}}{\text{H}_2}$ ratio and CO gas lifetimes. Observing edge-on belts enables rovibrational absorption spectroscopy against the stellar background. We present near-IR CRIRES+ spectra of HD 110058 and HD 131488 which provide the first direct probe of H$_2$ gas in CO-rich exocometary belts. We target the H$_2$ (v=1-0 S(0)) line at 2223.3 nm and and the $^{12}$CO $v=2\rightarrow0$ rovibrational lines in the range 2333.8-2335.5 nm and derive constraints on column densities along the line-of-sight to the stars. We strongly detect $^{12}$CO but not H$_2$ in the CRIRES+ spectra. This allows us to place $3σ$ lower limits on the $\frac{\text{CO}}{\text{H}_2}$ ratios of $> 1.35 \times 10^{-3}$ and $> 3.09 \times 10^{-5}$ for HD 110058 and HD 131488 respectively. These constraints demonstrate that at least for HD 110058, the exocometary gas is compositionally distinct and significantly H$_2$-poor, compared to the $<10^{-4}$ $\frac{\text{CO}}{\text{H}_2}$ ratios typical of protoplanetary disks. We also find H$_2$ alone is unlikely to shield CO over the lifetime of the systems. Overall this suggests that the gas in CO-rich belts is most likely not primordial in origin, supporting the presence of exocometary gas. △ Less

Submitted 4 November, 2025; v1 submitted 3 November, 2025; originally announced November 2025.

Comments: Submitted to A&A, 15 pages, 13 figures

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. IV. Lens Mass and Distance Measurements

Authors: Sean K. Terry, Etienne Bachelet, Farzaneh Zohrabi, Himanshu Verma, Alison Crisp, Macy Huston, Carissma McGee, Matthew Penny, Natasha S. Abrams, Michael D. Albrow, Jay Anderson, Fatemeh Bagheri, Jean-Phillipe Beaulieu, Andrea Bellini, David P. Bennett, Galen Bergsten, T. Dex Bhadra, Aparna Bhattacharya, Ian A. Bond, Valerio Bozza, Christopher Brandon, Sebastiano Calchi Novati, Sean Carey, Jessie Christiansen, William DeRocco , et al. (32 additional authors not shown)

Abstract: As part of the Galactic Bulge Time Domain Survey (GBTDS), the Nancy Grace Roman Galactic Exoplanet Survey (RGES) will use microlensing to discover cold outer planets and free-floating planets unbound to stars. NASA has established several science requirements for the GBTDS to ensure RGES success. A key advantage of RGES is Roman's high angular resolution, which will allow detection of flux from ma… ▽ More As part of the Galactic Bulge Time Domain Survey (GBTDS), the Nancy Grace Roman Galactic Exoplanet Survey (RGES) will use microlensing to discover cold outer planets and free-floating planets unbound to stars. NASA has established several science requirements for the GBTDS to ensure RGES success. A key advantage of RGES is Roman's high angular resolution, which will allow detection of flux from many host stars. One requirement specifies that Roman must measure the masses and distances of 40% of detected planet hosts with 20% precision or better. To test this, we simulated microlensing events toward the GBTDS fields and used Fisher matrix analysis to estimate light curve parameter uncertainties. Combining these with Roman imaging observables (lens flux, relative lens-source proper motion), we estimated the achievable precision of lens mass and distance measurements. Using pyLIMASS, a publicly available code for estimating lens properties, we applied this analysis to 3,000 simulated events. Assuming the Cassan et al. (2012) exoplanet mass function, we find that >40% of host stars meet the required 20% precision threshold, confirming that the GBTDS can satisfy the mission requirement. We validated our approach by comparing our inferred lens masses and distances to empirical measurements from detailed image-constrained light curve modeling of historical microlensing events with Hubble and Keck follow-up imaging. Our results agree within roughly 1 sigma, demonstrating that both approaches yield consistent and reliable mass and distance estimates, and confirming the robustness of our simulations for Roman-era microlensing science. △ Less

Submitted 24 October, 2025; v1 submitted 15 October, 2025; originally announced October 2025.

Comments: Updated. 29 pages, 8 figures, 6 tables, submitted to AJ

Suppression of scalar perturbations due to a heavy axion

Authors: Kai-Ge Zhang, Jian-Feng He, Chengjie Fu, Zong-Kuan Guo

Abstract: A fast-rolling axion can transfer its kinetic energy to gauge fields via the Chern-Simons coupling, leading to copious production of gauge quanta during inflation. The amplified gauge fields act as a source for both scalar and tensor perturbations. In this work, we propose a mechanism for suppressing scalar perturbations while sourcing strong tensor perturbations. We present an implementation of s… ▽ More A fast-rolling axion can transfer its kinetic energy to gauge fields via the Chern-Simons coupling, leading to copious production of gauge quanta during inflation. The amplified gauge fields act as a source for both scalar and tensor perturbations. In this work, we propose a mechanism for suppressing scalar perturbations while sourcing strong tensor perturbations. We present an implementation of such a mechanism, demonstrating that sourced tensor perturbations are expected to be detected by upcoming next-generation CMB experiments. △ Less

Submitted 3 October, 2025; originally announced October 2025.

Comments: 10 pages, 6 figures

Towards the Giant Radio Array for Neutrino Detection (GRAND): the GRANDProto300 and GRAND@Auger prototypes

Authors: GRAND Collaboration, Jaime Álvarez-Muniz, Rafael Alves Batista, Aurélien Benoit-Lévy, Teresa Bister, Martina Bohacova, Mauricio Bustamante, Washington Carvalho, Yiren Chen, LingMei Cheng, Simon Chiche, Jean-Marc Colley, Pablo Correa, Nicoleta Cucu Laurenciu, Zigao Dai, Rogerio M. de Almeida, Beatriz de Errico, João R. T. de Mello Neto, Krijn D. de Vries, Valentin Decoene, Peter B. Denton, Bohao Duan, Kaikai Duan, Ralph Engel, William Erba , et al. (96 additional authors not shown)

Abstract: The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of ultra-high-energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interaction -- gamma rays, and, especially, neutrinos. GRAND will do so using large arrays of radio ant… ▽ More The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of ultra-high-energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interaction -- gamma rays, and, especially, neutrinos. GRAND will do so using large arrays of radio antennas that look for the radio signals emitted by the air showers initiated by the interactions of the UHE particles in the atmosphere. Since 2023, three small-scale prototype GRAND arrays have been in operation: GRAND@Nançay in France, GRAND@Auger in Argentina, and GRANDProto300 in China. Together, their goal is to validate the detection principle of GRAND under prolonged field conditions, achieving efficient, autonomous radio-detection of air showers. We describe the hardware, software, layout, and operation of the GRAND prototypes and show the first radio spectra measured by them. Despite challenges, the successful operation of the prototypes confirms that the GRAND instrumentation is apt to address the goals of the experiment and lays the groundwork for its ensuing stages. △ Less

Submitted 25 September, 2025; originally announced September 2025.

Comments: 28 pages, 16 figures, 2 tables

Observational Constraints on Evolution of Dust Disc Properties in Upper Scorpius

Authors: Paola Pinilla, Anibal Sierra, Nicolas T. Kurtovic, Rossella Anania, Sean Andrews, John Carpenter, Osmar Guerra-Alvarado, Feng Long, Sebastian Marino, Miguel Vioque, Ke Zhang

Abstract: Protoplanetary discs in the Upper Scorpius star-forming region are excellent laboratories to investigate late stages of planet formation. In this work, we analyse the morphology of the dust continuum emission of 121 discs from an ALMA Band 7 survey of the Upper Scorpius region. This analysis is done in the visibility plane, to measure the flux, geometry and characterise potential structures. We co… ▽ More Protoplanetary discs in the Upper Scorpius star-forming region are excellent laboratories to investigate late stages of planet formation. In this work, we analyse the morphology of the dust continuum emission of 121 discs from an ALMA Band 7 survey of the Upper Scorpius region. This analysis is done in the visibility plane, to measure the flux, geometry and characterise potential structures. We compare the results with state-of-the art gas and dust evolution models that include external photoevaporation, with mild values of the $F_{\rm{UV}}$ of 1-40$G_0$. From the visibility analysis, 52 of the 121 discs are resolved (43%). From the resolved discs, 24 discs have structures and 28 remain as smooth discs at the mean resolution scale of $\sim$0.1$^{\prime \prime}$ (~14au). Our results show no significant dust disc size evolution of the surviving discs in UpperSco when compared to discs in younger star-forming regions, such as Lupus. We find a strong, steeper-than-previously-reported correlation between dust disc size and disc millimeter continuum luminosity, in agreement with drift-dominated dust evolution models. We also find positive correlations between the dust disc mass vs. stellar mass and dust disc size vs. stellar mass. The slope of the dust disc size vs. stellar mass relationship is steeper compared to younger star forming regions. Additionally, we observe no significant correlation between dust disc properties and the environmental $F_{\rm{UV}}$, consistent with models predicting that dust disc properties are primarily shaped by drift and dust traps. Our models predict that gas disc masses and sizes should be highly affected by the moderate $F_{\rm{UV}}$ values that Upper Scorpius discs experience in contrast to the dust, highlighting the need for deeper and higher-resolution gas observations of these discs exposed to mild external photoevaporation. △ Less

Submitted 23 September, 2025; originally announced September 2025.

Comments: Accepted for publication in MNRAS, available tables at https://doi.org/10.5281/zenodo.17182603

KMT-2018-BLG-0029Lb and OGLE-2019-BLG-0960Lb: Mass Measurements for Two Super-Earth Microlensing Planets

Authors: Keming Zhang, Sean K. Terry, Joshua S. Bloom, B. Scott Gaudi, Jessica R. Lu

Abstract: KMT-2018-BLG-0029Lb and OGLE-2019-BLG-0960Lb were the lowest mass-ratio microlensing planets at the time of discovery. For both events, microlensing parallax measurements from the Spitzer Space Telescope implied lens systems that were more distant and massive than those inferred from the ground-based parallax. Here, we report on the detection of excess flux aligned to the event locations using Kec… ▽ More KMT-2018-BLG-0029Lb and OGLE-2019-BLG-0960Lb were the lowest mass-ratio microlensing planets at the time of discovery. For both events, microlensing parallax measurements from the Spitzer Space Telescope implied lens systems that were more distant and massive than those inferred from the ground-based parallax. Here, we report on the detection of excess flux aligned to the event locations using Keck Adaptive Optics imaging, which is consistent with the expected brightness of main-sequence hosts under the ground-based parallax, but inconsistent with that predicted by Spitzer. Based on the excess flux, ground-based parallax, and angular Einstein radius, we determine KMT-2018-BLG-0029Lb to be a $4.2\pm0.5 M_\oplus$ planet orbiting a $0.70\pm0.07 M_\odot$ host at a projected separation of $3.1\pm0.3$ au, and OGLE-2019-BLG-0960Lb to be a $2.0\pm0.2 M_\oplus$ planet orbiting a $0.40\pm0.03 M_\odot$ host at a projected separation of $1.7\pm0.1$ au. We report on additional light-curve models for KMT-2018-BLG-0029 under the generalized inner-outer (offset) degeneracy, which were not reported in the original analysis. We point out inconsistencies in the inner/outer labeling of the degenerate models in the lens and source planes, and advocate for the lens-plane convention, which refers to the planet being closer or further to the host star compared to the image it perturbs. Lastly, we discuss the possibility of breaking this degeneracy via ground concurrent observations with the Roman Space Telescope. △ Less

Submitted 25 August, 2025; originally announced August 2025.

Comments: 11 pages, 5 figures, 2 tables. Accepted to the Astronomical Journal

Cosmic cascades: How disk substructure regulates the flow of water to inner planetary systems

Authors: Sebastiaan Krijt, Andrea Banzatti, Ke Zhang, Paola Pinilla, Till Kaeufer, Edwin A. Bergin, Colette Salyk, Klaus Pontoppidan, Geoffrey A. Blake, Feng Long, Jane Huang, María José Colmenares, Joe Williams, Adrien Houge, Mayank Narang, Miguel Vioque, Michiel Lambrechts, L. Ilsedore Cleeves, Karin Öberg, the JDISCS collaboration

Abstract: The influx of icy pebbles to the inner regions of protoplanetary disks constitutes a fundamental ingredient in most planet formation theories. The observational determination of the magnitude of this pebble flux and its dependence on disk substructure (disk gaps as pebble traps) would be a significant step forward. In this work we analyze a sample of 21 T Tauri disks (with ages… ▽ More The influx of icy pebbles to the inner regions of protoplanetary disks constitutes a fundamental ingredient in most planet formation theories. The observational determination of the magnitude of this pebble flux and its dependence on disk substructure (disk gaps as pebble traps) would be a significant step forward. In this work we analyze a sample of 21 T Tauri disks (with ages $\approx 0.5{-}2\mathrm{~Myr}$) using JWST/MIRI spectra homogeneously reduced with the JDISCS pipeline and high-angular-resolution ALMA continuum data. We find that the 1500/6000 K water line flux ratio measured with JWST - a tracer of cold water vapor and pebble drift near the snowline - correlates with the radial location of the innermost dust gap in ALMA continuum observations (ranging from 8.7 to 69 au), confirming predictions from recent models that study connections between the inner and outer disk reservoirs. We develop a population synthesis exploration of pebble drift in gapped disks and find a good match to the observed trend for early and relatively effective gaps, while scenarios where pebble drift happens quickly, gaps are very leaky, or where gaps form late are disfavored on a population level. Inferred snowline pebble mass fluxes (ranging between $10^{-6}$ and $10^{-3}~M_\oplus/\mathrm{yr}$ depending on gap position) are comparable to fluxes used in pebble accretion studies and those proposed for the inner Solar System, while system-to-system variations suggest differences in the emerging planetary system architectures and water budgets. △ Less

Submitted 14 August, 2025; originally announced August 2025.

Comments: Accepted for publication in ApJL, 15 pages, 6 figures

Causal evidence for the primordiality of colours in trans-Neptunian objects

Authors: Benjamin L. Davis, Mohamad Ali-Dib, Yujia Zheng, Zehao Jin, Kun Zhang, Andrea Valerio Macciò

Abstract: The origins of the colours of Trans-Neptunian Objects (TNOs) represent a crucial unresolved question, central to understanding the history of our Solar System. Recent observational surveys revealed correlations between the eccentricity and inclination of TNOs, and their colours. This rekindled the long-standing debate on whether these colours reflect the conditions of TNO formation or their subseq… ▽ More The origins of the colours of Trans-Neptunian Objects (TNOs) represent a crucial unresolved question, central to understanding the history of our Solar System. Recent observational surveys revealed correlations between the eccentricity and inclination of TNOs, and their colours. This rekindled the long-standing debate on whether these colours reflect the conditions of TNO formation or their subsequent evolution. We address this question using a model-agnostic, data-driven approach that unanimously converges to a common causal graph from the analysis of two different datasets, each from two different conditional independence test methods. For evaluation, we demonstrate how our model is consistent with the currently-accepted paradigms of TNOs' dynamical histories, without involving any orbital modelling or physics-based assumptions. Our causal model (with no knowledge of the existence of Neptune) predicts the need for an unknown confounding variable, consistent with Neptune's effects. The model predicts that the colour of TNOs is the root cause of their inclination distribution, rather than the other way around. This strongly suggests that the colours of TNOs reflect an underlying dynamical property, most likely their formation location. Our model excludes formation scenarios that invoke substantial colour modification by subsequent evolution. We conclude that the colours of TNOs are predominantly primordial. △ Less

Submitted 13 August, 2025; originally announced August 2025.

Comments: 9 pages, 5 figures, and 1 table; accepted by the Monthly Notices of the Royal Astronomical Society Letters

Journal ref: Monthly Notices of the Royal Astronomical Society: Letters, Volume 543, Issue 1, October 2025, Pages L34-L42

End-to-end reconstruction of ultra-high energy particle observables from radio detection of extensive air showers

Authors: Kewen Zhang, Duan Kaikai, Ramesh Koirala, Matías Tueros, Chao Zhang, Yi Zhang

Abstract: The radio detection of very inclined air showers offers a promising avenue for studying ultra-high-energy cosmic rays (UHECRs) and neutrinos. Accurate reconstruction methods are essential for investigating the properties of primary particles. Recently, we developed an analytical least-squares method to reconstruct the electric field using three polarization components. The reconstruction yields no… ▽ More The radio detection of very inclined air showers offers a promising avenue for studying ultra-high-energy cosmic rays (UHECRs) and neutrinos. Accurate reconstruction methods are essential for investigating the properties of primary particles. Recently, we developed an analytical least-squares method to reconstruct the electric field using three polarization components. The reconstruction yields no bias, with a 68\% confidence interval of [-0.02, 0.02], and a standard deviation of 0.04. Using this reconstructed electric field, we perform a realistic reconstruction of the the properties of primary particles. We employ a spherical wave model combined with an angular distribution function (ADF) for arrival direction reconstruction, achieving an angular resolution of 0.04$^\circ$. This paper also presents an energy reconstruction in which we account for the effects of geosynchrotron radiation in inclined air showers, we implement an air density correction in the energy reconstruction, resulting in a 10\% resolution in energy estimation. These findings demonstrate the reliability and effectiveness of our reconstruction methodology, paving the way for future detection experiments using sparse antenna arrays. △ Less

Submitted 23 July, 2025; originally announced July 2025.

Decadal evolution of a repeating fast radio burst source

Authors: P. Wang, J. S. Zhang, Y. P. Yang, D. K. Zhou, Y. K. Zhang, Y. Feng, Z. Y. Zhao, J. H. Fang, D. Li, W. W. Zhu, B. Zhang, F. Y. Wang, Y. F. Huang, R. Luo, J. L. Han, K. J. Lee, C. W. Tsai, Z. G. Dai, H. Gao, X. P. Zheng, J. H. Cao, X. L. Chen, E. Gugercinoglu, J. C. Jiang, W. C. Jing , et al. (26 additional authors not shown)

Abstract: The origin of fast radio bursts (FRBs), the brightest cosmic radio explosions, is still unknown. Bearing critical clues to FRBs' origin, the long-term evolution of FRBs has yet to be confirmed, since the field is still young and most FRBs were seen only once. Here we report clear evidence of decadal evolution of FRB~20121102A, the first precisely localized repeater. In conjunction with archival da… ▽ More The origin of fast radio bursts (FRBs), the brightest cosmic radio explosions, is still unknown. Bearing critical clues to FRBs' origin, the long-term evolution of FRBs has yet to be confirmed, since the field is still young and most FRBs were seen only once. Here we report clear evidence of decadal evolution of FRB~20121102A, the first precisely localized repeater. In conjunction with archival data, our FAST and GBT monitoring campaign since 2020 reveals a significant 7% decline of local dispersion measure (DM). The rotation measure (RM) of 30,755$\pm$16 $\mathrm{rad\,m^{-2}}$ detected in the last epoch represents a 70% decrease compared to that from December 2016. The $σ_{RM}$ parameter, which describes the complexity of the magneto-ionic environment surrounding the source, was shown to have decreased by 13%. These general trends reveal an evolving FRB environment, which could originate from an early-phase supernova associated with an enhanced pair wind from the FRB central engine. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Comments: 85 pages, 14 figures, under review of Nature Astronomy

Learning Null Geodesics for Gravitational Lensing Rendering in General Relativity

Authors: Mingyuan Sun, Zheng Fang, Jiaxu Wang, Kunyi Zhang, Qiang Zhang, Renjing Xu

Abstract: We present GravLensX, an innovative method for rendering black holes with gravitational lensing effects using neural networks. The methodology involves training neural networks to fit the spacetime around black holes and then employing these trained models to generate the path of light rays affected by gravitational lensing. This enables efficient and scalable simulations of black holes with optic… ▽ More We present GravLensX, an innovative method for rendering black holes with gravitational lensing effects using neural networks. The methodology involves training neural networks to fit the spacetime around black holes and then employing these trained models to generate the path of light rays affected by gravitational lensing. This enables efficient and scalable simulations of black holes with optically thin accretion disks, significantly decreasing the time required for rendering compared to traditional methods. We validate our approach through extensive rendering of multiple black hole systems with superposed Kerr metric, demonstrating its capability to produce accurate visualizations with significantly $15\times$ reduced computational time. Our findings suggest that neural networks offer a promising alternative for rendering complex astrophysical phenomena, potentially paving a new path to astronomical visualization. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Comments: ICCV 2025

The Giant Radio Array for Neutrino Detection (GRAND) Collaboration -- Contributions to the 39th International Cosmic Ray Conference (ICRC 2025)

Authors: Jaime Álvarez-Muñiz, Rafael Alves Batista, Aurélien Benoit-Lévy, Teresa Bister, Martina Bohacova, Mauricio Bustamante, Washington Carvalho Jr., Yiren Chen, LingMei Cheng, Simon Chiche, Jean-Marc Colley, Pablo Correa, Nicoleta Cucu Laurenciu, Zigao Dai, Rogerio M. de Almeida, Beatriz de Errico, João R. T. de Mello Neto, Krijn D. de Vries, Valentin Decoene, Peter B. Denton, Bohao Duan, Kaikai Duan, Ralph Engel, William Erba, Yizhong Fan , et al. (113 additional authors not shown)

Abstract: The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned observatory of ultra-high-energy particles of cosmic origin, with energies in excess of 100 PeV. GRAND uses large surface arrays of antennas to look for the radio emission from extensive air showers that are triggered by the interaction of ultra-high-energy cosmic rays, gamma rays, and neutrinos in the atmosphere or underground.… ▽ More The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned observatory of ultra-high-energy particles of cosmic origin, with energies in excess of 100 PeV. GRAND uses large surface arrays of antennas to look for the radio emission from extensive air showers that are triggered by the interaction of ultra-high-energy cosmic rays, gamma rays, and neutrinos in the atmosphere or underground. In particular, for ultra-high-energy neutrinos, the future final phase of GRAND aims to be sensitive enough to detect them in spite of their plausibly tiny flux. Three prototype GRAND radio arrays have been in operation since 2023: GRANDProto300, in China, GRAND@Auger, in Argentina, and GRAND@Nançay, in France. Their goals are to field-test the GRAND detection units, understand the radio background to which they are exposed, and develop tools for diagnostic, data gathering, and data analysis. This list of contributions to the 39th International Cosmic Ray Conference (ICRC 2025) presents an overview of GRAND, in its present and future incarnations, and a first look at data collected by GRANDProto300 and GRAND@Auger, including the first cosmic-ray candidates detected by them. △ Less

Submitted 13 July, 2025; originally announced July 2025.

Comments: Note: To access the list of contributions, please follow the "HTML" link that can be found on the arXiv page

Electric-Field Reconstruction for Radio Detection of Inclined Air Showers in Three Polarizations

Authors: Kewen Zhang, Lukas Gülzow, Tim Huege, Ramesh Koirala, Pengxiong Ma, Matías Tueros, Xin Xu, Chao Zhang, Pengfei Zhang, Yi Zhang

Abstract: Accurate reconstruction of the electric field produced by extensive air showers is essential for the radio-detection technique, as the key parameters of interest of the primary particles that generated the showers are the amplitude, polarization, frequency spectrum, and energy fluence carried by the electric field at each receiving radio antenna. Conventional electric-field reconstruction methods… ▽ More Accurate reconstruction of the electric field produced by extensive air showers is essential for the radio-detection technique, as the key parameters of interest of the primary particles that generated the showers are the amplitude, polarization, frequency spectrum, and energy fluence carried by the electric field at each receiving radio antenna. Conventional electric-field reconstruction methods primarily focus on antennas with two horizontal polarizations. In this work, we introduce an analytic $χ^2$ minimization method that is applicable to both two and three polarizations. This solution has been verified for simple and realistic antenna responses, with a particular focus on inclined air showers. Our method achieves standard deviations better than 4\% and 6\% for the estimation of the Hilbert peak envelope amplitude of the electric field and the energy fluence, respectively, with an antenna-response-dependent bias. Additionally, we have studied the dependence of the method with arrival direction showing that it has a good performance in the zenith range from 63$^\circ$ up to 80$^\circ$. This work also demonstrates that incorporating vertically polarized antennas enhances the precision of the reconstruction, leading to a more accurate and reliable electric-field estimation for inclined air showers. △ Less

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

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2023). 10 pages, 4 figures

Report number: PoS(ICRC2025)447

Progress of the GRANDProto300 Project

Authors: Pengxiong Ma, Yi Zhang, Xing Xu, Bohao Duan, Shen Wang, Kewen Zhang, Pengfei Zhang, Xin Xu

Abstract: GRANDProto300 (hereafter referred to as GP300) is a pioneering prototype array of the GRAND experiment. It consists of 300 radio antennas and will cover an area of 200 km$^2$ in a radio-quiet region of western China. Serving as a test bench for the GRAND experiment, GRANDProto300 aims to achieve autonomous radio detection and reconstruction of highly inclined air showers. It is designed to detect… ▽ More GRANDProto300 (hereafter referred to as GP300) is a pioneering prototype array of the GRAND experiment. It consists of 300 radio antennas and will cover an area of 200 km$^2$ in a radio-quiet region of western China. Serving as a test bench for the GRAND experiment, GRANDProto300 aims to achieve autonomous radio detection and reconstruction of highly inclined air showers. It is designed to detect ultra-high-energy cosmic rays in the energy range of $10^{16.5}$-$10^{18}$ eV at a rate comparable to that of the Pierre Auger Observatory. Over the past two years, significant improvements have been made to both the hardware and firmware of GP300. Currently, 65 antenna units have been deployed at the site by June 2025. We present the current status of detector commissioning, including updates on hardware, calibration results such as GPS timing and antenna positioning. Additionally, we discuss the solar radio bursts associated with solar flares, the galactic radio emissions detected, and preliminary cosmic ray surveys. △ Less

Submitted 8 July, 2025; originally announced July 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2025). 8 pages, 9 figures

Report number: PoS(ICRC2025)453

Introduction to the Chinese Space Station Survey Telescope (CSST)

Authors: CSST Collaboration, Yan Gong, Haitao Miao, Hu Zhan, Zhao-Yu Li, Jinyi Shangguan, Haining Li, Chao Liu, Xuefei Chen, Haibo Yuan, Jilin Zhou, Hui-Gen Liu, Cong Yu, Jianghui Ji, Zhaoxiang Qi, Jiacheng Liu, Zigao Dai, Xiaofeng Wang, Zhenya Zheng, Lei Hao, Jiangpei Dou, Yiping Ao, Zhenhui Lin, Kun Zhang, Wei Wang , et al. (97 additional authors not shown)

Abstract: The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific inst… ▽ More The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific instruments, i.e. Multi-band Imaging and Slitless Spectroscopy Survey Camera (SC), Multi-Channel Imager (MCI), Integral Field Spectrograph (IFS), Cool Planet Imaging Coronagraph (CPI-C), and THz Spectrometer (TS). Using these instruments, CSST is expected to make significant contributions and discoveries across various astronomical fields, including cosmology, galaxies and active galactic nuclei (AGN), the Milky Way and nearby galaxies, stars, exoplanets, Solar System objects, astrometry, and transients and variable sources. This review aims to provide a comprehensive overview of the CSST instruments, observational capabilities, data products, and scientific potential. △ Less

Submitted 19 September, 2025; v1 submitted 6 July, 2025; originally announced July 2025.

Comments: 48 pages, 12 figures, 1 table. Accepted for publication in SCIENCE CHINA Physics, Mechanics & Astronomy

Causal Evidence for the Primordiality of Colors in Trans-Neptunian Objects

Authors: Benjamin L. Davis, Mohamad Ali-Dib, Yujia Zheng, Zehao Jin, Kun Zhang, Andrea Valerio Macciò

Abstract: The origins of the colors of Trans-Neptunian Objects (TNOs) represent a crucial unresolved question, central to understanding the history of our Solar System. Recent observational surveys have revealed correlations between the eccentricity and inclination of TNOs and their colors. This has rekindled the long-standing debate on whether these colors reflect the conditions of TNO formation or their s… ▽ More The origins of the colors of Trans-Neptunian Objects (TNOs) represent a crucial unresolved question, central to understanding the history of our Solar System. Recent observational surveys have revealed correlations between the eccentricity and inclination of TNOs and their colors. This has rekindled the long-standing debate on whether these colors reflect the conditions of TNO formation or their subsequent collisional evolution. In this study, we address this question with 98.7% certainty, using a model-agnostic, data-driven approach based on causal graphs. First, as a sanity check, we demonstrate how our model can replicate the currently accepted paradigms of TNOs' dynamical history, blindly and without any orbital modeling or physics-based assumptions. In fact, our causal model (with no knowledge of the existence of Neptune) predicts the existence of an unknown perturbing body, i.e., Neptune. We then show how this model predicts, with high certainty, that the color of TNOs is the root cause of their inclination distribution, rather than the other way around. This strongly suggests that the colors of TNOs reflect an underlying dynamical property, most likely their formation location. Moreover, our causal model excludes formation scenarios that invoke substantial color modification by subsequent irradiation. We therefore conclude that the colors of TNOs are predominantly primordial. △ Less

Submitted 4 July, 2025; originally announced July 2025.

Comments: Accepted to ML4Astro 2025 (Machine Learning for Astrophysics workshop at ICML 2025)

Gravitational Waves from Gauge Quanta Produced during Inflation

Authors: Kai-Ge Zhang, Jian-Feng He, Chengjie Fu, Zong-Kuan Guo

Abstract: A fast-rolling axion can transfer its kinetic energy to a gauge field via the Chern-Simons coupling, leading to copious production of gauge quanta, which can act as a source of gravitational waves (GWs) with potentially observable amplitudes. In this work, we investigate GW production in a spectator axion model when strong backreaction is taken into account. We find that decreasing the decay const… ▽ More A fast-rolling axion can transfer its kinetic energy to a gauge field via the Chern-Simons coupling, leading to copious production of gauge quanta, which can act as a source of gravitational waves (GWs) with potentially observable amplitudes. In this work, we investigate GW production in a spectator axion model when strong backreaction is taken into account. We find that decreasing the decay constant of the axion enhances GW production. Since the initial value of the axion is larger than its quantum fluctuations, such a condition imposes a lower bound on the axion dacay constant, which sets an upper bound on the amplitude of the energy spectrum of GWs. As a result, the amplitude of the predicted GW energy spectrum is lower than $10^{-10}$ in the nHz to mHz frequency range. △ Less

Submitted 18 October, 2025; v1 submitted 3 July, 2025; originally announced July 2025.

Comments: 11 pages, 4 figures

Journal ref: Phys. Rev. D 112, 083530 (2025)

Exploring the Frontiers of Cosmic Ray Physics: Perspectives on GRANDProto300 and the GRAND Project

Authors: Kewen Zhang, Yi Zhang, Yi-Qing Guo

Abstract: The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned large-scale radio array designed to detect ultra-high-energy cosmic rays (UHECRs, $E > 100$ PeV) and neutrinos. Employing cost-effective antennas distributed across vast areas, GRAND is optimized to observe the rare flux of ultra-high-energy particles with high precision. The GRANDProto300 (GP300) pathfinder array, currently und… ▽ More The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned large-scale radio array designed to detect ultra-high-energy cosmic rays (UHECRs, $E > 100$ PeV) and neutrinos. Employing cost-effective antennas distributed across vast areas, GRAND is optimized to observe the rare flux of ultra-high-energy particles with high precision. The GRANDProto300 (GP300) pathfinder array, currently under deployment, targets the $10^{16.5} - 10^{18}$ eV range and is anticipated to achieve approximately 15\% energy resolution and 20g/cm$^2$ $X_{\mathrm{max}}$ precision. This level of precision enables accurate measurements of the fine structure of the energy spectrum, mean logarithmic mass ($\langle \ln A \rangle$), and proton flux within this range. After five years of data collection, the sensitivity for detecting anisotropy could reach $5 \times 10^{-3}$ for energies below $10^{17.1}$ eV. With its substantially larger effective area, GRAND extends these capabilities to the highest energies ($\sim 10^{20}$ eV), offering enhanced statistics and sensitivity for spectral, composition, and anisotropy measurements within one year for UHECRs. △ Less

Submitted 19 June, 2025; originally announced June 2025.

A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for In Situ Massive Star Formation Beyond the Optical Radius

Authors: Pinjian Chen, Bingqiu Chen, Haibo Yuan, Xuan Fang, Xiaodian Chen, Chao-Wei Tsai, Kai Zhang, Xiaowei Liu

Abstract: While massive stars are known to shape galactic ecosystems, their formation has long been assumed to require the high-density environments of inner galactic disks. This paradigm is challenged by mounting evidence of young massive stars in extended galaxy outskirts, yet direct confirmation of in situ massive star formation in such extreme low-density environments remains scarce. Here, we present th… ▽ More While massive stars are known to shape galactic ecosystems, their formation has long been assumed to require the high-density environments of inner galactic disks. This paradigm is challenged by mounting evidence of young massive stars in extended galaxy outskirts, yet direct confirmation of in situ massive star formation in such extreme low-density environments remains scarce. Here, we present the discovery of LAMOST J0048+4154, a massive yellow supergiant situated at a deprojected galactocentric distance of ~34 kpc in M31, making it the most distant massive star confirmed in this galaxy. Through spectroscopic and photometric analyses, we classify J0048+4154 as an F5-F8I supergiant with an effective temperature of $6357^{+121}_{-118}$ K and a luminosity of $\log L/L_{\odot} = 5.00^{+0.06}_{-0.06}$, corresponding to an ~18 $M_{\odot}$ progenitor and an age of ~10 Myr. FAST H I observations reveal close spatial and kinematic alignment between the star and a faint H I external arm, suggesting in situ formation in a region of low gas density. The presence of other UV-bright, early-type stars in the vicinity further supports low-level recent star formation in M31's very outer disk. These findings challenge the prevailing assumption that massive star formation is confined to inner disks or classical star-forming regions and underscore the need to re-examine the role of spiral galaxy outskirts in fueling and sustaining star formation. J0048+4154 thereby expands our understanding of the extent of M31's young stellar component and exemplifies how outer disks may harbor conditions conducive to forming massive stars, despite low-density environments. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Comments: 12 pages, 8 figures, accepted for publication in AJ

New tests of cosmic distance duality relation with DESI 2024 BAO observations

Authors: Qiumin Wang, Shuo Cao, Jianyong Jiang, Kaituo Zhang, Xinyue Jiang, Tonghua Liu, Chengsheng Mu, Dadian Cheng

Abstract: In this paper, we test the cosmic distance duality relation (CDDR), as required by the Etherington reciprocity theorem, which connects the angular diameter distance and the luminosity distance via the relation \( D_{\rm L}(z) = D_{\rm A}(z)(1+z)^2 \). Our analysis is based on the latest baryon acoustic oscillation (BAO) measurements provided by the Dark Energy Survey (DES), the Baryon Oscillation… ▽ More In this paper, we test the cosmic distance duality relation (CDDR), as required by the Etherington reciprocity theorem, which connects the angular diameter distance and the luminosity distance via the relation \( D_{\rm L}(z) = D_{\rm A}(z)(1+z)^2 \). Our analysis is based on the latest baryon acoustic oscillation (BAO) measurements provided by the Dark Energy Survey (DES), the Baryon Oscillation Spectroscopic Survey (BOSS)/Extended BOSS (eBOSS), and the Dark Energy Spectroscopic Instrument (DESI) surveys. Specifically, an unbiased test of the CDDR is performed through a novel, model-independent method inspired by the two-point diagnostic approach, with DES-SN5YR and Pantheon type Ia supernova (SN Ia) sample reconstructed using the Artificial Neural Network (ANN) technique. This methodology effectively eliminates all nuisance parameters, including the sound horizon scale \( r_{\rm d} \) from BAO and the absolute magnitude \( M_{\rm B} \) from SN Ia. A set of \( N-1 \) independent CDDR ratios \( η_{ij} \) are constructed for statistical analysis. At the current observational level, no significant deviation from the CDDR is observed at low redshifts, whereas we find positive evidence ($>2σ$ C.L.) of deviation from the CDDR at two high redshifts ($z=2.33$ and $z=2.334$). Therefore, our results confirm that the BAO measurement provides a powerful tool to test such fundamental relation in modern cosmology. △ Less

Submitted 15 June, 2025; originally announced June 2025.

Comments: 10 pages, 6 figures

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): XII. Extreme millimetre variability detected in a Class II disc

Authors: James M. Miley, Laura M. Perez, Carolina Agurto-Gangas, Anibal Sierra, Leon Trapman, Miguel Vioque, Nicolas Kurtovic, Paola Pinilla, Ilaria Pascucci, Ke Zhang, Rossella Anania, John Carpenter, Lucas A. Cieza, Dingshan Deng, Camilo Gonzalez-Ruilova, Giovanni P. Rosotti, Dary A. Ruiz-Rodriguez, Estephani E. TorresVillanueva

Abstract: Variability of millimetre wavelength continuum emission from Class II protoplanetary disks is extremely rare, and when detected it is usually interpreted as originating from non-thermal emission mechanisms that relate to the host star itself rather than its disk. During observations made as part of the AGE-PRO ALMA Large program, significant variability in the brightness of the 2MASS J16202863-244… ▽ More Variability of millimetre wavelength continuum emission from Class II protoplanetary disks is extremely rare, and when detected it is usually interpreted as originating from non-thermal emission mechanisms that relate to the host star itself rather than its disk. During observations made as part of the AGE-PRO ALMA Large program, significant variability in the brightness of the 2MASS J16202863-2442087 system was detected between individual executions. We report the observed properties of the variability detected at millimetre wavelengths and investigate potential driving mechanisms. To investigate the nature of the variability we construct a light curve from the continuum observations and analyse imaged constructed from both flaring and quiescent emission. We characterise the dust disk around the star through analysis in the image and visibility plane, and carry out kinematic analysis of the CO(2-1) emission from the gas disk. The continuum flux decays by a factor of 8 in less than an hour, and by a factor of 13 within 8 days. The peak brightness coincides with an expected brightness maximum extrapolated from the periodicity of previously observed optical variability. The flare is most likely the product of synchrotron emission in the close vicinity of the star. The nature of the millimetre flare closely resembles those detected in very close binary systems, and may be due to the interaction of magnetic fields in an as yet undetected binary. Alternatively if the central host is a single-star object, the flare may be due to the interaction of magnetic field loops at the stellar surface or a strong accretion burst. △ Less

Submitted 11 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): XI. Beam-corrected gas disk sizes from fitting 12CO moment zero maps

Authors: Leon Trapman, Miguel Vioque, Nicolás T. Kurtovic, Ke Zhang, Giovanni P. Rosotti, Paola Pinilla, John Carpenter, Lucas A. Cieza, Ilaria Pascucci, Rossella Anania, Carolina Agurto-Gangas, Dingshan Deng, James Miley, Laura M. Pérez, Anibal Sierra, Benoît Tabone, Dary A. Ruíz-Rodríguez, Camilo González-Ruilova, Estephani TorresVillanueva

Abstract: The inward drift of mm-cm sized pebbles in protoplanetary disks has become an important part of our current theories of planet formation and, more recently, planet composition as well. The gas-to-dust size ratio of protoplanetary disks can provide an important constraint on how pebbles have drifted inward provided that observational effects, especially resolution, can be accounted for. Here we pre… ▽ More The inward drift of mm-cm sized pebbles in protoplanetary disks has become an important part of our current theories of planet formation and, more recently, planet composition as well. The gas-to-dust size ratio of protoplanetary disks can provide an important constraint on how pebbles have drifted inward provided that observational effects, especially resolution, can be accounted for. Here we present a method for fitting beam-convolved models to integrated intensity maps of line emission using the astropy python package and use it to fit 12 CO moment zero maps of ten Lupus and ten Upper Scorpius protoplanetary disks from the AGE-PRO ALMA Large Program, a sample of disks around M3-K6 stars that cover the ~1 to 6 Myr of gas disk evolution. From the unconvolved best fit models we measure the gas disk size (RCO,90%[model]), which we combine with the dust disk size (Rdust,90%[FRANK]) from continuum visibility fits from Vioque et al. (2025, in press.) to compute beam-corrected gas-to-dust size ratios. In our sample we find gas-to-dust size ratios between ~1 and ~5.5, with a median value of 2.78(+0.37,-0.32). Contrary to models of dust evolution that predict an increasing size ratio with time, we find that the younger disks in Lupus have similar (or even larger) median ratios (3.02(+0.33,-0.33)) than the older disks in Upper Sco (2.46(+0.53,-0.38)). A possible explanation to this discrepancy is that pebble drift is halted in dust traps combined with truncation of the gas disk by external photo-evaporation in Upper Sco, although survivorship bias could also play a role. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO. Code available at https://zenodo.org/records/15360478

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): X. Dust Substructures, Disk Geometries, and Dust-disk Radii

Authors: Miguel Vioque, Nicolás T. Kurtovic, Leon Trapman, Anibal Sierra, Laura M. Pérez, Ke Zhang, Pietro Curone, Giovanni P. Rosotti, John Carpenter, Benoît Tabone, Paola Pinilla, Dingshan Deng, Ilaria Pascucci, James Miley, Carolina Agurto-Gangas, Lucas A. Cieza, Rossella Anania, Dary A. Ruiz-Rodriguez, Camilo González-Ruilova, Estephani E. TorresVillanueva, Aleksandra Kuznetsova

Abstract: We perform visibility fitting to the dust continuum Band 6 1.3 mm data of the 30 protoplanetary disks in the AGE-PRO ALMA Large Program. We obtain disk geometries, dust-disk radii, and azimuthally symmetric radial profiles of the intensity of the dust continuum emission. We examine the presence of continuum substructures in the AGE-PRO sample by using these radial profiles and their residuals. We… ▽ More We perform visibility fitting to the dust continuum Band 6 1.3 mm data of the 30 protoplanetary disks in the AGE-PRO ALMA Large Program. We obtain disk geometries, dust-disk radii, and azimuthally symmetric radial profiles of the intensity of the dust continuum emission. We examine the presence of continuum substructures in the AGE-PRO sample by using these radial profiles and their residuals. We detect substructures in 15 out of 30 disks. We report five disks with large ($>$15 au) inner dust cavities. The Ophiuchus Class I disks show dust-disk substructures in $\sim80\%$ of the resolved sources. This evidences the early formation of substructures in protoplanetary disks. A spiral is identified in IRS 63, hinting to gravitational instability in this massive disk. We compare our dust-disk brightness radial profiles with gas-disk brightness radial profiles and discuss colocal substructures in both tracers. In addition, we discuss the evolution of dust-disk radii and substructures across Ophiuchus, Lupus, and Upper Scorpius. We find that disks in Lupus and Upper Scorpius with large inner dust cavities have typical gas-disk masses, suggesting an abundance of dust cavities in these regions. The prevalence of pressure dust traps at later ages is supported by a potential trend with time with more disks with large inner dust cavities (or "transition disks") in Upper Scorpius and the absence of evolution of dust-disk sizes with time in the AGE-PRO sample. We propose this is caused by an evolutionary sequence with a high fraction of protoplanetary disks with inner protoplanets carving dust cavities. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO (submitted: October 7th 2024, accepted: January 14th 2025)

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): VIII. The impact of external photoevaporation on disk masses and radii in Upper Scorpius

Authors: Rossella Anania, Giovanni P. Rosotti, Matías Gárate, Paola Pinilla, Miguel Vioque, Leon Trapman, John Carpenter, Ke Zhang, Ilaria Pascucci, Lucas A. Cieza, Anibal Sierra, Nicolas T. Kurtovic, James Miley, Laura M. Pérez, Benôit Tabone, Michiel Hogerheijde, Dingshan Deng, Carolina Agurto-Gangas, Dary A. Ruiz-Rodriguez, Camilo González-Ruilova, Estephani E. TorresVillanueva

Abstract: Protoplanetary disk evolution can be deeply influenced by the UV radiation emitted by neighboring massive stars (mainly of spectral type O and B). We show that the process of external photoevaporation, which causes an outside-in depletion of disk material due to environmental UV radiation, can lead to a significant decrease in disk size, and moderate in disk mass and lifetime even at moderate irra… ▽ More Protoplanetary disk evolution can be deeply influenced by the UV radiation emitted by neighboring massive stars (mainly of spectral type O and B). We show that the process of external photoevaporation, which causes an outside-in depletion of disk material due to environmental UV radiation, can lead to a significant decrease in disk size, and moderate in disk mass and lifetime even at moderate irradiation levels (1-10 G$_{0}$). In this work we investigate the role of external photoevaporation in shaping the masses and sizes of the ten AGE-PRO disks in the Upper Scorpius region, which we estimate to be subject to FUV fluxes ranging between 2 and 12 G$_{0}$, on average. We compare the disk masses and sizes resulting from 1D numerical viscous evolution simulations in which the effect of external photoevaporation is included, to the values retrieved from the AGE-PRO observations. While the pure viscous framework fails in adequately explaining the observed disk properties in Upper Scorpius, with the inclusion of external photoevaporation we can successfully reproduce gas disk sizes for 7 out of 10 sources within a factor <2, when the initial disk mass is 1-10% of the stellar mass. We emphasize the importance of accounting for the environmental irradiation when comparing star-forming regions of different ages, even when moderate FUV irradiation fields are experienced, as in the case of Upper Scorpius. △ Less

Submitted 14 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: ApJ special issue of AGE-PRO

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): VII. Testing accretion mechanisms from disk population synthesis

Authors: Benoît Tabone, Giovanni P. Rosotti, Leon Trapman, Paola Pinilla, Ilaria Pascucci, Alice Somigliana, Richard Alexander, Miguel Vioque, Rossella Anania, Aleksandra Kuznetsova, Ke Zhang, Laura M. Pérez, Lucas A. Cieza, John Carpenter, Dingshan Deng, Carolina Agurto-Gangas, Dary A. Ruíz-Rodríguez, Anibal Sierra, Nicolás T. Kurtovic, James Miley, Camilo González-Ruilova, Estephani TorresVillanueva, Michiel R. Hogerheijde, Kamber Schwarz, Claudia Toci , et al. (2 additional authors not shown)

Abstract: The architecture of planetary systems depends on the evolution of the disks in which they form. In this work, we develop a population synthesis approach to interpret the AGE-PRO measurements of disk gas mass and size considering two scenarios: turbulence-driven evolution with photoevaporative winds and MHD disk-wind-driven evolution. A systematic method is proposed to constrain the distribution of… ▽ More The architecture of planetary systems depends on the evolution of the disks in which they form. In this work, we develop a population synthesis approach to interpret the AGE-PRO measurements of disk gas mass and size considering two scenarios: turbulence-driven evolution with photoevaporative winds and MHD disk-wind-driven evolution. A systematic method is proposed to constrain the distribution of disk parameters from the disk fractions, accretion rates, disk gas masses, and CO gas sizes. We find that turbulence-driven accretion with initially compact disks ($R_0 \simeq 5-20~$au), low mass-loss rates, and relatively long viscous timescales ($t_{ν,0} \simeq 0.4-3~$Myr or $α_{SS} \simeq 2-4 \times 10^{-4}$) can reproduce the disk fraction and gas sizes. However, the distribution of apparent disk lifetime defined as the $M_D/\dot{M}_*$ ratio is severely overestimated by turbulence-driven models. On the other hand, MHD wind-driven accretion can reproduce the bulk properties of the disk populations from Ophiuchus to Upper Sco assuming compact disks with an initial magnetization of about $β\simeq 10^5$ ($α_{DW} \simeq 0.5-1 \times 10^{-3}$) and a magnetic field that declines with time. More studies are needed to confirm the low masses found by AGE-PRO, notably for compact disks that question turbulence-driven accretion. The constrained synthetic disk populations can now be used for realistic planet population models to interpret the properties of planetary systems on a statistical basis. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): VI. Comparison of Dust Evolution Models to AGE-PRO Observations

Authors: Nicolas T. Kurtovic, Matias Gárate, Paola Pinilla, Ke Zhang, Giovanni P. Rosotti, Rossella Anania, Ilaria Pascucci, Benoît Tabone, Leon Trapman, Dingshan Deng, Miguel Vioque, John Carpenter, Lucas A. Cieza, Laura M. Pérez, Carolina Agurto-Gangas, Anibal Sierra, Dary A. Ruíz-Rodriguez, James Miley, Camilo González-Ruilova, Estephani Torres-Villanueva, Aleksandra Kuznetsova

Abstract: The potential for planet formation of a circumstellar disk depends on the dust and gas reservoirs, which evolve as a function of the disk age. The ALMA Large Program AGE-PRO has measured several disk properties across three star-forming regions of different ages, and in this study we compare the observational results to dust evolution simulations. Using DustPy for the dust evolution, and RADMC-3D… ▽ More The potential for planet formation of a circumstellar disk depends on the dust and gas reservoirs, which evolve as a function of the disk age. The ALMA Large Program AGE-PRO has measured several disk properties across three star-forming regions of different ages, and in this study we compare the observational results to dust evolution simulations. Using DustPy for the dust evolution, and RADMC-3D for the radiative transfer, we ran a large grid of models spanning stellar masses of 0.25, 0.50, 0.75, and 1.0 $M_\odot$, with different initial conditions, including: disk sizes, disk gas masses, and dust-to-gas ratio, and viscosity. Our models are performed assuming smooth, weakly, or strongly substructured disks, aiming to investigate if any observational trend can favor or exclude the presence of dust traps. The observed gas masses in the disks of the AGE-PRO sample are not reproducible with our models, which only consider viscous evolution with constant $α$, suggesting that additional physical mechanisms play a role in the evolution of the gas mass of disks. When comparing the dust continuum emission fluxes and sizes at 1.3 mm, we find that most of the disks in the AGE-PRO sample are consistent with simulations that have either weak or strong dust traps. The evolution of spectral index in the AGE-PRO sample is also suggestive of an unresolved population of dust traps. Future observations at high angular resolution are still needed to test several hypotheses that result from comparing the observations to our simulations, including that more massive disks in gas mass have the potential to form dust traps at larger disk radii. △ Less

Submitted 25 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO. New version with updated references

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): V. Protoplanetary gas disk masses

Authors: Leon Trapman, Ke Zhang, Giovanni P. Rosotti, Paola Pinilla, Benoît Tabone, Ilaria Pascucci, Carolina Agurto-Gangas, Rossella Anania, John Carpenter, Lucas A. Cieza, Dingshan Deng, Camilo González-Ruilova, Michiel R. Hogerheijde, Nicolás T. Kurtovic, Aleksandra Kuznetsova, James Miley, Laura M. Pérez, Dary A. Ruíz-Rodríguez, Kamber Schwarz, Anibal Sierra, Estephani TorresVillanueva, Miguel Vioque

Abstract: The evolution of the gas mass of planet-forming disks around young stars is crucial for our understanding of planet formation, yet it has proven hard to constrain observationally, due both to the difficulties of measuring gas masses and the lack of a homogeneous sample. Here we present a large grid of thermochemical models which we use to measure protoplanetary gas disk masses of AGE-PRO, the ALMA… ▽ More The evolution of the gas mass of planet-forming disks around young stars is crucial for our understanding of planet formation, yet it has proven hard to constrain observationally, due both to the difficulties of measuring gas masses and the lack of a homogeneous sample. Here we present a large grid of thermochemical models which we use to measure protoplanetary gas disk masses of AGE-PRO, the ALMA survey of Gas Evolution in PROtoplanetary disks. AGE-PRO covers a sample of 30 disks around similar spectral type (M3-K6) stars with ages between 0.1 and 10 Myr. Our approach is to simultaneously fit observations of CO isotopologues and N2H+, a complementary molecule produced when CO freezes out. We find that the median gas mass of the three regions decreases over time, from 7.0(+4.4,-2.6)x10^-3 Msun in Ophiuchus (<1 Myr) to 9.4(+5.4,-3.4)x10^-4 Msun for Lupus (~1-3 Myr) and 6.8(+5.1,-2.8)x10^-4 Msun for Upper Sco (~2-6 Myr), with ~1 dex scatter in gas mass in each region. We note that the gas mass distributions for Lupus and Upper Sco look very similar, which could be due to survivorship bias for the latter. The median bulk CO abundance in the CO emitting layer is found to be a factor ~10 lower than the ISM value but does not significantly change between Lupus and Upper Sco. From Lupus to Upper Sco the median gas-to-dust mass ratio increases by a factor ~3 from ~40 to ~120, suggesting efficient inward pebble drift and/or the formation of planetesimals. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): IV. Dust and Gas Disk Properties in the Upper Scorpius Star-forming Region

Authors: Carolina Agurto-Gangas, L. M. Pérez, Anibal Sierra, James Miley, Ke Zhang, Ilaria Pascucci, Paola Pinilla, Dingshan Deng, John Carpenter, Leon Trapman, Miguel Vioque, Giovanni P. Rosotti, Nicolás Kurtovic, Lucas A. Cieza, Kamber Schwarz, Michiel R. Hogerheijde, Rossella Anania, Benoît Tabone, Estephani E. Torres-Villanueva, Dary A. Ruiz-Rodriguez, Camilo González-Ruilova

Abstract: The Atacama Large Millimeter/submillimeter Array (ALMA) large program AGE-PRO explores protoplanetary disk evolution by studying gas and dust across various ages. This work focuses on ten evolved disks in Upper Scorpius, observed in dust continuum emission, CO and its isotopologues, and N$_2$H$^+$ with ALMA Bands 6 and 7. Disk radii, from the radial location enclosing 68% of the flux, are comparab… ▽ More The Atacama Large Millimeter/submillimeter Array (ALMA) large program AGE-PRO explores protoplanetary disk evolution by studying gas and dust across various ages. This work focuses on ten evolved disks in Upper Scorpius, observed in dust continuum emission, CO and its isotopologues, and N$_2$H$^+$ with ALMA Bands 6 and 7. Disk radii, from the radial location enclosing 68% of the flux, are comparable to those in the younger Lupus region for both gas and dust tracers. However, solid masses are about an order of magnitude below those in Lupus and Ophiuchus, while the dust spectral index suggests some level of dust evolution. These empirical findings align with a combination of radial drift, dust trapping, and grain growth into larger bodies. A moderate correlation between CO and continuum fluxes suggests a link between gas and dust content, through the increased scatter compared to younger regions, possibly due to age variations, gas-to-dust ratio differences, or CO depletion. Additionally, the correlation between C$^{18}$O and N$_2$H$^+$ fluxes observed in Lupus persists in Upper Sco, indicating a relatively stable CO gas abundance over the Class II stage of disk evolution. In conclusion, the AGE-PRO survey of Upper Scorpius disks reveals intriguing trends in disk evolution. The findings point towards potential gas evolution and the presence of dust traps in these older disks. Future high-resolution observations are needed to confirm these possibilities and further refine our understanding of disk evolution and planet formation in older environments. △ Less

Submitted 12 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: Published in ApJ for the special issue of AGE-PRO

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): III. Dust and Gas Disk Properties in the Lupus Star-forming Region

Authors: Dingshan Deng, Miguel Vioque, Ilaria Pascucci, Laura M. Pérez, Ke Zhang, Nicolás T. Kurtovic, Leon Trapman, Estephani E. TorresVillanueva, Carolina Agurto-Gangas, John Carpenter, Paola Pinilla, Uma Gorti, Benoît Tabone, Anibal Sierra, Giovanni P. Rosotti, Lucas A. Cieza, Rossella Anania, Camilo González-Ruilova, Michiel R. Hogerheijde, James Miley, Dary A. Ruiz-Rodriguez, Maxime Ruaud, Kamber Schwarz

Abstract: We present Band 6 and Band 7 observations of 10 Lupus disks around M3-K6 stars from the ALMA survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program. In addition to continuum emission in both bands, our Band 6 setup covers the $\mathrm{{}^{12}CO}$, $\mathrm{{}^{13}CO}$ and $\mathrm{C^{18}O}\,J$=2-1 lines, while our Band 7 setup covers the $\mathrm{N_2H^+}\,J$=3-2 line. All of our s… ▽ More We present Band 6 and Band 7 observations of 10 Lupus disks around M3-K6 stars from the ALMA survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program. In addition to continuum emission in both bands, our Band 6 setup covers the $\mathrm{{}^{12}CO}$, $\mathrm{{}^{13}CO}$ and $\mathrm{C^{18}O}\,J$=2-1 lines, while our Band 7 setup covers the $\mathrm{N_2H^+}\,J$=3-2 line. All of our sources are detected in $\mathrm{{}^{12}CO}$ and $\mathrm{{}^{13}CO}$, 7 out of 10 are detected in $\mathrm{C^{18}O}$, and 3 are detected in $\mathrm{N_2H^+}$. We find strong correlations between the CO isotopologue line fluxes and the continuum flux densities. With the exception of one disk, we also identify a strong correlation between the $\mathrm{C^{18}O}\,J$=2-1 and $\mathrm{N_2H^+}\,J$=3-2 fluxes, indicating similar CO abundances across this sample. For the two sources with well-resolved continuum and $\mathrm{{}^{12}CO}\,J$=2-1 images, we find that their gas-to-dust size ratio is consistent with the median value of $\sim 2$ inferred from a larger sample of Lupus disks. We derive dust disk masses from continuum flux densities. We estimate gas disk masses by comparing $\mathrm{C^{18}O}\,J$=2-1 line fluxes with those predicted by the limited grid of self-consistent disk models of Ruaud et al. (2022). A comparison of these mass estimates with those derived by Trapman et al. (2025), using a combination of CO isotopologue and $\mathrm{N_2H^+}$ line emission, shows that the masses are consistent with each other. Some discrepancies appear for small and faint disks, but they are still within the uncertainties. Both methods find gas disk masses increase with dust disk masses, and gas-to-dust mass ratios are between $10-100$ in the AGE-PRO Lupus sample. △ Less

Submitted 8 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: Published in ApJ for the special issue of AGE-PRO

Journal ref: 2025ApJ...989....3D

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): II. Dust and Gas Disk Properties in the Ophiuchus Star-forming Region

Authors: Dary A. Ruíz-Rodríguez, Camilo González-Ruilova, Lucas A. Cieza, Ke Zhang, Leon Trapman, Anibal Sierra, Paola Pinilla, Ilaria Pascucci, Laura M. Pérez, Dingshan Deng, Carolina Agurto-Gangas, John Carpenter, Benoît Tabone, Giovanni P. Rosotti, Rossella Anania, James Miley, Kamber Schwarz, Aleksandra Kuznetsova, Miguel Vioque, Nicolas Kurtovic

Abstract: The ALMA survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program aims to trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks. This paper presents Band-6 ALMA observations of 10 embedded (Class I and Flat Spectrum) sources in the Ophiuchus molecular cloud, with spectral types ranging from M3 to K6 stars, which serve as the evolutionary start… ▽ More The ALMA survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program aims to trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks. This paper presents Band-6 ALMA observations of 10 embedded (Class I and Flat Spectrum) sources in the Ophiuchus molecular cloud, with spectral types ranging from M3 to K6 stars, which serve as the evolutionary starting point in the AGE-PRO sample. While we find 4 nearly edge on disks (>70 deg.), and 3 highly inclined disks (>60 deg.) in our sample, we show that, as a population, embedded disks in Ophiuchus are not significantly contaminated by more evolved, but highly inclined sources. We derived dust disk masses from the Band 6 continuum and estimated gas disk masses from the C18O and C17O lines. The mass estimates from the C17O line are slightly higher, suggesting C18O emission might be partially optically thick. While the 12CO and 13CO lines are severely contaminated by extended emission and self-absorption, the C18O and C17O lines allowed us to trace the radial extent of the gaseous disks. From these measurements, we found that the C18O and C17O fluxes correlate well with each other and with the continuum fluxes. Furthermore, the C18O and C17O lines present a larger radial extension than disk dust sizes by factors ranging from 1.5 to 2.5, as it is found for Class II disks using the radial extension of the 12CO. In addition, we have detected outflows in three disks from 12CO observations. △ Less

Submitted 25 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJ for the special issue of AGE-PRO

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): I. Program Overview and Summary of First Results

Authors: Ke Zhang, Laura M. Pérez, Ilaria Pascucci, Paola Pinilla, Lucas A. Cieza, John Carpenter, Leon Trapman, Dingshan Deng, Carolina Agurto-Gangas, Anibal Sierra, Nicolás T. Kurtovic, Dary A. Ruíz-Rodríguez, Miguel Vioque, James Miley, Benoît Tabone, Camilo González-Ruilova, Rossella Anania, Giovanni P. Rosotti, Estephani TorresVillanueva, Michiel R. Hogerheijde, Kamber Schwarz, Aleksandra Kuznetsova

Abstract: We present the ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO), a Large Program of the Atacama Large Millimeter/submillimeter Array (ALMA). AGE-PRO aims to systematically trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks. It uses a carefully selected sample of 30 disks around M3-K6 stars in three nearby star-forming regions: Ophiuchus (0.5… ▽ More We present the ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO), a Large Program of the Atacama Large Millimeter/submillimeter Array (ALMA). AGE-PRO aims to systematically trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks. It uses a carefully selected sample of 30 disks around M3-K6 stars in three nearby star-forming regions: Ophiuchus (0.5-1 Myr), Lupus (1-3 Myr), and Upper Sco (2-6 Myr). Assuming the three regions had similar initial conditions and evolutionary paths, we find the median gas disk mass appears to decrease with age. Ophiuchus disks have the highest median gas mass (6 M$_{\rm Jup}$), while the Lupus and Upper Sco disks have significantly lower median masses (0.68 and 0.44 M$_{\rm Jup}$, respectively). Notably, the gas and dust disk masses appear to evolve on different timescales. This is evidenced by the median gas-to-dust mass ratio, which decreases from 122 in the youngest disks ($<$1 Myr) to 46 in Lupus disks, and then increases to 120 in the Upper Sco disks. The median gas disk sizes range between 74-110 au, suggesting that typical gas disks are much smaller than those of well-studied, massive disks. Population synthesis models suggest that magneto-hydrodynamic wind-driven accretion can reproduce median disk properties across all three regions, when assuming compact disks with a declining magnetic field over time. In contrast, turbulent-driven models overestimate gas masses of $>$1 Myr disks by an order of magnitude. Here we discuss the program's motivation, survey design, sample selection, observation and data calibration processes, and highlight the initial results. △ Less

Submitted 25 August, 2025; v1 submitted 12 June, 2025; originally announced June 2025.

Comments: first paper of the ApJ special issue of AGE-PRO, udpated for AGE-PRO formal references

New Symbiotic Stars from LAMOST DR10 Spectra and Multi-band Photometry

Authors: Jing Chen, Liang Wang, Yin-Bi Li, Xiao-Xiao Ma, A-Li Luo, Zi-Chong Zhang, Ming-Yi Ding, Kai Zhang

Abstract: Symbiotic star (SySt) is long-period interacting binary system, typically consisting of a white dwarf and a red giant surrounded by a nebula. These systems are natural astrophysical laboratories for investigating binary star evolution. In this paper, we identified nine SySts from the LAMOST DR10 low-resolution spectra survey, seven of which were previously known, while two are newly identified. In… ▽ More Symbiotic star (SySt) is long-period interacting binary system, typically consisting of a white dwarf and a red giant surrounded by a nebula. These systems are natural astrophysical laboratories for investigating binary star evolution. In this paper, we identified nine SySts from the LAMOST DR10 low-resolution spectra survey, seven of which were previously known, while two are newly identified. Initially, we selected LAMOST spectra exhibiting typical SySt emission lines (e.g., $\rm H_α, ~H_β, ~H_γ, ~and ~He II$). Subsequently, we utilized the distribution of known SySts on the HR diagram to select SySt candidates, and visually inspected their spectra. Ultimately, we classified all nine as S-type SySts using the $J - H$ vs. $H - K$ diagram. Additionally, based on multi-band photometric data from GALEX, Gaia, 2MASS, ALLWISE, and several X-ray catalogs, we found 12 accreting-only SySt (acc-SySt) candidates, characterized by concurrent ultraviolet and infrared excess and accretion process. Furthermore, we estimated the white dwarf temperatures by fitting their observed SEDs using a combination of Kurucz stellar atmosphere model and Koester white dwarf model. We compared the accretion rates of acc-SySt candidates and confirmed SySts, and found they have similar accretion rate distribution, providing evidence that these acc-SySt candidates constitute bona fide SySts. △ Less

Submitted 10 June, 2025; originally announced June 2025.

Comments: 13 pages, 8 figures, Accepted by ApJ

The Impact of Fiber Cross Contamination on Radial Velocity Precision

Authors: Chenyang Ji, Sharon Xuesong Wang, Kai Zhang, Liang Wang

Abstract: High-resolution spectrographs with precise radial velocity (PRV) capabilities require careful considerations in instrumental design and data processing in order to reach the 10 cm/s-level precision, which is needed for detecting Earth-like planets. In this work, we investigate the impact of fiber cross contamination on the RV precision via simulations, as modern PRV spectrographs often have multip… ▽ More High-resolution spectrographs with precise radial velocity (PRV) capabilities require careful considerations in instrumental design and data processing in order to reach the 10 cm/s-level precision, which is needed for detecting Earth-like planets. In this work, we investigate the impact of fiber cross contamination on the RV precision via simulations, as modern PRV spectrographs often have multiple fiber traces on their spectral images. We simulated extracted 1-D spectra under the preliminary design of CHORUS, short for the Canary Hybrid Optical high-Resolution Ultra-stable Spectrograph, a dual-arm PRV spectrograph under construction for the Gran Telescopio de Canarias. We considered two types of fiber cross contaminations: contamination from calibration traces to neighboring science traces (or cal-sci contamination) and between science traces (or sci-sci contamination). We present results in four different scenarios: photon noise only, cal-sci contamination only, sci-sci contamination only, and all effects combined. For the preliminary design of CHORUS, we estimated that the cal-sci contamination fraction is smaller than 0.0001% in flux across the whole CCD for either arm, resulting in a negligible impact on the RV precision. Assuming worst-case scenarios, we estimated the sci-sci contamination to be up to 0.1% in some traces, corresponding to an additional RV error of up to 10 cm/s. We demonstrate the importance of considering fiber-trace spacing and cross contamination in PRV spectrographs, and we recommend careful design, operation, and spectral extraction algorithms to minimize and mitigate cross contamination to achieve the best possible instrumental RV precision. △ Less

Submitted 26 May, 2025; originally announced May 2025.

Comments: 16 pages, 14 figures, accepted for publication in PASP

The JDISC Survey: Linking the Physics and Chemistry of Inner and Outer Protoplanetary Disk Zones

Authors: Nicole Arulanantham, Colette Salyk, Klaus Pontoppidan, Andrea Banzatti, Ke Zhang, Karin Öberg, Feng Long, John Carr, Joan Najita, Ilaria Pascucci, María José Colmenares, Chengyan Xie, Jane Huang, Joel Green, Sean M. Andrews, Geoffrey A. Blake, Edwin A. Bergin, Paola Pinilla, Miguel Vioque, Emma Dahl, Eshan Raul, Sebastiaan Krijt, the JDISCS Collaboration

Abstract: Mid-infrared spectroscopy of protoplanetary disks provides a chemical inventory of gas within a few au, where planets are readily detected around older stars. With the JWST Disk Infrared Spectral Chemistry Survey (JDISCS), we explore demographic trends among 31 disks observed with MIRI (MRS) and with previous ALMA millimeter continuum imaging at high angular resolution (5-10 au). With these S/N… ▽ More Mid-infrared spectroscopy of protoplanetary disks provides a chemical inventory of gas within a few au, where planets are readily detected around older stars. With the JWST Disk Infrared Spectral Chemistry Survey (JDISCS), we explore demographic trends among 31 disks observed with MIRI (MRS) and with previous ALMA millimeter continuum imaging at high angular resolution (5-10 au). With these S/N $\sim$200-450 spectra, we report emission from H$_2$O, OH, CO, C$_2$H$_2$, HCN, CO$_2$, [Ne II], [Ne III], and [Ar II]. Emission from H$_2$O, OH and CO is nearly ubiquitous for low-mass stars, and detection rates of all molecules are higher than for similar disks observed with Spitzer-IRS. Slab model fits to the molecular emission lines demonstrate that emission from C$_2$H$_2$, HCN, and possibly CO$_2$ is optically thin; thus since column densities and emitting radii are degenerate, observations are actually sensitive to the total molecular mass. C$_2$H$_2$ and HCN emission also typically originate in a hotter region ($920^{+70}_{-130}$, $820^{+70}_{-130}$ K, respectively) than CO$_2$ ($600^{+200}_{-160}$ K). The HCN to cold H$_2$O luminosity ratios are generally smaller in smooth disks, consistent with more efficient water delivery via icy pebbles in the absence of large dust substructures. The molecular emission line luminosities are also correlated with mass accretion rates and infrared spectral indices, similar to trends reported from Spitzer-IRS surveys. This work demonstrates the power of combining multi-wavelength observations to explore inner disk chemistry as a function of outer disk and stellar properties, which will continue to grow as the sample of observed Class II systems expands in the coming JWST observation cycles. △ Less

Submitted 25 June, 2025; v1 submitted 12 May, 2025; originally announced May 2025.

Comments: Accepted for publication in The Astronomical Journal; 43 pages, 21 figures; slab model fits for all targets will be included in the online journal and are available at https://github.com/narulanantham/JDISCS_Cyc1_slabmodelfits.git; updated y-axis label on Figure 17 on 25 June 2025

Hot Holographic 2-flavor Quark Star

Authors: Le-Feng Chen, Jing-Yi Wu, Hao Feng, Tian-Shun Chen, Kilar Zhang

Abstract: Applying the holographic 2-flavor Einstein--Maxwell-dilaton model, the parameters of which are fixed by lattice QCD, we extract the equations of state for hot quark--gluon plasma around the critical point at T=182 MeV, and have corresponding quark star cores constructed. By further adding hadron shells, the mass range of the whole stars spans from 2 to 17 solar masses, with the maximum compactness… ▽ More Applying the holographic 2-flavor Einstein--Maxwell-dilaton model, the parameters of which are fixed by lattice QCD, we extract the equations of state for hot quark--gluon plasma around the critical point at T=182 MeV, and have corresponding quark star cores constructed. By further adding hadron shells, the mass range of the whole stars spans from 2 to 17 solar masses, with the maximum compactness around 0.22. This result allows them to be black hole mimickers and candidates for gap events. The I--Love--Q--C relations are also analyzed, which show consistency with the neutron star cases when the discontinuity at the quark--hadron interface is not large. Furthermore, we illustrate the full parameter maps of the energy density and pressure as functions of the temperature and chemical potential and discuss the constant thermal conductivity case supposing a heat source inside. △ Less

Submitted 20 June, 2025; v1 submitted 7 May, 2025; originally announced May 2025.

Comments: 22 pages, 9 figures; v2: typos corrected; v3: minor revisions, references added, published version

ExoALMA XIII. gas masses from N2H+ and C18O: a comparison of protoplanetary gas disk mass measurement techniques

Authors: Leon Trapman, Cristiano Longarini, Giovanni P. Rosotti, Sean M. Andrews, Jaehan Bae, Marcelo Barraza-Alfaro, Myriam Benisty, Gianni Cataldi, Pietro Curone, Ian Czekala, Stefano Facchini, Daniele Fasano, Mario Flock, Misato Fukagawa, Maria Galloway-Sprietsma, Himanshi Garg, Cassandra Hall, Jane Huang, John D. Ilee, Andres F. Izquierdo, Kazuhiro Kanagawa, Geoffroy Lesur, Giuseppe Lodato, Ryan A. Loomis, Ryuta Orihara , et al. (15 additional authors not shown)

Abstract: The gas masses of protoplanetary disks are important but elusive quantities. In this work we present new ALMA observations of N2H+ (3-2) for 11 exoALMA disks. N2H+ is a molecule sensitive to CO freeze-out and has recently been shown to significantly improve the accuracy of gas masses estimated from CO line emission. We combine these new observations with archival N2H+ and CO isotopologue observati… ▽ More The gas masses of protoplanetary disks are important but elusive quantities. In this work we present new ALMA observations of N2H+ (3-2) for 11 exoALMA disks. N2H+ is a molecule sensitive to CO freeze-out and has recently been shown to significantly improve the accuracy of gas masses estimated from CO line emission. We combine these new observations with archival N2H+ and CO isotopologue observations to measure gas masses for 19 disks, predominantly from the exoALMA Large program. For 15 of these disks the gas mass has also been measured using gas rotation curves. We show that the CO + N2H+ line emission-based gas masses typically agree with the kinematically measured ones within a factor 3 (1-2σ). Gas disk masses from CO + N2H+ are on average a factor 2.3(+0.7,-1.0) x lower than the kinematic disk masses, which could suggest slightly lower N2 abundances and/or lower midplane ionization rates than typically assumed. Herbig disks are found to have ISM level CO gas abundances based on their CO and N2H+ fluxes, which sets them apart from T-Tauri disks where abundances are typically 3-30x lower. The agreement between CO + N2H+ -based and kinematically measured gas masses is promising and shows that multi-molecule line fluxes are a robust tool to accurately measure disk masses at least for extended disks. △ Less

Submitted 30 April, 2025; v1 submitted 27 April, 2025; originally announced April 2025.

Comments: 20 pages, 9 figures, 4 tables. This paper is part of the exoALMA Focus Issue of The Astrophysical Journal Letters

A Multi-line Analysis of the Distribution and Excitation of CS and H$_2$CS in the HD 163296 Disk

Authors: Charles J. Law, Romane Le Gal, Yoshihide Yamato, Ke Zhang, Viviana V. Guzmán, Claudio Hernández-Vera, L. Ilsedore Cleeves, Greta Guidi, Alice S. Booth

Abstract: The abundance and distribution of sulfur-bearing molecules in protoplanetary disks directly influences the composition and potential habitability of nascent planets in addition to providing powerful probes of the physical gas conditions in the disks themselves. Here, we present new and archival ALMA and SMA observations of CS and H$_2$CS, and their C$^{34}$S and H$_2$C$^{34}$S isotopologues, at hi… ▽ More The abundance and distribution of sulfur-bearing molecules in protoplanetary disks directly influences the composition and potential habitability of nascent planets in addition to providing powerful probes of the physical gas conditions in the disks themselves. Here, we present new and archival ALMA and SMA observations of CS and H$_2$CS, and their C$^{34}$S and H$_2$C$^{34}$S isotopologues, at high-angular resolution (${\approx}$0."2-0."4; 20-40 au) in the HD 163296 disk, which reveal a central cavity and multi-ringed emission structure. These observations comprise the most comprehensive, multi-line CS data in a planet-forming disk to date, spanning a wide range of excitation conditions from E$_{\rm{u}}$=7.1 K to 129.3 K, and include new detections of C$^{34}$S, H$_2$CS, and H$_2$C$^{34}$S in this system. Using these data, we derive spatially-resolved rotational temperature and column density profiles for all species. We find a column density ratio N(H$_2$CS)/N(CS) $\approx$ 0.5, which is comparable to that of the similar MWC 480 disk and suggests that organic sulfur compounds may constitute a large fraction of the volatile sulfur reservoir in disks around Herbig stars generally. We derive $^{32}$S/$^{34}$S ratios of ${\approx}$5 (CS/C$^{34}$S) and ${\approx}$2 (H$_2$CS/H$_2$C$^{34}$S) based on disk-averaged and spatially-resolved analyses. Both values are consistent across these two pairs of optically-thin molecules and are well-below the expected ISM ratio of ${\approx}$22, suggesting significant sulfur fractionation. We also constrain the CS emitting layer ($z/r\lesssim 0.1$) using the vertical separations of the disk surfaces in the channel maps and based on the known 2D gas structure of the HD 163296 disk combined with our excitation analysis. △ Less

Submitted 20 March, 2025; originally announced March 2025.

Comments: 22 pages, 13 figures, accepted for publication in ApJ

Ring or no ring -- Revisiting the Multiphase Nuclear Environment in M31

Authors: Zongnan Li, Zhao Su, Sumin Wang, Yufan F. Zhou, Zhiyuan Li, Xuanyi Lyu, Fanyi Meng, Kai Zhang, Di Li, Chaowei Tsai, Jingwen Wu, Jiachang Zhang

Abstract: Nuclear rings, prevalent in barred galaxies, are essential to understanding gas transport toward galactic nuclei. However, the peculiar nuclear ring in our neighboring galaxy M31 remains poorly understood. Here we present a comprehensive study of this multiphase gas structure, originally revealed by its dust emission, based on newly acquired CO mappings and archival spectroscopic imaging of atomic… ▽ More Nuclear rings, prevalent in barred galaxies, are essential to understanding gas transport toward galactic nuclei. However, the peculiar nuclear ring in our neighboring galaxy M31 remains poorly understood. Here we present a comprehensive study of this multiphase gas structure, originally revealed by its dust emission, based on newly acquired CO mappings and archival spectroscopic imaging of atomic hydrogen and warm ionized gas, along with custom numerical simulations. These multi-wavelength data offer an unprecedented view of the surface mass density and kinematics of the nuclear ring, challenging the notion of it being a single coherent structure. In particular, the ring shows significant asymmetry in its azimuthal mass distribution, with neutral gas concentrated in the northeast and ionized gas prominent in the southwest. The observed off-centered and lopsided morphology disfavors an interpretation of gas streamers or resonance rings driven solely by a barred potential known to exist in M31. Furthermore, the ring's line-of-sight velocity distribution suggests circular motion in a plane inclined by $\sim 30^\circ$ relative to M31's outer disk, implying external torque likely from M32's recent close-in passage. Our hydrodynamical simulations tracking the evolution of nuclear gas of M31 influenced by both a barred potential and an oblique collision with M32, reveal the natural formation of asymmetric spiral arms several hundred Myr after the collision, which could appear ring-like under appropriate viewing angles. Therefore, we suggest that M31's nuclear gas structure, instead of being a persisting rotating ring, comprises recently formed, asymmetric spirals with a substantial tilt. △ Less

Submitted 15 March, 2025; originally announced March 2025.

Comments: 24 pages, 10 figures, accepted for publication in ApJ

Tiny-Scale Properties within the Interstellar Medium towards PSR J1644$-$4559: I. Observational Evidence of Turbulence-induced Tiny Scale Atomic Structures

Authors: Mengting Liu, Di Li, J. R. Dawson, Joel M. Weisberg, Snežana Stanimirović, George Hobbs, Simon Johnston, Lawrence Toomey, Siyao Xu, Chao-Wei Tsai, Donghui Quan, Stacy Mader, James A. Green, Lei Zhang, Ningyu Tang, Pei Wang, Kai Zhang, Pei Zuo, Gan Luo, Yi Feng, Shi Dai, Aditi Kaushik, Mengyao Xue, Chenchen Miao

Abstract: We investigated HI absorption toward a single pulsar, PSR J1644$-$4559, and its variability over timescales from days to years, using Murriyang, CSIRO's Parkes Radio Telescope. Our 19 epochs of spectral observations, spanning 1.2 years with intervals as short as 1 day, provide the most comprehensive cadence coverage for monitoring HI absorption to date. We identified two significant detections of… ▽ More We investigated HI absorption toward a single pulsar, PSR J1644$-$4559, and its variability over timescales from days to years, using Murriyang, CSIRO's Parkes Radio Telescope. Our 19 epochs of spectral observations, spanning 1.2 years with intervals as short as 1 day, provide the most comprehensive cadence coverage for monitoring HI absorption to date. We identified two significant detections of tiny-scale atomic structure (TSAS) with spatial scales ranging from a lower limit of $\sim$11 au to an upper limit of 165 au, both exhibiting integrated signal-to-noise ratios exceeding 5.0. We find a relationship between linear size and optical depth variation in the cold neutral medium (CNM) component hosting the TSAS, described by a power-law relationship, $Δτ_{\rm int} = Δτ_0 (ΔL)^{(α-2)/2}$, with $α= 4.1 \pm 0.4$. This is the first observational evidence explicitly connecting TSAS to turbulence in CNM. This power-law index is significantly steeper than previously reported values for the CNM, where $α$ ranges from 2.3 to 2.9, but similar to those observed in the warm ionized gas. Additionally, we observe no significant variation in $α$ across the entire range of spatial scales traced in our study, indicating that turbulence may be cascading down and dissipating at smaller scales. While there is no precise proper motion measurement for this pulsar, our estimates for the turbulence dissipation in the CNM place the lower and upper limits at less than 0.03 au and 0.4 au, respectively. △ Less

Submitted 12 March, 2025; originally announced March 2025.

Comments: 37 pages, 19 figures, accepted for publication in ApJS

An active repeating fast radio burst in a magnetized eruption environment

Authors: Y. Li, S. B. Zhang, Y. P. Yang, C. W. Tsai, X. Yang, C. J. Law, R. Anna-Thomas, X. L. Chen, K. J. Lee, Z. F. Tang, D. Xiao, H. Xu, X. L. Yang, G. Chen, Y. Feng, D. Z. Li, R. Mckinven, J. R. Niu, K. Shin, B. J. Wang, C. F. Zhang, Y. K. Zhang, D. J. Zhou, Y. H. Zhu, Z. G. Dai , et al. (13 additional authors not shown)

Abstract: Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild magneto-ionic environmental variations, possibly attributed to plasma turbulence or geometric configuration variation in a binary system. Here we report an abrupt magneto-ionic environment variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift 0.1839. In… ▽ More Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild magneto-ionic environmental variations, possibly attributed to plasma turbulence or geometric configuration variation in a binary system. Here we report an abrupt magneto-ionic environment variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift 0.1839. Initially, its Faraday rotation measure (RM) was $21 \pm 96~{\rm rad~m^{-2}}$ over 17 months. In December 2023, it jumped to $1976.9~{\rm rad~m^{-2}}$, exceeding twenty times of the standard deviation of the previous RM variation, and returned to the typical values within two weeks. Such a drastic RM variation suggests a dense magnetized clump moving across the line of sight, possibly due to coronal mass ejection associated with a stellar flare. It indicates that the FRB likely has a companion star that produced the stellar flare. △ Less

Submitted 6 March, 2025; originally announced March 2025.

Comments: 43 pages, 9 figures, under review in Science, the authors' original version

Massive vector field perturbations in the Schwarzschild spacetime from supersymmetric gauge theory

Authors: Xian-Hui Ge, Masataka Matsumoto, Kilar Zhang

Abstract: We unify the dynamics of massive vector (Proca) fields in Schwarzschild spacetime with supersymmetric gauge theories through the Seiberg-Witten/quasinormal mode (SW/QNM) duality. By mapping Proca perturbations-specifically monopole and odd-parity modes governed by confluent Heun equations-to the quantum Seiberg-Witten curve, we establish a gauge-gravity correspondence. Leveraging instanton countin… ▽ More We unify the dynamics of massive vector (Proca) fields in Schwarzschild spacetime with supersymmetric gauge theories through the Seiberg-Witten/quasinormal mode (SW/QNM) duality. By mapping Proca perturbations-specifically monopole and odd-parity modes governed by confluent Heun equations-to the quantum Seiberg-Witten curve, we establish a gauge-gravity correspondence. Leveraging instanton counting, we analytically compute QNM and quasi-bound state frequencies to high precision, resolving spectral properties non-perturbatively. Our results align with numerical benchmarks while extending the SW framework beyond scalar fields. △ Less

Submitted 29 August, 2025; v1 submitted 21 February, 2025; originally announced February 2025.

Comments: 19 pages, 3 tables, 2 figures; v2: minor revisions, published version

Strong backreaction of gauge quanta produced during inflation

Authors: Jian-Feng He, Kai-Ge Zhang, Chengjie Fu, Zong-Kuan Guo

Abstract: During inflation an axion field coupled to a gauge field through a Chern-Simons term can trigger the production of gauge quanta due to a tachyonic instability. The amplification of the gauge field modes exponentially depends on the velocity of the axion field, which in turn slows down the rolling of the axion field when backreaction is taken into account. To illustrate how the strength of the Cher… ▽ More During inflation an axion field coupled to a gauge field through a Chern-Simons term can trigger the production of gauge quanta due to a tachyonic instability. The amplification of the gauge field modes exponentially depends on the velocity of the axion field, which in turn slows down the rolling of the axion field when backreaction is taken into account. To illustrate how the strength of the Chern-Simons coupling and the slope of the axion potential influence the particle production, in this paper we consider a toy model in which the axion field is a spectator with a linear potential. In the strong backreaction regime, the energy density of the gauge field quasiperiodically oscillates. The steep slope of the axion potential linearly increases the peak amplitude of the energy density while the strong coupling linearly decreases the peak amplitude. Additionally, we calculate the energy spectrum of gravitational waves. △ Less

Submitted 19 May, 2025; v1 submitted 15 February, 2025; originally announced February 2025.

Journal ref: Phys. Rev. D 111, 103525, 2025

Testing the cosmic distance duality relation using Type Ia supernovae and BAO observations

Authors: Fan Yang, Xiangyun Fu, Bing Xu, Kaituo Zhang, Yang Huang, Ying Yang

Abstract: In this work, we propose to utilize the observed ratio of spherically-averaged distance to the sound horizon scale from Baryon Acoustic Oscillation (BAO) data to test the cosmic distance duality relation (CDDR) by comparing the luminosity distances (LDs) obtained from Type Ia supernovae (SNIa) observations with angular diameter distances (ADDs) derived from these ratio measurements, using a cosmol… ▽ More In this work, we propose to utilize the observed ratio of spherically-averaged distance to the sound horizon scale from Baryon Acoustic Oscillation (BAO) data to test the cosmic distance duality relation (CDDR) by comparing the luminosity distances (LDs) obtained from Type Ia supernovae (SNIa) observations with angular diameter distances (ADDs) derived from these ratio measurements, using a cosmological-model-independent method. To match the LDs with the ADDs at the identical redshifts, we employ two methods: a compressed form of the Pantheon sample and a hybrid approach that combines the binning method with an artificial neural network (ANN). The Hubble parameter $H(z)$ at any redshift is reconstructed from the observed Hubble parameter data with the ANN to derive the ADD. To avoid potential biases resulted from the specific prior values of the absolute magnitude $M_{\rm B}$ of SNIa and the sound horizon scale $r_{\rm d}$ from BAO measurements, we introduce the fiducial parameter $κ\equiv10^{M_{\rm B} \over 5}\, r_{\rm d}^{3 \over 2} $ and marginalize their impacts by treating them as nuisance parameters with flat prior distributions in our statistical analysis. Subsequently, we update the measurements of ratio of the transverse comoving distance to the sound horizon scale from the latest BAO data released by the Dark Energy Spectroscopic Instrument (DESI) collaboration for CDDR testing. Our results indicate that BAO observation provides a powerful tool for testing the CDDR, independent of both the absolute magnitude $M_{\rm B}$ and sound horizon scale $r_{\rm d}$, as well as any cosmological model. △ Less

Submitted 7 February, 2025; originally announced February 2025.

Comments: Accepted by EPJC 22 pages, 4 figures

Emission from multiple molecular isotopologues in a high-inclination protoplanetary disk

Authors: Colette Salyk, Klaus M. Pontoppidan, Andrea Banzatti, Edwin Bergin, Nicole Arulanantham, Joan Najita, Geoffrey A. Blake, John Carr, Ke Zhang, Chengyan Xie

Abstract: We present a MIRI-MRS spectrum of the high-inclination protoplanetary disk around the solar-mass (K0) star MY Lup, obtained as part of the JWST Disk Infrared Spectral Chemistry Survey (JDISCS). The spectrum shows an unusually weak water emission spectrum for a disk around a star of its spectral type, but strong emission from CO$_2$, HCN, and isotopologues of both molecules. This includes the first… ▽ More We present a MIRI-MRS spectrum of the high-inclination protoplanetary disk around the solar-mass (K0) star MY Lup, obtained as part of the JWST Disk Infrared Spectral Chemistry Survey (JDISCS). The spectrum shows an unusually weak water emission spectrum for a disk around a star of its spectral type, but strong emission from CO$_2$, HCN, and isotopologues of both molecules. This includes the first ever detection of C$^{18}$O$^{16}$O and H$^{13}$CN in an inner disk, as well as tentative detections of C$^{17}$O$^{16}$O and HC$^{15}$N. Slab modeling provides molecular temperatures, column densities and emitting areas of the detected molecules. The emitting molecular gas is cold compared to that of other observed protoplanetary disk spectra. We estimate the isotopologue ratios of CO$_2$ and HCN, albeit with significant uncertainty. We suggest that the unusual spectrum of MY Lup arises from a combination of inner disk clearing, which removes emission from warm water, and its nearly edge-on inclination, which enhances line-of-sight column densities, although unusual chemistry may also be required. MY Lup's spectrum highlights the potential to detect and measure trace isotopologues to study isotopic fractionation in protoplanetary disks; observations at higher spectral resolving power is needed to constrain the isotopologue ratios to greater precision. △ Less

Submitted 7 February, 2025; originally announced February 2025.

Comments: 20 pages, 18 figures. Accepted for publication in the Astronomical Journal