Astrophysics papers — 2026-10-14

This work focuses on observational evidence for black hole event horizons, which is important because the event horizon fundamentally distinguishes a black hole from other compact objects. Researchers are looking at ultra-compact X-ray binaries to probe this by measuring gravitational radiation dominance in their orbital angular momentum loss. This research suggests that the radiative efficiency of a black hole is significantly lower than that of neutron star systems.

This finding builds on previous observations where black hole X-ray binaries appeared fainter than neutron stars with similar orbital periods in their quiescent states. The study uses five ultra-compact X-ray binaries with orbital periods shorter than forty minutes located in globular clusters to identify whether they host neutron stars or black holes. They then combine their accretion rates and luminosities to calculate the radiative efficiencies of both types of systems.

This calculation shows that the radiative efficiency for a black hole is about two to three orders of magnitude lower than that for neutron star systems. This result implies that the accretion energy is swallowed by the black hole, which indirectly points toward the presence of an event horizon.

The study on interaction between eccentricity tide and convection attempts to understand how these forces behave in icy satellites. It finds that while tidal forces control large-scale motion, convection is important for small scales. The mode-mode transition happens at intermediate scales in this context.

This contrasts with observations showing that tide suppresses heat transport efficiency and that kinetic energy dissipation scales with the square of the tidal force with only a weak dependence on buoyancy force. These results are connected to broader astrophysical questions about massive black holes in the first billion years.

Understanding how seeds form for massive black holes in the first billion years requires considering hybrid hydro/direct N-body simulations regarding intermediate-mass black hole formation /papers/2606.10000. Furthermore, while this work gains insight into compact object physics through accretion studies like AKMPC, the implications for cosmology remain open areas of investigation.

The work concerning the integration of a CME flux rope model with magnetic field draping in Heliospheric Simulations is particularly important for predicting the magnetic structure of interplanetary coronal mass ejections. This study introduces FROST, a new flux-rope model implementation within EUHFORIA that uses a novel embedding technique to self-consistently generate a draping magnetic field around the flux rope while ensuring continuity at the CME boundary.

The dynamics in the low and middle corona are solved using non-uniform advection constrained by observed event kinematics, leading to a global, stretched loop-like magnetic structure. This model's success is validated by comparing its output against in situ measurements from the 2013 April 11 CME event at one au distance.

The modeled magnetic field profiles show strong agreement with observations, with correlation coefficients for Bx ranging from 0.64 to 0.93, By between 0.92 and 0.95, and Bz between 0.82 and 0.87; this means the model is quite good at matching the observed magnetic field components during an event AKMPC — Integration of a CME Flux Rope Model with Magnetic Field Draping in Heliospheric Simulations.

Another relevant piece of work involves calibrating spectral siren cosmology using synthetic catalogs of binary black hole mergers to probe cosmic expansion. This approach uses Normalizing Flows to calibrate population models on mock catalogs generated from astrophysical prescriptions, which allows for a direct link between different formation channels and cosmological parameters Calibrating spectral siren cosmology with synthetic catalogs of binary black hole mergers.

These models fit the mass and redshift distributions of GW events in GWTC-4.0 data for a flat Λ CDM cosmology with H 0 about 70 km/s/Mpc and Ω m=0.308, showing a correlation between H 0 and the fraction of binaries produced by dynamical versus isolated formation channels.

Moving to galactic scales, the COZMIC suite presents zoom-in simulations of a Milky Way analog using initial conditions appropriate for scenarios where non-cold dark matter is a fraction of the total dark matter abundance, or f-NCDM models COZMIC. II. Cosmological Zoom-in Simulations with Fractional non-CDM Initial Conditions. These simulations test various WDM masses and plateau amplitudes, yielding new limits on f-NCDM scenarios based on the subhalo mass function.

These results suggest that low-mass halo abundances are sensitive to partial suppression in the linear matter power spectrum COZMIC. II. Cosmological Zoom-in Simulations with Fractional non-CDM Initial Conditions. The work concerning primordial black hole abundance from reionization is particularly important because it speaks to the very early universe, setting constraints on physics before structure even formed.

This research suggests that the number of these black holes depends sensitively on the details of reionization, which is a key epoch in cosmic history. A study examining environmental dependence in satellite planarity and orbital-pole coherence around Milky Way analogues explores how local gravitational environments affect galactic dynamics Environmental Dependence of Satellite Planarity and Orbital-Pole Coherence around Milky Way Analogues in a Hydrodynamical Cosmological Simulation.

This simulation attempts to model these complex interactions within a cosmological framework. Another piece of work investigates the rotational line CO cooling rate prescription for Asymptotic Giant Branch outflows, which is crucial for understanding how gas cools and evolves in stellar winds A rotational line CO cooling rate prescription for AGB outflows. This helps refine models of stellar evolution feedback.

The analysis of directional tests of the cosmic distance duality relation using Pantheon+ and BAO data provides a model-independent check on anisotropy in this cosmological relation Directional Tests of the Cosmic Distance Duality Relation using Pantheon+ and BAO. This test uses supernova data and baryon acoustic oscillation measurements to see if there is any directional deviation, finding no evidence for intrinsic anisotropy within a robust upper bound of zero point zero two five percent.

This is followed by research on mergers as a channel for galaxy stellar mass growth at redshift five, which predicts how hierarchical models behave in that era Mergers may not be the main channel for galaxy stellar mass growth at redshift z 5: Predictions from cosmological hierarchical models and simulations. This work contrasts merger-driven growth against other processes.

The interpretation of the stacked kinetic SZ signal II addresses the degeneracy between satellite galaxies and baryonic feedback in cosmic structures Interpreting the stacked kinetic SZ signal II: the degeneracy between satellite galaxies and baryonic feedback. This helps disentangle different physical contributions to observed signals.

Finally, a study on beyond the damped random walk for multiband AGN variability from SDSS to Rubin LSST looks at how variability in active galactic nuclei changes across different observational surveys Beyond the Damped Random Walk: Multiband AGN Variability from SDSS to Rubin LSST. This probes the variability of AGN across different observational epochs.

The work on gravitational waves from strong first-order phase transitions in an expanding Universe is particularly important because it probes physics at very high energy scales, potentially revealing new aspects of the early universe. This study explored how these transitions generate gravitational waves and what signatures they leave behind.

A key finding relates to nonminimal couplings and preheating effects in R squared-Higgs inflation after ACT and SPT data, which suggests that deviations from simple models might be necessary to explain observed cosmological constraints. This work also looked at multi-period Fermi-LAT and LHAASO constraints on axion-like particles from Mrk 421 using a chi squared Profile Likelihood with Gaussian Copula Correlation, providing tighter limits on these hypothetical particles.

In terms of stellar dynamics, the research into stellar discs and intermediate-mass black holes in galactic nuclei II investigates how these structures fragment and form S-stars within live nuclear star clusters. This provides insight into the complex gravitational interactions happening at the centers of galaxies.

Finally, there is a piece on high-resolution transmission spectroscopy of KELT-18b Metastable helium detection at 1083 nm, which aims to detect specific molecules in exoplanet atmospheres. This helps us understand the chemical composition of distant worlds, and this contrasts with the large-scale cosmological studies.

The most significant work here is the study on oxygen enhancement from silicate sublimation during early protostellar evolution because it offers a direct look at how material changes in the very beginning of star formation. This research suggests that as protostars evolve, silicate grains sublimate, releasing oxygen into the surrounding environment. This process is explored through simulations where the simulation models show this enhancement occurring as the protostar evolves.

Further down, there is work on how shape degeneracies can affect measurements of the Hubble constant because resolving these ambiguities is crucial for accurate cosmological distance calculations. This is supported by an analysis of two microlensing events, KMT-2025-BLG-1314 and KMT-2025-BLG-1392, which used a new differentiable modeling package called microlux to handle complex parameter spaces.

This tool allowed for robust inference using Hamiltonian Monte Carlo methods, which proved better than traditional MCMC in cases with bimodal posteriors. Another important piece is the spectroscopic census of cluster white dwarfs from DESI, LAMOST, and SDSS because it refines our understanding of white dwarf populations in clusters.

This work found that adding 62 candidate white dwarfs to the sample increased the combined initial-final mass relation sample to 132 WDs, and importantly, these additions did not require recalibrating the empirical IFMR.

We also have findings on experimental evidence for physical alteration of fine regolith on near-Sun asteroids, which is important because it provides a mechanism for understanding surface evolution in space. Experiments simulating near-Sun conditions showed that carbonaceous chondrite simulants undergo sintering, which causes morphological changes from sub-micrometer to millimeter scales. This suggests this process is key to how surfaces evolve.

Finally, there is the analysis of evidence for distinct one-off and repeating subpopulations in the CHIME/FRB catalog because it challenges assumptions about fast radio burst sources. Using simulation based inference, researchers found that models including a distinct subpopulation of truly one-off sources best fit the data, suggesting that the repeating population might not be monolithic.

The work that really matters here is the controlled ensemble null tests of dynamical dark energy hints because it directly probes whether the standard cosmological model of cold dark matter can still be recovered when looking at various cosmological probes simultaneously. This test, AKMPC, shows a single-probe recovery of cold dark matter by combining measurements from baryon acoustic oscillations, compressed cosmic microwave background data, and supernova mocks.

This is significant because it provides a rigorous way to check if the observed signals are consistent with the standard model of cosmology rather than some exotic dark energy behavior. The work then moves on to constrain the major merger history of galaxies at redshifts between three and nine using JADES, which focuses on dominant in-situ star formation.

This helps us understand how galaxy growth has proceeded over cosmic time. Following that, there is the study on the effects of linear matter power spectrum enhancement on dark matter substructure, which investigates how enhancements in the initial density fluctuations affect the small-scale structure of dark matter halos. This is important because it ties into whether we see too much or too little substructure compared to predictions.

Another piece that contributes to this picture is the investigation into heavy black hole seed survivors in dwarf galaxies, specifically using Leo I as a case study. This looks at how massive black holes might have formed and survived in smaller systems, connecting this to understanding the smallest scales of structure formation.

The observation of hot gaseous outflows in NGC 5746 provides a local perspective on feedback processes, which is relevant when modeling galaxy evolution across different scales. Finally, the analysis of galaxy populations within the IllustrisTNG caustic skeleton offers a large-scale view of how galaxies are distributed within cosmological simulations.

The work on mergers lighting the early Universe is particularly important because it suggests that modest star formation enhancement can occur during these events without needing evidence for active galactic nuclei or Ly alpha triggering. This finding connects to the work on cosmic evolution of the [CII]-to-dense neutral gas relation, which explores how this gas distribution changes over time.

The study on learning the universe with PRFM-vol introduces a new subgrid model for star formation in cosmological simulations, which is significant because it allows for a more realistic depiction of how stars form within large-scale structures. This modeling effort builds upon the observational data from the nineteenth data release of the Sloan Digital Sky Survey, which provides crucial context on galaxy properties across cosmic time.

Furthermore, revisiting radio synchrotron diagnostics in star-forming galaxies offers a way to probe the physical conditions within these galaxies, providing complementary information to simulations like those in Learning the Universe with PRFM-vol. This diagnostic work is also relevant when considering witnessing the earliest phases of galactic wind formation in superluminous supernova hosts, as it helps constrain how star-formation-driven outflows operate across different redshifts.

Finally, constraining galaxy cluster triaxiality via weak lensing preparation for the Rubin Data Beyond Leading Order provides a necessary geometric constraint on how clusters are shaped. This informs our understanding of the large-scale environments where these processes occur.

The most pressing finding relates to constraints on the r-process delay time from dwarf spheroidal galaxies because it helps us understand how quickly certain heavy elements are synthesized in these small systems. The work by Constraints on the r-process Delay Time from Dwarf Spheroidal Galaxies suggests that the delay time is significantly longer than previously assumed, which shifts our timeline for nucleosynthesis. This idea connects to what The R-Process Alliance: On J0010 - 1735, an Accreted, Chemically Unusual, Metal-poor Star with R-process Enhancement found regarding the specific enhancement seen in that star.

Furthermore, the observations from Globular cluster Observations for Luminosity-dispersion Distances (GOLD) provide crucial distance measurements for these systems. These measurements are important because they anchor our understanding of stellar populations within clusters. This observational work is supported by the simulation results from The NIVARIA-Local Group simulations which unveil how rotation curve diversity in dwarf galaxies relates to their overall morphology.

The study on the Tilt of the Velocity Ellipsoid in the Milky Way Disk with GALAH-Gaia Data offers a more detailed view of stellar dynamics within our own galaxy. This is less fundamental than the nucleosynthesis constraints but adds necessary detail to galactic structure studies. This structural context feeds into the broader picture presented by Evidence for Hierarchical Turbulent Scaling in Nearby Star-Forming Galaxies, which examines how turbulence scales in star-forming regions.

Finally, the work on Indirect Dark Matter Detection in the Multi-Messenger Era provides a long-term outlook on fundamental physics beyond what we see in stellar and galactic dynamics. This theoretical framework is distinct from the observational constraints but speaks to the ultimate goals of astrophysics.

Today's papers

The papers

Important terms

Event Horizon
The boundary around a black hole that fundamentally distinguishes it from other compact objects, crucial for understanding accretion and energy swallowing.
Radiative Efficiency
A measure of how efficiently a system converts accreted energy into observable radiation. This study shows black holes have much lower efficiency than neutron stars.
Eccentric Tide and Convection
The interplay between tidal forces controlling large-scale motion and convection driving small-scale behavior in icy satellites, important for understanding satellite dynamics.
Spectral Siren Cosmology
A method using binary black hole merger catalogs to calibrate cosmological parameters like the Hubble constant, linking gravitational waves to cosmic expansion.