Solar and Stellar Astrophysics
Jiaqi Ying, Brian Chaboyer, Phillip A. Cargile et al. (+2 more)
We present the Dartmouth
Stellar Evolution Emulator (DSEE), a flow-based
stellar evolution model emulator trained on a comprehensive database comprising over eight million evolutionary tracks that vary across twenty input-physics dimensions and span broad ranges in mass and composition. DSEE learns phase-conditioned
stellar state snapshots, unifying track and isochrone construction as marginals of one generative model. It delivers continuous interpolation across high-dimensional physics, probabilistic predictions with calibrated credible intervals, and orders-of-magnitude speedups over direct modeling. Validation against current
stellar evolution models shows high fidelity across the HR diagrams, while distributional tests recover the full distributions obtained from brute-force Monte Carlo sampling. To broaden impact, DSEE is integrated into the open-source CONF1DENCE package, enabling fast, end-to-end creation of
stellar tracks and isochrones. CONF1DENCE includes the ability to make uncertainty-aware age determinations for clusters taking into account observational effects. CONF1DENCE replaces bespoke, fixed-physics grids with a generative, physics-marginalized emulator, setting a practical new standard for
stellar modeling and enabling survey-scale analyses with rigorous uncertainty.
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All authors Jiaqi Ying, Brian Chaboyer, Phillip A. Cargile, Wenxin Du, George Dufresne
Astrophysics of Galaxies
Introducing sapphire: Towards Hybrid Physics-Informed, Data-Driven Modeling of Galaxy Formation
Viraj Pandya, Greg L. Bryan, T. Lucas Makinen et al. (+18 more)
Semi-analytic models (SAMs) have been treating
galaxy populations as dynamical systems for $\gtrsim50$ years, but their
evolution equations remain poorly constrained. We introduce sapphire, a modular, automatically differentiable, GPU-accelerated SAM written in JAX. For the first time, we compute exact Jacobian and Hessian
matrices of a
galaxy formation SAM, using the Pandya et al. (2023) nonlinear differential equation system as an example. These allow efficient, interpretable local and global sensitivity analyses, which reveal that
supernova energy loading is the key astrophysical parameter. We use gradient descent and
Hamiltonian Monte Carlo (HMC) to perform comprehensive mock parameter recovery tests. These indicate that the $z=0$
stellar-to-
halo-mass relation alone does not contain enough information to infer many astrophysical parameters. Using observations of
star-forming
galaxies from the MaNGA survey and the Behroozi et al. (2019) empirical model as one baseline, we derive multiple posteriors assuming different combinations of data, including $z=0$ interstellar medium gas fractions and
metallicities. The inferred physical parameters suggest that
galaxies self-regulate their
star formation primarily through preventative rather than ejective feedback, though this remains uncertain due to the lack of satellite
galaxies, black holes and multi-phase
galactic atmosphere physics. Both Fisher and HMC forecasts demonstrate the potential of sapphire to enable precision inference for
galaxy formation and cosmology in a hybrid physics-informed, data-driven way, but more work is needed to expand its library of models and methods. We make sapphire publicly available at https://github.com/virajpandya/sapphire.
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All authors Viraj Pandya, Greg L. Bryan, T. Lucas Makinen, Austen Gabrielpillai, Christopher Carr, Drummond B. Fielding, Lars Hernquist, Matthew Ho, Kartheik Iyer, Christian Kragh Jespersen, Sophie Koudmani, Marta Laska, Pablo Lemos, Christopher C. Lovell, Lucia A. Perez, William F. Robinson Jr., Rachel S. Somerville, Tjitske K. Starkenburg, Richard Stiskalek, Bryan Terrazas, G. Mark Voit
Solar and Stellar Astrophysics
A Quadruple Excess in Wide Binary Systems: Evidence for Correlated Binary Formation
Dolev Bashi, Cathie J. Clarke and Vasily Belokurov
Understanding the multiplicity of
stellar systems and the correlations between their hierarchical components provides crucial insights into
star formation processes. If binary companions form independently in each component of a wide binary (WB), the fraction of quadruple systems, i.e., 2+2 configurations where both components are themselves close binaries (CBs), should equal the product of individual CB fractions. Using
Gaia DR3 radial velocity spectroscopy (RVS) data for WB systems, we measure the CB fraction $p$ and quadruple fraction $P_{2+2}$, suggesting an enhancement factor $\kappa = P_{2+2}/p^2 = 2.34_{-0.11}^{+0.12}$, significantly exceeding unity expected under a statistical model of independence. We confirm the significance of this excess by performing two sets of tests: (1) shuffling WB pairings while preserving the overall $\Delta G$ distribution shows no significant enhancement, ruling out selection effects; (2) simulations preserving the spectral type (temperature-dependent) CB fraction also yield the same null excess. When examined as a function of WB separation, the enhancement remains strong at separations $\leq 5\,000$ AU, but shows a decline towards unity at the widest separations ($\geq 10\,000$ AU). An independent proper motion anomaly (PMa) consistency check confirms the enhancement, suggesting a similar value. We further find that the enhancement declines with increasing peculiar velocity, suggesting that dynamical processing in older or dynamically hotter populations may transform 2+2 quadruples into triples over time. Our results provide strong evidence for correlated binary formation processes operating in WB systems.
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Astrophysics of Galaxies
Dust and Grain Size Evolution in Galaxy Simulations: What Matters and What Does Not
Massimiliano Parente, Desika Narayanan and Paul Torrey
We present the first implementation of an evolving
dust grain size distribution (GSD) within a semi-analytic cosmological model (SAM) of
galaxy evolution. This flexible model self-consistently accounts for
stellar dust production, shattering, coagulation,
accretion of gas-phase metals, and destruction in
supernova-driven shocks and hot gas, successfully reproducing key observational constraints. The purpose of this paper is to present the key physical elements of this novel
dust implementation in a SAM and to explore controlled numerical experiments to identify the mechanisms shaping the GSD and extinction law in
galaxies. Our results show that the GSD evolves from a large-grain-dominated regime at high
redshift to a flatter, MRN-like shape at low
redshift. This transition occurs earlier for massive
galaxies, at a characteristic
metallicity determined by the
galaxy depletion time. The resulting extinction curves show an increase of the UV/optical slope and a pronounced $2175$ A bump toward lower
redshift, in good agreement with the extinction properties of the MW. Through numerical experiments, we find that once
stars provide the initial reservoir of large grains, shattering and ISM
accretion are the principal mechanisms driving the growth of small grains. When
accretion is included, the model robustly reproduces the observed $z \approx 0$
dust masses, largely independent of the specific assumptions adopted for grain-size physics. The extinction properties of MW-like
galaxies are also generally recovered, except in extreme cases, such as when grain velocities in turbulent media are assumed to be independent of grain size.
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High Energy Astrophysical Phenomena
An archival search for gamma-ray bursts gravitationally lensed by galaxy clusters
Dan Ryczanowski, Benjamin P. Jones, Benjamin P. Gompertz et al. (+1 more)
Discoveries of gamma-ray bursts (GRBs) have become commonplace in recent decades, totalling $\mathcal{O}(10^4)$ unique detections across various missions. However, there have been no confirmed discoveries of a gravitationally-lensed GRB, despite expected
lensing rates of $\sim1$ in $10^{3}$. In light of this, we complete an archival search for lensed GRBs by cross-matching well-localised Swift/XRT-detected bursts with a large all-sky sample of
galaxy clusters as potential lenses. We find a total of 17 candidate lensed GRBs defined by a 2 arcminute search radius from a cluster in our sample. 14 of our candidates are either confirmed to be at higher
redshifts than their cross-matched cluster, or are consistent with a higher
redshift origin based on the Amati relation between $E_{p,i}$ and $E_{\rm iso}$ of GRBs, indicating they are, at some level, lensed by their nearby cluster. Using the Amati relation and the lens-GRB separation, we quantify the magnification experienced by each GRB. We find $\mu < 10$ for all except for one candidate, GRB~071031, which is consistent with $\mu > 10$, but is uncertain. Another candidate, GRB~050509B, does not have a directly measured
redshift, but was previously assumed to be at the
redshift of its nearby cluster, $z=0.225$. We produce a lens model of this cluster and show that GRB~050509B is consistent with $z>1$ and magnified by $\mu\simeq2-6$. We present these findings in anticipation of future lensed GRB discoveries enabled by facilities such as the Vera C. Rubin Observatory in the coming years.
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All authors Dan Ryczanowski, Benjamin P. Jones, Benjamin P. Gompertz, Graham P. Smith
High Energy Astrophysical Phenomena
A Unified Model for Shock Interaction and $\gamma$-Ray Emission in Classical Novae
Rebecca Diesing and Brian Metzger
We present a parameterized ("toy") model for shock interaction and $\gamma$-ray emission in classical novae, in which a white
dwarf envelope of mass $M_{\rm env}$ is removed over a timescale $\tau$ (proportional to the nova speed class, $t_{2}$) in an
outflow that accelerates on the same timescale to a terminal speed $v_{\rm f}$. Particle acceleration occurs at the reverse shock generated when the
outflow collides with a thin, dense shell of slower material released earlier. Accelerated
protons are then advected into the shell, where for typical ${ M_{\rm env}, \tau, \text{and } v_{\rm f}}$ they radiate in the calorimetric limit, consistent with correlated optical and $\gamma$-ray emission seen in well-sampled novae. The maximum
proton energy, set by a Hillas-like argument, scales with the thickness of the hot post-shock region. Recent work shows turbulent mixing of hot post-shock gas with cooler dense gas may limit this thickness to $\lesssim 10^{-4}$ of the shock radius, explaining low X-ray luminosities. Using this empirically motivated thickness, and assuming efficient
magnetic amplification, we predict maximum
proton energies $E_{\rm max} \sim 10$ GeV, consistent with $\gamma$-ray spectra of
Fermi-detected novae near optical peak ($\sim \tau$). However, as the shock and post-shock layer expand, $E_{\rm max}$ can grow to $\gtrsim 10$ TeV on timescales of a few $\tau$, enabling potential detection by atmospheric Cherenkov
telescopes. We encourage TeV follow-up of
Fermi-detected novae weeks to months after the optical/GeV peak and quantify the most promising events.
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High Energy Astrophysical Phenomena
Anisotropic hybrid stars: Interplay of superconductivity and magnetic field leading to gravitational waves
Zenia Zuraiq and Banibrata Mukhopadhyay
Neutron stars, at their cores, are highly dense and, thus, are expected to have a number of exotic processes. This includes a possible phase transition to deconfined
quark matter at the core, leading to a hybrid
star. The
quark matter is expected to additionally be color superconducting. The physics of superconductivity plays an important role in understanding the high density matter in the interiors of
neutron/hybrid
stars. At their high densities, additionally, both
proton superconductivity and
neutron superfluidity are expected. We study the effect of superconducting (
quark/
proton) matter, along with the internal
magnetic field, leading to pressure anisotropy within hybrid
stars. We aim to probe the effect of superconductivity, especially from color superconducting
quarks, in hybrid
star structure. We propose new phenomenological model anisotropy profiles within a one-dimensional framework. We model
quark matter using the vector interaction enhanced Bag model, and
hadron matter with the DD2 equation of state. A Maxwell construction joins both phases. We further investigate the possible observational signatures of these hybrid
stars. These include mass enhancement and continuous gravitational waves, possibly arising from the anisotropy induced deformation, helping us further constrain our model and its physical parameters.
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Astrophysics of Galaxies
Wild is the wind from low-luminosity AGN: A jet-driven gas bubble blowing out a massive CO-dark outflow in ESO 420-G13
J.A. Fernández-Ontiveros, L. Spinoglio, M. Pereira-Santaella et al. (+8 more)
We present JWST/MIRI mid-infrared integral field spectroscopy combined with ALMA CO(2-1) observations of the post-starburst
galaxy ESO 420-G13, hosting a low-luminosity AGN. The unprecedented spatial and spectral resolution of MIRI enables a detailed study of the molecular and ionised gas kinematics, excitation, and energetics in the
nuclear kiloparsec, revealing the impact of AGN feedback in a system with modest radiative output. Despite its faint
radio and X-ray emission ($L_{2-10keV} \sim 10^{40}$ erg/s), ESO 420-G13 exhibits powerful kinetic feedback in the form of massive molecular and ionised gas
outflows, with a total kinetic power of $\sim 1.4 \times 10^{41}$ erg/s. This corresponds to a jet-ISM coupling efficiency of ~3.8%, within the range observed in more powerful AGN. The feedback is driven by a previously undetected compact jet, traced by collimated coronal-line and extended X-ray emission to >870 pc from the
nucleus. The interaction is strongest ~370 pc north of the
nucleus, where a fast ionised gas stream emerges perpendicular to the jet axis, coinciding with a bend in the jet direction. Enhanced velocity dispersion in warm H$_2$ surrounds this gas stream, consistent with an expanding molecular bubble. Massive molecular
outflows are detected at its edges; the blueshifted
outflow is devoid of CO emission, likely due to CO destruction in shocks or by
cosmic rays from the jet-ISM interaction. About 5% of the central molecular reservoir has already been expelled, and the remaining gas is turbulent and warm, suggesting an ongoing phase of AGN-driven feedback in this post-starburst
galaxy. Our results highlight the enormous potential of mid-IR imaging spectroscopy to uncover jet-driven feedback in low-luminosity AGN. Without the spatially resolved MIRI diagnostics, the kinetic power of the AGN in ESO 420-G13 and its role in shaping the host
galaxy ISM would have remained hidden.
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All authors J.A. Fernández-Ontiveros, L. Spinoglio, M. Pereira-Santaella, A. Hernán-Caballero, E. Hatziminaoglou, E. Pérez-Montero, J.M. Vílchez, B. Pérez-Díaz, R. Amorín, M.A. Malkan, K.M. Dasyra
Astrophysics of Galaxies
Collisional Dynamics of Stars and Dark Matter in Ultra-Faint Galaxies
Raphaël Errani, Nicolas Esser, Jorge Peñarrubia et al. (+1 more)
We use controlled N-body simulations to study the collisional exchange of energy between
stars and dark matter in ultra-faint
galaxies. We find that dynamical friction between
stars and subsolar-mass dark matter particles results in the depletion of dark matter from the
galaxies' centers, thereby transforming dark matter cusps into constant-density cores. The process is particularly effective in tidally limited
galaxies with low
stellar velocity dispersion. As high-mass
stars sink toward the center of the dark matter
halo, the dynamical-to-
stellar mass ratio within the
stellar half-light radius decreases monotonically. The
stellar population of a dark matter-dominated
galaxy is thereby compacted into a dense,
baryon-dominated cluster, surrounded by a dark matter
halo. Such a cluster would share the chemical composition of an ultra-faint
galaxy, yet would be virtually dark matter-free within its half-light radius. We moreover find that the collisional cooling with dark matter particles provides an efficient pathway for the formation of
stellar binaries in the contracting cluster. The contraction is eventually slowed down due to the decreasing central dark matter densities and the formation of
stellar binaries. Our models highlight that the dynamical processes governing the faintest
galaxies give rise to a rich phenomenology, blurring the line between the dynamics of globular clusters and
galaxies.
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All authors Raphaël Errani, Nicolas Esser, Jorge Peñarrubia, Matthew G. Walker
High Energy Astrophysical Phenomena
Zooming in on radio relics – II. How relic morphology probes density fluctuations at the edge of galaxy clusters
Joseph Whittingham, Christoph Pfrommer, Maria Werhahn et al. (+2 more)
Gas properties in the outer intracluster medium (ICM) are not well-constrained, as traditional probes lose sensitivity at Mpc distances. We show that the morphology of
radio relics effectively encodes the power spectrum of the surrounding density fluctuations, and that they hence represent a new observational window. To demonstrate this, we use cosmologically motivated shock-tube simulations in which we systematically vary the coherence length, amplitude, and power-law slope of the upstream density power spectra. We then post-process our simulations with the
cosmic ray electron spectral solver, Crest, thereby producing a suite of mock
radio relics. We find that the downstream morphology of our simulated relics is independently sensitive to each of the aforementioned parameters. Specifically, we show that observed 'double strand' features can be formed by curved shock fronts in projection, and that the scale of these features maps directly to the fluctuation coherence length. Increasing the fluctuation amplitude, meanwhile, progressively lengthens the downstream extent of the relic, thus explaining why relics are observed to be broader than the idealised expectation. It also broadens the Mach number distribution across the shock, which simultaneously increases the integrated
radio flux density and produces patchier emission. Finally, steepening the power-law slope makes 'double strand' features more likely, and additionally increases both the number of
radio filaments oriented parallel to the shock front and their spacing. At higher Mach numbers, steepening the power-law slope can further lead to the production of curved
radio filaments, which trace large eddies. We apply our analysis to the Toothbrush and Sausage relics, and find evidence for a typical fluctuation coherence length of ~500 kpc, a non-uniform amplitude, and power spectra that are steeper than a Kolmogorov-like scaling.
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All authors Joseph Whittingham, Christoph Pfrommer, Maria Werhahn, Léna Jlassi, Philipp Girichidis
Instrumentation and Methods for Astrophysics
Science of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS)
Yuki Inoue, Hsiang-Yu Huang, Vivek Kumar et al. (+3 more)
The frequency band between $0.1$ and $10\mathrm{Hz}$ remains largely unexplored in gravitational-wave astronomy due to strong seismic, Newtonian, and suspension thermal noise that limit ground-based detectors. The Cryogenic sub-Hz cROss torsion-bar detector with
quantum NOn-demolition Speed meter (CHRONOS) is a novel detector concept designed to access this frequency range from the ground. CHRONOS combines cryogenic torsion-bar test masses with a triangular Sagnac interferometer implementing a speed-meter readout, which suppresses
quantum radiation-pressure noise and enables
quantum non-demolition measurements in the sub-Hz regime. The detector targets a strain sensitivity of $h \sim 10^{-18}\mathrm{Hz^{-1/2}}$ around $2\mathrm{Hz}$ and
stochastic gravitational wave background of $\Omega_{GW} \sim 2\times 10^{-3}$ at $2\mathrm{Hz}$. This sensitivity opens a new observational window between space-based detectors such as LISA and ground-based interferometers, enabling observations of intermediate-mass black hole binaries, searches for
stochastic gravitational-wave backgrounds, and tests of macroscopic
quantum measurements.
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All authors Yuki Inoue, Hsiang-Yu Huang, Vivek Kumar, Mario Juvenal S. Onglao II, Daiki Tanabe, Ta-Chun Yu
Solar and Stellar Astrophysics
Testing the 3-equation Kuhfuss Convection Model using the Sun
T. A. M. Braun, F. Ahlborn, F. Kupka et al. (+1 more)
Simplified, one-dimensional models are necessary to model convection in the context of
stellar evolution. By including the non-local effects of convection, turbulent convection models describe convection in a more physical way compared to mixing length theory, which is typically used in one-dimensional
stellar evolution models. We recently showed that the 1-equation Kuhfuss turbulent convection model is not sufficient to model the
solar convective envelope satisfactorily. Using the Sun as a
benchmark, we test the physically more complete 3-equation Kuhfuss turbulent convection model. We calculate a
solar calibrated model with the 3-equation Kuhfuss turbulent convection model using the one-dimensional
stellar evolution code GARSTEC. We compare the predicted interior structure of the model with helioseismic measurements of the Sun. Furthermore, we investigate how the free parameters and the closure relations of the 3-equation model influence the results. We find that, with the 3-equation model, the temperature gradient at the inner boundary of the convective envelope is modelled more realistically compared to the mixing length theory or the 1-equation model. This also improves the agreement for the sound speed profile between the model and the Sun, and reduces the asteroseismic surface effect. However, close to the surface, the 3-equation model results in a layer having an unphysical, negative temperature gradient. This layer is connected to the closure relations used in the 3-equation model. Our results demonstrate the capabilities of turbulent convection models, and can serve as a next step towards an improved and more realistic modelling of convection in
stellar evolution codes.
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All authors T. A. M. Braun, F. Ahlborn, F. Kupka, A. Weiss
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Massive Exchange and the Sign of the Equilateral Bispectrum
Diptimoy Ghosh, Suvashis Maity and Farman Ullah
We study the inflationary bispectrum generated by the tree-level exchange of a massive hidden-sector scalar during inflation. When the interaction between the inflaton and the hidden sector arises only from the leading boost-breaking operator of the Effective Field Theory (EFT) of inflation, the equilateral bispectrum for principal-series scalar exchange is known to be universally negative, independent of the sign of the coupling. We revisit this result within the full EFT operator basis. Using bootstrap methods, we construct the de Sitter-invariant seed four-point function and obtain the inflationary bispectrum via weight-shifting operators and a soft-limit procedure. While the equilateral bispectrum remains strictly negative when only the leading interaction is present, additional operators generate independent cubic structures whose contributions compete in the equilateral configuration. As a result, the sign of the bispectrum is no longer universal. We derive a critical ratio of interaction coefficients that separates regions of positive and negative equilateral bispectrum. We further study the effects of reduced sound speed $c_s<1$ and the exchange of multiple particles. In both cases, the critical ratio is modified, and for multi-particle exchange a positive equilateral bispectrum can arise even when the higher-order operator is subdominant. Our results show that the negativity of the equilateral bispectrum from massive exchange is not generic, but reflects a restricted operator structure in the EFT of inflation.
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Instrumentation and Methods for Astrophysics
Deep Spectroscopy with DESI for Photometric Redshift Training and Calibration
Biprateep Dey, Jeffrey A. Newman, Tianqing Zhang et al. (+62 more)
Deep spectroscopic samples can be used to improve photometric
redshift (photo-$z$) estimates and reduce uncertainties on
redshift distributions. Such improvements can increase the cosmological constraining power of large imaging-based experiments such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) and mitigate what may be a limiting systematic effect. We present results from the “DESI-Deep pilot” program, which was designed to assess the capability of the Dark Energy Spectroscopic Instrument (DESI) on the 4m Mayall
telescope to measure
redshifts of
galaxies as faint as expected
lensing samples for early LSST data ($m_i \leq 24.5$). We find that DESI is remarkably efficient at this task, with
redshift success rates comparable to the results of observations from 10m-class
telescopes with only $\sim2\times$ longer integration time (rather than $\sim 8\times$ longer as would be expected from aperture-area scaling), while simultaneously achieving $\sim30$ times larger multiplexing. We also find that the signal-to-noise ratio of the spectra scales as expected for background-limited observations even for the longest exposure times ($\sim 7$ hours) and faintest targets in the program. These results demonstrate that DESI could provide the definitive
redshift sample for the early years of LSST with a modest investment of observing time. Based upon the results of this program, we provide updated predictions for the time required to collect
benchmark samples for photo-$z$ training and calibration using a variety of spectroscopic facilities. Finally, we describe a potential "DESI-Deep" survey designed to train and calibrate photo-$z$'s for imaging experiments, and provide forecasts of its impact on cosmological inference.
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All authors Biprateep Dey, Jeffrey A. Newman, Tianqing Zhang, J. Aguilar, S. Ahlen, A. Anand, B. Andrews, S. Bailey, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. Cuceu, K. S. Dawson, A. de la Macorra, J. Della Costa, Arjun Dey, P. Doel, S. Ferraro, A. Font-Ribera, E. Gaztañaga, Satya Gontcho A Gontcho, D. Gruen, G. Gutierrez, J. Guy, H. K. Herrera-Alcantar, K. Honscheid, M. Ishak, R. Joyce, R. Kehoe, D. Kirkby, T. Kisner, A. Kremin, O. Lahav, M. Landriau, L. Le Guillou, A. Leauthaud, M. E. Levi, M. Manera, P. Martini, J. McCullough, A. Meisner, R. Miquel, J. Moustakas, A. D. Myers, J. Myles, S. Nadathur, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, H. Seo, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, N. Weaverdyck, R. H. Wechsler, R. Zhou, H. Zou
High Energy Astrophysical Phenomena
Observational distinguishability of the Kerr and Kerr-Hayward metrics to EHT
Nikola Bukowiecka, Angelo Ricarte, Prashant Kocherlakota et al. (+1 more)
Astrophysical black holes appear well-represented by the Kerr metric, whose maximal analytic extension contains a ringlike
curvature singularity. We study a phenomenological regularized modification of Kerr, the modified Kerr-Hayward metric, which removes
curvature blowup at the level of the stationary metric while preserving in detail many features of polarized black hole images now testable by the Event Horizon
Telescope (EHT). To establish this, we produce new general relativistic magnetohydrodynamics (GRMHD) simulations of a magnetized
plasma in a Kerr-Hayward spacetime, then we extend the EHT analysis framework to perform polarized radiative transfer in this spacetime. We detail our methodology for implementing this modified spacetime into an open-source pipeline. From fluid quantities such as the
magnetic flux parameter and jet efficiency, to image quantities such as the polarization pattern and the
photon ring structure, our results for the Kerr-Hayward metric appear functionally indistinguishable from the Kerr metric. Our study finds that under the assumptions of a fixed-background GRMHD and polarized radiative transfer pipeline, this regularized phenomenological modification to the Kerr metric can yield observables that are effectively indistinguishable in EHT measurements.
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All authors Nikola Bukowiecka, Angelo Ricarte, Prashant Kocherlakota, Cora Prather
Instrumentation and Methods for Astrophysics
Investigating ACS/WFC Amp-to-Amp Sensitivities
Gagandeep S. Anand and Norman A. Grogin
Recently, the ACS team applied an Ubercal framework to assess the photometric repeatability of
stars observed across the WFC detector using 15 years of post-SM4 calibration data in the globular cluster 47 Tuc (Ryan et al., 2024). A surprising finding was an apparent 0.05 mag global difference in sensitivity between the WFC1 and WFC2 chips, which had not been seen in prior tests of sensitivity variations around the field-of-view. Given the many degenerate variables within the Ubercal framework such as CTE losses, time-dependent sensitivity, and flat-field corrections, we obtained new calibration data to perform a straightforward test of the reported $\sim$5$\%$ flux offset between detectors. We observed three white
dwarf standards with three filters at four positions on the detector (each on a different amplifier), but with the same number of x and y pixel transfers to mitigate differential CTE-related effects. For the F606W and F814W filters, the agreements are good to 0.4$\%$ on average, and always 1$\%$ or better in individual cases. The consistency of these two filters over all three
stars and the four dither positions provides very strong evidence against the large global sensitivity offset between WFC1 and WFC2 as seen in the Ubercal work. Larger variations seen in the bluer F435W filter are likely a result of a sensitivity of the flat field in that filter to underlying spectral type, warranting a future solution.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Posterior Predictive Checks for Gravitational-wave Populations: Limitations and Improvements
Simona J. Miller, Sophia Winney, Katerina Chatziioannou et al. (+1 more)
When selecting a model to characterize an astrophysical population, it is crucial to assess whether that model fits the data and, if not, how it can be improved. To this end, posterior predictive checks (PPCs) are a widely-used statistical test of model fit when inferring gravitational-wave source populations. However, PPCs exhibit limitations when assessing single-event parameters with large measurement uncertainty, like the
spin tilt angles of the binary black holes (BBHs) observable with the LIGO-Virgo-KAGRA (LVK) detectors. When single-event inference is prior-dominated, traditional PPCs fail to flag even very poor model fits. In this work, we assess the efficacy of various alternative PPCs on poorly-constrained parameters. We compare PPCs conducted on event- vs. data-level parameters (e.g. posterior samples vs. maximum likelihood points), and explore two additional event-level PPCs: partial predictive checks and split predictive checks. Independent of measurement uncertainty, we find that PPCs on maximum likelihood parameters are always more discerning of model misspecification than any event-level PPC. However, when investigating simulated GWTC-3.0-like catalogs, none of the alternative PPCs show significant improvement over those traditionally used, indicating that at that sensitivity, any limited information in the data about
spin tilts is insufficient to diagnose model misspecification. Finally, we apply our suite of PPCs to the
spin magnitude and tilt distributions inferred in the most recent LVK catalog, GWTC-4.0. We conclude that the Gaussian Component
Spins model used therein under-predicts BBHs with large
spin magnitudes and over-predicts those with perfectly anti-aligned tilts.
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All authors Simona J. Miller, Sophia Winney, Katerina Chatziioannou, Patrick M. Meyers
Cosmology and Nongalactic Astrophysics
Hunting Dark Matter with the Einstein Telescope
A.J. Iovino, M. Maggiore, N. Muttoni et al. (+1 more)
Too light
primordial black holes evaporate and are therefore strongly constrained by various bounds, e.g.
Cosmic Microwave Background distortion. However, if they are formed strongly clustered, the corresponding
haloes may collapse into heavier black holes which may form the entirety of the dark matter of the universe. The indirect signal of such a scenario is the production of a flat
stochastic background of gravitational waves which is detectable by the Einstein
Telescope.
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All authors A.J. Iovino, M. Maggiore, N. Muttoni, A. Riotto
Earth and Planetary Astrophysics
Star-planet magnetic interactions in photoevaporating exoplanets: enhanced power due to atmospheric escape
Andrés Presa, Aline A. Vidotto and Filip Elekes
Observations of periodic
stellar activity near the transit phase of a close-in
exoplanet provide evidence of
star-
planet magnetic interactions (SPMI), similar to the
magnetic coupling between Jupiter and its moons. Comparing the power associated with SPMI signals to analytical theories offers a way to constrain exoplanetary
magnetic fields, but models based on moon-magnetosphere analogs often underpredict observed energy fluxes. Unlike moons, many close-in
exoplanets are extended, highly irradiated gas
giants undergoing significant photoevaporation. However, it is not known how atmospheric escape influences the
star-
planet magnetic coupling. Here, we present three-dimensional radiation magneto-hydrodynamic simulations that simultaneously model planetary evaporation and SPMI in a hot Jupiter
planet embedded in a magnetised
stellar wind. Our simulations reveal the formation of
magnetic structures known as Alfvén wings, which transport
magnetic energy away from the
planet. When the dayside mass-loss rate $\dot{M}_d$ of the
planet lies below a threshold $\dot{M}_0$ defined by pressure balance between the planetary and
stellar winds ($\dot{M}_d \leq \dot{M}_0$), the maximal power delivered to the
star matches predictions from the Alfvén wing model. For higher escape rates, the planetary
outflow opens additional
magnetic flux, and the SPMI power increases proportionally with $(\dot{M}_d / \dot{M}_0)^{1/2}$. Applying this scaling law to the HD18973 system, we find that a $50$ G
planet could reproduce the observed power if $\dot{M}_d \sim 5 \times 10^{11}$ g/s. Although this signal likely represents only a fraction of the total power, additional mechanisms could amplify the energy budget. These results show that photoevaporating
exoplanets in sub-Alfvénic orbits constitute promising targets for SPMI observations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
$\xi R\phi^2$ non-minimal coupling, and the long range gravitational potential for different spin fields from 2-2 scattering amplitudes
Avijit Sen Majumder, Ayan Kumar Naskar and Sourav Bhattacharya
In this paper, we investigate the long range gravitational effect of
curvature-scalar field non-minimal coupling in the form of $\xi R \phi^2$, in the perturbative
quantum gravity framework. Such coupling is most naturally motivated from the renormalisation of a scalar field theory with a quartic self interaction in a curved spacetime background. This coupling results in two scalar-$n$ graviton vertices which contain no explicit momenta of the scalar, qualitatively different from the usual, e.g., $\kappa h^{\mu\nu}T_{\mu\nu}$-type minimal matter-graviton vertices. Assuming the dimensionless coupling parameter $\xi$ to be small, we compute the 2-2 scattering Feynman amplitudes between such scalars up to ${\cal O}(G^2 \xi)$. From the non-relativistic limit of these amplitudes, we compute the corresponding long range gravitational potential. There exists no tree level contribution $({\cal O}(\xi G))$ here, and hence the one loop ${\cal O}(G^2 \xi)$ result is leading. Recently, the effect of a cosmological constant in such non-minimal interaction and the subsequent gravitational potential was computed. In this work, we take the cosmological constant to be vanishing. The resulting potential is found to have $r^{-4}$ leading behavior. We further extend these results for scalar-massive
spin-1 and massive
spin-1/2 scattering.
Spin and polarisation dependence of the two body potential have been explicitly demonstrated. We discuss some possible physical implications of these results.
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Cosmology and Nongalactic Astrophysics
Lyman-$\alpha$ Forest Signatures of Mixed Fuzzy and Cold Dark Matter
Yourong Frank Wang
We investigate Lyman-alpha forest flux statistics in mixed fuzzy dark matter (FDM) and cold dark matter (CDM) cosmologies using the Fluctuating Gunn–Peterson Approximation (FGPA) applied to hybrid Schrödinger–Poisson and $N$-body simulations. We evolve the dark matter distribution from $z = 120$ to $z = 2$ for an
axion mass $m_\text{A} = 10^{-24}\,\text{eV}$ and FDM fraction $f_\text{A} = 0.1$, and compare three simulations sharing random phases: a $\Lambda$CDM baseline, an MDM realisation evolved with full wave-mechanical (Schrödinger–Poisson) dynamics, and a particle-only ($N$-body) MDM proxy with matched initial total-matter density power and CDM-like initial velocities. Because the initial velocity prescriptions differ, the comparison combines an inherited velocity offset with the subsequent dynamical
evolution. By $z=4$ the nonlinear matter power spectra of the two MDM treatments differ by only $\sim25$ per cent at $k\sim10\,h\,\mathrm{Mpc}^{-1}$, whereas their (unfiltered) line-of-sight velocity power spectra differ more at the same scale, the full treatment retaining $\sim44$ per cent of the $N$-body velocity power. The corresponding \LyA flux power spectra differ by $21$ per cent at $z = 4$ and $3$ per cent at $z = 2$ at $k = 0.1\,\mathrm{s\,km^{-1}}$, with the difference growing toward higher
redshift and smaller scales. The flux statistics therefore depend on the velocity prescription and not only on the matter power spectrum, and a particle-only proxy based on suppressed initial density power does not reproduce them within this framework. The analysis is idealised: it is dark-matter-only, relies on the FGPA with a prescribed thermal state, and uses only a preliminary neutral-hydrogen-weighted velocity diagnostic. Establishing whether the difference survives baryonic response and thermal-history uncertainty requires full hydrodynamical simulations.
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Astrophysics of Galaxies
cuRAMSES: Scalable AMR Optimizations for Large-Scale Cosmological Simulations
Juhan Kim
We present cuRAMSES, a suite of advanced domain decomposition strategies and algorithmic optimizations for the ramses adaptive mesh refinement (AMR) code, designed to overcome the communication,
memory, and solver bottlenecks inherent in massive cosmological simulations. The central innovation is a recursive k-section domain decomposition that replaces the traditional
Hilbert curve ordering with a hierarchical spatial partitioning. This approach substitutes global all-to-all communications with neighbour-only point-to-point communications. By maintaining a constant number of communication partners regardless of the total rank count, it significantly improves strong scaling at high concurrency. To address critical
memory constraints at scale, we introduce a Morton-key hash table for octree-neighbour lookup alongside on-demand array allocation, drastically reducing the per-rank
memory footprint. Furthermore, a novel spatial hash-binning
algorithm in box-type local domains accelerates
supernova and AGN feedback routines by over two orders of magnitude (an about 260 times speedup). For hybrid architectures, an automatic CPU/GPU dispatch model with GPU-resident mesh data is implemented and benchmarked. The multigrid Poisson solver achieves a 1.7 times GPU speedup on H100 and A100 GPUs, although the Godunov solver is currently PCIe-bandwidth-limited. The net improvement is about 20 per cent on current PCIe-connected hardware, and a performance model predicts about 2 times on tightly coupled architectures such as the NVIDIA GH200. Additionally, a variable-Nrank restart capability enables flexible I/O workflows. Extensive diagnostics verify that all modifications preserve mass, momentum, and energy conservation, matching the reference
Hilbert-ordering run to within 0.5 per cent in the total energy diagnostic.
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Earth and Planetary Astrophysics
The Cohesive Object Sequence: The Mass-Density Distribution of Astronomical Objects from Asteroids to Stars
Gabriel M Steward and Matthew Hedman
Plotting the mass-density of a wide range of astronomical objects as a function of their mass reveals that the vast majority of these objects fall along a “cohesive object sequence” that extends all the way from asteroids to the largest
stars. Trends and features within this sequence reflect fundamental astronomical processes and phenomena, including the gravitational contraction of progressively higher-mass
planets and the onset of
nuclear reactions within
stars. Meanwhile, compact
stellar remnants fall well off this sequence, reflecting their extreme natures. This type of plot is therefore useful both for showcasing the relationships and connections between a wide range of astronomical objects and for clarifying the distinctions used to identify particular types of objects.
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Cosmology and Nongalactic Astrophysics
Testing parity with composite-field spectra of BOSS and DESI luminous red galaxies
Zucheng Gao, Marina S. Cagliari, Azadeh Moradinezhad Dizgah et al. (+1 more)
Detection of parity violation on cosmological scales would have profound implications for fundamental physics. Motivated in part by recent measurements of parity-odd four-point correlation functions in BOSS and DESI luminous red
galaxy samples, which probe parity violation in the scalar sector, we present the first measurement of parity-odd kurto spectra in spectroscopic
galaxy survey data. We analyse two composite-field spectra, $\mathcal{P}_{2\times2}$ (vector–pseudo-vector) and $\mathcal{P}_{3\times1}$ (scalar–pseudo-scalar). Compared with parity-odd four-point correlation function analyses, the kurto-spectrum formalism performs physically motivated compression on the trispectrum into a substantially lower-dimensional data vector, allowing direct estimation of covariance
matrices from mock catalogues and reducing sensitivity to covariance-modelling systematics. Using null-hypothesis $\chi^2$ tests and cross-patch consistency checks, we find no evidence for a cosmological parity-violating signal in either survey. We examine the impact of the adopted mock catalogues and find that the high-fidelity mocks provide a better match to the data of both surveys than the approximate mocks. The DESI DR1 measurements exhibit a scatter smaller than that of BOSS DR12 by about a factor of four, consistent with the improved statistical precision expected from the higher tracer number density. Future DESI data releases, with larger volume and number density, together with larger suites of high-fidelity mocks, can enable significantly sharper tests of parity violation using kurto spectra.
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All authors Zucheng Gao, Marina S. Cagliari, Azadeh Moradinezhad Dizgah, Zvonimir Vlah
Solar and Stellar Astrophysics
Orbital inclination estimates for overcontact binaries using the derivatives of light curves
Shinjirou Kouzuma
The orbital inclination of an eclipsing binary is generally determined through light curve analysis. Binary parameters in the light curve analysis are typically constrained through the use of optimization and sampling techniques. We propose a new simple method, based on the derivatives of light curves, for estimating the orbital inclinations of overcontact systems. Our sample consists of 89670 synthetic light curves for overcontact binaries, covering a parameter space typical of overcontact systems. We classified the sample light curves on the basis of a recently proposed classification scheme: DP, SPp, SPb, SPf, and SPs types. For each type, we found that the orbital inclination is closely associated either with the time interval between local extrema in the derivatives of light curves or with the depth of the local minimum at phase 0.5 in the second derivative. Using regression analysis of the identified associations, we developed empirical formulae to estimate the orbital inclinations for each type of light curve. We also provide the associated uncertainties for the estimated inclinations. Application of the proposed method to real overcontact binary data demonstrated that our method can reasonably estimate both the inclinations and their uncertainties.
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Astrophysics of Galaxies
An 18 - 25 GHz spectroscopic survey of southern hemisphere dense cores
Dariusz C. Lis, Karen Willacy, Liton Majumdar et al. (+3 more)
We extended the
radio K-band spectroscopic survey for organics in southern hemisphere dense cores by observing seven sources using NASA's Deep Space Network 70-m
antenna in Canberra, Australia, over the frequency range of 18 to 25 GHz. Molecular column densities of NH$_3$, $c$-C$_3$H$_2$, HC$_3$N, HC$_5$N, CCS, C$_3$S, and $c$-C$_3$HD were derived for each source assuming LTE. The resulting column density ratios were compared with predictions of a state-of-the art astrochemical model to constrain the C/O ratio and chemical age of each source. Most cores have similar C/O ratios of $0.5 - 0.7$, much different from the best studied TMC-1 dense core characterized by a high C/O ratio of $\sim 1.4$. The chemical ages of the cores are also similar and fall between 0.6 and 5~Myr. The less dense cores tend to have the oldest chemical ages, as might be expected given that chemical timescales scale with density. Our results showcase the synergistic approach of combining
radio observations using the DSS-43
antenna with state-of-the-art astrochemical models to study the chemical composition of southern hemisphere dense cores, enabling constraints on their C/O ratios and chemical ages, which remain largely unexplored.
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All authors Dariusz C. Lis, Karen Willacy, Liton Majumdar, Jorge L. Pineda, Susanna Widicus Weaver, Shinji Horiuchi
Earth and Planetary Astrophysics
The Transit Timing and Transmission Spectrum of Hot Jupiter WASP-43 b from a decade of Multi-band Transit Follow-up Observations
Napaporn A-thano, Supachai Awiphan, Eamonn Kerins et al. (+21 more)
We present a new set of 35 transit light curves of the hot Jupiter WASP-43~b, obtained through the SPEARNET network. These
datasets were analyzed together with previously published ground-based observations, as well as space-based data from TESS, HST, and JWST, to refine the planetary parameters of WASP-43~b. A total of 188 mid-transit times, measured with TransitFit, were analyzed for potential timing variations. The transit timing variations do not show any significant evidence of orbital decay. Atmospheric
retrievals using HST/WFC3 G141 transmission spectra suggest that higher-temperature solutions are associated with higher water abundances. However, when these data are combined with observations from ground-based
telescopes, TESS, and JWST, the increased modeling complexity across the broad wavelength baseline presents significant challenges for atmospheric characterization. These results highlight that high-precision, multi-instrument
datasets will be necessary to break existing degeneracies in the atmospheric modeling of this target in the future.
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All authors Napaporn A-thano, Supachai Awiphan, Eamonn Kerins, Akshay Priyadarshi, Iain McDonald, Ing-Guey Jiang, Yogesh C. Joshi, Fan Yang, Ida Janiak, Patcharawee Munsaket, Yasir Abdul Qadir, Ronnakrit Rattanamala, Orarik Tasuya, Ekburus Boonsoy, Nuanwan Sanguansak, Rattiyakorn Rattanasai, Thammasorn Padjaroen, Siramas Komonjinda, Sawatkamol Pichadee, Ananpol Sudsap, Smanchan Chandaiam, Boonyarit Choonhakit, Suwanit Wutsang, Vik S Dhillon
High Energy Astrophysical Phenomena
Testing X-ray Periodicity and Long-Term Trend in PG 1553+113 via Targeted Swift-XRT Monitoring
P. Peñil, N. Torres-Albà, L. Marcotulli et al. (+5 more)
PG~1553+113 is the blazar with the most-significantly detected periodic patter in its multiwavelength (MWL) emission, making it one of the most promising candidates for hosting a supermassive black hole binary. However, the presence of this periodic behavior in the X-ray band remains under debate, largely due to the lack of continuous monitoring. This has led to differing conclusions in previous studies. In addition, we aim to examine whether the recently identified linear long-term trends in the gamma-ray and optical bands also exist in the X-ray regime. Here, we evaluate the 2.1-year period in the X-ray light curve of PG 1553+113 using two dedicated monitoring campaigns with Swift-XRT and UVOT, guided by predictions of future oscillation phases. We also examine whether the long-term trend is present in X-rays, the potential periodic behavior of the X-ray power-law
photon index, and its potential correlation to the X-ray flux. As a result, we find tentative evidence for a correlation between the predicted high-emission states in the gamma-ray band and those observed in the X-ray and UV bands. Therefore, we do not find a strong evidence of the same periodic pattern in X-ray. In addition, we find that the X-ray light curve is consistent with the presence of a long-term linear trend, in agreement with those previously reported in gamma-ray, optical, and
radio. Overall, these results indicate that the X-ray emission is likely to share the same long-term behavior observed in the gamma-ray and optical bands. Nevertheless, the pronounced
stochastic variability that characterizes the X-ray light curve limits our ability to draw firm conclusions regarding the presence of the periodic behavior.
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All authors P. Peñil, N. Torres-Albà, L. Marcotulli, A. Domínguez, M. Ajello, A. Rico, S. Buson, S. Adhikari
Earth and Planetary Astrophysics
Study of the migration of Earth-like planets in planetesimal disks and the formation of debris disks
O. S. Oleynik and V. V. Emel'yanenko
The aim of this study is to investigate the interaction of Earth-mass
planets with a planetesimal disk. It is shown that an Earth-mass
planet, initially located near the inner boundary of the planetesimal disk, migrates into the disk. The depth of penetration of the
planet into the disk is a random quantity determined by the angular momentum distribution of planetesimals approaching the
planet. However, at a certain stage, the direction of the
planet's migration changes, and the
planet returns to the inner boundary of the disk. During such reversible migration, the
planet perturbs the orbits of planetesimals and increases their relative velocities in the region of the disk traversed during its migration. The relative velocities of planetesimals increase to values sufficient for their fragmentation in collisions. Our estimates show that, after the passage of an Earth-mass
planet through the outer planetesimal disk, the mean relative velocities in the main part of the disk increase to values sufficient to disrupt monolithic basaltic planetesimals with sizes of 40 km. Thus, the interaction of even a relatively low-mass
planet (of order an Earth mass) with a planetesimal disk can lead to the formation of
dust particles observed in outer debris disks.
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High Energy Astrophysical Phenomena
Developing Pre-Supernova Neutrino Support for sntools
Ellie O'Brien, Susan Cartwright and Patrick Stowell
The first detection of
supernova burst
neutrinos was achieved through the observation of SN1987A, almost four decades ago. However,
neutrinos produced during the burning stages of a
star prior to core collapse are yet to be detected. Detection of pre-
supernova neutrinos could provide an early warning of an imminent
supernova and allow the scientific community time to focus their resources on the observation and study of such an event leading to better understanding of these rare phenomena. Integrating pre-
supernova models into a
neutrino event generator would help to provide a unified framework for studying these
neutrinos in current and next generation detectors. sntools is a
neutrino event generator for
supernova burst
neutrinos, originally developed to study
supernova model discrimination with Hyper-Kamiokande. Work to add support for pre-
supernova event generation to sntools is presented, detailing the adaptations and additions to the code, with emphasis on how time binning can be optimised for a robust simulation, and also detailing the status of the validation process. The current status and capabilities of the package will be explained alongside plans for any further work and the intended use for the new functionality within the Hyper-Kamiokande Collaboration.
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