Cosmology and Nongalactic Astrophysics
The Coherence Principle: A Falsifiable Prior for Model Selection from the Grammar of Theories
Raul Jimenez, Carlos Peña Garay, Fergus Simpson et al. (+1 more)
Bayesian model selection in cosmology and particle physics is often performed where posterior odds inherit a strong, often unacknowledged dependence on the prior assigned to competing models. Standard responses – reference priors, hierarchical priors, or appeals to naturalness – ignore relevant theoretical knowledge or rely on criteria hard to define operationally. We propose the Coherence Principle: a reproducible prescription for assigning model priors according to compatibility with the validated structure of an existing theory. This structure, or grammar, includes
symmetries, conservation laws, locality, Lorentz invariance, and universality patterns. Unmotivated violations of these rules incur a coherence cost, converted into a prior weight through a maximum-
entropy exponential form controlled by one calibratable parameter $\alpha$. The resulting prior is distinct from both the
Bayesian Occam factor and naturalness: it penalizes not parameter volume or fine tuning, but departures from validated theoretical grammar. We illustrate the principle with examples from cosmology and fundamental physics:
neutrino mass mechanisms, dark energy and modified
gravity, inflation, beyond-Standard-Model sectors, and hierarchical astrophysical inference. We test it also on four historical cases – general relativity, Pauli's
neutrino, parity violation, and special relativity – where evidential and theoretical contexts can be reconstructed. These examples show that it favors the historically successful choice when the proper grammar is defined in the correct domain and time. The Coherence Principle makes explicit a common but usually tacit part of physical
reasoning: trust in validated structural rules. It turns this judgment into a transparent, testable, and overrulable component of
Bayesian inference, leaving empirical likelihoods free to dominate when data are sufficiently constraining.
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All authors Raul Jimenez, Carlos Peña Garay, Fergus Simpson, Licia Verde
Solar and Stellar Astrophysics
ISOSCELES Project: II. Modelling galactic B-type stars for fast and $\delta-$slow wind regimes
N. Machuca, M. Curé, I. Araya et al. (+5 more)
Radiation-driven winds in B-type
stars play a key role in their
evolution, yet their hydrodynamical structure remains uncertain, particularly in evolved objects. While the classical fast solution of the modified CAK theory is widely adopted, it does not always reproduce the optical wind diagnostics of B-type
giants and supergiants. We investigate the applicability of the classical fast and $\delta$-slow hydrodynamical solutions to B-type
stellar winds through a homogeneous spectroscopic analysis based on optical diagnostics. We analysed 50
Galactic B-type
stars spanning luminosity classes I to V using mid- and high-resolution optical spectra from the IACOB, ESO-UVES, and CASLEO
datasets. Synthetic spectra were taken from the ISOSCELES grid, which combines hydrodynamical wind models computed with Hydwind and NLTE radiative transfer with Fastwind.
Stellar and wind parameters were derived through a multi-line $\chi^2$ fitting procedure using hydrogen, helium, and silicon lines. We find evidence for different preferred hydrodynamical regimes across luminosity classes. Most supergiants ($\sim$96%) and
giants ($\sim$88%) are better reproduced by $\delta$-slow models, characterised by higher ionisation parameters, slower terminal velocities ($v_\infty \lesssim 300$,km,s$^{-1}$, and denser
outflows. In contrast, most
dwarfs and subgiants ($\sim$88%) are more consistent with the classical fast solution, showing higher $v_\infty$ and lower $\dot{M}$. These trends suggest a dichotomy between luminosity classes. Our results indicate that the $\delta$-slow solution provides a viable framework for modelling the optical spectra of evolved B-type
stars, whereas fast solutions remain adequate for less evolved objects. The ISOSCELES grid provides a physically motivated basis for interpreting optical wind diagnostics and motivates future multi-wavelength studies of B-type
stellar winds.
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All authors N. Machuca, M. Curé, I. Araya, R. O. J. Venero, L. S. Cidale, C. Arcos, S. Simón-Díaz, A. Lobel
High Energy Astrophysical Phenomena
Short-Duration Gamma-ray Burst and Afterglow Rates in the Rubin and Roman Era
Tzvetelina Dimitrova and Nathaniel Butler
Short-duration gamma-ray burst (sGRB) afterglows that follow BNS-gravitational wave (GW) events are essential for understanding the tension between the observed sGRB rate and BNS merger rate, heightened by the recent conclusion of aLIGO O4 with no new confirmed BNS detections. Using a probabilistic sGRB world model derived from a source BNS merger population, we simulate afterglow emission with AfterglowPy to investigate detection prospects of afterglows in the new era of optical surveys, and probe their multi-messenger implications. The predicted sGRB/BNS association is strongly dependent on sGRB beaming, which may be constrained by orphan afterglows (OA) - that arise from events with no
prompt $\gamma$-ray detection. We conclude that the Vera C. Rubin Observatory's Large Synoptic Survey
Telescope (LSST) may detect an afterglow sample sufficient in constraining sGRB jetting, with an estimated $5.3^{+1.7}_{-1.2}$ on-axis afterglow and $11^{+5}_{-3}$ OA detections per year; while the deep sensitivity of the Roman Space
Telescope appears promising for probing the faint end of afterglow events in targeted follow-up strategies. The detection of afterglows in upcoming LIGO runs is possible but challenging, as we predict fewer than $\approx 1.4$ LSST or Roman discoverable events per year within the projected aLIGO O5 BNS range across all considered jet models and observing scenarios. We update previous sGRB-BNS rate predictions, finding that continued non-detection of a BNS in O5 would require revisiting key assumptions underlying sGRB-BNS models.
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Instrumentation and Methods for Astrophysics
Modeling Doppler Shifts in Radial-Velocity Data with Deep Learning toward Earth-mass Exoplanet Detection
Isidro Gómez-Vargas, Xavier Dumusque, Yinan Zhao et al. (+2 more)
Detecting the tiny Doppler shifts induced by Earth-mass
planets in
stellar radial-velocity measurements remains extremely challenging due to
stellar activity. Many deep-learning methods performing well on simulated data remain difficult to apply reliably on real
stellar spectra. The aim of this work is to develop a deep-learning framework that generalizes to real, unseen spectra and improves the detectability of Earth-mass
planets in radial-velocity data. We train artificial neural networks on HARPS-N
solar spectra with injected planetary signals, using physics-motivated spectral representations based on flux and line-formation temperature, together with their velocity gradients. Two training strategies are explored: hold-out testing and cross-validation. Model robustness is enhanced through genetic-
algorithm-based hyperparameter optimization, and predictive uncertainty is quantified using Monte Carlo dropout. Our most precise neural network model reliably retrieves, under the cross-validation strategy, the amplitudes, phases, and orbital periods of planetary signals with amplitudes greater than or equal to 25 cm/s and periods between 10 and 550 days. In addition, in all cases tested here, the successfully recovered signals correspond to the most significant peaks in the periodograms of the Doppler-shift predictions. Temperature-based spectral-shell representations consistently outperform flux-based shells. We also release doppleriann, a Python package implementing the proposed framework. Our results demonstrate that combining physically motivated spectral representations with deep learning provides a promising pathway toward the detection of Earth-mass
planets in radial-velocity data from real observations, supported by a modeling framework that is both physically grounded and statistically rigorous, incorporating uncertainty quantification and optimized training strategies.
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All authors Isidro Gómez-Vargas, Xavier Dumusque, Yinan Zhao, Khaled Al Moulla, Michael Cretignier
Cosmology and Nongalactic Astrophysics
CMBComp: A Simple and Accurate Compressed CMB Likelihood for Dark Energy, Curvature, and Massive Neutrinos
Amogh Srivastav, Prakhar Bansal and Dragan Huterer
We present CMBComp, a compact and accurate compressed
cosmic microwave background (CMB) likelihood that captures the dominant
geometric information of the full CMB likelihood derived from the combined SPT-3G D1 + ACT DR6 + Planck PR3 primary CMB anisotropy + Planck PR4/NPIPE CMB-
lensing dataset, which we collectively refer to as SPA. The compression is fast to evaluate and trivial to implement in standard inference pipelines. We construct and validate it in five model spaces: the spatially flat cosmological-constant model ($\Lambda$CDM), and its dynamical-dark-energy ($w_0w_a$CDM), massive-
neutrino ($\nu\Lambda$CDM), non-flat ($o\Lambda$CDM), and joint massive-
neutrino–dynamical-dark-energy ($\nu w_0 w_a$CDM) extensions. Five compressed likelihoods are introduced, corresponding to two three-parameter compressions for the dark-energy sector (CMB-3 for $\Lambda$CDM and CMB-3w for $w_0w_a$CDM), two four-parameter compressions for the
neutrino sector (CMB-4$\nu$ for $\nu\Lambda$CDM and CMB-4$\nu$w for $\nu w_0 w_a$CDM), and a four-parameter
curvature compression (CMB-4k for $o\Lambda$CDM). Combining each compressed likelihood with the DESI DR2
baryon acoustic oscillation (BAO) data, we demonstrate that the resulting posteriors agree to high precision with those obtained from the corresponding full-CMB chains. CMBComp is therefore particularly well suited to cosmological inference for models that modify the late-time expansion history, enabling accurate CMB constraints to be incorporated into new analyses with minimal computational overhead and without reliance on a full Boltzmann-solver-based inference pipeline. The compressed likelihood files and example notebooks accompanying CMBComp are made publicly available at https://github.com/Amoghsriv/CMBComp.
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Cosmology and Nongalactic Astrophysics
Covariance shrinkage for cosmological inference with Sellentin-Heavens-type likelihoods
Mattera Raffaele
Covariance
matrices used in astronomical and cosmological parameter inference are often estimated from a finite number of simulations, so covariance uncertainty can affect posterior calibration and parameter constraints. We study covariance regularisation from the perspective of likelihood-based inference with simulation-estimated covariance
matrices. First, we analyse scalar covariance scaling under the Gaussian plug-in likelihood and the covariance-marginalised Sellentin–Heavens likelihood. Using an expected negative log-likelihood loss, we show that Hartlap covariance-side scaling is recovered as the optimum under the Gaussian plug-in likelihood, whereas the unscaled sample covariance is optimal under the Sellentin–Heavens likelihood. This shows that scalar covariance corrections are likelihood-dependent and that an additional Hartlap-type global scaling is not favoured once covariance uncertainty is marginalised through the Sellentin–Heavens likelihood. We then introduce a shrinkage formulation in which the sample covariance is regularised towards a spherical target and the shrinkage intensity is treated as an auxiliary inferential quantity. A prior is assigned to the shrinkage intensity, the likelihood induces its posterior distribution, and the final parameter posterior is obtained by marginalising over it. Monte Carlo experiments show that shrinkage substantially improves covariance conditioning, while marginalisation over the shrinkage intensity propagates uncertainty about the amount of regularisation into posterior inference. The proposed approach provides a simple way to combine covariance-marginalised likelihood inference with structural regularisation of noisy simulation-estimated covariance
matrices.
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Cosmology and Nongalactic Astrophysics
Impact of inhomogeneous curvature on growth rate measurements from magnitude fluctuations
Andrew Nguyen, Chris Blake and Hayley J. Macpherson
Our interpretation of current cosmological observations rests on the assumptions of homogeneity and isotropy, leading to uniform background
curvature and expansion characterised by the Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime metric. However, the large-scale structure of the Universe is non-uniform in detail, inducing inhomogeneous
curvature and scale factor variations. In this paper, we use numerical cosmological simulations generated in full General Relativity to study the impact of inhomogeneous spacetime on the magnitude fluctuations of distant objects, focusing on their use as a probe of the growth rate of
cosmic structure. We quantify the distortions in the magnitude correlation spectrum as a function of angular scale and
redshift, and use these distortions to infer the systematic offset in the growth rate measurement. We find that at $z \lesssim 0.2$, the systematic offset in growth rate measurements between the full numerical relativity and FLRW treatments is sub-dominant to the statistical error of current
datasets, confirming that FLRW modelling is adequate for current low-
redshift peculiar velocity experiments. Future
datasets extending to higher
redshift may require theoretical models that additionally incorporate the contributions of gravitational
lensing and inhomogeneous
curvature.
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Astrophysics of Galaxies
The Contribution of Disrupted Dense Star Clusters to Gaia's Compact Object Binaries
Aryanna Schiebelbein-Zwack, Claire S. Ye, Marta Reina-Campos et al. (+3 more)
We present the first model of the Milky Way's detectable compact object–luminous
star binary population from disrupted dense
star clusters. We bridge large-scale cosmological
star cluster formation with high-resolution dynamical
evolution of compact object binaries by mapping the predicted
star clusters from the EMP-Pathfinder simulations to $N$-body Cluster Monte Carlo models. We predict that approximately $3\times10^5$ white
dwarfs (WDs), $1.5\times10^5$ black holes (BHs), and $1\times10^3$
neutron stars (NSs) in binaries with luminous companions are released to the
Galaxy from now-disrupted dense
star clusters throughout the history of the Milky Way. Synthetic observations modeled with the gaiamock pipeline reveal that the modeled
Gaia DR3 yields are sparse ($\approx 2$ WDs, 0 NS, 0 BHs at 90% credibility), with the majority lying beyond the detection horizon.
Gaia DR4 is expected to increase the observational yield of these systems only marginally, as the benefits of an expanded search volume are largely offset by the diminished astrometric and photometric precision of more distant sources ($\approx 14$ WDs, 0 NS, 0 BHs). While the underlying BH binary population is similar to that of WDs, they are detected far less frequently; they tend to pair with lower-mass, dimmer companions and have less temporal coverage of their long orbital periods. For NSs, we suggest that the observed over-representation of metal-poor,
halo systems is inconsistent with an origin in disrupted dense
star clusters. Instead, the observed
Gaia NS population could reflect the
accretion history of metal-poor,
dwarf galaxies into the Milky Way, isolated binary
star evolution, or
supernova physics.
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All authors Aryanna Schiebelbein-Zwack, Claire S. Ye, Marta Reina-Campos, Aeysha Munawwarah, Kareem El-Badry, Pranav Nagarajan
Earth and Planetary Astrophysics
Super-earths and mini-neptunes follow different orbital period-eccentricity relations
Ke-Ting Shin, Dong-Sheng An, Ji-Wei Xie et al. (+2 more)
Many
exoplanets have been observed with radius sizes between that of Earth and that of Neptune and are thus classified into two groups: super-earths (SEs) and mini-neptunes (MNs). There are no SEs and MNs in the
Solar System, and the mechanisms responsible for their formation and
evolution are debated. We investigate the relationships between the orbital period and eccentricity of SEs and MNs using both ensemble analyses and individual measurements. We found that MNs follow an anti-correlation between orbital period and eccentricity, but SEs follow a different relation, possibly in the opposite direction. These trends imply that MNs and SEs are dynamically distinct populations. We suggest that SEs have been more strongly influenced by violent processes such as gravitational scattering and
giant impacts, whereas MNs predominantly experienced quiescent secular
evolution.
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All authors Ke-Ting Shin, Dong-Sheng An, Ji-Wei Xie, Ji-Lin Zhou, Fei Dai
Astrophysics of Galaxies
Reconstructing Galactic Gravitational Potentials from Stellar Kinematics with Physics-Informed Neural Networks
Charlotte Myers, Nathaniel Starkman and Lina Necib
The gravitational potential of a
galaxy encodes its mass distribution, formation history, and dark matter
halo structure. Accurate potential models are therefore critical for interpreting
stellar kinematics, orbital dynamics, and the influence of satellite systems like the Large Magellanic Cloud. Analytic potential models offer interpretability and efficiency but struggle to capture complex, non-axisymmetric structure and time-dependent perturbations. Neural network-based methods can capture this complexity but offer little interpretability. We introduce a physics-informed neural network (PINN) framework that combines data-driven learning with embedded physical constraints, available as the open-source package GalactoPINNS. Trained on acceleration measurements, the framework captures complex, small-scale features while preserving global physical consistency. We test on systems of increasing complexity, from controlled analytic
halos to cosmological simulations of Milky Way-like
galaxies, achieving sub-percent acceleration errors with orbit reconstruction that consistently outperforms analytic baselines. Additionally, we implement a
Bayesian neural network to provide spatially calibrated uncertainty estimates, and a time-dependent extension to capture smooth temporal
evolution. By treating an analytic model as a structured prior and learning corrections on top of it, the method retains physical interpretability while gaining the flexibility to represent realistic
galactic potentials, making it well suited for Milky Way modeling and dynamical inference in the era of current and upcoming large-scale surveys.
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Astrophysics of Galaxies
The Lumina Project: Intergalactic Clumping and Recombination Sinks
Ali Sadain, Aaron Smith, Oliver Zier et al. (+10 more)
Recombinations during the Epoch of Reionization are intrinsically inhomogeneous, with different regions of the intergalactic medium contributing unevenly depending on their density, temperature, ionization state, and spatial patchiness. We combine the high- and medium-resolution 95.5 cMpc Thesan-1 andh Thesan-2 runs with the significantly larger 500 cMpc Lumina simulation to measure clumping factors and recombination rates consistently across different resolutions and box sizes. We consider the standard ionized hydrogen clumping factor, $C_{\rm HII} \equiv \langle n_{\rm HII}^2\rangle/\langle n_{\rm HII}\rangle^2$, and a recombination-weighted clumping factor, $C_{\rm rec}$. Despite differences in resolution, volume, and reionization history, the simulations show an approximately universal clumping
evolution at the 10-20% level when parametrized by the global ionized fraction $x_{\rm HII}$ rather than by
redshift. Across all simulations, $C_{\rm rec}$ remains systematically below $C_{\rm HII}$, with the discrepancy increasing toward lower
redshift as photoheating suppresses recombinations. In \lumina, the density-only prescription overpredicts the instantaneous recombination rate by factors of 1.29 at $z\approx8$ and 1.84 at $z\approx5$, and the cumulative recombination count by a factor of 1.45 by $z\approx5$. Mapping the recombination budget in the joint overdensity-temperature plane reveals that the dominant recombination ridges closely follow simple analytic thermal
equilibrium bands. Finally, we introduce a phase-space recombination integral and define a phase-space clumping factor, $C_{\rm ps}(\Delta,T)$, which isolates the intrinsic recombination enhancement associated with ionization structure and thermal state at fixed overdensity and temperature.
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All authors Ali Sadain, Aaron Smith, Oliver Zier, Hyunbae Park, Teodora-Elena Bulichi, Xuejian Shen, Rahul Kannan, Rongrong Liu, Yuan Bian, Volker Springel, Mark Vogelsberger, Sonja M. Koehler, Lars Hernquist
Cosmology and Nongalactic Astrophysics
Consistency of DES and DESI distances and the Standard Cosmological Model
Richard Watkins, Cordelia Trueax and Hume A. Feldman
We test the consistency of the
cosmic distance-
redshift relation inferred from the
cosmic microwave background (CMB), the Dark Energy Spectroscopic Instrument (DESI)
baryon acoustic oscillation measurements, and the Dark Energy Survey (DES) Type Ia
supernovae within the framework of flat $\Lambda$CDM. DESI recovers the CMB-constrained parameter combination $(r_d h)(\Omega_m/0.3)^{0.4}$ with sub-percent precision, demonstrating excellent agreement between BAO measurements at $z \sim 1$ and the acoustic scale at recombination. Imposing the CMB constraint yields an estimate of $\Omega_m$ that is slightly lower than, but only in mild tension with, the Planck value. The high-
redshift DES
supernova sample is well described by the standard cosmological model, whereas the current low-
redshift anchor sample exhibits a systematic offset of $\sim 0.05$ mag that drives much of the apparent preference for evolving dark energy. Preliminary data from the Dark Energy Bedrock All-Sky
Supernova Program (DEBASS) do not show this offset, suggesting that unresolved low-
redshift systematics may account for the discrepancy. These results suggest that a single flat $\Lambda$CDM model accurately describes the distance-
redshift relation from the local Universe to recombination, placing increasingly stringent constraints on new-physics explanations of the Hubble tension.
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Solar and Stellar Astrophysics · Cross-listed from nucl-th
Universality and variability of the heavy r-process element abundance pattern from a nonequilibrium approach
David Blaschke, Friedrich K. Röpke and Gerd Röpke
A striking feature in the observed chemical composition of the majority of
stars is the universality of the relative abundances of the heavy elements, although some outliers exist. We demonstrate that a nonequilibrium freeze-out approach provides a natural way of accounting for the typical abundance pattern and its variation. Here, we use a phenomenological method to characterize the coarse-grained distribution of heavy $r$-process elements in several astrophysical objects. The Lagrange parameters show only minor fluctuations when comparing different
stars. Larger deviations are observed in
stars with low
metallicity. The variations in the Lagrange parameters for these
stars are presented. The determination of the Lagrange parameters can be instrumental in identifying possible sources for the formation of heavy elements. In particular, density fluctuations are considered as a source for the production of heavy elements in the early Universe.
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Cosmology and Nongalactic Astrophysics
The three-dimensional shapes of the galaxy cluster intracluster medium in eRASS1
S. Kulkarni, J. S. Sanders, E. Bulbul et al. (+2 more)
The three-dimensional shapes of clusters are important for understanding the astrophysics of the clusters and as a probe in cosmological studies. We estimate the most probable three-dimensional shape of
galaxy clusters in the first eROSITA All-sky survey eRASS1 using stereology. Our sample is the largest well-defined sample of clusters, and the most probable shape estimated using our method can be used as a prior for cluster shape models in cosmological, cluster, and weak
lensing studies. The first all-sky survey with SRG/ eROSITA resulted in a sample of approximately 12,000 optically confirmed
galaxy groups and clusters. We used a well-defined subsample of 3254 clusters from the eRASS1 survey and estimated the most probable shape of the clusters by constraining the probability density function (PDF) of the ellipticity of the clusters. We simulated the projected appearance of clusters with a distribution of three-dimensional shapes (prolate and oblate) and obtained the distribution of their ellipticity. This distribution was then compared with the measured distribution of ellipticities from the eRASS1 cluster sample to infer the three-dimensional shapes consistent with the data. We used Monte Carlo methods to estimate the most probable axial ratios l, w, where l $\equiv$ L/T ,w $\equiv$ W/T , and L, W, T are major, intermediate, and minor axes of the cluster. We did not require any additional probe (optical, SZ, etc.) to constrain the probable shape of the clusters. We describe the ellipticity PDF of the eRASS1 clusters with a normal distribution mean ($\mu$) = 0.79 and a standard deviation ($\sigma$) = 0.25. The most probable shape of the clusters in our eRASS1 subsample is estimated to be (l, w) = (1.51 $\pm$ 0.27, 1.17 $\pm$ 0.27), with prolate shapes being preferred over oblate shapes.
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All authors S. Kulkarni, J. S. Sanders, E. Bulbul, A. Liu, M. E. Ramos-Ceja
Earth and Planetary Astrophysics
Revisiting the Exo-Mercury Candidate GJ 367 b with ESPRESSO and a Self-Consistent Tidal Distortion Model
Rena A. Lee, Fei Dai, Ellen M. Price et al. (+18 more)
We report revised mass and radius measurements for GJ 367 b, an ultra-short-period (7.7 hr) sub-Earth in a multi-
planet system orbiting a nearby (~9 pc) M
dwarf host. Previous mass and radius measurements have suggested GJ 367 b has an anomalously high bulk density, close to that of solid iron. The existence of such an iron-rich
planet is in tension with established
planet formation scenarios. We utilized newly available TESS short-cadence photometry to constrain the radius of GJ 367 b to 0.736 +/- 0.035 R_Earth. We consider observational and modeling effects such as photometric dilution,
stellar activity, and
tidal distortion to account for possible inaccuracies in the
star and
planet radius measurements. From our radial velocity (RV) analysis using VLT/ESPRESSO data covering nearly the full orbit in a single night, we find a mass of 0.503 +/- 0.078 M_Earth, corresponding to a bulk density of 6.9 +1.6/-1.4 g cm-1. We present a new
tidal distortion and interior composition modeling framework to assess the iron mass fraction of GJ 367 b. Considering several different interior composition assumptions and radial aspect ratios, we find an iron fraction of ~50-70%, which is broadly consistent with that of Mercury and not as iron rich as previously suggested.
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All authors Rena A. Lee, Fei Dai, Ellen M. Price, Te Han, Davide Gandolfi, Mathias Zechmeister, Gu{\dh}mundur Stefánsson, Jiayin Dong, Simon H. Albrecht, Kristine W.F. Lam, Federica Chiti, Jennifer L. van Saders, Daniel Huber, Heather A. Knutson, Karen A. Collins, Michael Zhang, Leslie A. Rogers, Eleonora Armano, Casey L. Brinkman, Nicholas Saunders, Daniel Hey
High Energy Astrophysical Phenomena
Late-time JWST/NIRCam Observations of the Extremely Long-duration GRB 250702B/EP 250702a and Its Host Galaxy
Huei Sears, Jean J. Somalwar, Ryan Chornock et al. (+22 more)
We present JWST/NIRCam observations of the extremely long-duration gamma-ray burst (GRB) 250702B taken at ~ 95 days post-GRB (observer frame). The observations of the host
galaxy reveal a single
galaxy with a prominent
dust lane observed nearly edge-on. Prospector modeling of the host
galaxy photometry finds a high
stellar mass (log(M_*/M_Sun) = 11.0 +0.2/-0.3) and large
dust column (A_V = 2.8 +/- 0.3 mag), in agreement with previous results. If GRB 250702B is a collapsar-driven GRB, the host
galaxy is the brightest (in rest-frame r and rest-frame H) and most massive compared to GRB hosts at similar
redshifts. The transient localization is near the
dust lane, and while we find no evidence for transient emission in F277W, F356W, and F444W, forced photometry in F150W and F200W reveals possible ~ 3 sigma detections of the transient at m_{F150W} ~ 27.9 AB mag and m_{F200W} ~ 27.4 AB mag. If these are secure detections, they are indicative of a late-time light curve flattening. This behavior is consistent with that of jetted
tidal disruption events (TDEs); however, it is also consistent with a
supernova plus GRB afterglow model. Alternatively, if these are upper limits, they are consistent with, but do not further constrain, the extrapolated power-law decline of the afterglow. The ambiguity of the possible detection of the transient in F150W and F200W highlights the need for late-time template observations with JWST/NIRCam.
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All authors Huei Sears, Jean J. Somalwar, Ryan Chornock, Tanmoy Laskar, Andrew Levan, Raffaella Margutti, Brendan O'Connor, Nayana A. J., Tomas Ahumada, Kate D. Alexander, Igor Andreoni, Akash Anumarlapudi, Jonathan Carney, James Freeburn, Lluís Galbany, Benjamin P. Gompertz, Or Graur, Saarah Hall, Xander J. Hall, Erica Hammerstein, Saurabh W. Jha, Mansi M. Kasliwal, Dheeraj Pasham, Itai Sfaradi, Yuhan Yao
Astrophysics of Galaxies
TNG SAM: Bridging Hydrodynamical Complexity and Semi-Analytic Efficiency to Model Galaxy Formation
Osase Omoruyi, Bryan A. Terrazas, Yossi Oren et al. (+5 more)
All cosmological models of
galaxy formation must navigate the trade-off between physical accuracy and computational efficiency. Hydrodynamical simulations provide spatially resolved predictions for the co-
evolution of dark matter, gas,
stars, and black holes, but rely on phenomenological subgrid models for small-scale processes (e.g.,
star formation). Semi-analytic models (SAMs), by contrast, gain efficiency through simplified, analytic treatments of the same processes, at the cost of reduced predictive scope. In this work, we leverage the strengths of the Santa Cruz SAM and the IllustrisTNG hydrodynamical simulation to develop the TNG SAM. Calibrated to reproduce
baryon cycling in
stellar feedback-dominated TNG
galaxies ($\sim 10^{10}M_\odot < M_{200} < 10^{12}M_\odot$), the TNG SAM introduces several key updates to the Santa Cruz framework regarding: 1)
halo gas (re-)
accretion efficiency, 2) a cooling model that moves beyond the traditional cold/hot mode dichotomy, 3) explicit treatment of both
galactic- and
halo-scale
outflows, 4)
star formation efficiency, and 5) the circulation of metals between
galaxies and their surroundings. These changes enable the TNG SAM to reproduce TNG's flow of gas and metals from the scale of the
galaxy to the
halo, as well as global
galaxy (e.g.,
stellar mass) and
halo (e.g. hot
halo gas mass) properties within $\lesssim 30\%$ accuracy out to $z=6$. This work demonstrates that, with appropriate calibration, SAMs can capture the complex physics of
galaxy formation modeled in hydrodynamical simulations while providing a flexible framework for studying
galaxy evolution across the large cosmological volumes targeted by future observational surveys.
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All authors Osase Omoruyi, Bryan A. Terrazas, Yossi Oren, Austen Gabrielpillai, Viraj Pandya, Rachel S. Somerville, Amiel Sternberg, Lars E. Hernquist
Astrophysics of Galaxies
A Long Period Stellar-Mass Black Hole Binary in $\omega$ Centauri
Matthew Whitaker, Evan Kerr, Anil Seth et al. (+16 more)
Modern simulations of
stellar dynamics in globular clusters peg a dominant role for
stellar-mass black holes, but direct evidence for black holes in clusters remains limited. We present the discovery of an astrometric
stellar-mass black hole–main sequence
star binary in $\omega$ Centauri, the most massive
Galactic globular cluster, using Hubble Space
Telescope data from the oMEGACat project and additional JWST data that span a total of 23 years. The luminous companion to the black hole is a main-sequence turnoff
star, and has a period of $94^{+63}_{-42}$ years, a semi-major axis of $31^{+15}_{-12}$ AU, and an eccentricity of $e=0.72^{+0.08}_{-0.13}$. Since we observe the binary during periastron, the mass of the black hole is well-constrained even though we only observe a partial orbit: the inferred black hole mass is $4.46^{+1.22}_{-1.01}$ M$_\odot$. We call this black hole oMEGACat BH-2. This is the first astrometric discovery of a
stellar-mass black hole in a globular cluster, and is the longest period black hole binary system yet discovered. The low mass of this black hole is perhaps surprising given the low
metallicity of the cluster, and shows that at least some low-mass black holes form at
metallicity $Z<10^{-3}$. We find that the binary is almost certainly dynamically formed and is soft, with an expected binary disruption timescale of $\sim$800 Myr. While the total number of black hole binaries in $\omega$ Centauri is uncertain, we show that existing surveys only cover a small area of parameter space, and that the presence of additional detectable black hole binaries is likely.
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All authors Matthew Whitaker, Evan Kerr, Anil Seth, Maximilian Häberle, Jay Strader, Jay Anderson, Andrea Bellini, Callie Clontz, Zack Freeman, Massimo Griggio, Sebastian Kamann, Mattia Libralato, Nadine Neumayer, Elena González Prieto, Carl L. Rodriguez, Sara Saracino, Peter Smith, Glenn van de Ven, Zixian Wang
Astrophysics of Galaxies
Compact Core, Extended Reach: A Bipolar kpc-Scale Elongation in a Little Red Dot at $z \approx 5.5$
Zhiyuan Ji, Yang Sun, Mauro Giavalisco et al. (+7 more)
Little Red Dots (LRDs) appear extremely compact at rest-frame optical wavelengths, yet many show extended rest-frame UV morphology revealing more complex internal structure. We present a combined analysis of VLT/MUSE rest-frame UV integral-field spectroscopy and continuum-subtracted [O III], H$\beta$, and H$\alpha$+[N II] emission-line maps from JWST/NIRCam imaging at sub-kpc resolution for LRD-204851 at $z=5.482$ in GOODS-S. We find that LRD-204851 hosts a remarkably thin, bipolar, elongated structure passing through the optical continuum centroid and extending several kpc on either side, traced by both the UV continuum and the rest-frame optical emission lines, with a bright [O III] clump-like structure $\sim$2 kpc to the south-east of the centroid. The MUSE observations reveal a double-peaked Ly$\alpha$ profile, with a broad and bright near-systemic red peak and a relatively faint peak blueshifted by $\sim$430 km s$^{-1}$, accompanied by a tentative N V $\lambda 1238$ detection at similar velocity. In narrow-band imaging extracted from the MUSE IFU cube, both the blue Ly$\alpha$ peak and the tentative N V emission lean toward this same south-eastern direction. Independently, radiative-transfer modeling of the integrated Ly$\alpha$ profile favors a biconical low-column-density cavity in a dense, slowly expanding neutral envelope, in support of the bipolar geometry traced by the line maps. Together, these results suggest that the elongated emission of LRD-204851 is connected to radiation and/or gas flow from its central engine through a low-column-density channel with a small opening angle that may trace either a slow
outflow or a quasi-static ionization cone. LRD-204851 is one of the first LRDs where the central engine's impact on its host
galaxy is potentially directly observable on kpc scales.
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All authors Zhiyuan Ji, Yang Sun, Mauro Giavalisco, Yongda Zhu, George H. Rieke, Christina C. Williams, Michael V. Maseda, Jianwei Lyu, Marcia Rieke, Sandro Tacchella
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Orbital evolution of asymmetric binaries within accreting environments
Albert Radulea, Marcelo E. Rubio, Konstantinos Kritos et al. (+1 more)
Extreme mass-ratio inspirals embedded in
accretion disks provide a natural arena for studying the interplay between relativistic orbital dynamics and environmental effects. In this work, we develop a framework to investigate the secular
evolution of compact objects repeatedly crossing an
accretion disk around a supermassive black hole. The orbital motion is modeled through Kerr geodesics, while disk interactions are encoded through effective prescriptions for mass
accretion and dynamical friction. We find that disk-induced dissipation generically drives a two-stage
evolution characterized by rapid
alignment of the orbital plane with the disk, followed by slower eccentricity damping. By systematically comparing the dynamics with a purely Keplerian treatment, we show that cumulative relativistic effects produce deviations even at large orbital separations, where the Keplerian approximation would naively be expected to remain accurate. These discrepancies grow through repeated disk crossings and become increasingly pronounced in more relativistic orbital configurations. We further investigate the impact of the
accretion-disk model by comparing the Sirko-Goodman and Novikov-Thorne prescriptions. Relativistic disk structures predict systematically lower densities and larger scale heights, leading to weaker orbital dissipation and slower secular
evolution. By contrast, the
spin of the central black hole has only a minor effect on the overall circularization efficiency. Our results demonstrate the importance of consistently modeling both relativistic orbital dynamics and disk structure when studying compact objects embedded in AGN disks, and provide a framework for exploring their long-term
evolution, as well as a possible connection to quasi-periodic eruptions.
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All authors Albert Radulea, Marcelo E. Rubio, Konstantinos Kritos, Andrea Maselli
Earth and Planetary Astrophysics · Cross-listed from cs.LG
ThousandWorlds: A benchmark for climate emulation of potentially habitable exoplanets
Edward T. Stevenson, Mei Ting Mak, Eric Wolf et al. (+4 more)
The search for life beyond Earth will depend on detecting faint signatures in the atmospheres of potentially habitable
exoplanets. Interpreting those signatures requires understanding the host
planet's
climate: the same molecule may signal life on one
planet and abiotic chemistry on another. Global
climate models (GCMs) provide this understanding, but individual runs can require up to millions of core-hours and substantial domain expert time. Machine-learning emulators could remove this bottleneck, but progress has been limited by the absence of a curated, multi-model exoclimate
dataset. We introduce ThousandWorlds, an ML-ready
benchmark for exoclimate emulation and for the broader regime of low-data, multi-simulator, parameter-to-field regression. The
dataset contains approximately 1,700 simulations from five GCMs, mapping eight
planet parameters to 3D atmospheric fields including temperature, humidity, winds, clouds, and radiation. Three nested subsets define progressively harder challenges: single-simulator regression, multi-simulator regression with complete observations, and multi-simulator regression with structured missingness. We propose two evaluation protocols: one for ranking methods, and one that measures performance relative to the disagreement between GCMs themselves. We evaluate ten baselines spanning simple methods, trees, deep learning, and Gaussian processes. GP-based methods perform best, suggesting that ThousandWorlds exposes a regime where off-the-shelf deep learning does not yet succeed. Data: https://doi.org/10.57967/hf/8695. Code: https://github.com/edstevenson/ThousandWorlds.
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All authors Edward T. Stevenson, Mei Ting Mak, Eric Wolf, Denis E. Sergeev, Tobi Hammond, N. J. Mayne, Miles Cranmer
Earth and Planetary Astrophysics
The Maximum Density of a Collisionally-Produced Planet is A Function of its Mass and Orbital Period
Madison Brady and Darryl Seligman
There are many different theoretical explanations for the formation of high-density Mercury-like
planets, but concrete evidence for any of these formation mechanisms remains elusive. A popular explanation for dense
planets is the collisional hypothesis, which states that iron-rich
planets can be formed as the products of high-energy, mantle-stripping impacts. Planetesimal collision simulations predict that higher-velocity collisions can form higher-density
planets. Motivated by the characteristics of the high-density, short-period (P=0.3d) GJ 367b, we study the results of previously-published smoothed-particle hydrodynamics (SPH) simulations on
exoplanet collisions, combining these with models describing the likely collision velocities of these objects, to investigate the relationship between the core mass fractions (CMFs) of
exoplanets, their masses, and their orbital periods. We predict that collisionally-produced super-Mercuries should be more common (and more dense) at low masses and short orbital periods. This correlation may enable us to pinpoint the formation mechanism of super-Mercuries as the population of observed targets grows. Afterwards, we connect our hypothesis to the observed Mercury-like population of high-density
exoplanets, and find that GJ\,367\,b is the best exoplanetary candidate for collisional formation.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Weak corrections to Minimal Dark Matter annihilations
Dario Buttazzo, Mateusz Duch, Pier Paolo Giardino et al. (+1 more)
We compute the one-loop weak corrections to the annihilation cross sections of fermionic Minimal Dark Matter multiplets. Infrared divergences cancel in the dominant $s$-wave combination relevant for the thermal relic abundance. Instead, infrared-enhanced corrections affect velocity-suppressed rates, through a Sudakov/Sommerfeld interplay. The corrections grow with the multiplet size and are at the $5\%$ level in the most motivated cases: the Higgsino-like doublet, the wino-like triplet, the stable quintuplet.
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All authors Dario Buttazzo, Mateusz Duch, Pier Paolo Giardino, Alessandro Strumia
Astrophysics of Galaxies
Diverse Histories and Common Origins of Nitrogen-enhanced JWST Galaxies
Vadim Rusakov, Christopher J. Conselice, Thomas Harvey et al. (+2 more)
Early JWST spectra revealed
galaxies with a strong nitrogen excess challenging
galactic chemical
evolution models. Using public JWST surveys, we construct a sample of 76 N/O-enhanced
galaxies (NOEGs) at 4 $<z<$ 8.5, the largest at high
redshift to date. The NOEG fraction rises from $\sim$3% to $\sim$18% between $z\sim$ 4 and 7 - well above the $\sim$2% measured locally - potentially driven by burstier, cluster-dominated
star formation. Stacked spectra of the most nitrogen-rich
galaxies show signatures of low-
metallicity Wolf-Rayet (WR)
stars, a likely source of primary nitrogen within the first few Myr of a starburst, with UV and optical continua dominated by young
stellar emission and Balmer jumps evident in some cases. Many NOEGs also exhibit ionised
outflows: 40% show secondary [O III] and H$\alpha$ components, while stacked spectra of the remainder reveal a broadened, offset H$\alpha$ without forbidden-line counterparts, suggesting
dust-attenuated or faded
outflows. The continuum in the latter shows a weak Balmer break, indicating these
galaxies are past their most recent burst. This suggests that
outflows dilute gas
metallicity after the first few Myr of the initial enrichment and enable renewed N/O enhancement driven by low-
metallicity Asymptotic
Giant Branch (AGB)
stars. We conclude that NOEGs are caught briefly after a recent starburst: either within $\sim$10 Myr, when WR winds drive nitrogen enrichment, or after 30-40 Myr, when AGB winds take over - following an
outflow driven by radiative or
supernova feedback, consistent with recent chemical
evolution models.
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All authors Vadim Rusakov, Christopher J. Conselice, Thomas Harvey, Jordan C. J. D'Silva, Duncan Austin
Instrumentation and Methods for Astrophysics
Polarisation and Faraday rotation measure imaging at metre wavelengths with sub-arcsecond resolution: a foundational calibration strategy
R. J. van Weeren, J. M. G. H. J. de Jong, X. K Le Saux et al. (+12 more)
Low-frequency
radio polarimetric observations provide a powerful probe of
magnetic fields in astrophysical sources and the intervening medium, as well as magnetospheric emission from compact objects such as
pulsars, magnetically active
stars, brown
dwarfs, and planetary aurorae. With baselines of up to 2000 km, LOFAR offers a unique opportunity to study the low-frequency polarised Universe at sub-arcsecond resolution. However, polarimetric studies with LOFAR have so far been limited to angular resolutions of about 6 arcsec, resulting in stronger beam depolarisation. Here we present a calibration strategy that enables full-resolution polarimetric imaging with the LOFAR pan-European array. Our method applies full-Jones corrections to the international stations using an in-field unpolarised calibrator. In addition, when a sufficiently bright polarised source is present in the field, multi-epoch observations can be aligned in Faraday depth using a visibility-based correction that accounts for polarisation angle and rotation measure offsets. This approach enables deeper combined imaging and deconvolution. We apply this strategy to the LOFAR ELAIS-N1 field, combining four 8 h observations for a total integration time of 32 h. At 0.3 arcsec resolution, we detect two previously known polarised sources identified in lower-resolution studies, resolve additional polarised components, and localise emission regions with sub-arcsecond precision. We also identify a new polarised source and detect circularly polarised emission from the binary M-
dwarf system CR Draconis, measuring its proper motion across epochs. These results demonstrate that sub-arcsecond polarimetry at metre wavelengths is now feasible with LOFAR, opening new science opportunities in the LOFAR2.0 era.
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All authors R. J. van Weeren, J. M. G. H. J. de Jong, X. K Le Saux, V. A. Chakawri, Q. W. E. van Zegveld, D. de Jong, S. P. O'Sullivan, F. Sweijen, V. H. Mahatma, E. De Rubeis, L. K. Morabito, D. Alonso-López, A. Bonafede, C. Horellou, M. van der Wild