Solar and Stellar Astrophysics
Parker Solar Probe observations of solar energetic particle (SEP) events with inverse velocity arrival (IVA) features
Zigong Xu, C. M. S. Cohen, R. A. Leske et al. (+21 more)
In SEP events, velocity dispersion (VD) is characterized by the earlier arrival of faster, higher-energy particles relative to slower ones, assuming negligible acceleration time and transport effects. The "Labor Day event" at Parker
Solar Probe (PSP) on 2022 September 5 provided a unique arrival profile, in which the medium energy (~ few MeV) particles arrive earlier than both lower and higher energy particles. This created a so-called "nose" structure in the intensity spectrogram formed by measurements from the two energetic particle instruments, EPI-Lo and EPI-Hi, of the Integrated Science Investigation of the Sun (ISOIS) suite. Unlike typical VD, the delayed arrival of higher energy particles compared to medium energy particles, i.e., the "inverse velocity arrival" (IVA), could be caused by various acceleration, transport, and instrumental effects, including shock acceleration. By applying a new method based on the contour-line of the intensity, we found 14 IVA events in the ISOIS observations up to the end of 2024. Several parameters that may modify velocity dispersion characteristics are further explored including the spacecraft radial distance, the speed of corresponding CMEs and shocks, the angle between the shock normal and the upstream
magnetic field, and the spacecraft
magnetic footpoint longitudinal separation from the
flare location. The energy of the early arriving particles, i.e., the nose energy, can be grouped into low (L, <0.5 MeV), medium(M, 0.5 - 5 MeV), and high(H, >5 MeV) categories. Most (11/14) of the IVA events have medium nose energies. This SEP list provides ingredients for examination of shock acceleration in the inner heliosphere, and the existence of IVA events sheds new light on the acceleration and propagation of SEPs.
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All authors Zigong Xu, C. M. S. Cohen, R. A. Leske, G. D. Muro, A. C. Cummings, O. M. Romeo, D. Lario, D. J. McComas, M. E. Cuesta, S. Pak, L. Y. Khoo, H. A. Farooki, M. M. Shen, S. Kasapis, E. R. Christian, D. G. Mitchell, R. L. McNutt, A. Kouloumvakos, J. Grant Mitchell, G. D. Berland, N. A. Schwadron, M. E. Wiedenbeck, M. L. Stevens, R. C. Allen
Astrophysics of Galaxies
Cosmological Simulation with Population III Stellar Feedback and Metal Enrichment I: Model Description And Convergence Test
Bocheng Zhu and Liang Gao
We present SPARK (Simulation of Pop III in Arepo with Radiation and Kinetic feedback) framework, a new Pop III + Pop II subgrid framework implemented in the moving-mesh code arepo, designed to study the impact of Pop III feedback on
star formation in the early universe. The framework combines
primordial non-
equilibrium chemistry, metal-line cooling, IMF-sampled
stellar evolution with SN feedback, and approximate Lyman-Werner (LW) and ionizing radiation transport. We run a suite of $1c{\rm Mpc}/h$ box simulations with different initial conditions and resolutions from $z=127$ to $z=10$. The highest gas mass and spatial resolution in the fiducial simulation reach $\sim10\,{\rm M_{\odot}}$ and $\sim4\,{\rm pc}$, respectively. The model successfully reproduces the Pop II
star formation rate density (SFRD) consistent with previous theoretical works across all initial conditions, with minor variation mainly driven by local
halo interactions and LW irradiation. We find that the volume filling factor of metal-enriched gas converges to $\sim0.5-2\%$ at $z=10$, with scatter driven by
stochastic and mixing model variations. Convergence is achieved once subhalos with $M_{\rm subhalo}\gtrsim 10^{6.5}\,{\rm M_{\odot}}$ are resolved, and the total
stellar mass at $z=10$ is largely insensitive to initial conditions or the resolution considered in this work. A fiducial simulation requires $\sim 10^4$ CPU hours, making the framework computationally tractable for larger box simulations and enabling future large parameter studies of
stellar physics or environment effects such as Pop III IMF variations, X-ray radiation, or the streaming velocity at high
redshift.
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High Energy Astrophysical Phenomena
Correlated and uncorrelated Monte Carlo neutron capture rate variations in weak $\textit{r}$-process simulations
Atul Kedia, Jeffrey M. Berryman, Jonathan Cabrera Garcia et al. (+7 more)
Reliable predictions of weak rapid
neutron capture ($\textit{r}$-process) abundances require a systematic treatment of
nuclear physics uncertainties, especially
neutron capture rates far from stability. We employ new
neutron capture rates from cross sections calculated with Yet Another Hauser-Feshbach Code ($\texttt{YAHFC}$) using an uncertainty-quantified Koning-Delaroche potential modified for use on
neutron-rich systems. Using these rates as a baseline, we perform Monte-Carlo studies with independent rate variations (uncorrelated Monte Carlo) and find correlations between specific
neutron capture rates and the resulting elemental abundances for the three weak r-process scenarios: two separate simulations of
neutron star merger remnant
accretion disks and a simulation of a magnetorotational
supernova. We discuss the underlying
nuclear dynamics that give rise to these correlations and the role of astrophysical conditions in them. We demonstrate how reducing the uncertainty in these rates would improve the prospects for conducting precision $\textit{r}$-process studies in the future. We additionally present a correlated Monte Carlo study, which incorporates the full covariance
matrix that describes the relationships between individual
neutron capture rates that arise from an uncertainty-quantified optical potential. We find that the magnitude of the uncertainty in the abundance pattern is similar to that produced by an uncorrelated Monte Carlo that employs only the on-diagonal components of the covariance
matrix. We show how correlations restructure how the abundances co-vary, but do not necessarily decrease the overall uncertainty envelope.
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All authors Atul Kedia, Jeffrey M. Berryman, Jonathan Cabrera Garcia, Jutta E. Escher, Oliver C. Gorton, Erika M. Holmbeck, Gail C. McLaughlin, Cole D. Pruitt, Andre Sieverding, Rebecca Surman
High Energy Astrophysical Phenomena
Broadband Timing and Spectral Study of Accreting Millisecond X-ray Pulsar SAX J1808.4$-$3658 during Its 2022 Outburst
Rahul Sharma, Andrea Sanna and Prince Sharma
We report on our investigation of the NuSTAR and AstroSat observations along with simultaneous NICER observations of the accreting millisecond X-ray
pulsar SAX J1808.4$-$3658, obtained during its tenth outburst from 2022. The NuSTAR observation captured the source near the outburst peak, while AstroSat observed it during the decay phase. Coherent pulsations at $\sim$401 Hz were detected throughout the outburst, with the fundamental amplitude in the 3–30 keV range increasing from $\sim$4% near the peak to $\sim$6% during the decay. The pulsations display strong energy dependence and negative time lags of $\sim$0.2–0.3 ms, with harder
photons leading softer ones. The broadband spectra in both epochs are well described by a soft thermal component and Comptonized continuum, together with a prominent relativistic reflection component. As the outburst evolved, the continuum softened ($\Gamma$ increasing from $\sim$1.88 to $\sim$1.99) and the coronal electron temperature decreased ($kT_{\rm e}$ from $\sim$31 to $\sim$18 keV), consistent with enhanced Compton cooling at lower
accretion rates. The ionization parameter declined ($\log \xi$ from $\sim$3.4 to $\sim$1.8) while the reflection fraction increased, suggesting a changing
accretion geometry with a more compact corona and a larger disk covering fraction during the decay phase. The X-ray luminosity decreased by a factor of $\sim$3 between the two epochs. Our results suggest the coupled
evolution of the corona, disk, and magnetosphere as the mass
accretion rate declines.
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Astrophysics of Galaxies
Abundances in 78 metal-rich bulge spheroid stars from APOGEE
H. Ernandes, B. Barbuy, C. Chiappini et al. (+9 more)
The inner
Galaxy is the most complex region of the Milky Way, comprising the bulge, inner thin and thick discs, and inner
halo; the formation of the bar transferred gas and
stars from the disc inward.
Accretion of
dwarf galaxies also occurred over the
Galaxy's lifetime, merging with the original bulge. In this work, we constrain the metal-rich
stars of the earliest spheroidal bulge. To study the oldest bulge
stars, distributed in a spheroid, we applied kinematical and dynamical criteria in the metal-rich range [Fe/H] > -0.8. This complements our previous analysis of a symmetric sample with [Fe/H] < -0.8. We derived individual abundances through spectral synthesis for C, N, O, Al, P, S, K, Mn, and Ce using
stellar parameters from APOGEE DR17, and compared the results with literature data and chemical-
evolution models. The alpha elements Mg, Si, and Ca, and iron-peak elements V, Cr, Co, and Ni follow the expected trends relative to the models. Mn shows secondary behaviour. S and K display significant
star-to-
star scatter but remain broadly compatible with predictions. Phosphorus and cerium show an excess around [Fe/H] $\sim$ -0.7, more pronounced than in the metal-poor sample, suggesting a distinctive signature of the earliest bulge population. Diagrams of [Mg/Mn] versus [Al/Fe] and [Ni/Fe] versus [(C+N)/O] indicate an in situ origin for most
stars. At super-
solar metallicities, a subset shows enhanced K and Mn (possibly S) with low [Ce/Fe], hinting at enrichment linked to the
nuclear disc and bar, and tracing a chemically distinct population shaped by the innermost
Galaxy.
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All authors H. Ernandes, B. Barbuy, C. Chiappini, S. Feltzing, A. Pérez-Villegas, A.C.S. Friaça, S. O. Souza, R.P. Nunes, A.B.A. Queiroz, J. G. Fernández-Trincado, A.L. Rocha de Abreu, A. Plotnikova
High Energy Astrophysical Phenomena
The Role of Faraday Rotation in the Polarization of the X-rays from Magnetically Powered Black Hole Coronas
Henric Krawczynski
Magnetic reconnection is one of the
prime candidate mechanisms that may energize the
plasma emitting the strongly polarized X-ray emission from black hole X-ray binaries (BHXRBs) in their hard states. The mechanism requires strong
magnetic fields in the upstream
plasma entering the reconnection layer, and weaker, but still substantial,
magnetic fields in the downstream regions. In this Letter, we estimate the coronal
magnetic fields for three different
magnetic energy dissipation mechanisms: plasmoid-dominated
magnetic reconnection, fast collisionless reconnection, and
magnetic field relaxation. We show that the lack of strong Faraday depolarization constrains viable models and can be used to
benchmark numerical
accretion flow models. We conclude by discussing the difficulties of disentangling the various effects that can depolarize the signals from BHXRBs at low energies. We furthermore emphasize that Faraday rotation is unlikely to play a role in the polarization of the coronal X-ray emission of active
galactic nuclei.
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High Energy Astrophysical Phenomena
First-Principles Polar-Cap Currents in Multipolar Pulsar Magnetospheres
Chun Huang
X-ray pulse-profile modeling of millisecond
pulsars offers a direct route to measuring
neutron star masses and radii, thereby constraining the dense-matter equation of state. However, standard analyses typically rely on ad hoc hotspot parameterizations rather than self-consistent physical models. While connecting surface heating directly to the magnetospheric geometry provides a more natural physical pathway, computing global magnetospheric solutions is too computationally expensive to perform on-the-fly during parameter inference. In this work, we bridge this gap by deriving fully analytic, first-principles expressions for surface return currents in mixed dipole–quadrupole magnetospheres. Working within force-free electrodynamics, we generalize the field-aligned current invariant $\Lambda$, the crucial scalar that maps the far-zone
magnetic structure to the near-zone heating rate, from the standard dipole approximation to arbitrary quadrupolar configurations. We demonstrate that even when the quadrupole component is sub-dominant in the far zone (the mixing regime), using a dipole-based heating prescription fails to capture the significant enhancement or suppression of the return-current density on the polar cap. Our consistent quadrupole-aware framework reveals that these multipolar currents redistribute the surface heating, leading to systematic discrepancies in predicted pulse profiles that are amplified by atmosphere beaming and can reach $\sim 30\%$ near pulse peaks. These results provide a rigorous analytic foundation for mapping global
magnetic geometry to surface heating in multipolar magnetospheres, enabling physically consistent inference beyond the idealized dipole approximation.
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Instrumentation and Methods for Astrophysics
New Time-Dependent WFC3/IR Inverse Sensitivities
Annalisa Calamida, Mariarosa Marinelli, Varun Bajaj et al. (+2 more)
We present new time-dependent inverse sensitivities for the WFC3/IR channel. These were calculated using the sensitivity change slopes measured by \citet{2024wfc..rept....6M} and photometry of five CALSPEC standards (the white
dwarfs GRW+70~5824, GD~153, GD~71, G191B2B, and the G-type
star P330E) collected from 2009 to 2023. The new inverse sensitivities account for losses of 1-2% over 15 years, depending on wavelength, and provide an internal photometric precision better than 0.5% for all wide–, medium–, and narrow-band filters. An updated version of calwf3 (v3.7.2) has been developed for use with a new time-dependent image photometry table (IMPHTTAB) and will be used to update the image header photometric keywords following MAST reprocessing, expected in late-2024. Alternatively, the new inverse sensitivities may be computed by the user for a specific observation date by running stsynphot.
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All authors Annalisa Calamida, Mariarosa Marinelli, Varun Bajaj, Aidan Pidgeon, Jennifer Mack
Earth and Planetary Astrophysics
TSSC comet-centered data products from TESS 3I/ATLAS observations
Jorge Martinez-Palomera, Amy Tuson and TESS Science Support Center
3I/ATLAS is the third known interstellar object to pass through our
Solar System. NASA's Transiting
Exoplanet Survey Satellite (TESS) made dedicated observations of 3I/ATLAS between 15 – 22 January 2026 (Sector 1751), capturing high-cadence observations at 200s and 20s cadence. We present two High Level Science Products (HLSPs): (1) comet-centered image time series, corrected for background scattered light and
stars; and (2) aperture light curves extracted from the corrected images. We created these data products using the official TESS products and they are publicly available at the Mikulski Archive for Space
Telescopes (MAST). TESS's high-precision, near-continuous photometry will provide unique insights into the comet's activity following its closest approach to the Sun. The TESS Science Support Center (TSSC) has created these data products to facilitate scientific analyses by the TESS and
Solar System communities.
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Astrophysics of Galaxies
Eye of the beholder: Observer reference frame bias in Hickson-like compact groups of galaxies
A. Zandivarez, E. Diaz-Gimenez and A.R. Callen
[Abridged] We investigate how the identification of Hickson-like CGs depends on the observer's reference frame, quantifying how frequently the same system would be recognised from different vantage points. Using a mock lightcone built from the Millennium I Simulation plus a semi-analytic model of
galaxy formation, we identified 7709 CGs when applying the standard Hickson-like criteria. For each CG, we placed 1000 random observers on a surrounding sphere and reapplied the velocity and compactness requirements to test recoverability. We also examined the variation of population and local isolation. The velocity concordance criterion shows modest sensitivity to the observer's location: 10% of CGs fail for some observers, typically groups with members with high peculiar velocities (>1000 km/s). The compactness requirement is far more fragile, as 44% of CGs are missed by most observers, and these systems are very elongated or are chance
alignments in real space. Tightening selection limits reduces this dependence. Lowering the surface brightness threshold to $\mu \leq 23 \ mag/arcsec^2$ reduces the compactness dependence to 16%, while reducing the velocity limit to $\Delta V\leq 250 \ km/s$ lowers velocity-driven failures to less than 4%. Applying both cuts simultaneously yields up to 84% observer-independent groups, although with a substantially smaller sample. Population and isolation are affected by bright interlopers seen from different directions. While such interlopers are common, they have only a minor effect on the compactness and velocity concordance criteria; however, the local isolation is commonly broken. Observer frame effects, dominated by the compactness criterion, can significantly bias Hickson-like CG samples. However, adjusting surface brightness and velocity difference thresholds allows users to balance the physical reliability according to their specific scientific goals.
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Cosmology and Nongalactic Astrophysics
Assembly bias and local Primordial non-Gaussianity from DESI DR1 Quasars
E. Fondi, L. Verde, E. Chaussidon et al. (+40 more)
The analysis of the large-scale clustering of
quasars (QSO) observed by the Dark Energy Spectroscopic Instrument (DESI) represents a promising avenue for constraining local
Primordial non-Gaussianity (PNG), parameterized by $f_{\rm NL}$. The signal to be constrained is the scale-dependent bias induced in the 2-point clustering of the considered tracer sample. The resulting constraints on $f_{\rm NL}$, however, are fully degenerate with the local PNG bias parameter $b_{\phi}$, dependent on the assembly bias parameter $p$. Using IllustrisTNG hydrodynamical simulations, we select a QSO sample reflecting the selection criteria and properties of DESI QSOs, and provide a robust prior for $p$, and thus for $b_{\phi}$, building on the findings of Fondi et al. 2024. We find a distribution with mean $\bar{p}\simeq1.4$ with weak
redshift dependence, stable to selection noise and consistent with the expected recent merger history typical of
quasar-hosting
halos. By comparing with the CAMELS simulations we demonstrate that this prior is robust to astrophysical assumptions and
cosmic variance. Finally, applying this prior to the DESI DR1
dataset, we derive updated constraints on local PNG, obtaining $f_{\rm NL}=-3.3\pm9.2$.
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All authors E. Fondi, L. Verde, E. Chaussidon, J. Aguilar, S. Ahlen, S. BenZvi, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, P. Doel, S. Ferraro, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, H. K. Herrera-Alcantar, D. Huterer, M. Ishak, R. Joyce, A. Kremin, O. Lahav, C. Lamman, M. Landriau, L. Le Guillou, M. Manera, P. Martini, A. Meisner, R. Miquel, S. Nadathur, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, D. Sprayberry, G. Tarlé, B. A. Weaver, H. Zou
High Energy Astrophysical Phenomena
Precursors in tidal disruption events: repeating, fast, and AGN-hosted TDEs
Patrik Milán Veres
Context.
Tidal disruption events (TDEs) are rare transients that provide important insights into the physics of
galactic nuclei. A recently identified feature in their optical light curves is the presence of early bump-like structures (precursors) that appear before the onset of the main
flare or during its rise. Aims. We aim to build and study the first sample of precursor TDEs in order to improve our understanding of these features, which could be key to revealing the origin of the optical emission in TDEs. Methods. We compiled all known precursor TDEs from the literature, searched for additional candidates, and analyzed them as a sample. Results. We find that precursor TDEs predominantly fall within the repeating TDE, fast TDE, and TDE in active
galactic nucleus (AGN) subclasses. We reveal a positive correlation between the occurrence time of the precursors relative to the main peak and the central black hole mass. Conclusions. We suggest that the precursors appear due to interactions between the incoming
stellar debris and the disk or leftover material from an earlier disruption (repeating and fast TDEs) or a stable pre-existing disk (TDEs in AGNs). Precursors are therefore potentially key signatures of repeating partial TDEs in previously quiescent
galaxies.
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Earth and Planetary Astrophysics
Bayesian Analysis for Remote Biosignature Identification on exoEarths (BARBIE) IV: Analyzing CO2 Detections in the Near-IR to Determine the Long-Wavelength Cut-off for the Habitable Worlds Observatory Coronagraph
Celeste Hagee, Natasha Latouf, Avi M. Mandell et al. (+3 more)
We present our analysis of how the detectability of carbon dioxide (CO2) on an Earth-like
planet varies with respect to signal-to-noise ratio (SNR), wavelength, and molecular abundance. Using the
Bayesian Analysis for Remote Biosignature Identification on exoEarths (BARBIE) methodology, we can inform the optimal long-wavelength cut-off for the future Habitable Worlds Observatory (HWO) coronagraph. We test 25 evenly-spaced 20% bandpasses between 0.8-2.0{\mu}m, and simulate data spanning a range of SNRs and molecular abundance to analyze the relationship between wavelength and detectability for different planetary archetypes. We examine abundance levels from varying Earth epochs and a Venus-like archetype to investigate how detectability would change throughout the
evolution of a rocky
planet. Here, we present our results on the planetary conditions and technological requirements to strongly detect CO2. In addition, we analyze the degeneracy of CO2 with carbon monoxide (CO), methane (CH4), and water (H2O). We determine that any abundance of CO does not achieve strong detections and that CH4 and H2O play a pivotal role in the ability to detect CO2. We conclude that the optimal long-wavelength cut-off for the Habitable Worlds Observatory coronagraph should be 1.68{\mu}m.
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All authors Celeste Hagee, Natasha Latouf, Avi M. Mandell, Michael D. Himes, Michael Dane Moore, Geronimo L. Villanueva
Earth and Planetary Astrophysics
Excitation and Damping of Oscillation Modes in Gaseous Planets
Jim Fuller, Marzia Parisi, Steve Markham et al. (+2 more)
The excitation and damping mechanisms for oscillation modes of gas
giant planets are undetermined. We show that differential rotation may greatly enhance convective viscosity in
giant planets, resulting in damping times of $t_{\rm damp} \sim 10^5-10^6 \, {\rm years}$ for f~modes and low-order p~modes. Radiative
diffusion damps p~modes on time scales of $t_{\rm damp} \sim 10^3-10^7 \, {\rm years}$. While the lethargic convective motions cannot effectively excite f~mode or p~modes, storms driven by condensation of water and/or silicates may play a role. High-order p~modes are most effectively excited by cometary/asteroid impacts. Applying these calculations to
solar system
planets, water storms, rock storms, and impacts may all contribute to exciting the observed f~modes amplitudes of Saturn via ring seismology. Similar f~mode amplitudes with fractional gravitational perturbations of $\delta \Phi/\Phi \sim 10^{-10}-10^{-9}$ are expected for Jupiter and Uranus, apart from their lowest $\ell$ f~modes which could have larger gravitational perturbations of $\delta \Phi/\Phi \sim 10^{-7}$. Rock storms may contribute to mode driving in Jupiter, while water storms are more important for Uranus. The highest-amplitude p~modes are predicted to have periods of $\sim$10-30 minutes, with surface velocities of $\sim$10 cm/s for Jupiter and Saturn, and $\sim$1 cm/s for Uranus. These oscillation modes may be detectable with radial velocity measurements, ring seismology, or spacecraft Doppler tracking. However, both the damping and excitation physics are uncertain by orders of magnitude, so more careful examination of the relevant physics is required for robust estimates.
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All authors Jim Fuller, Marzia Parisi, Steve Markham, A. James Friedson, J. R. Fuentes
Cosmology and Nongalactic Astrophysics
Sign-Switching Dark Energy: Smooth Transitions with Recent DESI DR2 Observations
Beñat Ibarra-Uriondo and Mariam Bouhmadi-López
Sign-switching dark energy provides a novel mechanism for modifying the late-time expansion history of the Universe without invoking additional fields or finely tuned initial conditions. In this work, we investigate a class of background–level cosmological models in which the dark energy contribution changes sign at a transition
redshift $z_\dagger$, producing a sharp deviation from standard $\Lambda$CDM dynamics. We confront these models with a comprehensive set of cosmological observations, including Planck 18
cosmic microwave background (CMB) measurements, DESI DR2 Baryonic Acoustic Oscillation (BAO) data and the Pantheon+ $\&$ SH0ES Type Ia
supernova sample (SN). Using a full Markov Chain Monte Carlo (MCMC) analysis, we find that the sign-switching scenario significantly alleviates the Hubble tension while obtaining better results when statistically comparing with $\Lambda$CDM, as quantified by the Akaike and
Bayesian information Criteria. Although the model is explored only at the background level, the improvement in the inferred Hubble constant demonstrates that sign-switching dark energy offers a promising and physically economical pathway toward resolving late-universe discrepancies.
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Cosmology and Nongalactic Astrophysics
An analytic approximation to the covariance between pre- and post-reconstruction galaxy two-point statistics
M. Maus, A. Baleato Lizancos, M. White et al. (+2 more)
We present a simple analytic approximation for the covariance between pre-reconstruction
galaxy power spectrum measurements and post-reconstruction two-point correlation functions. This cross-covariance is essential for joint analyses that combine full-shape clustering information with
baryon acoustic oscillation (BAO) measurements, as commonly performed in modern spectroscopic surveys. Our model builds on the disconnected contribution to the covariance and accounts for the damping of correlations due to the BAO reconstruction process. We validate our analytic prescription against numerical simulations from the Dark Energy Spectroscopic Instrument (DESI), testing both idealized cubic geometries and realistic survey configurations including complex footprints and fiber assignment effects. Despite neglecting survey window functions in the analytic calculation, we find excellent agreement with simulation-based covariances and demonstrate that cosmological parameter constraints are virtually unchanged when using our approximation. Our results show that the pre-post cross-covariance is sufficiently small that even approximate treatments are adequate for cosmological inference, opening a pathway toward fully analytic covariance
matrices for next-generation
galaxy surveys.
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All authors M. Maus, A. Baleato Lizancos, M. White, A. de Mattia, S. Chen
Astrophysics of Galaxies
A tight relation between the distribution of globular clusters and dark matter in AS1063
J.M. Diego, C. Goolsby, C.J. Conselice et al. (+1 more)
Based on deep high resolution JWST images of AS1063, and after a careful masking of artifacts, extended features in the cluster, and background
galaxies (including known lensed ones), we have identified tens of thousands of unresolved point sources in the central region of the
galaxy cluster. We extended the identification of these point sources up to 1.18 Mpc from the center of the cluster using data in the second module. Most of these sources are expected to be globular clusters orbiting in the deep potential well of the cluster, but also the surviving compact cores of satellite
galaxies. We study the distribution of the globular clusters and compared it with the distribution of mass from a lens model derived from the same JWST data. We find a very tight correlation between the two distributions, but also some differences, including a more concentrated distribution for the globular clusters than for dark matter. We explored the possibility of using the distribution of globular clusters as a proxy for the
lensing mass. We find that a simple smoothing kernel can transform the discrete distribution of point sources into a continuous two-dimensional distribution that matches well the
lensing convergence. This suggests that globular clusters can be used as tracers of the dark matter distribution in other massive clusters where gravitational
lensing constraints are scarce but globular clusters can be detected more easily, for instance in low
redshift galaxy clusters.
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All authors J.M. Diego, C. Goolsby, C.J. Conselice, J.M. Palencia
Astrophysics of Galaxies
Searching for the Shortest-wavelength Aromatic Infrared Bands: No Evidence for the Predicted 1.05 $\mu$m Polycyclic Aromatic Hydrocarbon Feature
Dennis Lee, Brandon S. Hensley, Tzu-Ching Chang et al. (+1 more)
Polycyclic aromatic hydrocarbons (PAHs) are responsible for a variety of near- and mid-infrared spectral features in
Galactic and extragalactic sources. A feature at 1.05 $\mu$m arising from electronic transitions in PAH cations is predicted by laboratory experiments but has never been observationally confirmed. We conduct a dedicated search for this feature in absorption on a highly-extinguished sight line toward BD+40 4223, a blue supergiant in Cyg OB2, using the TripleSpec spectrograph at Palomar Observatory. We place a $5\sigma$ upper limit on the feature strength of $\Delta\tau_{1.05}/A_{V} < 5.6 \times10^{-3}$, ruling out theoretical estimates with $> 10\sigma$ significance. We constrain the effective temperature of BD+40 4223 to be $\log_{10}\left(T_{\rm eff}\right)=4.41\pm0.03$ and infer that it is veiled by $6.39\pm0.05$ magnitudes of visual extinction, consistent with but more constraining than previous determinations. As
dust on the sight line toward BD+40 4223 appears typical of the diffuse interstellar medium, this non-detection challenges existing models of PAH material properties and/or charge distribution.
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All authors Dennis Lee, Brandon S. Hensley, Tzu-Ching Chang, Olivier Doré
Cosmology and Nongalactic Astrophysics
A boost in the precision of cluster-mass models: Exploiting the extended surface brightness of the lensed supernova Refsdal host galaxy
S. Schuldt, C. Grillo, A. Acebron et al. (+4 more)
Combining deep Hubble Space
Telescope (HST) images and extensive data from the Multi-Unit Spectroscopic Explorer, we present new mass models of the cluster MACS J1149.5+2223, strongly
lensing the
supernova (SN) Refsdal, fully exploiting the source surface-brightness distribution of the SN host for the first time. In detail, we incorporated 77,000 HST pixels, in addition to the known 106 point-like multiple images, in our modeling. We considered four different models to explore the effect of the relative weighting of the point-like multiple image positions and flux distribution of the SN host on the model optimization. When the SN host's extended image is included, we find that the statistical uncertainties of all 34 free model parameters are reduced by factors ranging from one to two orders of magnitude compared to the statistical uncertainty of the point-like only model, irrespective of the adopted different image weights. We quantified the remarkably increased level of precision with which the cluster's total mass and the predicted time delays of the SN Refsdal multiple image positions can be reconstructed. We also show the delensed image of the SN host, a spiral
galaxy at zSN = 1.49, in multiple HST bands. In all those applications, we obtain a significant reduction of the statistical uncertainty, which is now below the level of even the small systematic uncertainty on the mass model that could be assessed by the different approaches. These results demonstrate that with extended image models of
lensing clusters it is possible to measure the cluster's total mass distribution, the values of the cosmological parameters, and the physical properties of high-
redshift sources with an unparalleled precision, making the typically not-quantified systematic uncertainties now crucial.
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All authors S. Schuldt, C. Grillo, A. Acebron, P. Bergamini, A. Mercurio, P. Rosati, S. H. Suyu
High Energy Astrophysical Phenomena
Unraveling the Origin of Unequal Mass Gravitational Wave Events: Insights from a Galactic High Mass X-ray Binary
Neev Shah, Mathieu Renzo, Koushik Sen et al. (+2 more)
The catalog of Gravitational Wave (GW) events is rapidly growing, providing key insights into the
evolution of massive binaries and compact object formation. However, a key challenge is to explain the origin of exceptional events such as GW190814, among the most asymmetric mass-ratio mergers to date ($q\approx 0.1$). We show that it shares an evolutionary pathway with the most unequal mass
Galactic High Mass X-ray Binary (HMXB) 4U 1700-37/ HD 153919. We demonstrate this unique connection by utilizing a rich set of existing observational constraints for the HMXB and compute detailed binary
evolution models to explain its formation history. We find that conservative mass transfer, along with a directed natal kick are essential to explain its current state. We show that this system is unlikely to form a GW source due to a failed Common Envelope (CE) phase in the future, in agreement with previous work. With additional models, we show that a similar pathway naturally forms GW190814-like events, provided the first phase of mass transfer remains conservative, and the first-born (lower mass) compact object receives a large natal kick ($\gtrsim 100\,\mathrm{km/s}$) for the subsequent CE phase to be successful and form a asymmetric mass-ratio GW source. Anchored by the number of analogous
Galactic HMXBs, we estimate rates for such GW events, which broadly agree with their observed rate. Our work demonstrates a unified formation pathway for highly asymmetric mass-ratio HMXBs and GW events. Moreover, it highlights the critical role of finding and characterizing local analogs in different evolutionary phases, and using them as a bridge to understand the origin of GW sources, especially the outliers like GW190814.
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All authors Neev Shah, Mathieu Renzo, Koushik Sen, Aldana Grichener, Katelyn Breivik
Astrophysics of Galaxies
Direct pathway to the Early Supermassive Black Holes: A Red Super-Eddington Quasar in a Massive Starburst Host at $z=7.2$
Qinyue Fei, Seiji Fujimoto, Gabriel Brammer et al. (+24 more)
We present a panchromatic optical-mm characterization of GNz7q, a recently identified X-ray weak, rapidly growing red
quasar embedded within a dusty starburst
galaxy at $z=7.1899$, using the full suite of JWST/NIRCam, NIRSpec, MIRI, and archival NOEMA observations. Our deep NIRSpec/G395M spectroscopy reveals unambiguous broad Balmer emission (FWHM $=2221\pm20$kms$^{-1}$), confirming a super-Eddington accreting black hole ($\lambda_{\rm Edd}=2.7\pm0.4$) with a mass of $\log(M_{\rm BH}/M_{\odot})=7.55\pm0.34$, using
accretion-rate corrected BH mass
estimators. After subtracting the point source, we robustly detect
stellar emission from the host
galaxy across multiple NIRCam and MIRI filters. Out joint morphological-spectral analysis yields a
stellar mass of $\log (M_*/M_\odot)=10.5\pm0.4$ and an intense
star formation rate of ${\rm SFR}=330\pm97\,M_\odot\,\rm yr^{-1}$, confirming the host as a massive, dusty starburst
galaxy. We find that GNz7q lies on the local $M_{\rm BH}$-$M_*$ relation ($M_{\rm BH}/M_*\simeq 0.001$) and is well positioned to evolve into the locus of massive SDSS
quasars with $\log (M_{\rm BH}/M_\odot)\approx 9$ and $M_*\approx 10^{11}\,M_\odot$ at $z\sim 6$, owing to its remarkably rapid growth in both the black hole and its host
galaxy. This stands in stark contrast to many recently reported JWST AGN populations at similar
redshifts, including the little red dots (LRDs), whose weak or undetected
star formation makes it difficult for them to grow into the massive
galaxies hosting SDSS-like
quasars. These results suggest that GNz7q marks as a rare, pivotal phase of early BH-
galaxy co-eolution, plausibly providing a crucial direct pathway to the supermassive black hole systems within the first billion years of the Universe.
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All authors Qinyue Fei, Seiji Fujimoto, Gabriel Brammer, Ruancun Li, Luis C. Ho, Volker Bromm, Javier Álvarez-Márquez, Yoshihisa Asada, Guillermo Barro, Luis Colina, Pratika Dayal, Steven L. Finkelstein, Johan P.U. Fynbo, Michele Ginolfi, Kohei Inayoshi, Vasily Kokorev, Gene C. K. Leung, Jorryt Matthee, Romain A. Meyer, Rohan P. Naidu, Masafusa Onoue, Pablo G. Pérez-González, Charles L. Steinhardt, Francesco Valentino, Fabian Walter, Mengyuan Xiao, Haowen Zhang
Astrophysics of Galaxies
What Suppresses Star Formation in Bulge-Dominated Early-Type Galaxies?
Lori E. Porter, S. M. R. Jeffreson, Greg L. Bryan et al. (+1 more)
We investigate the physical origin of
star formation suppression in gas-rich early-type
galaxies using five high-resolution hydrodynamical idealized
galaxy simulations, performed with the moving-mesh code AREPO. These simulations include one Milky Way-like
galaxy and four early-type
galaxies, of which one early-type
galaxy is found to have significantly less
star formation despite a substantial molecular gas reservoir. We apply a modified virial
theorem to the overdensities in each
galaxy to quantify the forces regulating their stability and thus
star formation. We find evidence that, in the suppressed
galaxy, strong Coriolis forces driven by elevated
galactic shear may inhibit gravitational collapse. This is caused by the
galaxy's high central compactness, providing a physical mechanism for the suppression of
star formation that does not require the removal of molecular gas. In contrast, less compact early-type
galaxies host more
gravity-dominated clouds and therefore exhibit higher
star formation rates. However, we find that this gravitational stability occurs without significantly increasing the classical Toomre-Q parameter, and therefore a new criterion for suppressed
star formation may be needed. We also discuss the impact of our choice of overdensity scale and connections to observations of molecular clouds.
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All authors Lori E. Porter, S. M. R. Jeffreson, Greg L. Bryan, Lars Hernquist
Instrumentation and Methods for Astrophysics
GAMERA-OP: A three-dimensional finite-volume MHD solver for orthogonal curvilinear geometries
Hongyang Luo, Binzheng Zhang, Jiaxing Tian et al. (+6 more)
We present GAMERA-OP (Orthogonal-Plus), a three-dimensional finite-volume magnetohydrodynamics (MHD) solver for orthogonal curvilinear geometries. The solver advances
magnetic fields using constrained transport to preserve $\nabla\!\cdot\!\mathbf{B}=0$ to machine precision and employs geometry-consistent high-order reconstruction with an enhanced Partial Donor
Cell method (e-PDM) that accounts for geometry
curvature. Flexible numerics include various numerical fluxes and time integrators. In axial symmetric coordinates, angular momentum are preserved to round-off, and a ring-averaging treatment near the axis relaxes CFL constraints while maintaining divergence-free
magnetic fields. Optional capabilities include the semi-relativistic (Boris) correction, background-field splitting, and an anisotropic MHD formulation. Rewritten in C, the code adopts a modular design that simplifies case setup and facilitates the addition of physics modules and coupling to other first-principles codes. Standard
benchmarks across multiple geometries verify the code's high accuracy, low numerical
diffusion, and robust handling of coordinate singularities and rotating flows. GAMERA-OP provides a practical, high-order framework for space and astrophysical
plasma applications where orthogonal curvilinear coordinates and exact angular-momentum conservation are advantageous.
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All authors Hongyang Luo, Binzheng Zhang, Jiaxing Tian, Jinshu Cai, Junjie Chen, Enhao Feng, Zhiqi Zheng, Sheng Xi, John G. Lyon
High Energy Astrophysical Phenomena
Ubiquitous yet forgotten: broad absorptions in the optical spectra of low-mass X-ray binaries
D. Mata Sanchez, T. Munoz-Darias, J. Casares et al. (+2 more)
Optical outburst spectra of low-mass X-ray binaries enable studies of extreme
accretion and ejection phenomena. While some of their spectroscopic features have been analysed in detail, the appearance of broad absorptions in the optical regime has been traditionally neglected. In this work, we introduce the first population study dedicated to these features with the aim to understand their fundamental properties and discuss them in the context of their origin. We complement the study with a spectroscopic database of six low-mass X-ray binaries during outburst, in order to assess their
evolution. We find that broad absorptions are ubiquitous, with the majority of black hole low-mass X-ray binaries exhibiting them in spite of a typically scarce outburst coverage. Their detection does not depend on the orbital inclination or the compact object nature, but they seem favoured in systems with orbital periods shorter than < 11 h. They predominantly occur in the hydrogen Balmer series, being stronger at shorter wavelengths, and they are detected across all X-ray states. We find that the normalised depth of these broad absorptions is anti-correlated with the system luminosity, and that they show constant line ratios over the whole sample. Based on these properties, we favour a scenario where BAs arise from a stable, optically thick layer of the
accretion disc, below the hotter chromosphere-like region producing the emission line components. Our study is consistent with the continuous presence of broad absorptions during the whole outburst, with their visibility being conditioned by the emission lines filling the broad absorption profile and veiling by the X-ray reprocessed continuum.
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All authors D. Mata Sanchez, T. Munoz-Darias, J. Casares, M. A. P. Torres, M. Armas Padilla
Cosmology and Nongalactic Astrophysics
Reionization Bubbles from Real-Space Cross Correlations of Line Intensity Maps
Emilie Thélie, Sarah Libanore, Yonatan Sklansky et al. (+2 more)
We propose a new way to reconstruct the ionized-bubble size distribution during the Epoch of Reionization (EoR) through the real-space cross-correlation of 21-cm and
star-forming line-intensity maps. Understanding the
evolution and timing of the EoR is crucial for both astrophysics and cosmology, and a wealth of information on the first sources can be extracted from the study of ionized bubbles. Nevertheless, directly mapping bubbles is challenging due to the high
redshifts involved, possible selection biases, and foregrounds in 21-cm maps. Here, we exploit the real-space cross-correlation $\xi_{21,\nu}$ between 21-cm and line-intensity mapping (LIM) signals to reconstruct the
evolution of bubble sizes during reionization. For the first time, we show that $\xi_{21,\nu}(r)$ departs from a saturation level for each separation $r$ when bubbles of size $r$ begin to form, providing a handle for the onset of bubbles of each radius. Moreover, we demonstrate that $\xi_{21,\nu}$ evolves from positive to negative as the EoR progresses, reaching a minimum (i.e. maximum anti-correlation) when bubbles of radius $r$ reach peak abundance. We show that these results are robust to changes in the astrophysical model as well as the timing/
topology of reionization. This real-space observable complements usual
Fourier-space
estimators by capturing the localized nature of bubbles, offering new insights into the sources driving
cosmic reionization.
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All authors Emilie Thélie, Sarah Libanore, Yonatan Sklansky, Julian B. Muñoz, Ely D. Kovetz
High Energy Astrophysical Phenomena
The Wandering Supermassive Black Hole Powering the off-nuclear TDE AT2024tvd
M. Guolo, A. Mummery, S. van Velzen et al. (+11 more)
We present an analysis of the spectral energy distribution (SED) of the off-
nuclear tidal disruption event (TDE) AT2024tvd during its late-time plateau phase, combining X-ray spectra and UV/optical photometry. Using a fully relativistic, compact
accretion disk model with self-consistent inner-disk Comptonization, we reproduce the observed SED without significant residuals. The inferred black hole mass ${\rm log}{10}(M{\bullet}/M_\odot) \approx 6.0 \pm 0.2$, and the inferred disk parameters place AT2024tvd within known TDE-disk scaling relations ($L_{\rm bol}^{\rm disk}/L_{\rm Edd} \propto T_{\rm p}^4 \propto M_{\bullet}^{-1}$, $L_{\rm plat} \propto M_{\bullet}^{2/3}$, $R_{\rm out}/r_{\rm g} \propto M_{\bullet}^{-2/3}$). Our results show that: (i) there is no detected
star cluster or
dwarf galaxy associated with the source, down to a mass limit of $\log_{10}(M_{\rm gal}/M_{\odot}) \leq 7.6$; (ii) the black hole is a wandering supermassive, rather than intermediate-mass, black hole; and (iii) the source represents an extreme case of black hole-to-host mass ratio, with $M_{\bullet}/M_{\rm gal} > 3\%$, consistent with a heavily tidally stripped
nucleus. The latter aligns with cosmological simulations predicting that surviving host remnants of most wandering black holes should not retain a detectable
stellar overdensity when located at small
halo-centric distances. We discuss differences with previous analyses of this source and highlight why our modeling approach provides a more physically consistent solution with more reliable parameter inference.
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All authors M. Guolo, A. Mummery, S. van Velzen, M. Nicholl, S. Gezari, Y. Yao, K. C. Chambers, T. de Boer, M. E. Huber, C.-C. Lin, T. B. Lowe, E. A. Magnier, G. Paek, R. Wainscoat
Cosmology and Nongalactic Astrophysics
The Dark Side of the Moon: Listening to Scalar-Induced Gravitational Waves
D. Blas, J. W. Foster, Y. Gouttenoire et al. (+4 more)
The collapse of large-amplitude
primordial curvature perturbations into planetary-mass
primordial black holes generates a scalar-induced gravitational wave background in the $\mu $Hz frequency range that may be detectable by future Lunar
Laser Ranging and Satellite
Laser Ranging data. We derive projected constraints on the
primordial black hole population from a null detection of
stochastic gravitational wave background by these experiments, including the impact of the standard model electroweak phase transition on the abundance of planetary-mass
primordial black holes. We also discuss the connection between the obtained projected constraints and the recent microlensing observations by the HSC collaboration of the Andromeda
Galaxy.
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All authors D. Blas, J. W. Foster, Y. Gouttenoire, A. J. Iovino, I. Musco, S. Trifinopoulos, M. Vanvlasselaer
Cosmology and Nongalactic Astrophysics
Status of the $S_8$ Tension: A 2026 Review of Probe Discrepancies
Ioannis Pantos and Leandros Perivolaropoulos
The parameter $S_8 \equiv \sigma_8 (\Omega_m/0.3)^{0.5}$ quantifies the amplitude of matter density fluctuations. A persistent discrepancy exists between early-universe CMB observations and late-universe probes. This review assesses the “$S_8$ tension” against a new 2026 baseline: a unified “Combined CMB” framework incorporating Planck, ACT DR6, and SPT-3G. This combined analysis yields $S_8 = 0.836^{+0.012}_{-0.013}$, providing a higher central value and reduced uncertainties compared to Planck alone. Compiling measurements from 2019–2026, we reveal a striking bifurcation: DES Year 6 results exhibit a statistically significant tension of $2.4\sigma$–$2.7\sigma$ in $S_8$ \citep{DESY6}, whereas KiDS Legacy results demonstrate statistical consistency at $<1\sigma$ \citep{Wright2025}. We examine systematic origins of this dichotomy, including photometric
redshift calibration, intrinsic
alignment modeling, and shear measurement pipelines. We further contextualize these findings with cluster counts (where eROSITA favors high values while SPT favors low),
galaxy-
galaxy lensing, and
redshift-space distortions. The heterogeneous landscape suggests survey-specific systematic effects contribute substantially to observed discrepancies, though new physics beyond $\Lambda$CDM cannot be excluded.
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Cosmology and Nongalactic Astrophysics
Extending the Cosmological Collider: New Scaling Regimes and Constraints from BOSS
Daniel Green, Jiashu Han and Benjamin Wallisch
Primordial non-Gaussianity generated by additional fields during inflation offers a compelling observational target. Heavy fields imprint characteristic oscillatory signals in non-Gaussian correlation functions of the inflaton, a process sometimes referred to as cosmological-
collider physics. These distinct signatures are compelling windows into ultra-high-energy physics, but are often suppressed, making standard equilateral non-Gaussianity the most promising discovery channel in many scenarios. In this paper, we show that direct couplings between the inflaton and additional fields can lead to a wide variety of novel, observationally relevant signals which open new parameter regimes that simultaneously exhibit the characteristics of light and heavy fields. We identify these
primordial signatures in the late-time observables of the large-scale structure of the Universe, where they most significantly modify the scale-dependent bias of the
galaxy power spectrum to include an oscillatory modulation around a non-trivial power law. We explore the full range of parameters that phenomenologically arise in these models and study the sensitivity of current and future
galaxy surveys, finding that this new class of
primordial non-Gaussianity is particularly accessible in near-term surveys due to its oscillatory feature. Finally, we perform an analysis of existing data from the final release of the
Baryon Oscillation Spectroscopic Survey (BOSS DR12). While we find no evidence for a signal, we demonstrate significant improvements in sensitivity over respective non-oscillatory scenarios and place the first constraints on this extended parameter space of oscillatory non-Gaussianity.
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Earth and Planetary Astrophysics
Oxygen left behind: Atmospheric Enrichment due to Fractionation in Sub-Neptunes using BOREAS
Marilina Valatsou, Caroline Dorn, Pierlou Marty et al. (+1 more)
The
evolution of exoplanetary atmospheres is strongly influenced by atmospheric escape, particularly for close-in
planets. Fractionation during atmospheric loss can preferentially remove lighter elements such as hydrogen, while retaining heavier species like oxygen. In this study, we investigate how and under what conditions hydrodynamic escape and chemical fractionation jointly shape the mass and composition of
exoplanet atmospheres, especially for mixed H2 + H2O atmospheres. We develop BOREAS, a self-consistent mass loss model coupling a 1D Parker wind formulation with a mass-dependent fractionation scheme, which we apply across a range of
planet masses, radii,
equilibrium temperatures, and incident XUV fluxes, allowing us to track hydrogen and oxygen escape rates at different snapshots in time. We find that oxygen is efficiently retained over most of the parameter space. Significant oxygen loss occurs under high incident XUV fluxes, while at intermediate fluxes oxygen loss is largely confined to low-
gravity planets. Where oxygen is retained, irradiation is too weak to drive significant escape of hydrogen and thus limiting atmospheric enrichment. By contrast, our model predicts that sub-Neptunes undergo substantial atmospheric enrichment over approx. 200 Myr when hydrogen escape is efficient and accompanied by partial oxygen entrainment. Notably, our results imply that sub-Neptunes near the radius valley can evolve into water-rich
planets, in agreement with GJ 9827 d. Present-day water-rich atmospheres may have originated from water-poor envelopes under some conditions, highlighting the need to include chemical fractionation in
evolution models. BOREAS is publicly available.
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All authors Marilina Valatsou, Caroline Dorn, Pierlou Marty, James E. Owen