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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 1 September

Astrophysics of Galaxies

The GOGREEN Survey: AI Powered Deconvolution Lifts The Veil on Outside-in Environmental Quenching at z > 1

Aurelien Henry, Gillian Wilson, Gregory Rudnick et al. (+10 more)

A powerful probe of the physical processes that quench star formation in dense environments is determining where within galaxies star formation is suppressed. At high redshift, the spatial resolution of multi-band imaging limits such measurements. We use deep-learning-based deconvolution to recover spatially resolved optical and near-infrared photometry for galaxies in nine GOGREEN clusters at 1<z<1.4, using customized models trained on HST and JWST imaging. Using resolved rest-frame UVJ colors, we classify galaxies by the star-forming states of their inner and outer regions into predominantly star-forming, predominantly quiescent, inside-quenched, or outside-quenched. We find that 24% of galaxies classified as quiescent from their integrated colors retain significant star formation. The predominantly quiescent fraction increases with stellar mass and is higher in clusters than in the field while the cluster quenched fraction excess is, when limiting to predominantly quenched galaxies, approximately 20%. Contrary to previous GOGREEN studies using integrated colors, we find this excess to be independent of stellar mass, demonstrating that partially quenched galaxies can bias measurements based on integrated colors. Among galaxies retaining significant star formation, outside-quenched galaxies are substantially more common than inside-quenched galaxies and have a fraction excess of (22.8+/-5.8)% in clusters relative to the field at low masses. This provides evidence that clusters preferentially suppress star formation in the outskirts of low-mass galaxies. Our results demonstrate the importance of spatially resolved classifications for interpreting environmental quenching at z~1 and the potential of deep-learning-based deconvolution to recover such information from large ground-based imaging datasets.
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All authors Aurelien Henry, Gillian Wilson, Gregory Rudnick, Pascale Jablonka, Utsav Akhaury, Craig Brooks, Michael Balogh, Ben Forrest, Adam Muzzin, Visal Sok, Mohamed H. Abdullah, M.E. Wisz, Elias Works

Instrumentation and Methods for Astrophysics

Curving X-ray detectors for astrophysics applications

Eric D. Miller, James A. Gregory, Keith Warner et al. (+14 more)

Next-generation X-ray optics will revolutionize high-energy astrophysics, yet they present several challenges to design a complementary focal plane. In particular, the focal surface is curved, requiring many small, flat sensors to achieve a large field. We present work building on MIT Lincoln Laboratory technology to curve the sensor itself, improving image quality and reducing complexity. Applying this technology to back-illuminated, large-format CCDs having well-characterized X-ray response, we describe the process and report success curving functional BI CCDs to a 2.5-m radius of curvature, achieving RMS curvature deviations less than 1 micron. We confirm that there is no appreciable increase in dark current and that the spectroscopic performance across the 0.3-6 keV band remains excellent. These results demonstrate that curved, large-format X-ray sensors are realizable, and the process can be extended to silicon detectors with other architectures, including active pixel sensors.
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All authors Eric D. Miller, James A. Gregory, Keith Warner, Beverly LaMarr, Gregory Prigozhin, Marshall W. Bautz, Harry R. Clark, Michael J. Cooper, Kevan A. Donlon, Catherine E. Grant, WeiLin Hu, Mallory A. Jensen, Jill Juneau, Renee D. Lambert, Christopher W. Leitz, David Volfson, Douglas J. Young

Instrumentation and Methods for Astrophysics

The ViSta method for optimized stacking of broadband interferometric data in the Fourier domain

Martina Torsello, Marcella Massardi, Elisabetta Liuzzo et al. (+3 more)

We present the optimized version of ViSta, a visibility-domain stacking method that combines interferometric observations in the Fourier domain from radio to sub-millimeter wavelengths. By stacking visibilities directly and transforming them into the rest frame, ViSta enhances the signal, suppresses noise, and improves image reconstruction through extended uv-coverage. ViSta outperforms image stacking when individual sources are too faint to detect, achieving higher SNR in the low-signal and extended regime. This new optimized version features a C++/OpenMP kernel which replaces CASA demanding functions, enabling GPU acceleration while minimising memory usage and intermediate data products. The method is highly flexible, allowing stacking regardless of array configuration, spectral setup, or telescope. In the SKA era, where visibilities will not be routinely preserved, ViSta helps in assessing the information lost in the image-plane transition and in exploiting the vast amount of data still stored in interferometric archives.
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All authors Martina Torsello, Marcella Massardi, Elisabetta Liuzzo, Gayathri Gururajan, Francesca Perrotta, Andrea Lapi

Astrophysics of Galaxies

EWOCS-IX: JWST/NIRCam observations of Westerlund 2 - Identification of candidate substellar members

V. Almendros-Abad, M.G. Guarcello, K. Muzic et al. (+26 more)

[Abridged] Investigating substellar populations in young massive clusters offers crucial insights into the formation of brown dwarfs (BDs) and the role of environmental conditions in shaping their properties. Westerlund 2 (Wd2), as one of the nearest dense and massive clusters in the Milky Way, represents an ideal laboratory for studying the effects of high stellar density and ionizing radiation from massive stars on BD formation. This paper presents deep JWST/NIRCam observations of Wd2 in a large number of filters between 1.15 and 4.1 $\mu m$. Our analysis focuses on identifying and characterizing the BD population within the cluster. We carried out PSF photometry on deep JWST/NIRCam data obtained in 4 wide and 6 medium-band filters, using DOLPHOT. The resulting catalog was used to identify BD candidates in Wd2 through spectral energy distribution (SED) fitting with atmospheric models. The 50% detection limit of our NIRCam catalog is $\sim$0.015-0.02 $M_\odot$, at the distance, age, and extinction of Wd2, providing the deepest view of a supermassive star cluster to date. We identify 353 substellar candidates. Most candidates (301) lie above the 10 Myr isochrone in the Hertzsprung–Russell diagram consistent with cluster membership, which are defined as strong candidates. Comparison with a control field indicates a contamination level of $\lesssim$5% for the strong candidate sample down to masses of $\sim$0.01–0.015~$M_\odot$. We identify 73 candidates exhibiting infrared excess indicative of circumstellar disks. These objects occupy the expected infrared-excess locus in de-reddened color diagrams and represent $27.7^{+3.4}_{-3.2}$% of the candidates detected in F410M. The resulting catalog provides a well-characterized sample for future spectroscopic confirmation and subsequent studies of the substellar population of Wd2.
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All authors V. Almendros-Abad, M.G. Guarcello, K. Muzic, A. Scholz, M. Andersen, A. Bayo, W. Best, D. Capela, M. Gennaro, A. Ginsburg, J.B. Lovell, K. Monsch, E. Moraux, L. Prisinzano, T. Rom, E. Sabbi, P. Zeidler, C. Argiroffi, R. Bonito, D. Calzetti, V. Cusimano, F. Damiani, J.J. Drake, T.J. Haworth, N.D. Richardson, M. Robberto, S. Sciortino, N.J. Wright, T. Ziliotto

Cosmology and Nongalactic Astrophysics

Blast.jl: Differentiable Non-Limber Power Spectra for Joint Clustering, Shear, and CMB lensing Analyses

Sofia Chiarenza, Marco Bonici, Stefano Camera et al. (+4 more)

Upcoming large-scale structure surveys require accurate theoretical predictions for angular power spectra on the largest angular scales, where the commonly used Limber approximation breaks down and multiple relativistic and observational effects become relevant. At the same time, modern cosmological analyses increasingly rely on gradient-based inference techniques, motivating the development of fast, fully differentiable algorithms. In this work, we present a major extension of Blast.jl, a numerical toolkit for the efficient computation of non-Limber angular power spectra. Building on the Chebyshev-polynomial decomposition of the original framework, the updated algorithm incorporates redshift-space distortions, magnification bias, primordial non-Gaussianity, intrinsic alignments, CMB lensing, and the integrated Sachs-Wolfe effect, while remaining fully differentiable through custom automatic differentiation rules. Despite the increased physical complexity, the algorithm retains favorable scaling by precomputing all cosmology-independent quantities. We validate the expanded framework against brute-force integration and established cosmological codes, and provide a detailed analysis of the trade-off between computational speed and precision as a function of the algorithm hyperparameters. We demonstrate the readiness of Blast.jl for gradient-based inference through a simulated likelihood analysis with LSST Y10-like mock data, recovering unbiased cosmological and nuisance parameter constraints from a 35-parameter model using gradient-based samplers.
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All authors Sofia Chiarenza, Marco Bonici, Stefano Camera, Giulio Fabbian, Carlos García-García, Alex Krolewski, Will J. Percival

Solar and Stellar Astrophysics

Mass-dependent multiplicity fraction in low mass stars revealed by Gaia astrometry

Ben Pennell, Hans-Walter Rix, Kareem El-Badry et al. (+3 more)

Stellar multiplicity at different orbital periods is probed by different techniques: radial velocities at the shortest periods, direct imaging at the longest, and astrometry in between. Gaia DR3 provides unprecedented astrometric information to constrain binary populations with periods of tens to thousands of days. Beyond the small fraction of direct orbit solutions, Gaia publishes coarser astrometric diagnostics for all objects, such as on-sky accelerations, jerks, or the single-star goodness-of-fit measure, RUWE. We show that these diagnostics together are sensitive to a far wider range of orbital periods than orbit solutions alone. Built on the Gaiamock emulator, we develop a forward-modelling framework to constrain rates of multiplicity from Gaia data, using all astrometric solution types. We apply this framework to $366~027$ primaries of $0.2$–$0.75\,M_\odot$ between $50$ and $200$ pc, including vastly more M-dwarfs than previous multiplicity studies. For fiducial models of the period and mass-ratio distributions, the inferred multiplicity fraction is approximately constant at ${\sim}45\%$ from the solar-type regime down to $0.4\,M_\odot$, only then dropping to ${\sim}15\%$ by $0.2\,M_\odot$. This mass-multiplicity relationship revises the conventional picture of a monotonically rising mass–multiplicity relation, and aligns the upper M-dwarf regime with solar-type stars rather than placing it on a continuous decline.
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All authors Ben Pennell, Hans-Walter Rix, Kareem El-Badry, Sahar Shahaf, Johanna Müller-Horn, Jiadong Li

Solar and Stellar Astrophysics

Chemical evolution of Na, Mg, and Al in the Galactic bulge from UVES data

R. P. Nunes, B. Barbuy, C. Chiappini et al. (+9 more)

The formation of the Galactic bulge remains incompletely understood, with evidence pointing to different stellar populations, including a bar-driven component, an inner-disk population, and an older spheroidal component. Chemical abundances provide critical constraints on the origin of these populations, particularly for odd-Z elements such as Na and Al, as well as Mg, whose behaviour at high metallicity is still a matter of debate. We aim to investigate the presence of overabundances of Na, Mg, and Al in Galactic bulge stars, with particular emphasis on the metal-rich regime, and to evaluate their consistency with predictions from chemical evolution models. We re-derived the abundances of Na, Mg, and Al for a sample of 55 bulge red giants previously analysed in the literature. Our study is based on high-resolution UVES spectra obtained with the ESO Very Large Telescope and employs spectrum synthesis using the Turbospectrum code, with updated atomic and molecular line lists. We find somewhat lower abundances of Mg and Al at the metal-rich end than previous studies, while a fraction of the metal-rich stars still exhibit significant Na enhancements. These enhancements persist when different sets of stellar parameters are adopted, indicating that they are robust. The presence of Na-enhanced stars at high metallicity is difficult to reconcile with standard chemical evolution models and suggests additional enrichment processes in the bulge, or a particular behaviour of stellar yields with metallicity. The Na enhancement could be due to metallicity-dependent yields from massive stars, not taken into account in available models, and/or enrichment by asymptotic giant branch stars, or due to second-generation stars evaporated from globular clusters, the latter option arising because for the metal-rich ([Fe/H]>0) stars a Na-O anti-correlation appears to occur.
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All authors R. P. Nunes, B. Barbuy, C. Chiappini, A. Friaça, M. C. Jelin, V. Hill, M. Zoccali, A. Renzini, A. Pérez-Villegas, H. Ernandes, S. O. Souza, M. J. Castro

Astrophysics of Galaxies

Dark Matter Halo Tumbling Induced by Torques from Massive Mergers

Neil Ash and Monica Valluri

Dark Matter halos exhibit slow tumbling known as `figure rotation'. Figure rotation occurs in roughly $80\%$ of isolated $\Lambda$CDM halos and is relatively unaffected by baryonic feedback, making it an attractive and relatively unexplored test for $\Lambda$CDM. However, galaxy mergers are capable of exerting strong torques on a host halo's quadrupole, warranting an investigation of whether such interactions are capable of influencing figure rotation. Using isolated $N-$body simulations and 6 TNG50 halos containing MW analog galaxies, we investigate figure rotation in the context of massive mergers. For isolated galaxies we find that massive mergers elicit rotation of the host halo in both a rapid transient phase during the satellite infall with pattern speeds between $10^\circ-60^\circ$ Gyr$^{-1}$, and post-merger as a steady tumbling with pattern speeds between $2^\circ-40^\circ$ Gyr$^{-1}$ lasting for at least $6-8$ Gyr. Both transient and long-lived tumbling depend on the trajectory of the infalling satellite. We find that figure rotation can be induced by radial mergers with no orbital angular momentum, suggesting that tidal torques from the satellite are a driving mechanism. Meanwhile, TNG50 halos show quadrupole tumbling modified during major mergers in both pattern speed (3/6 halos) and rotation axis orientation (6/6 halos). Quadrupole tumbling remains stable after the last major merger in 5 of our 6 halos. Our results suggest that, rather than tracing the early tidal shear, figure rotation at present day may instead retain a dynamical memory of a halo's last major merger.
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Earth and Planetary Astrophysics

Precise Stellar Age Constraints and Habitable Zone Evolution in Exoplanet Systems

Grace Henry, Ted von Hippel and Anna Childs

Accurate stellar ages are fundamental to interpreting the evolutionary histories of habitable zone (HZ) planets. Because stellar luminosity evolves over time, HZ boundaries migrate outward, meaning that present-day HZ planets may have experienced different irradiation environments earlier in their evolution. Accurate ages are therefore required to estimate HZ residence times and place planetary habitability in an evolutionary context. We use the Bayesian Analysis of Stellar Evolution with nine parameters (BASE-9) code to constrain ages and masses for exoplanet host stars with planets located in the HZ. Our sample includes single stars with effective temperatures of 4475-7200 K that host planets within their calculated HZ boundaries. We fit isochrones to broadband photometry from Gaia DR3, Pan-STARRS, and 2MASS jointly with Gaia parallaxes, spectroscopic metallicities, and extinction estimates, and assess the resulting age posterior distributions. Using these age constraints, we track HZ migration along stellar evolutionary sequences to estimate continuous HZ residence times, allowing us to identify ideal targets for followup high resolution characterization. Because isochrones separate most strongly near and beyond the main-sequence turnoff, our analysis emphasizes evolved and turnoff hosts, where BASE-9 produces the tightest constraints. We quantify age precision across the sample, yielding highly precise ages for subgiants and evolved main-sequence or turnoff stars, and less precise but measurable ages for lower main-sequence hosts. The final catalog provides our age constraints for 149 HZ planets around 146 host stars and supports evolutionary interpretations of planetary histories.
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Earth and Planetary Astrophysics

IFU Observations of Comet 3I/ATLAS = C/2025 N1 (ATLAS) using the Hobby-Eberly Telescope with the VIRUS Instrument

Anita Cochran, Gregory Zeimann, Emmanuel Jehin et al. (+2 more)

We observed interstellar object 3I/ATLAS = C/2025 N1 (ATLAS) on 9 December 2025 UT with the VIRUS spectrograph on the Hobby-Eberly Telescope. VIRUS is a low spectral resolving power, multi-IFU, optical spectrograph. We used a single IFU for the observations and were able to obtain spectra spaced every one arcsec (1327 km) from the optocenter out to about 85,000 km in the sunward direction. The spectra include molecular features normally seen in the optical for spectra of Solar System comets, with the addition of many very strong lines of FeI and NiI. We modeled these observations using the Haser (1957) model framework and find that the data can only be fit if we assume that the outflow velocity of the gas is half that of comets in our Solar System observed at the same heliocentric distance. We derived Haser model scale lengths for three NiI and four FeI lines. We discuss the implication of the similarities and differences between this object and normal Solar System comets. The excellent spatial resolution of VIRUS, coupled with a FOV of 50X50 arcsecs and a geocentric distance of 1.83 au, allowed us to probe the coma of 3I in great detail.
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All authors Anita Cochran, Gregory Zeimann, Emmanuel Jehin, Hideyo Kawakita, Adam McKay

High Energy Astrophysical Phenomena

The Mass-Ratio Distribution of the Low-Mass Binary Black Hole Subpopulation: A Natural Outcome of Isolated Binary Evolution

Monica Gallegos-Garcia, Anarya Ray, Vicky Kalogera et al. (+7 more)

The observed merging binary black hole population is increasingly consistent with being composed of a mixture of subpopulations, each likely the result of different formation mechanisms. In particular, the low-mass subpopulation, with primary black hole masses below $\approxeq 15\,M_{\odot}$, has been attributed to mergers formed through isolated binary evolution. We use the binary population synthesis code POSYDON to study the mass ratio $(q)$ distribution of binary black hole mergers from isolated binary evolution and compare to the observed low-mass subpopulation. We explore variations in supernova remnant prescriptions, common-envelope efficiency, and black hole accretion efficiency. We find that our models have a preference for asymmetric $q$, most with a broad peak near $q\approxeq0.5-0.7$, and a near-equal-mass component whose relative strength varies across models. This resultant $q$ distribution is consistent with the $q$ distribution of the low-mass subpopulation observed with gravitational waves. We find that for the majority of models these features arise from physically distinct formation subchannels: the asymmetric peak reflects contributions from common-envelope and stable mass-transfer systems, while the near-equal-mass component traces double-core common envelope and contact systems. We conclude that the features in the $q$ distribution of the observed low-mass subpopulation emerge naturally from isolated binary evolution across a range of model assumptions. As the gravitational-wave catalog continues to grow, the relative strength of these $q$ features will provide an increasingly powerful diagnostic of isolated binary evolution and its formation subchannels.
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All authors Monica Gallegos-Garcia, Anarya Ray, Vicky Kalogera, Max Briel, Michael Zevin, Abhishek Chattaraj, Zepei Xing, Jeff J. Andrews, Seth Gossage, Philipp M. Srivastava

Astrophysics of Galaxies

Virgo Filaments VIII: Characterizing the Structural Parameters of Virgo Galaxies with Machine Learning to Probe Environmental Quenching

Kim Conger, Gregory Rudnick, Rose A. Finn et al. (+9 more)

A persistent challenge in galaxy evolution involves disentangling the many correlated properties in order to isolate the effects of a galaxy's environment on its star formation history. To address this multidimensionality problem, we apply k-means clustering to 2831 galaxies in the extended regions around the Virgo cluster to define objective, reproducible subsets of structurally similar galaxies. Using measurements of size, light distribution, and stellar mass, k-means partitions these galaxies into three feature classes (FCs): dwarfs, spheroids, and large disks. In addition to being structurally different, these FCs show distinct offsets from the star-forming main sequence to $>3\sigma$ significance, with the spheroid population systematically shifted to lower star formation rates. Examining environmental dependence within each FC, we find that denser environments are associated with progressively stronger quenching. However, star formation for the dwarf and large disk galaxies is not strongly affected until the rich group and cluster environments. For the spheroid galaxies, star formation instead smoothly decreases as environment density increases. We verify that these trends are not driven by differences in Sersic index within each environment, suggesting that the effectiveness of environmental quenching depends on the galaxy's structural class. Our results speak to the utility of a simple machine learning model to create broad classes of structurally similar galaxies based on a small set of parameters, which has important implications for navigating this data rich era of astronomy.
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All authors Kim Conger, Gregory Rudnick, Rose A. Finn, Rebecca A. Koopmann, Benedetta Vulcani, Dennis Zaritsky, Gianluca Castignani, Francoise Combes, Gabriella De Lucia, Matteo Fossati, Gautam Nagaraj, Daria Zakharova

Instrumentation and Methods for Astrophysics

Learning and Predicting the Nonlinear Variability of X-ray Binaries with the Koopman Operator

Eric Miao, Ruo-Yu Shang, Kaya Mori et al. (+1 more)

X-ray variability in compact-object binaries encodes the nonlinear dynamics of corona-jet interactions and accretion disk instabilities. Standard timing techniques characterize periodic and quasi-periodic variability well, but do not model underlying nonlinear dynamics or forecast their evolution. We apply Koopman operator theory and a data-driven approximation, extended dynamic mode decomposition (EDMD), to X-ray light curves for the first time. Koopman theory represents nonlinear evolution as an infinite-dimensional linear operator $\mathcal{K}$, whose eigendecomposition separates a complex system into independently evolving linear modes. We derive that each Koopman eigenfunction contributes a Lorentzian peak to the power spectrum, giving quasi-periodic oscillations a dynamical interpretation in which process noise damps modes and broadens their peaks. In both chaotic Duffing oscillator simulations and $\sim$30 yr of RXTE ASM and MAXI monitoring of the X-ray binary 4U 1705-44, the slowest-varying eigenfunction partitions state space into low- and high-flux regimes, changing sign days to weeks before transitions become visible in the light curve. Iterating $\mathcal{K}$ additionally yields flux forecasts on days-to-weeks horizons. The strengths of this framework are its generality across linear and nonlinear systems, its intrinsic interpretability through decomposed modes carrying explicit dynamical meaning, and its predictive power from propagating learned dynamics forward. These results establish Koopman operator theory as a new frontier of astrophysical timing and help advance interpretable machine learning for scientific discovery and understanding.
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All authors Eric Miao, Ruo-Yu Shang, Kaya Mori, Reshmi Mukherjee

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Tremaine-Gunn Control: Evading Bounds on Light Fermion Dark Matter

Joel Barir, Diego Blas, Anubhav Mathur et al. (+1 more)

Pauli exclusion is often regarded as imposing a model-independent lower bound on the mass of fermionic dark matter in galaxies. We show that dark-sector interactions can substantially weaken this conclusion. In particular, eV-scale fermions can form bound structures with the characteristic sizes and densities of dwarf galaxies, thereby circumventing the conventional Tremaine-Gunn mass constraint. Within these objects, the degeneracy pressure is balanced by an attractive finite-range scalar Yukawa force that is significantly stronger than gravity. The interaction acts on dwarf-galaxy scales while remaining screened on larger scales. We derive the evolution of the resulting dark-matter fluid and identify a viable cosmological history in which structures first form gravitationally, with the new interaction becoming active only at late times. As a proof of concept, we construct a model in which a single late-time phase transition generates the required dynamics. These results provide a new route to exceptionally light fermionic dark matter and demonstrate that dark-sector interactions can qualitatively alter conventional phase-space limits.
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All authors Joel Barir, Diego Blas, Anubhav Mathur, Tomer Volansky

Earth and Planetary Astrophysics

From orbit to ground: pre-impact meteorite strewn field predictions for imminent impactors and meteorite recovery

Anna Moscati, Marco Fenucci, Laura Faggioli et al. (+3 more)

The flux of meteoroids reaching the Earth is continuous, ranging from microscopic grains to occasional metre and decametre scale bodies. The smallest ones fully ablate in the upper atmosphere, whereas sufficiently large or strong objects survive entry and deposit fragments on the ground as meteorites. Predicting where these fragments land, and reconstructing the atmospheric trajectory and fragmentation sequence that produced them, is central both to hazard assessment and to the recovery of freshly fallen material. The accuracy of such predictions, however, remains limited by poorly constrained fragmentation processes and by sparse, heterogeneous observational coverage of individual events. Traditional strewn field simulations rely on detailed fireball data and event-specific assumptions on fragment masses, aerodynamics, and breakup. These approaches are effective for well-instrumented events, but their applicability degrades rapidly when observations are sparse, often resulting in huge uncertainties. We present an ab initio framework predicting strewn fields of near-Earth asteroids directly from pre-impact orbital solutions. It propagates luminous trajectory and dark flight using a physics-based translational dynamics model and realistic atmospheric conditions, without requiring fireball triangulation or event-specific tuning. Validation against recent asteroid falls with recovered meteorites shows agreement with observations, with nominal solutions reproducing fall locations within 100-200 m. The new method has been integrated into the ESA Aegis pipeline, which now enables hours-ahead computation of impact locations, supporting recovery efforts, minimizing contamination, and, where warranted by object size and predicted ground hazard, civil-protection decision making.
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All authors Anna Moscati, Marco Fenucci, Laura Faggioli, Marco Micheli, Francisco Ocaña, Juan Luis Cano

Earth and Planetary Astrophysics

Mass constraints for the K2-223 system planets: An ultra-short-period sub-Earth, a short-period super-Earth, and a tentative long-period giant planet

Dawid Jankowski, Grzegorz Nowak, Gaia Lacedelli et al. (+23 more)

We present mass constraints of two short-period Earth-sized planets transiting K2-223 based on high-precision radial velocity measurements from HARPS-N and ESPRESSO, as well as a tentative indication of an outer Jupiter-like planet orbiting the G1V dwarf K2-223. With a radius of $R_\mathrm{b}=0.79\pm0.10$ $\mathrm{R_{\oplus}}$ and a 3$\sigma$ upper mass limit $M_\mathrm{b}<2.8$ $\mathrm{M_{\oplus}}$, K2-223 b belongs to the small group of known sub-Earth planets and is currently the smallest known ultra-short-period planet ($P_\mathrm{b}\approx$ 0.5 day) transiting a solar-type star. With a radius of $R_\mathrm{c}=1.41\pm0.15$ $\mathrm{R_{\oplus}}$, a mass of $M_\mathrm{c}=4.2\pm1.3$ $\mathrm{M_{\oplus}}$, and a density of $\rho_\mathrm{c}=8.3\pm3.7$ $\mathrm{g\,cm^{-3}}$, K2-223 c is a short-period ($P_\mathrm{c}\approx$ 4.5 days) super-Earth. Based on almost 6.5 years of radial velocity monitoring of K2-223 with the HARPS-N spectrograph, we identified a tentative giant planet with an orbital period of $P_\mathrm{d}=4.53^{+0.32}_{-0.34}$ $\mathrm{years}$ and a minimum mass of $1.29^{+0.23}_{-0.17}$ $\mathrm{M_{\rm Jup}}$. Two close-in small planets accompanied by a distant candidate Jupiter-like companion would make K2-223 a system with a rare architecture. This is valuable for testing scenarios of planetary formation and evolution. The extreme proximity of K2-223 b to the parent star means that relativistic and tidal perturbations to Newtonian gravity need to be considered. We discuss the timescales and amplitudes of these effects in the context of the radial velocity model and dynamical simulations of the K2-223 multiple-planet system. We also present a parametrisation of the planets with directly measured masses, radii, and bulk densities in terms of the orbital period normalised by the Roche period. This provides an alternative representation in the context of the Neptune desert.
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All authors Dawid Jankowski, Grzegorz Nowak, Gaia Lacedelli, Enric Pallé, Krzysztof Goździewski, Thomas Masseron, Ilaria Carleo, Rafael Luque, Felipe Murgas, Davide Gandolfi, Artie P. Hatzes, William Cochran, Pedro Figueira, Rafael A. García, Samuel Geraldía-González, Judith Korth, Pierrot Lamontagne, John H. Livingston, Savita Mathur, Giuseppe Morello, Jaume Orell-Miquel, Dinil B. Palakkatharappil, Carina M. Persson, Seth Redfield, Atanas K. Stefanov, Vincent Van Eylen

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Primordial Black Hole Assisted Dirac Leptogenesis

Marco Manno and Anish Ghoshal

Dirac leptogenesis offers a qualitatively different route to the baryon asymmetry: total lepton number is conserved, but equal and opposite asymmetries are stored in the Standard Model and right handed neutrino sectors, with only the visible component processed by electroweak sphalerons. We present the first dedicated study of how evaporating primordial black holes (PBHs) modify this mechanism. In a minimal charged-scalar mediator setup, we solve the coupled Boltzmann system including thermal production, Hawking emission of the mediator $X$ and of right handed neutrinos, the PBH contribution to the expansion rate, and entropy injection. We find that Hawking emission can populate $X$ in regions where thermal production is inefficient, allowing its subsequent CP-violating decays to enhance the baryon asymmetry. For representative benchmarks, PBHs extend the successful region from mediator masses around $10^9\,{\rm GeV}$ down to about $10^6\,{\rm GeV}$ and can compensate for smaller effective CP asymmetries. This effect is not universal: where thermal Dirac leptogenesis is already efficient, PBHs can instead reduce the final asymmetry. Their evaporation also deposits energy in the right handed neutrino sector and contributes to $\Delta N_{\rm eff}$. In the PBH parameter scan, part of the region that reproduces the observed baryon asymmetry lies below the Planck reference level $\Delta N_{\rm eff}=0.284$ and above the projected CMB-S4 sensitivity $\Delta N_{\rm eff}=0.06$.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

SN1987A constraints on the neutrino-dark-fermion interaction from resonant scattering with C$\nu$B

Christina Gao, Ke Hu, Kun-Feng Lyu et al. (+1 more)

Neutrino self-interactions mediated by a light scalar offer a compelling resolution to cosmological tensions and may naturally arise in neutrino mass generation mechanisms. When the scalar also couples to a light dark-sector fermion, supernova neutrinos can resonantly annihilate with the cosmic neutrino background (C$\nu$B) into invisible dark radiation, depleting the flux en route to Earth. We use this depletion to constrain the neutrino-scalar coupling from the SN1987A data. Within a Bayesian framework we analyze the data for two supernova neutrino emission models, a parameterized model and a 2D hydrodynamic simulation, and for two coupling types, a mass-independent one and a mass-proportional one. Our results show that new-physics limits from SN1987A cannot be quoted independently of the heavy-flavor emission, the flavor conversion, or the coupling structure. Finally, we forecast that a future high-statistics burst recorded by Hyper-Kamiokande would restore a meaningful upper bound even when flavor conversion is included.
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All authors Christina Gao, Ke Hu, Kun-Feng Lyu, Vincent Zou

High Energy Astrophysical Phenomena

Measuring Small-scale Turbulence in Supernova Remnants with Jitter Radiation

Emily Simon, Damiano Caprioli, Niccolò Bucciantini et al. (+2 more)

Hard X-ray emission from Cas A has been attributed to jitter radiation, implying magnetic turbulence on scales near or below the ion Larmor radius. We propose these fields arise from ion-scale micro-instabilities (e.g., mirror and firehose) in the shock downstream, and use high-resolution hybrid simulations to demonstrate the generation of such small-scale turbulence. Its spectral index, once numerical dissipation is accounted for, is consistent with that inferred for Cas A, suggesting that jitter radiation is a direct probe of ion-scale turbulence in supernova remnants.
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All authors Emily Simon, Damiano Caprioli, Niccolò Bucciantini, Emanuele Greco, Marco Miceli

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Axion Quality from Exact Proton Stability

Joe Davighi, Admir Greljo and Xavier Ponce Díaz

A discrete, anomaly-free $\mathbb Z_9$ gauge symmetry may persist to the deep infrared, exactly forbidding proton decay. This $\mathbb Z_9$ can emerge from Higgsing a lepton-flavour non-universal $U(1)_X$ that generates realistic neutrino masses and mixings through a high-scale seesaw and predicts an additional light Goldstone. Adding an anomaly-free chiral heavy-quark sector turns this mode into the QCD axion. The same selection rules that ban proton decay also forbid PQ-violating operators below a suitably high dimension, $d_{\rm PQ}\gtrsim10$, including operators involving the heavy quarks that radiatively match onto the scalar potential. We construct explicit models viable when PQ breaking occurs before or after inflation; in the latter case, avoiding stable heavy relics and eliminating the string-wall network tightly constrain the heavy-quark spectrum. We identify restricted regions of parameter space where thermal leptogenesis remains viable and, for $d_{\rm PQ}\geq13$, can coexist with a high-quality axion constituting all of the dark matter.
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Astrophysics of Galaxies

JWST Reveals a Candidate Supermassive Black Hole Binary at z=4.3 in the Brightest Sub-millimeter Galaxy in COSMOS-Web

Jed McKinney, Ansh Gupta, Julian B. Munoz et al. (+13 more)

We present JWST/NIRSpec PRISM and G395M grating spectroscopy for AzTEC-1, a massive sub-mm bright galaxy at $z=4.34$ in the COSMOS extragalactic field. The PRISM spectrum reveals strong H$\alpha$, a significant Balmer break, and no H$\beta$ detection, indicating a $100-400$ Myr-old stellar population and high dust attenuation. BPT line ratios indicate the presence of an Active Galactic Nucleus (AGN). Decomposing narrow and broad line components, we recover broad, blueshifted H$\alpha$ with a velocity offset of $1245{\,\rm km\,s^{-1}}$ from the systemic narrow line velocity and with FWHM$\,\sim2500\,{\rm km\,s^{-1}}$. AzTEC-1's smooth morphology and stellar age is suggestive of a past merger-induced starburst period that would have brought in a second supermassive black hole, raising the possibility for a binary supermassive black hole system. In this scenario, we assume that the lower mass black hole hosts a broad line region orbiting a quiescent primary. Evidence for an extended outflow is not found in the 2D spectrum, NIRCam imaging, resolved ALMA observations of dust continuum, or CO, [C II]$_{157\,\mu \rm m}$ and [N II]$_{\rm 205\,\mu m}$ kinematics. AzTEC-1's high central gas mass surface density and dynamically unstable gas disk indicates that massive gas clouds external to the candidate binary SMBH's orbit might have played a role in stalling infall from $\sim10$ Myr to $\sim100$ Myr through dynamical torques, which has been theorized to occur in the nuclei of massive galaxies like AzTEC-1. If the supermassive black hole binary is confirmed, AzTEC-1 would be an excellent laboratory into the astrophysics driving low-frequency gravitational wave detections.
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All authors Jed McKinney, Ansh Gupta, Julian B. Munoz, John Chisholm, Caitlin M. Casey, Stephanie M. Urbano Stawinski, Olivia Cooper, Erini Lambrides, Hollis Akins, Maximilien Franco, Archana Aravindan, Seiji Fujimoto, Kohei Inayoshi, Andreas L. Faisst, Jeyhan S. Kartaltepe, Michael Boylan-Kolchin

Astrophysics of Galaxies

The Comprehensive Investigations of the NGC 7419 Open Cluster and the New Perspective on Mass Populations

Nasser M. Ahmed, Remziye Canbay and Deniz Cennet Ç{\i}nar

We present a structural, kinematic, and photometric analysis of the young, red supergiant- and Be star-rich open cluster NGC 7419 using Gaia DR3 and 2MASS data. Using the HDBSCAN algorithm and conservative membership criteria, we identify 734 high-probability cluster members, separating the cluster from the dense Perseus Arm background. Isochrone fitting to the Gaia DR3 color-magnitude diagram, treating classical Be stars separately to account for their circumstellar excess, yields an age of 15 +/- 2 Myr, a distance of 3161 +/- 261 pc, a distance modulus of 12.50 +/- 0.08 mag, and a color excess E(GBP-GRP) = 2.58 +/- 0.06 mag. An independent 2MASS analysis gives a consistent distance modulus of 12.53 mag and E(J-Ks) = 0.99 mag. The Be stars show a prominent infrared excess in J-Ks, consistent with free-free and bound-free emission from circumstellar disks. We derive mean proper motions of -2.738 +/- 0.115 and -1.604 +/- 0.149 mas yr^-1 and a mean parallax of 0.288 +/- 0.062 mas, corresponding to a trigonometric distance of 3316 +/- 317 pc. The photometric distance is adopted as the primary estimate. A generalized King profile gives a core radius of 1.53 +/- 0.08 arcmin and a limiting radius of 8.16 +/- 1.1 arcmin. The stellar mass distribution is best described by a three-component Gaussian model, which we interpret as three distinct mass populations. Their coexistence and incomplete mixing are consistent with the young dynamical state of NGC 7419. Hierarchical formation provides a plausible framework for their origin.
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Astrophysics of Galaxies

The HERON Coma Project: Exploring the low-surface-brightness frontiers in the Coma cluster

Javier Román, R. Michael Rich, Pablo M. Sánchez-Alarcón et al. (+3 more)

The technical complexity of data processing and residual instrumental systematics remain among the main barriers to reaching the faintest low-surface-brightness (LSB) regimes in the local Universe. Here, we present the HERON Coma Project, a deep $g$- and $r$-band imaging campaign on the Coma cluster carried out with the LSB-optimized 71-cm Jeanne Rich Telescope. The observing and processing strategy combines accurate flat-fielding, sky-background modeling and extended point spread function (PSF) characterization. As representative scientific applications, we explore the complex associated with the giant elliptical galaxies NGC 4839 and NGC 4816, in the southwestern region of Coma. Spatially coherent emission is recovered in direct imaging to $\mu_{\overline{g+r}}\simeq30~\mathrm{mag\,arcsec^{-2}}$, consistent with the nominal sensitivity inferred from the scaling of the background fluctuations. The PSF-deconvolved photometric profiles of NGC 4839 and NGC 4816 are traced to generalized isophotal radii of 705 and 329 kpc, reaching $\mu_{\overline{g+r}}=32.2$ and $31.6~\mathrm{mag\,arcsec^{-2}}$, with data-derived signal-to-noise ratios of 4.1 and 7.0, respectively. The agreement between direct detection and the predictions from background fluctuations provides no clear evidence of a systematics-dominated detection floor over the surface brightness range and spatial scales examined. We also assess the observational challenges involved in extending reliable measurements to still fainter surface brightness levels. The HERON Coma Project opens a new window onto the faint stellar record of the complex and ongoing assembly of Coma, while demonstrating the potential of modest ground-based telescopes with suppressed instrumental reflections to provide highly competitive measurements of extended diffuse structures. We make the final calibrated images publicly available to the community.
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All authors Javier Román, R. Michael Rich, Pablo M. Sánchez-Alarcón, Yolanda Jiménez-Teja, Chester Li, Mónica Esquide

Astrophysics of Galaxies

Linking neutral gas inflows and outflows to offsets in the star-forming main sequence and mass-metallicity relation

S. Weng, M. Pieri, A. Saintonge et al. (+40 more)

Gas inflows and outflows regulate galaxy growth, but direct observational links between measured gas flows and galaxy scaling relations remain limited. Using ~6,000 star-forming galaxies with down-the-barrel Na I D absorption from DESI DR2, we examine how systems with detected neutral-gas inflows and outflows populate the star-forming main sequence (SFMS) and mass-metallicity relation (MZR). Inflow and outflow hosts are compared with stellar-mass- and redshift-matched controls, and with SFMS and MZR fits derived from galaxies without detected gas flows. Outflow hosts (v_flow $\leq$ -50 km s$^{-1}$) show enhanced sSFRs by 0.25-0.40 dex and elevated central metallicities by 0.04-0.06 dex in the lower-redshift sample. Slow inflow hosts (0 $<$ v_flow $<$ 100 km s$^{-1}$) show similarly enhanced sSFRs of 0.20-0.30 dex, but no significant metallicity offset, while fast inflow hosts (v_flow $\geq$ 100 km s$^{-1}$) show weaker SFR enhancement and modestly lower metallicities. Together, these trends support a regulator picture in which neutral gas flows trace different phases of the baryon cycle. Slow inflow hosts lie above the SFMS, consistent with accretion sustaining enhanced star formation without strong central metallicity dilution. This may indicate that inflowing gas is already metal-enriched or has mixed or enriched over extended timescales. By contrast, outflow hosts lie near the upper 1{$\sigma$} SFMS envelope, consistent with feedback regulating subsequent growth. Gas-flow hosts also show small but systematic offsets in the narrow 4000 Å break strength ($D_n$4000) relative to controls matched in redshift, stellar mass and SFR. Our results show that neutral gas flows are associated with population-level offsets from the SFMS and MZR, consistent with a baryon-cycle contribution to scaling-relation scatter.
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All authors S. Weng, M. Pieri, A. Saintonge, D. Scholte, D. Muñoz Santos, T. Hu, J. Aguilar, S. Ahlen, F. Beutler, D. Bianchi, D. Brooks, A. Carnero Rosell, F. J. Castander, T. Claybaugh, A. de la Macorra, B. Dey, P. Doel, V. A. Fawcett, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, A. Kremin, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, W. J. Percival, F. Prada, I. Pérez-Ràfols, C. Ravoux, G. Rossi, R. Ruggeri, E. Sanchez, C. Saulder, D. Schlegel, J. Silber, M. Siudek, G. Tarlé, B. A. Weaver, H. Zou

Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG

Generative Diffusion Surrogates with Analytical Variance Schedule

Patrick Reichherzer, Gianluca Gregori, David N. Hosking et al. (+1 more)

Stochastic transport describes physical systems in which an initially structured distribution spreads under unresolved forcing, scattering, or heterogeneous media. Useful surrogates for such systems should be probabilistic, time-resolved, and able to represent non-Gaussian distributional structure. Generative diffusion models, which corrupt data with Gaussian noise and learn a reverse flow back to structured states, have these properties. Their noise schedules, however, are usually chosen heuristically: image and audio generation—the canonical use cases—provide no physical clock. In transport, by contrast, the variance, or mean-square displacement, is often known from macroscopic theory or empirical scaling even when the full distribution is not. Here we prescribe the forward noising rate as the time derivative of this variance, turning generative time into a calibrated transport clock. The variance path is enforced by construction, while the learned score field represents how non-Gaussian structure inherited from entrance data is smoothed along that path, requiring no intermediate-time physical transport data. For ballistic-to-diffusive transport in turbulent plasmas, the surrogate matches test-particle distributions, reproduces the laboratory-measured variance scale, and tracks the simulated kurtosis evolution without schedule tuning, enabling calibrated emulation and likelihood-based inference.
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All authors Patrick Reichherzer, Gianluca Gregori, David N. Hosking, Subir Sarkar

Instrumentation and Methods for Astrophysics

CosmicPAH-IRDB: A Web Application for Including Anharmonicity in Simulated PAH Spectra for Astrophysics

Louan de Bentzmann, Christine Joblin, Karine Demyk et al. (+6 more)

Advances in infrared observations with the James Webb Space Telescope (JWST) call for new tools to exploit the information associated with the Aromatic Infrared Bands (AIBs), now observed in both distant galaxies and the embryos of planetary systems. The AIBs contain information about their carriers as well as the excitation conditions, making them powerful probes of the chemical and physical conditions of their environments - if their spectral information can be decoded. While large datasets of theoretical infrared spectra are becoming available, efforts have primarily focused on the contribution of chemical diversity to the AIBs. However, the results remain limited by the impact of the excitation process on the band profiles. The AIB carriers, thought to be polycyclic aromatic hydrocarbons (PAHs), are hot molecules, which affects their spectral characteristics. We report here our approach to quantify these effects empirically by collecting IR spectra - both experimental and theoretical - and studying the evolution of band positions and widths with temperature. We present our methodology, including the development of the CosmicPAH-IRDB web application and spectral database, along with the associated cosmicPAHmfit multi-component spectral fitting tool. Our philosophy emphasizes open sharing, user-friendly access, and machine readability. The web application, tool and their update are accessible via the Cosmic PAH portal (https://cosmic-pah.irap.omp.eu/)
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All authors Louan de Bentzmann, Christine Joblin, Karine Demyk, Giacomo Mulas, Dominique Toublanc, Vincent Marty, Axel Pérignon, Mickaël Boiziot, Jean-Michel Glorian

Instrumentation and Methods for Astrophysics

Amortized Opacity Marginalization Improves C/O Interval Calibration for Brown-Dwarf Retrievals

Kellen Heraty

Molecular line lists disagree at a level that measurably shifts retrieved C/O, so retrievals conditioned on a single list omit a dominant systematic from their error bars. Classical marginalization re-runs a full retrieval under K opacity realizations per object. We move that cost into simulation: while generating the training set we randomize opacities (smooth multiplicative Fourier fields in $\log\nu$ plus a discrete line-list mixture, under a deliberately broad prior informed by measured inter-list differences), so a neural posterior estimator learns an already-marginalized posterior. Conceptually, this is the amortized analogue of repeating a conventional retrieval under many plausible opacity realizations and averaging the resulting posteriors. On perturbed held-out spectra (n=2048) a standard NPE covers nominal 90% C/O intervals 43.3% of the time against 82.4% for a compute-matched marginalized network; three-seed control ensembles reach 93.2% on clean data but 61.4% under perturbation, against 89.4% marginalized, isolating the deficit as opacity-induced (TARP joint expected-coverage deviation 0.005 against 0.035 for a single control network). An axis ablation traces the gain to the continuous field (45.4% for the discrete swaps alone, 79.3% for the field alone). Applying the 105 real bad-pixel masks with median filling then collapsed the ensemble's C/O coverage from 0.901 to 0.479; retraining on the same mask distribution and pooling three such seeds returns a nominal 0.905 C/O and 0.891 overall under the full deployment path, still in simulation (n=1024, same 105 masks), at 0.21 to 0.31 of the prior width. On 105 JWST/G395H spectral products of 13 late-T/Y dwarfs, single marginalized networks bracket the Hood et al. (2024) T8 benchmark C/O where the control excludes it, a consistency check rather than a validation, at 1.6-2.6x wider intervals.
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Earth and Planetary Astrophysics

Constraining the Planetary Obliquity Distribution of Warm Jupiters

Caleb Lammers and Joshua N. Winn

Warm Jupiters are an intriguing class of planets with uncertain origins. Their planetary obliquities could help distinguish between different formation pathways: planet-planet scattering and migration across resonances can excite large obliquities, whereas in-situ formation would more naturally produce low obliquities. We searched for oblateness-related anomalies in the transit light curves of six observationally favorable warm Jupiters: TOI-201b, TOI-1670c, TOI-199b, Kepler-9c, Kepler-30c, and Kepler-553c. Each planet's light curve is consistent with a spherical planet and provides degenerate constraints on the planet's sky-projected oblateness and obliquity. To overcome these limitations, we performed hierarchical Bayesian modeling of the population-level obliquity distribution. Assuming warm Jupiters are as oblate as Saturn ($f \approx 0.1$), we find their median obliquity to be below $12^\circ$ with $90$% confidence and below Saturn's obliquity ($27^\circ$) with $93$% confidence. Jupiter-like oblateness ($f \approx 0.06$) and larger obliquities are allowed. Simulations of JWST observations predict that significantly tighter constraints can be derived.
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Astrophysics of Galaxies

The JWST Emission Line Survey (JELS): A narrow-band determination of the H$\alpha$ Luminosity Function and Cosmic Star Formation into the Epoch of Reionization

C. A. Pirie, K. J. Duncan, P. N. Best et al. (+19 more)

The recent star-formation activity in galaxies can be optimally traced by the H$\alpha$ emission line, with the resulting H$\alpha$ luminosity function (LF) at a given epoch providing a reliable probe of cosmic star formation. We present the first narrow-band determined H$\alpha$ LF into the Epoch of Reionization (EoR) at $z\sim6.1$, using 39 H$\alpha$ emitters selected from the JWST Emission Line Survey (JELS). The observed and dust-corrected LFs are broadly consistent with recent slitless spectroscopic measurements but show notable discrepancies with predictions from cosmological simulations, likely reflecting differences in emission-line and dust modelling. Fits combining multiple LF datasets help constrain the high-redshift faint-end slope of the H$\alpha$ LF ($-1.79<\alpha_{\rm{H\alpha}}<-1.62$), but there remains uncertainty in its evolution with redshift. Integrating the JELS dust-corrected H$\alpha$ LFs yields a star-formation rate density of $\log_{10}(\rho_{\rm{SFR_{H\alpha}}}\,/\,\rm{M_{\odot}\,yr^{-1}\,Mpc^{-3}})=-1.93\,^{+0.14}_{-0.12}$ or $-2.00\,^{+0.16}_{-0.10}$, assuming a continuum-to-line extinction ratios $\eta_{\rm{dust}}=A_{\rm{cont}}(\rm{6563\,\mathring{A}})/A_{\rm{H\alpha}}=1$ and 0.44, respectively. Both measurements are consistent within uncertainties with previous results using standard assumptions for the LF integration limit ($L_{\rm{H\alpha,\,lim}}$) and SFR calibration constant $\kappa_{\rm{H\alpha}}$, despite the uncertainties in the dust corrections. We explore the metallicity dependence of $\kappa_{\rm{H\alpha}}$ and find $\rho_{\rm{SFR_{H\alpha}}}$ decreases 0.43 dex compared to the fiducial result and is no longer consistent with UV-determined $\rho_{\rm{SFR}}$ at $z\sim6$. This work highlights the importance of narrow-band surveys in probing the faint H$\alpha$ population and providing new constraints on cosmic star-formation activity into the EoR.
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All authors C. A. Pirie, K. J. Duncan, P. N. Best, D. J. McLeod, C. L. Hale, R. K. Cochrane, S. R. Flury, H. M. O. Stephenson, M. I. Arnaudova, M. Brinch, J. S. Dunlop, E. Ibar, Z Li, J. Matthee, R. J. McLure, L. Ossa-Fuentes, A. L. Patrick, J. Selfridge, Ian Smail, D. Sobral, J. P. Stott, A. M. Swinbank

Earth and Planetary Astrophysics · Cross-listed from math.DS

Families of relative periodic orbits in the planar three-body problem via consecutive alignments

Joan Gimeno, Marc Jorba-Cuscó and Begoña Nicolás

Relative periodic orbits (RPOs) are solutions of the three-body problem that are periodic in a uniformly rotating reference frame and, in general, quasi-periodic in inertial coordinates. We present a numerical procedure for computing and continuing one-parameter families of RPOs of the planar Newtonian three-body problem. The method exploits consecutive syzygies, understood here as configurations in which the three bodies are aligned and their velocities satisfy the corresponding symmetry conditions. Matching the positions and momenta at two consecutive alignments reduces the computation of RPOs to a low-dimensional nonlinear problem. Its solutions are then numerically continued, and linear stability is determined from the nontrivial eigenvalues of the rotated monodromy matrix after removing the neutral directions associated with conserved quantities and continuous symmetries. The procedure is applied to several mass distributions and initial configurations, producing families of Poincaré, Hill, and binary-type solutions. These families exhibit transitions from nearly circular to highly eccentric motion, changes of stability near resonances and turning points, and absolute periodic solutions when the rotation angle is a rational multiple of 2{\pi}. In the Hill families, the continuation connects satellite configurations with circumstellar motion as the smallest body loses its gravitational binding to the intermediate body. Circumbinary and circumstellar configurations are also obtained in the binary regime. The results illustrate the dynamical diversity of RPOs and provide coherent three-body motions that can be used as prescribed trajectories in restricted four-body models.
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