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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 14 January

High Energy Astrophysical Phenomena

The NANOGrav 15 yr Data Set: Piecewise Power-Law Reconstruction of the Gravitational-Wave Background

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald et al. (+108 more)

The NANOGrav 15-year (NG15) data set provides evidence for a gravitational-wave background (GWB) signal at nanohertz frequencies, which is expected to originate either from a cosmic population of inspiraling supermassive black-hole binaries or new particle physics in the early Universe. A firm identification of the source of the NG15 signal requires an accurate reconstruction of its frequency spectrum. In this paper, we provide such a spectral characterization of the NG15 signal based on a piecewise power-law (PPL) ansatz that strikes a balance between existing alternatives in the literature. Our PPL reconstruction is more flexible than the standard constant-power-law model, which describes the GWB spectrum in terms of only two parameters: an amplitude A and a spectral index gamma. Concurrently, it better approximates physically realistic GWB spectra – especially those of cosmological origin – than the free spectral model, since the latter allows for arbitrary variations in the GWB amplitude from one frequency bin to the next. Our PPL reconstruction of the NG15 signal relies on individual PPL models with a fixed number of internal nodes (i.e., constant power law, broken power law, doubly broken power law, etc.) that are ultimately combined in a Bayesian model average. The data products resulting from our analysis provide the basis for fast refits of spectral GWB models.
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All authors Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, Jeremy G. Baier, Paul T. Baker, Bence Bécsy, Amit Bhoonah, Laura Blecha, Adam Brazier, Paul R. Brook, Sarah Burke-Spolaor, Rand Burnette, Robin Case, J. Andrew Casey-Clyde, Maria Charisi, Shami Chatterjee, Tyler Cohen, James M. Cordes, Neil J. Cornish, Fronefield Crawford, Thankful Cromartie, Kathryn Crowter, Megan E. DeCesar, Paul B. Demorest, Heling Deng, Lankeswar Dey, Timothy Dolch, Elizabeth C. Ferrara, William Fiore, Emmanuel Fonseca, Gabriel E. Freedman, Emiko C. Gardiner, Nate Garver-Daniels, Peter A. Gentile, Kyle A. Gersbach, Joseph Glaser, Brenda D. Gómez-Cortes, Deborah C. Good, Kayhan Gültekin, C. J. Harris, Jeffrey S. Hazboun, Ross J. Jennings, Aaron D. Johnson, Megan L. Jones, David L. Kaplan, Luke Zoltan Kelley, Matthew Kerr, Joey S. Key, Nima Laal, Michael T. Lam, William G. Lamb, Bjorn Larsen, T. Joseph W. Lazio, Natalia Lewandowska, Monica Leys, Tingting Liu, Duncan R. Lorimer, Jing Luo, Ryan S. Lynch, Chung-Pei Ma, Dustin R. Madison, Cayenne Matt, Alexander McEwen, James W. McKee, Maura A. McLaughlin, Natasha McMann, Bradley W. Meyers, Patrick M. Meyers, Chiara M. F. Mingarelli, Andrea Mitridate, Cherry Ng, David J. Nice, Stella Koch Ocker, Ken D. Olum, Timothy T. Pennucci, Benetge B. P. Perera, Polina Petrov, Nihan S. Pol, Henri A. Radovan, Scott M. Ransom, Paul S. Ray, Joseph D. Romano, Jessie C. Runnoe, Alexander Saffer, Shashwat C. Sardesai, Ann Schmiedekamp, Carl Schmiedekamp, Kai Schmitz, Brent J. Shapiro-Albert, Xavier Siemens, Joseph Simon, Sophia V. Sosa Fiscella, Ingrid H. Stairs, Daniel R. Stinebring, Kevin Stovall, Abhimanyu Susobhanan, Joseph K. Swiggum, Jacob Taylor, Stephen R. Taylor, Mercedes S. Thompson, Jacob E. Turner, Michele Vallisneri, Rutger van Haasteren, Sarah J. Vigeland, Haley M. Wahl, Si Wang, Kevin P. Wilson, Caitlin A. Witt, David Wright, Olivia Young

Earth and Planetary Astrophysics

High-fidelity lunar topographic reconstruction across diverse terrain and illumination environments using deep learning

Hao Chen, Philipp Gläser, Konrad Willner et al. (+1 more)

Topographic models are essential for characterizing planetary surfaces and for inferring underlying geological processes. Nevertheless, meter-scale topographic data remain limited, which constrains detailed planetary investigations, even for the Moon, where extensive high-resolution orbital images are available. Recent advances in deep learning (DL) exploit single-view imagery, constrained by low-resolution topography, for fast and flexible reconstruction of fine-scale topography. However, their robustness and general applicability across diverse lunar landforms and illumination conditions remain insufficiently explored. In this study, we build upon our previously proposed DL framework by incorporating a more robust scale recovery scheme and extending the model to polar regions under low solar illumination conditions. We demonstrate that, compared with single-view shape-from-shading methods, the proposed DL approach exhibits greater robustness to varying illumination and achieves more consistent and accurate topographic reconstructions. Furthermore, it reliably reconstructs topography across lunar features of diverse scales, morphologies, and geological ages. High-quality topographic models are also produced for the lunar south polar areas, including permanently shadowed regions, demonstrating the method's capability in reconstructing complex and low-illumination terrain. These findings suggest that DL-based approaches have the potential to leverage extensive lunar datasets to support advanced exploration missions and enable investigations of the Moon at unprecedented topographic resolution.
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All authors Hao Chen, Philipp Gläser, Konrad Willner, Jürgen Oberst

Earth and Planetary Astrophysics

Mass estimates of the young TOI-451 transiting planets: Multidimensional Gaussian Process on stellar spectroscopic and photometric signals

Oscar Barragán, Manuel Mallorquín, Jorge Fernández-Fernández et al. (+30 more)

The young TOI-451 planetary system, aged 125 Myr, provides a unique opportunity to test theories of planetary internal structures and atmospheric mass loss through examination of its three transiting planets. We present an exhaustive photometric and spectroscopic follow-up to determine the orbital and physical properties of the system. We perform multidimensional Gaussian Process regression with the code pyaneti on spectroscopic time-series and NGTS/LCO light curves to disentangle the stellar and planetary signal in ESPRESSO radial velocities. We show how contemporaneous photometry serves as an activity indicator to inform RV modelling within a multidimensional Gaussian Processes framework. We argue that this can be exploited when spectroscopic observations are adversely affected by low signal-to-noise and/or poor sampling. We estimate the Doppler semi-amplitudes of Kb = 2.6(+1.1,-1.2) m/s, Kc = 1.2(+1.0,-0.8) m/s and Kd = 2.7 +/- 1.2 m/s. This translates into 2-sigma mass estimates for TOI-451 b and d of Mb = 4.7(+2.1,-2.2) Earth masses and Md = 10.2(+4.6,-4.5) Earth masses, as well as a mass upper limit for TOI-451 c of Mc < 11.5 Earth masses. The derived planetary properties suggest that planets c and d contain significant hydrogen-rich envelopes. The inferred parameters of TOI-451 b are consistent with either a rocky world that still retains a small hydrogen envelope or a water world. These insights make the TOI-451 system an ideal laboratory for future follow-up studies aimed at measuring atmospheric compositions, detecting atmospheric mass-loss signatures, and further exploring planetary formation and evolution processes.
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All authors Oscar Barragán, Manuel Mallorquín, Jorge Fernández-Fernández, Faith Hawthorn, Alix V. Freckelton, Marina Lafarga, Michael Cretignier, Yoshi N. E. Eschen, Samuel Gill, Víctor J. S. Béjar, Nicolas Lodieu, Haochuan Yu, Thomas G. Wilson, David Anderson, Ioannis Apergis, Matthew Battley, Edward M. Bryant, Pía Cortés-Zuleta, Edward Gillen, James S. Jenkins, Baptiste Klein, James McCormac, Annabella Meech, Erik Meier-Valdés, Maximiliano Moyano, Annelies Mortier, Felipe Murgas, Louise D. Nielsen, Suman Saha, José I. Vines, Richard West, Peter J. Wheatley, Suzanne Aigrain

High Energy Astrophysical Phenomena

How Beaming Shapes the Demographics of Ultraluminous X-ray Sources?

Ying-Han Mao and Xiang-Dong Li

Ultraluminous X-ray sources (ULXs) are off-nuclear compact objects with apparent luminosities above 10^39 erg/s, often exceeding the Eddington limit for stellar-mass black holes. Beaming is a commonly invoked mechanism to explain their extreme brightness, and the dependence of the beaming factor on accretion rate is a critical parameter. In this work, we investigate how different beaming prescriptions affect the predicted properties of ULX populations. Using binary population synthesis, we construct synthetic X-ray luminosity functions (XLFs) for both classical and log-modified beaming models at solar and sub-solar metallicities. The classical model predicts a larger intrinsic number of bright ULXs, but strong beaming reduces their observable fraction, resulting in fewer visible ULXs compared to the log-modified model. The log-modified prescription yields a shallower slope at high-luminosity, aligning better with observed XLFs, and increases the fraction of observable neutron star ULXs above 10^39 erg/s. These results underscore the significant role of the beaming law in shaping ULX statistical distributions and assessing neutron star contributions to the population.
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Cosmology and Nongalactic Astrophysics

Collapse versus Disruption: The Fate of Compact Stellar Systems in Ultralight Dark Matter Halos

Yu-Ming Yang, Xiao-Jun Bi, Long Wang et al. (+1 more)

Interference of the ultralight dark matter (ULDM) field generates time-varying gravitational potential fluctuations, which stochastically heat stellar systems embedded in ULDM halos. Small-sized stellar systems are therefore often used to set stringent constraints on ULDM. However, the evolution of systems with sizes well below the ULDM de Broglie wavelength remains poorly explored. Using numerical simulations, we show that the evolution of compact stellar systems in ULDM halos is governed by the interplay between internal stellar relaxation and ULDM-induced heating. We find the following main results. First, in sufficiently compact systems, relaxation-driven core collapse dominates, allowing the system to remain bound and dense, while ULDM-induced stripping of outer stars further accelerates the collapse. Second, in more extended systems, ULDM heating dominates and ultimately disrupts the system. Near the disruption threshold, we identify systems resembling ultra-faint dwarfs like Segue 1. Third, we further introduce a dimensionless parameter to quantify the relative importance of heating and relaxation and finally lead to an evolutionary phase diagram. Our results reveal the rich and nontrivial dynamics of compact stellar systems in ULDM halos, indicating that precise system modeling is essential for robust ULDM constraints.
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All authors Yu-Ming Yang, Xiao-Jun Bi, Long Wang, Peng-Fei Yin

Earth and Planetary Astrophysics

True Masses using RV data with Hipparcos and Gaia Astrometry

G. Piccinini, A. Petralia, A. Sozzetti et al. (+3 more)

Long-period companions are detected and characterized thanks to long-baseline radial velocity surveys. Combining Doppler time-series with astrometry, and in particular with proper motion anomalies technique, it is possible to put strong constraints on their orbital inclination and true mass. This work aims to present a model that combines Hipparcos and Gaia astrometric data with radial velocity measurements to constrain the orbital inclinations and true masses of long-period companions. Additionally, we re-analyse a small sample of targets that have not yet been studied using this combined approach. This research leverages the simultaneous modelling of proper motion anomalies and radial velocities, in conjunction with an analysis of the sensitivity curve. This approach serves not only as a verification of the parameters but also as a means to acquire valuable insights into planetary systems. The new analyses reveal that some of the targets classified as brown dwarfs or small-mass stars have a planetary nature. HD 5388 b and HD 6718 b are likely planets. HD 141937 b is likely a planet, but the current dataset does not allow us to firmly constrain its true mass. HD 16760 b belongs to the brown dwarf regime and it has a probable second companion. 30 Ari B b falls within the stellar regime, but the presence of an additional stellar companion could compromise the reliability of the final results. For HD 148427 b, HD 96127 b and HIP 65891 b we determined a range for the orbital inclinations.
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All authors G. Piccinini, A. Petralia, A. Sozzetti, S. Benatti, D. Gandolfi, G. Micela

High Energy Astrophysical Phenomena

The Second CHIME/FRB Catalog of Fast Radio Bursts

The CHIME/FRB Collaboration: Thomas Abbott, Bridget C. Andersen, Shion Andrew et al. (+70 more)

We present a catalog of 4539 fast radio bursts (FRBs) observed with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope between 25 July 2018 and 15 September 2023. These bursts originate from 3641 unique sources, including 981 bursts from 83 known repeating sources. For each FRB, the catalog provides a $O(10')$ estimate of sky location along with corresponding measurements of cumulative exposure time and survey sensitivity over the observing period. It includes a total-intensity dynamic spectrum between 400 and 800 MHz at 0.983 ms resolution. From this spectrum, we constrain a model of the burst morphology and measure key parameters such as arrival time, intrinsic temporal width, dispersion measure, scattering time, and flux density. This second catalog includes all FRBs from the first catalog, with every event reprocessed using a uniform and improved analysis framework. We show that previously published inferences remain valid under the updated measurements. We assess consistency of the detection rate across observational parameters, present initial distributions of burst properties, and outline ongoing and future studies that will use this catalog to investigate the nature of FRBs and their utility as astrophysical and cosmological probes.
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All authors The CHIME/FRB Collaboration: Thomas Abbott, Bridget C. Andersen, Shion Andrew, Kevin Bandura, Mohit Bhardwaj, Yash Bhusare, Charanjot Brar, Tomas Cassanelli, Shami Chatterjee, Jean-Francois Cliche, Amanda M. Cook, Alice Curtin, Matt Dobbs, Fengqiu Adam Dong, Gwendolyn Eadie, Tarraneh Eftekhari, Emmanuel Fonseca, B. M. Gaensler, Deborah Good, Mark Halpern, Jason W. T. Hessels, Adaeze Ibik, Naman Jain, Ronniy C. Joseph, Zarif Kader, Victoria M. Kaspi, Afrokk Khan, Bikash Kharel, Ajay Kumar, T. L. Landecker, Dustin Lang, Adam E. Lanman, Magnus L'Argent, Mattias Lazda, Calvin Leung, Dong Zi Li, Chris J. Lintott, Robert Main, Kiyoshi W. Masui, Sujay Mate, Kyle McGregor, Ryan Mckinven, Juan Mena-Parra, Bradley W. Meyers, Daniele Michilli, Cherry Ng, Mason Ng, Kenzie Nimmo, Gavin Noble, Ayush Pandhi, Swarali S. Patil, Aaron B. Pearlman, Ue-Li Pen, Ziggy Pleunis, J. Xavier Prochaska, Masoud Rafiei-Ravandi, Scott Ransom, Andre Renard, Mawson W. Sammons, Ketan R. Sand, Paul Scholz, Vishwangi Shah, Kaitlyn Shin, Seth R. Siegel, Sloane Sirota, Kendrick Smith, Ingrid Stairs, David C. Stenning, Shriharsh P. Tendulkar, Keith Vanderlinde, Mike Walmsley, Haochen Wang, Dallas Wulf

Astrophysics of Galaxies

New Estimate for the Cosmic Ray-Induced $\rm H_2$ Photodissociation Rate in the Interstellar Medium

O. Sipilä, P. Caselli, M. Padovani et al. (+5 more)

In the interstellar medium, cosmic rays (CRs) generate a field of ultraviolet (UV) photons via the excitation and subsequent radiative decay of $\rm H_2$ molecules. This UV field is a major agent of ionization and dissociation in the inner regions of molecular clouds that are shielded from the effects of the interstellar radiation field. In particular, the dissociation of $\rm H_2$, by far the most abundant molecule in interstellar clouds, leads to the production of atomic hydrogen which then takes part in the production of a multitude of molecules, in particular complex organics on the surfaces of interstellar dust grains. Precise knowledge of the rates of CR-induced dissociation processes is thus crucial for constructing reliable chemical models. For the present paper, we have derived a new value of $k_{\rm diss, CR}(\mbox{$\rm H_2$})=0.831\zeta$ for the rate of $\rm H_2$ dissociation, where $\zeta$ is the CR ionization rate of $\rm H_2$. This prediction contrasts a previous value from the Leiden database which overestimated the rate due to an inconsistent treatment of the $\rm H_2$ abundances and photodissociation cross sections. By running a series of chemical models, we show that the overestimated dissociation rate has a large effect on the results of chemical simulations, with the abundance of methanol being overestimated by over one order of magnitude. Hence, we strongly recommend the adoption of our new estimate $k_{\rm diss, CR}(\mbox{$\rm H_2$})=0.831\zeta$ in all chemical models that include this process. Our newly derived value corresponds to $\rm H_2$ being purely in the para form ($J^{\prime\prime} = 0$). However, in the interiors of molecular clouds the $\rm H_2$ ortho-to-para ratio is low and using the rate for para-$\rm H_2$ is an adequate approximation.
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All authors O. Sipilä, P. Caselli, M. Padovani, D. Galli, T. Grassi, H. R. Hrodmarsson, S. S. Jensen, E. Roueff

Cosmology and Nongalactic Astrophysics

Time delay measurements with Broken Power Law model

Guanhua Rui, Bin Hu and Wei Du

One challenge in strong gravitational lensing cosmography is the measurement of time delays between multiple lensed images, which are essential for constraining the Hubble constant (\(H_0\)). In this study, we investigate how assumptions about the lens mass profile affect time-delay measurements in lensing systems. Specifically, we implement a Broken Power Law (BPL) mass model within the Lenstronomy framework (Birrer & Amara 2018), which introduces additional flexibility in the radial mass distribution and can phenomenologically capture deviations from a single power-law profile. This model is combined with a numerical approach to compute time delays at the image positions. We validate the BPL implementation using simulated lens systems and compare the results with those from the elliptical power-law (EPL) model. We then apply both model families to the quadruply imaged quasar WGD~2038–4008. Both models provide good fits to the imaging and kinematic data, with a slight preference for the BPL model. When the internal mass-sheet factor is allowed to vary, the inferred Hubble constant in a flat \(\Lambda\)CDM cosmology with fixed \(\Omega_{\rm m}=0.3\) is \(H_0 = 75.3^{+23.1}_{-16.3} \ \mathrm{km \ s^{-1} \ Mpc^{-1}}\) for the BPL model and \(H_0 = 61.1^{+19.2}_{-13.2} \ \mathrm{km \ s^{-1} \ Mpc^{-1}}\) for the EPL model. For comparison, in the diagnostic case with the internal mass-sheet factor fixed to unity under the same setup, we obtain \(H_0 = 74.2^{+20.3}_{-13.8} \ \mathrm{km \ s^{-1} \ Mpc^{-1}}\) for the BPL model and \(H_0 = 66.1^{+18.8}_{-12.8} \ \mathrm{km \ s^{-1} \ Mpc^{-1}}\) for the EPL model. This highlights how time-delay cosmography remains sensitive to assumptions about the lens mass profile. With current precision, this difference does not favor one cosmological scenario over another, but underscores the importance of flexible mass modeling.
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Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn

Semi-convection in rotating spherical shells: flows, layers and dynamos

Paul Pružina, Nathanaël Schaeffer and David Cébron

Large regions of giant planets are thought to possess unstable thermal gradients stabilised by gradients in heavy-element composition. The fluid can then develop semi-convection, a double-diffusive instability driven by the unequal molecular diffusivities of heat and composition. While previous studies have focus mainly on local Cartesian models, we investigate semi-convection in rotating spherical shells, the geometry relevant to planetary interiors, using direct numerical simulations In a first non-linear phase, the flow spontaneously forms concentric density staircases composed of well-mixed layers separated by thin, strongly stratified interfaces. We propose scalings for both the thickness of these layers and their survival time in terms of the rotation rate and stratification. Over longer timescales, layers merge to produce statistically steady states consisting either of a fully convective shell or of a convective layer overlain by a persistent stably stratified layer (SSL), depending on the balance between stratification and rotation. Dynamo simulations show that flow within the convective region can generate a self-sustained magnetic field, which is filtered by zonal flows in the overlying SSL. This results in a strongly dipolar and axisymmetric external field, in encouraging agreement with Saturn's magnetic field. Across the explored parameter range, both the Rossby number and the thickness of the stably stratified layer are governed by a single combination of control parameters. This enables identification of a regime favourable to planetary-like dynamos.
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High Energy Astrophysical Phenomena

How Plasma Properties of the Fanaroff-Riley Jet can Shape its Morphology

Priyesh Kumar Tripathi, Indranil Chattopadhyay, Raj Kishor Joshi et al. (+3 more)

Extragalactic jets are broadly classified into two categories based on radio observations: core-brightened jets, known as Fanaroff-Riley Type I (FR I), and edge-brightened jets, classified as Type II (FR II). This FR dichotomy may arise due to variation in the ambient medium and/or the properties of the jet itself, such as injection speed, temperature, composition, magnetization, etc. To investigate this, we perform large-scale three-dimensional magnetohydrodynamic (3D-MHD) simulations of low-power, supersonic jets extending to kiloparsec scales. We inject a jet beam carrying an initially toroidal magnetic field into a denser, unmagnetized, and stratified ambient medium through a cylindrical nozzle. Our simulations explore jets with varying injection parameters to investigate their impact on morphology and emission properties. Furthermore, we examine jets with significantly different plasma compositions, such as hadronic and mixed electron-positron-proton configurations, to study the conditions that may drive transitions between FR I and FR II morphologies. We find that, under the same injection parameters, mixed plasma composition jets tend to evolve into FR I structures. In contrast, electron-proton jets exhibit a transition between FR I and FR II morphologies at different stages of their evolution.
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All authors Priyesh Kumar Tripathi, Indranil Chattopadhyay, Raj Kishor Joshi, Ritaban Chatterjee, Sanjit Debnath, M. Saleem Khan

Cosmology and Nongalactic Astrophysics

Owl-z: a Bayesian tool to select z \geq 7 quasars

Meriam Ezziati, Roser Pello, Jean-Gabriel Cuby et al. (+9 more)

This paper presents Owl-z, a Bayesian code aiming at identifying z \geq 7 quasars in wide field optical and near-infrared surveys. By construction,the code can also be used to select objects that contaminate the high-z quasar population, i.e. brown dwarfs and early-type galaxies at intermediate redshifts. The code can be adapted for the selection of high-z galaxies, and although it has been tuned to the Euclid Wide Survey, it can be easily adapted to other photometric surveys. The code input data are the object's photometric data and its galactic longitude and latitude, and the code output data are the probabilities of the modelled populations of high-z quasars, brown dwarfs and early-type galaxies at intermediate redshift. As part of the validation, Owl-z could re-identify all spectroscopically confirmed quasars at z \geq 7, demonstrating the code's versatility in applying to different photometric catalogues. The performance of Owl-z, based on a metric combining completeness and purity called F-measure, is analysed in the case of Euclid using simulated data in a wide range of redshifts (7 \leq z \leq 12) and H-band Euclid magnitudes (18 \leq H_E \leq 24.5). The results show that Owl-z reaches full performance for bright sources (H_E \lesssim 22), independently of the redshift. We show that the probability threshold used to select promising quasar candidates can be adjusted after processing to fine-tune the F-measure value of candidates depending on their magnitude and redshift estimates. We show that for objects brighter than about two magnitudes above the survey detection limit, Owl-z provides a classification that will facilitate the optimisation of photometric and spectroscopic confirmation campaigns. In conclusion, Owl-z is a powerful public tool to help select high-z quasars, brown dwarfs or early-type galaxies at intermediate redshifts in Euclid or other wide-field surveys.
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All authors Meriam Ezziati, Roser Pello, Jean-Gabriel Cuby, Pierre Pudlo, François-Xavier Dupé, Jean-Charles Lambert, Jean-Charles Cuillandre, Olivier Ilbert, Sylvain de la Torre, Stéphane Arnouts, Eric Jullo, Daming Yang

Earth and Planetary Astrophysics

NIRPS tightens the mass estimate of GJ 3090 b and detects a planet near the stellar rotation period

Pierrot Lamontagne, Drew Weisserman, Charles Cadieux et al. (+148 more)

We present an updated characterization of the planetary system orbiting the nearby M2 dwarf GJ 3090 (TOI-177; $d = 22$ pc), based on new high-precision radial velocity (RV) observations from NIRPS and HARPS. With an orbital period of 2.85 d, the transiting sub-Neptune GJ 3090 b has a mass we refine to $4.52 \pm 0.47 M_{\oplus}$, which, combined with our derived radius of $2.18 \pm 0.06 R_{\oplus}$, yields a density of $2.40^{+0.33}_{-0.30}$ g cm$^{-3}$. The combined interior structure and atmospheric constraints indicate that GJ 3090 b is a compelling water-world candidate, with a volatile-rich envelope in which water likely represents a significant fraction. We also confirm the presence of a second planet, GJ 3090 c, a sub-Neptune with a 15.9 d orbit and a minimum mass of $10.0 \pm 1.3 M_{\oplus}$, which does not transit. Despite its proximity to the star's 18 d rotation period, our joint analysis using a multidimensional Gaussian process (GP) model that incorporates TESS photometry and differential stellar temperature measurements distinguishes this planetary signal from activity-induced variability. In addition, we place new constraints on a non-transiting planet candidate with a period of 12.7 d, suggested in earlier RV analyses. This candidate remains a compelling target for future monitoring. These results highlight the crucial role of multidimensional GP modelling in disentangling planetary signals from stellar activity, enabling the detection of a planet near the stellar rotation period that could have remained undetected with traditional approaches.
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All authors Pierrot Lamontagne, Drew Weisserman, Charles Cadieux, David Lafrenière, Alexandrine L'Heureux, Mykhaylo Plotnykov, Léna Parc, Atanas K. Stefanov, Leslie Moranta, René Doyon, François Bouchy, Jean-Baptiste Delisle, Louise D. Nielsen, Gaspare Lo Curto, Frédérique Baron, Susana C. C. Barros, Björn Benneke, Xavier Bonfils, Marta Bryan, Bruno L. Canto Martins, Ryan Cloutier, Nicolas B. Cowan, Daniel Brito de Freitas, Jose Renan De Medeiros, Xavier Delfosse, Elisa Delgado-Mena, Xavier Dumusque, David Ehrenreich, Pedro Figueira, Jonay I. González Hernández, Izan de Castro Leão, Christophe Lovis, Lison Malo, Claudio Melo, Lucile Mignon, Christoph Mordasini, Francesco Pepe, Rafael Rebolo, Jason Rowe, Nuno C. Santos, Damien Ségransan, Alejandro Suárez Mascareño, Stéphane Udry, Diana Valencia, Gregg Wade, Manuel Abreu, José Luan A. Aguiar, Khaled Al Moulla, Guillaume Allain, Romain Allart, Jose Manuel Almenara, Tomy Arial, Hugues Auger, Luc Bazinet, Nicolas Blind, David Bohlender, Étienne Artigau, Isabelle Boisse, Anne Boucher, Vincent Bourrier, Sébastien Bovay, Pedro Branco, Christopher Broeg, Denis Brousseau, Alexandre Cabral, Andres Carmona, Yann Carteret, Zalpha Challita, David Charbonneau, Bruno Chazelas, Catherine A. Clark, João Coelho, Marion Cointepas, Karen A. Collins, Kevin I. Collins, Uriel Conod, Eduardo Cristo, Ana Rita Costa Silva, Antoine Darveau-Bernier, Laurie Dauplaise, Roseane de Lima Gomes, João Faria, Dasaev O. Fontinele, Thierry Forveille, Yolanda G. C. Frensch, Jonathan Gagné, Frédéric Genest, Ludovic Genolet, João Gomes da Silva, Félix Gracia Témich, Nicole Gromek, Nolan Grieves, Olivier Hernandez, Melissa J. Hobson, H. Jens Hoeijmakers, Norbert Hubin, Neil J. Cook, Marziye Jafariyazani, Farbod Jahandar, Ray Jayawardhana, Hans-Ulrich Käufl, Dan Kerley, Johann Kolb, Vigneshwaran Krishnamurthy, Benjamin Kung, Pierre Larue, Henry Leath, Olivia Lim, Allan M. Martins, Elisabeth C. Matthews, Jaymie Matthews, Jean-Sébastien Mayer, Stan Metchev, Lina Messamah, Yuri S. Messias, Dany Mounzer, Nicola Nari, Ares Osborn, Mathieu Ouellet, Jon Otegi, Luca Pasquini, Vera M. Passegger, Stefan Pelletier, Céline Peroux, Caroline Piaulet-Ghorayeb, Emanuela Pompei, Anne-Sophie Poulin-Girard, José Luis Rasilla, Vladimir Reshetov, Jonathan Saint-Antoine, Mirsad Sarajlic, Ivo Saviane, Robin Schnell, Alex Segovia, Julia Seidel, Armin Silber, Peter Sinclair, Michael Sordet, Danuta Sosnowska, Avidaan Srivastava, Márcio A. Teixeira, Simon Thibault, Philippe Vallée, Thomas Vandal, Valentina Vaulato, Joost P. Wardenier, Bachar Wehbe, Ivan Wevers, François Wildi, Vincent Yariv, Gérard Zins

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Sub-Leading Logarithms for Scalar Potential Models on de Sitter

S. P. Miao, N. C. Tsamis and R. P. Woodard

The continual production of long wavelength scalars and gravitons during inflation injects secular growth into loop corrections which would be constant in flat space. One typically finds that each additional factor of the loop counting parameter can induce up to a certain number of logarithms of the scale factor. Loop corrections that attain this number are known as “leading logarithms”; those with fewer are sub-leading. Starobinsky's stochastic formalism has long been known to reproduce the leading logarithms of scalar potential models. We show that the first sub-leading logarithm is captured by applying the stochastic formalism to a certain part of the 1-loop effective potential. This is checked at 2-loops for a massless, minimally coupled scalar with a quartic self-interaction on de Sitter background.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Chiellini-Integrable Cosmologies with Phantom Divide Crossing

Soumya Chakrabarti and Nandan Roy

We investigate exact cosmological solutions with a massive scalar field minimally coupled to the Einstein-Hilbert action in General Relativity. For an extended Higgs-like scalar self-interaction, we find that the resulting field equations belong to the damped Ermakov-Painlevé II class and construct novel analytical solutions within the framework of the Chiellini integrability condition. We analyze whether the expanding branch of the solutions can describe a late-time cosmic acceleration, using a combined statistical analysis of BAO, CMB, cosmic chronometer and Pantheon+SHOES supernova datasets. A crucial outcome of this exercise is the analytical emergence of a smooth phantom divide crossing in the dark energy equation of state, achieved without introducing any pathological instabilities. The reconstruction yields a present-day Hubble parameter $H_0 \gtrsim 70 \,\mathrm{km\,s^{-1}\,Mpc^{-1}}$, with a reduced tension relative to the $\Lambda$CDM cosmology. The results indicate that Chiellini-integrable scalar cosmologies are capable of providing a robust and analytically controlled framework for modeling late-time cosmic acceleration and phantom divide crossing, offering a viable alternative to phenomenological dark-energy parametrizations.
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High Energy Astrophysical Phenomena

Detection of a puzzling dual-superorbital hard X-ray modulation in the X-ray binary GX 301-2

Haoyang Zhang and Li Zhang

The superorbital modulations (SMs) observed in wind-fed X-ray binaries remain a puzzling phenomenon in astrophysics. To investigate this behavior observationally, we analyzed the long-term hard X-ray light curve from the Swift/BAT 157-Month Hard X-ray Survey in X-ray binary GX 301-2. Using three timing analysis methods–the Lomb-Scargle periodogram, the weighted wavelet Ztransform, and Gaussian processes–we identify a rare dual-SM behavior in this source: the 115-day modulation exceeds the 5$\sigma$ global significance level, whereas the 65-day signal only marginally reaches the 4$\sigma$ level. Because the 115-day period is more consistent with the previously reported linear relation between orbital and superorbital periods, we interpret 115 days as the actual superorbital period, while the weaker and less stable 65-day period is its beat modulation with the orbital period.By assessing the applicability of different physical scenarios to our results, we suggest that this dual-SM behavior is most plausibly associated with corotating interaction regions (CIRs) in the stellar wind. This framework can also account for the observed linear orbital-superorbital relation, despite the unclear physical mechanism that sets the apparent ratio between the CIR and orbital periods across sources. Further long-term monitoring of this system, together with continued theoretical development of the CIR scenario, will be essential for clarifying the origin of wind-fed SMs.
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2601.09226 · 14 Jan · This paper is withdrawn because reanalysis shows that the reported 115- and 65-day signals are sampling aliases of the orbital modulation and its second harmonic in the monthly-binned Swift/BAT data. The claimed detection of two independent superorbital modulations and the associated physical interpretation are therefore not supported

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Astrophysics of Galaxies

The ALMaQUEST Survey XVII: Unveiling Multiple Quenching Pathways in Green Valley Galaxies via Molecular Gas and Quenching Timescale Analyses

Lihwai Lin, Po-Feng Wu, Mallory D. Thorp et al. (+6 more)

Statistically, green valley (GV) galaxies exhibit lower molecular gas fractions ($f_{gas}$) and reduced star formation efficiency (SFE) compared to star-forming galaxies. However, it remains unclear whether quenching is primarily driven by one factor or results from a combination of mechanisms in individual GV galaxies. In this study, we address this question by examining the spatial distributions of star formation and molecular gas in 28 GVs selected from the ALMaQUEST survey and additional literature samples. For each galaxy, we identify regions with suppressed specific star formation rate (sSFR) and measure $\Delta f_{gas}$ and $\Delta$SFE-offsets from the resolved scaling relations of the star-forming main sequence galaxies. By comparing the fraction of regions with negative $\Delta f_{gas}$ and $\Delta$SFE, we classify 35.7$\pm$13.2% (57.1$\pm$17.9%) of GV galaxies as $f_{gas}$-driven, 39.3$\pm$14.0% (39.3$\pm$14.0%) as SFE-driven, and 25.0$\pm$10.6% (3.6$\pm$3.6%) as mixed mode when adopting a fixed (variable) CO-to-$\rm H_{2}$ conversion factor ($\alpha_{CO}$). These results indicate that GVs undergo quenching through multiple pathways. As sSFR decreases from the main sequence to the green valley, we observe a transition toward predominantly SFE-driven quenching, possibly linked to internal processes such as morphological quenching or AGN activity. We further estimate the quenching timescale ($\tau_{decay}$), defined as the time from the peak SFR to 1/e (approximately 37%) of its value, using integrated MaNGA spectra. SFE-driven quenching is typically associated with short $\tau_{decay}$ , while $f_{gas}$-driven quenching shows a broader range. Overall, 75% of GVs exhibit $\tau_{decay}$ shorter than 1 Gyr, suggesting that quenching in most GVs proceeds rapidly, challenging purely slow-quenching scenarios like starvation.
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All authors Lihwai Lin, Po-Feng Wu, Mallory D. Thorp, Asa F. L. Bluck, Hsi-An Pan, Sara L. Ellison, Kate Rowlands, Justin Atsushi Otter, Sebastián F. Sánchez

Astrophysics of Galaxies

The Quasar Feedback Survey: Revealing the importance of sensitive radio imaging for AGN identification deeper into the radio-quiet regime

Ann Njeri, Chris M. Harrison, Preeti Kharb et al. (+8 more)

We present new sub-arcsecond ($\sim$0.3-1 arcsec; $\sim$1–3\,kpc) VLA imaging at 1.4\,GHz and 6\,GHz of 29 optically-selected, [O~iii] luminous ($L_{\rm [O III]}$ > 10$^{42.1}$\,erg\,s$^{-1}$), $z<0.2$ quasars drawn from the expanded Quasar Feedback Survey (QFeedS; with $L_\mathrm{1.4\,GHz} = 10^{22.6}$–10$^{26.3}$\,W\,Hz$^{-1}$). These 29 new objects occupy the low end of the radio-power distribution ($L_\mathrm{1.4\,GHz}$=$10^{22.63}$–10$^{23.45}$\,W\,Hz$^{-1}$) in the QFeedS sample and are nominally `radio quiet'. Despite this, we find widespread evidence of AGN-driven synchrotron activity. Nearly $\sim 31\,$per\,cent exhibit resolved radio structures on $\sim$0.1–20\,kpc scales consistent with compact jets or wind-driven outflows, and $\sim 90\,$per\,cent display steep spectra ($\alpha \lesssim -1$) indicative of optically thin synchrotron emission. Combining morphology, spectral index and brightness-temperature diagnostics, at least $\sim38\,$per\,cent of the sample show clear AGN signatures that cannot be explained by star formation alone. These constitute the first results from the expanded QFeedS (now 71 quasars spanning $\approx 4$ dex in radio power) and demonstrate that compact, low-power jets and AGN shocks are common deep inside the radio-quiet regime. A thorough understanding of feedback processes from quasars, deep into the `radio-quiet' regime, will be obtained by connecting these high resolution radio observations with multi-wavelength observations.
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All authors Ann Njeri, Chris M. Harrison, Preeti Kharb, David M. Alexander, Vincenzo Mainieri, Chiara Circosta, Victoria A. Fawcett, Darshan Kakkad, Dipanjan Mukherjee, Stephen Molyneux, Silpa Sasikumar

Astrophysics of Galaxies

Wind-fed Supermassive Black Hole Accretion in the Ultracompact Dwarf Galaxy M60-UCD1

Zhao Su, Zhiyuan Li and Meicun Hou

Ultracompact dwarf galaxies (UCDs) are thought to be remnants of stripped galactic nuclei, among which a handful are known to host a central supermassive black hole (SMBH). As in stripped nuclear star clusters, the SMBHs in UCDs may be fed by stellar winds from old stellar populations, in the absence of substantial gas reservoirs and galactic inflows. In this work, we investigate such a wind-fed accretion scenario for M60-UCD1, which harbors a confirmed $2\times10^7~M_\odot$ SMBH and exhibits X-ray emission suggestive of SMBH accretion signature. Using three-dimensional hydrodynamical simulations, we simulate the SMBH accreting stellar winds from approximately 1500 asymptotic giant branch stars, and explore the role of ram pressure from the ambient interstellar or intracluster medium. After 5 Myr, the majority of the stellar winds form a cold gas disk ($\sim1000~M_\odot$) within $\sim10~\rm pc$ as well as the SMBH's gravitational sphere of influence. Within the inner $10^4~r_{\rm g}$, this disk transitions into a hot ($\sim10^7-10^9~\rm K$), geometrically thick corona that dominates the X-ray emission. The SMBH achieves an accretion rate of $\sim10^{-5}~M_\odot~\rm yr^{-1}$, yielding an X-ray luminosity of $\sim7\times10^{37}~\rm erg~s^{-1}$, well consistent with observations. Including ram pressure stripping reduces both the accretion rate and luminosity by about a factor of two. Our results suggest that the X-ray counterpart of M60-UCD1 originates from a weakly accreting SMBH fed by stellar winds, with broader insights into the feeding mechanisms of central massive black holes and the origins of X-ray sources in other UCDs.
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Cosmology and Nongalactic Astrophysics

Tidal alignment and tidal torquing modeling for the cosmic shear three-point correlation function and mass aperture skewness

Rafael C. H. Gomes, Kyle Miller, Sunao Sugiyama et al. (+3 more)

We present a model for the intrinsic alignment contamination of the shear three-point correlation function and skewness of the mass aperture statistic using the tidal alignment and tidal torquing (TATT) formalism. We compute the intrinsic alignment bispectra components in terms of the TATT model parameters. We consider two effective field theory approaches in the literature, relate them to the TATT model parameters and an extension to TATT that includes the velocity-shear (VS) parameter. We compare the impact of changing between NLA, TATT, and TATT+VS on the theoretical computation of the 3PCF using the best fit parameters and tomographic redshift distributions from Dark Energy Survey Year 3. We find that the TATT model significantly impacts the skewed triangle configurations of the 3PCF. Additionally, including the higher-order effects from TATT can introduce opposite effects on the two-point function and on the mass aperture skewness, damping the signal of the former while boosting the signal of the latter. We argue that a joint 2PCF+3PCF analysis with the TATT model can help break the degeneracy between its model parameters and provide more robust constraints on both cosmology and intrinsic alignment amplitude parameters. We show that typical values of order unity for the intrinsic alignment parameters introduce differences of around $10\%$ between NLA and TATT predictions.
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All authors Rafael C. H. Gomes, Kyle Miller, Sunao Sugiyama, Jonathan Blazek, Thomas Bakx, Bhuvnesh Jain

Solar and Stellar Astrophysics

The Progenitor of the Type II-Plateau SN 2025pht in NGC 1637: The Dustiest, Most Luminous Red Supergiant So Far?

Schuyler D. Van Dyk, Tamas Szalai, Gagandeep S. Anand et al. (+14 more)

We provide a characterization of the red supergiant (RSG) progenitor candidate for the nearby Type II-plateau supernova (SN) 2025pht in NGC 1637. The star was first detectable in 2001 by the Hubble Space Telescope (HST) and then again in a dozen bands by the James Webb Space Telescope (JWST) in 2024. This "quasi-snapshot" of the star's nature almost immediately prior to explosion is unprecedented. The RSG varied in brightness, and we posit that it could have been a pulsating variable, possibly with a long period of ~660 days. The largest uncertainty is the host-galaxy distance, which we establish to be 11.67+/-0.27 Mpc. The star was also heavily extinguished by interstellar dust internal to the host, with visual extinction A_V(host)~1.7 mag (total A_V(tot)~1.8 mag). Dust radiative-transfer modeling reveals the star's circumstellar medium to be quite dusty and silicate-rich, yielding a bolometric luminosity as high as log(L_bol/L_Sun)=5.16+/-0.03 and a cool effective temperature T_eff=2100–2500 K. The available HST optical data had no bearing on the shape of the candidate's observed spectral energy distribution – for the first time, without the archival JWST observations we would not have been able to detect and characterize the candidate at all. The SN 2025pht progenitor candidate, although quite similar to that of SN 2023ixf, may be the most luminous star identified to date.
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All authors Schuyler D. Van Dyk, Tamas Szalai, Gagandeep S. Anand, Thomas G. Brink, Noah Zimmer, Dan Milisavljevic, Ori D. Fox, Jacob E. Jencson, WeiKang Zheng, Alexei V. Filippenko, Lukasz Wyrzykowski, Przemyslaw J. Mikolajczyk, Krzysztof Kotysz, F.-J. Hambsch, Agata Wozniak, Michal Zejmo, Andrea Reguitti

Earth and Planetary Astrophysics

Ring-Gap Structures in the Class I Circumstellar Disk of CrA IRS 2 Associated with Magnetic Flux-Driven Bubble

Ayumu Shoshi, Masayuki Yamaguchi, Mitsuki Omura et al. (+4 more)

Recent ALMA observations with 0”.1 resolution reveal characteristic substructures in circumstellar disks around young Class I sources, providing clues to the early stages of morphological disk evolution. In this paper, we applied PRIISM imaging to ALMA archival Band 6 continuum data of the circumstellar disk around the Class I protostar CrA IRS 2, located in the Corona Australis molecular cloud, which is associated with an extended gas ring attributed to magnetic flux advection driven by interchange instability. The dust continuum image with 1.5 times higher spatial resolution than conventional imaging revealed, for the first time, the early-phase circumstellar disk with both inner central hole and outer ring-gap structures, making CrA IRS 2 the youngest system exhibiting such features based on the bolometric temperature of $T_{\rm bol}$=235 K. To examine planet-disk interaction as one possible origin of the outer ring-gap structure, we found the measured depth and width to be consistent with planet-disk interaction models, suggesting the existence of a giant planet with a mass of 0.1-1.8 $M_{\rm Jup}$. The additional mechanism required for rapid planet formation could be the magnetic flux dissipation driven by the interchange instability, which suppresses MRI-driven turbulence and extends the dead zone, allowing efficient dust growth and the early formation of planets. This system thus provides new insight into how substructures and planet formation can emerge during the early, accreting phase of disk evolution.
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All authors Ayumu Shoshi, Masayuki Yamaguchi, Mitsuki Omura, Kazuki Tokuda, Naofumi Fukaya, Kengo Tachihara, Masahiro. N. Machida

High Energy Astrophysical Phenomena

Pre-Supernova Eruptions Triggered by Sudden Energy Deposition in Low-Mass Core-Collapse Supernova Progenitors

Shuai Zha, Han Lin, Xuefei Chen et al. (+1 more)

In low-mass core-collapse supernova (CCSN) progenitors, nuclear burning beyond oxygen can become explosive under degenerate conditions, triggering eruptive mass loss before the final explosion. We investigate such pre-SN eruptions using SNEC hydrodynamic simulations and realistic stellar models, parameterizing the nuclear energy deposition as a fraction of the binding energy of the combined He layer and H-rich envelope. For the lowest-mass model (9 $M_\odot$), the ejecta mass ($M_{\rm ej}$) scales with the energy gained by the H-rich envelope via a power law (index$\sim$3.5). Across 9-10 $M_\odot$, this relation shows limited scatter within a factor of $\sim$2.6, enabling an estimation of the gained energy from $M_{\rm ej}$. The shock passage also flattens the bound envelope, which can affect the SN light curve morphology and provide another diagnostic for the eruption. Then, we compute the associated precursor light curves for the 9 $M_\odot$ model with the multi-group radiative-transfer code STELLA. These signals are typically faint, with bolometric luminosities of $\sim10^{39}$ erg s$^{-1}$ lasting hundreds of days. Their cool black-body spectra make them brighter in the infrared, yet several magnitudes fainter than observed pre-SN precursors at the threshold for full envelope ejection. To aid future studies, we make our post-eruption stellar profiles and precursor light curves publicly available.
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All authors Shuai Zha, Han Lin, Xuefei Chen, Zhanwen Han

High Energy Astrophysical Phenomena

Upper limits on microhertz gravitational waves from supermassive black-hole binaries using PSR J1909-3744 data from the second IPTA data release

Jing Zou, Jingbo Wang Jianping Yuan, De Zhao et al. (+4 more)

We present the results of a search for gravitational waves (GWs) from individual sources using high-cadence observations of PSR J1909\(-\)3744 obtained during an intensive observing campaign with the International Pulsar Timing Array second data release (IPTA-DR2) between July 2010 and November 2012. The observations, conducted at three different radio frequencies with the Nançay Radio Telescope (NRT) and Parkes Telescope (PKS) and five frequencies with the Green Bank Telescope (GBT), enabled precise corrections for dispersion measure effects and scattering variations. After these corrections, the timing residuals showed an unmodeled periodic noise component with an amplitude of 340 ns. Our analysis yields upper limits on the GW strain from individual sources, constraining it to be below \(1.9 \times 10^{-14}\) at 71 nHz and \(2.3 \times 10^{-13}\) at 1 \textmu Hz for average sky locations, while for optimal source locations the limits improve to \(6.2 \times 10^{-15}\) and \(8.9 \times 10^{-14}\) at the same frequencies, respectively. Our new limits are about a factor of 1.52 more stringent than those of Perera et al. based on an earlier EPTA data.
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All authors Jing Zou, Jingbo Wang Jianping Yuan, De Zhao, Yirong Wen, Wei Li, Na Wang, Yong Xia

High Energy Astrophysical Phenomena

The effect of inverse Compton losses on particle acceleration in three-dimensional relativistic reconnection

Ian Bowyer, Dimitrios Giannios and Lorenzo Sironi

Relativistic magnetic reconnection is a key mechanism for dissipating magnetic energy and accelerating particles in astrophysics. In the absence of radiative cooling, recent particle-in-cell (PIC) simulations have shown that high-energy particles gain most of their energy in the upstream region, during a short-lived "free phase" where they meander between the two sides of the layer; when they get captured/trapped by the downstream flux ropes, they undergo a "trapped phase", where no significant energization occurs. Here, we perform a suite of 3D PIC simulations of relativistic reconnection including inverse Compton (IC) losses in the weakly cooled regime in which the radiation-reaction-limited Lorentz factor $\gamma_{\rm rad}$ exceeds the magnetization $\sigma$. We show that electron cooling losses do not appreciably alter the reconnection rate, the structure of the layer, and the physics of particle acceleration in the free phase, so the spectrum of free electrons is $dN_{\rm free}/d\gamma \propto \gamma^{-1}$, as in the uncooled case. The spectrum of trapped electrons above the cooling break $\gamma_{\rm cool}$ (in the range $\gamma_{\rm cool}<\gamma<\gamma_{\rm rad}$) is $dN/d\gamma \propto \gamma^{-3}$, steeper than the scaling $dN/d\gamma \propto \gamma^{-2}$ of uncooled simulations. This confirms that no significant particle energization occurs during the trapped phase. Our results validate the model by arXiv:2302.12269 for particle acceleration in 3D relativistic reconnection, and imply that radiative emission models of reconnection-powered astrophysical sources should employ a two-zone structure, that differentiates between free, rapidly accelerating particles and trapped, passively cooling particles.
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Tuesday 13 January

Solar and Stellar Astrophysics

The IRIS$^{2+}$ inversion tool: recovering the radiative losses and the thermodynamics in the lower solar atmosphere

Alberto Sainz Dalda, Jaime de la Cruz Rodríguez, Viggo Hansteen et al. (+2 more)

We introduce an improved and fast inversion tool that is able to provide the thermodynamics of the solar atmosphere from the photosphere to the top of the chromosphere, as well as the integrated radiative losses in the chromosphere for data observed by the Interface Region Imaging Spectrograph (IRIS). This NASA mission has been observing the Sun and providing, among other kinds of data, multi-line spectral observations sensitive to changes in the lower solar atmosphere since 2013. In this paper, we explain the new inversion tool IRIS$^{2+}$ based on the IRIS$^{2+}$ database, which is based on 135,472 synthetic representative profiles (RP), each of them consisting of 6 chromospheric lines and 6 photospheric lines, their corresponding representative model atmospheres (RMA), and the integrated radiative losses (IRL) associated with these atmospheres. A nearest neighbor (k-nn) model algorithm is trained with the synthetic representative profiles to predict the closest RP in the database to the one observed, at which point IRIS$^{2+}$ assigns the RMA and the IRL to the location of that observed profile. We have compared the results obtained by IRIS$^{2+}$ with results obtained from the state-of-the-art inversion code STiC, which is also used to build the IRIS$^{2+}$ database. We find that the thermodynamics and the IRL obtained with both methods are comparable in most cases. Therefore, IRIS$^{2+}$ is a fast and reliable inversion tool that provides approximate values of the thermodynamic state and the radiative losses in the lower solar atmosphere for a large variety of solar scenes observed with IRIS.
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All authors Alberto Sainz Dalda, Jaime de la Cruz Rodríguez, Viggo Hansteen, Bart De Pontieu, Milan Gošić

Solar and Stellar Astrophysics

A Multi-Method Age Determination for the Ursa Major Moving Group

Julia Sheffler, Max Clark, Melinda Soares-Furtado et al. (+4 more)

The Ursa Major Moving Group (UMa) is one of the closest stellar associations, yet its age has remained controversial, with published estimates ranging from 200 Myr to 1 Gyr. We present a comprehensive age analysis using the largest sample of candidate UMa members to date. Using Gaia DR3, we identify 1172 stars within 100 pc of the Sun with 3D kinematic motions consistent with group membership. We determine the age of UMa's dominant population using three independent methods: lithium equivalent widths $(393.6^{+85.1}_{-80.9}\,\mathrm{Myr})$, gyrochronology $(428 \pm 93\,\mathrm{Myr})$, and photometric variability indicators $(449^{+114}_{-79}\,\mathrm{Myr})$. The three methods converge on a consistent age of $418^{+32}_{-34}\,\mathrm{Myr}$. While our kinematic selection includes field stars that share UMa's space motion but are not coeval members, the convergent age determinations clearly identify a dominant population that formed together approximately 400 Myr ago. These stars are important benchmarks for studies of stellar rotation, magnetic activity evolution, and lithium depletion. The presence of systems such as HD~63433, a young multiplanet host within the group, further illustrates the value of UMa as a laboratory for early planetary system evolution. Our expanded catalog of kinematic candidates lays the groundwork for spectroscopic membership confirmation, refined mapping of the group's structure and chemistry, and future investigations of both stellar and planetary evolution at this key epoch.
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All authors Julia Sheffler, Max Clark, Melinda Soares-Furtado, Adam Distler, Ritvik Sai Narayan, Jenna Karcheski, Kenneth Nordsieck

Astrophysics of Galaxies

Spatially Resolved Star Formation relations in local LIRGs along the complete merger sequence

M. Sánchez-García, T. Díaz-Santos, L. Barcos-Muñoz et al. (+25 more)

We investigate the properties of the interstellar medium (ISM) at ~100 pc scales in a sample of 27 nearby luminous infrared galaxies (LIRGs) spanning the entire merger sequence. In particular, we study the relations between star-formation (SF) and molecular gas surface density as a function of the interaction stage using two complementary approaches: beam-sized (unresolved, line-of-sight) regions and physically identified molecular gas clumps. To map the distribution of molecular gas we use ALMA CO(2-1) observations, while SF is traced using HST Pa-alpha or Pa-beta images. We derive spatially resolved Kennicutt-Schmidt (KS) relations for each galaxy. When using beam-sized regions, we find that 67% of galaxies follow a single relation between Sigma_SFR and Sigma_H2. However, in the remaining galaxies, the relation splits into two branches, indicating the presence of a duality in this relation. In contrast, when using physical gas clumps, the duality disappears and all galaxies show a single trend. We also study other ISM/clump properties as a function of the merger stage. We find that isolated galaxies and systems in early stages of interaction exhibit lower amounts of gas and SF. As the merger progresses, however, the amount of gas in the central kpc of the galaxy undergoing the merger increases, along with the SFR, and the slope of the KS relation becomes steeper, indicating an increase in SF efficiency of the gas clumps. Clumps in late-stage mergers are predominantly located at small distances from the nucleus, confirming that most of the activity is concentrated in the central regions. Finally, the relation between the SF efficiency and the boundedness parameter evolves from being roughly flat in the early stages of the merger to becoming positive in the final phases, indicating that clump self-gravity only starts to regulate the SF process between the early- and mid-merger stages.
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All authors M. Sánchez-García, T. Díaz-Santos, L. Barcos-Muñoz, A. S. Evans, Y. Song, M. Pereira-Santaella, S. García-Burillo, S. T. Linden, C. Ricci, L. Lenkic, A. Zanella, L. Armus, C. Eibensteiner, Y.-H. Teng, A. Saravia, V. A. Buiten, G. C. Privon, N. Torres-Albà, T. Saito, K. L. Larson, M. Bianchin, A. M. Medling, T. Lai, G. P. Donnelly, V. Charmandaris, T. Bohn, C. M. Lofaro, G. Meza

Earth and Planetary Astrophysics

Depletion of moderately volatile elements by pebble accretion in Earth-like planets

Peter L. Olson, Zachary D. Sharp and Susmita Garai

Protoplanets growing by pebble accretion capture massive hydrogen-helium atmospheres from the surrounding nebula. Pebbles settling through such atmospheres continuously release gravitational potential energy, heating both the atmosphere and the pebbles. Under these conditions, atmosphere temperatures above large protoplanets are sufficiently high to melt silicate pebbles, support long-lived magma oceans, and drive evaporation of volatile species. Because these atmospheres are open to the nebula, some amount of volatile loss is inevitable. Here we analyze the depletion of moderately volatile elements from terrestrial protoplanets undergoing pebble accretion. We consider chondrule-size silicate pebbles enriched in Si, Na, K, and Zn relative to Earth, settling through a hydrogen-helium-rich atmosphere containing these same volatiles. We show that volatile depletion depends critically on protoplanet mass, the timescale of atmosphere exhaust, and the pebble composition. The protoplanetary mass effect is especially strong. For exhaust timescales of a few centuries, we find that substantial depletion of Zn begins around 0.4 Earth mass, and for Na and K around 0.6 Earth mass, with negligible depletion of these elements at smaller masses. Using a pebble composition that matches Earth's major element abundances, broad agreement with Earth's depletion trend for moderately volatile elements is found by merging a large (approximately 0.7 Earth mass) volatile-depleted target protoplanet with one or more smaller, less-depleted impactors.
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Earth and Planetary Astrophysics

Formation and evolution of planetary systems

S. I. Ipatov

Various problems of the formation and evolution of planetary systems are studied. Most of the studies are devoted to the Solar System. The collapse of the presolar cloud and the accumulation of planets are studied. The author considers the formation of the Earth-Moon system, binary trans-Neptunian objects, and the axial rotations of planets. He discusses the formation of asteroid and trans-Neptunian belts, including the evolution of resonant asteroid orbits and the formation of the Kirkwood gaps in the asteroid belt. The book discusses the migration of bodies during the formation of the Solar System and at present, including a discussion of the delivery of icy bodies from beyond the ice line to the terrestrial planets and the formation of craters on the Moon. The Deep Impact mission is discussed; during this mission the impact module of the spacecraft collided with the comet Tempel 1. The book studies the migration of dust in the Solar System and the formation of the zodiacal belt, as well as the migration of bodies and dust particles ejected from the terrestrial planets and the Moon. The author considers the migration of bodies in some exoplanetary systems (Proxima Centauri, Trappist 1, and Gliese 581), the spectra of Earth-like exoplanets with different rotation periods, as well as the efficiency of exoplanet searches using microlensing observations with various telescopes. English text is only in the list of publications and in the contents. An English reader can look the contents to find an interesting section. In this section he can find the numbers for relative publications. Using these numbers and the list of publications, he can find the websites where he can upload free files with these publications, and then he can read relevant papers in English and can get more detailed information than in this book.
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