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Papers

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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 3 January

Earth and Planetary Astrophysics · Cross-listed from eess.SY

Compensating Star-Trackers Misalignments with Adaptive Multi-Model Estimation

Ridma Ganganath, Simone Servadio and David Daeyoung Lee

This paper presents an adaptive multi-model framework for jointly estimating spacecraft attitude and star-tracker misalignments in GPS-denied deep-space CubeSat missions. A Multiplicative Extended Kalman Filter (MEKF) estimates attitude, angular velocity, and gyro bias, while a Bayesian Multiple-Model Adaptive Estimation (MMAE) layer operates on a discrete grid of body-to-sensor misalignment hypotheses. In the single-misalignment case, the MEKF processes gyroscope measurements and TRIAD-based attitude observations, and the MMAE updates a three-dimensional grid over the misalignment vector. For a dual-misalignment configuration, the same MEKF dynamics are retained, and the MMAE bank is driven directly by stacked line-of-sight measurements from two star trackers, forming a six-dimensional grid over the two misalignment quaternions without augmenting the continuous-state dimension. A novel diversity metric, $\Psi$, is introduced to trigger adaptive refinement of the misalignment grid around a weighted-mean estimate, thereby preventing premature collapse of the model probabilities and concentrating computation in the most likely region of the parameter space. Monte Carlo simulations show arcsecond-level misalignment estimation and sub-degree attitude errors for both estimation problems, with estimation errors remaining well-bounded, proving robustness and consistency. These results indicate that the proposed MEKF–MMAE architecture enables accurate, autonomous, and computationally efficient in-flight calibration for resource-constrained spacecraft, and establishes dual star-tracker misalignment estimation as a practical option for deep-space CubeSat missions.
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Astrophysics of Galaxies

Chemical enrichment in the Ophiuchus cluster core studied by high-resolution XRISM spectroscopy

Kotaro Fukushima, Yutaka Fujita, Kosuke Sato et al. (+2 more)

Galaxy clusters provide an ideal laboratory for investigating the chemical enrichment history of the universe because they host the hot intracluster medium (ICM), which contains various chemical elements. The X-ray observations have constituted a unique way to measure the element abundance and composition of the ICM due to their prominent emission lines in the 0.1-10 keV range. We explore the metal abundances and chemical enrichment in the cool-core galaxy cluster, Ophiuchus, by using a 217 ks XRISM data set. The abundances of Si, S, Ar, Ca, Cr, Mn, Fe, and Ni are accurately determined using high-resolution spectroscopy. We find that the average uncertainties of chemical composition, which are reported as X/Fe ratios, are only 10-20%. The X/Fe abundance pattern of the Ophiuchus centre is remarkably consistent with solar, which is reminiscent of the Hitomi constraint on the Perseus core. The observed abundance pattern can be replicated globally by linear combination models of core-collapse, including massive progenitors, and Type Ia supernovae. While nucleosynthesis models typically underestimate the Ca/Fe ratio, a substantial contribution of Ca-rich gap transients may help improve the deficit of Ca. High-resolution spectroscopic data can enable us to estimate the underlying impact on the chemical enrichment from subclasses of Type Ia supernovae.
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All authors Kotaro Fukushima, Yutaka Fujita, Kosuke Sato, Yasushi Fukazawa, Marie Kondo

Astrophysics of Galaxies

Exploring the formation mechanisms of tidal structures in globular clusters of extragalactic origin

Shouzhi Wang, Jundan Nie, Biwei Jiang et al. (+3 more)

Tidal structures around globular clusters provide valuable insights into cluster evolution and the hierarchical assembly of the Milky Way. Using wide-field imaging data from the DESI Legacy Survey combined with a color-magnitude matched-filter technique, we perform a systematic analysis of extra-tidal features in 28 Galactic globular clusters of likely extragalactic origin, representing the largest homogeneous sample examined in this context to date. The clusters display diverse morphologies: 12 exhibit tidal tails, 9 show diffuse envelopes, and 7 reveal no clear extra-tidal features. Notably, we report the first detection of an extended tidal structure around the Sagittarius-associated cluster Terzan 7. To explore the underlying drivers, we compare intrinsic properties, orbital dynamics, and possible accretion associations across morphological groups. From the parameter distributions, complemented by Kolmogorov-Smirnov tests, we find that total mass, escape velocity, concentration, tidal filling factor, pericentric radius, eccentricity and radial angle in action-angle coordinates are all likely group-sensitive parameters. These results suggest that both internal cluster properties and orbital configurations play important roles in shaping extra-tidal morphologies. In addition, the cluster's accretion history shows no clear correlation with the presence of tidal features, indicating that it is not a direct driver of outer structure formation. Overall, the diversity of tidal structures is unlikely to be governed by a single factor, but instead reflects the interplay between internal dynamical evolution and the external Galactic environment. This study provides the most comprehensive constraints so far on the physical processes driving extra-tidal structures in accreted globular clusters.
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All authors Shouzhi Wang, Jundan Nie, Biwei Jiang, Hao Tian, Chao Liu, Ying-Hua Zhang

Cosmology and Nongalactic Astrophysics · Cross-listed from cond-mat.quant-gas

Ground State and Collective Modes of Bose-Einstein Condensates in Newtonian and MOND-inspired gravitational potentials

Ning Liu

We analytically and numerically study the ground state and collective dynamics of Bose-Einstein condensates in two traps: a Newtonian potential and a logarithmic potential inspired by Modified Newtonian Dynamics (MOND). In the ground state, the MOND potential supports bound states only in the deep-MOND regime, where the condensate becomes significantly larger than its Newtonian counterpart. The size increases with repulsive coupling parameter $\beta$ in both potentials. A clear scaling law of the size with $\beta^{1/3}$ emerges in the MOND case and is confirmed numerically over a wide parameter range, while for the Newtonian potential no simple scaling law exists as the Thomas-Fermi approximation ceases to be valid. For the dynamics, we derive and solve equations for the monopole collective mode. The larger MOND-bound condensate oscillates at a lower frequency, which scales as $\beta^{-1/3}$ in the strong-interaction limit. These scaling laws provide insights for quantum-simulation experiments aiming to probe modified-gravity scenarios with cold atoms.
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Cosmology and Nongalactic Astrophysics

Testing supermassive primordial black holes with lensing signals of binary black hole merges

Huan Zhou, Bin Liu, Zheng-Xiang Li et al. (+2 more)

Next-generation ground-based gravitational wave (GW) detectors are expected to observe millions of binary black hole mergers, a fraction of which will be strongly lensed by intervening galaxies or clusters, producing multiple images with characteristic distribution of time delay. Importantly, the predicted rate and properties of such events are sensitive to the abundance and distribution of strong lensing objects which directly depends on cosmological models. One such scenario posits the existence of supermassive primordial black holes (SMPBHs) in the early universe, which would enhance the formation of dark matter halos. This mechanism has been proposed to explain the abundance of high-redshift galaxies observed by James Webb Space Telescope. Crucially, the same cosmological model with SMPBHs would also leave a distinct imprint on the population of strongly lensed GWs. It predicts both an increased event rate and a modified distribution of time delays between the multiple images. Therefore, we propose statistical measurements of the rate and time delay distribution of strong lensing GW events as a powerful probe to directly constrain the abundance of SMPBHs. Considering $\Lambda$CDM cosmology with (non-)clustered SMPBHs, we find that the abundance of SMPBHs $f_{\rm PBH}$ with masses above $10^8~M_{\odot}$ is constrained to be $\sim10^{-4}$ at $95\%$ confidence level. It will be comparable and complementary to the currently available constraint from large scale structure observations.
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All authors Huan Zhou, Bin Liu, Zheng-Xiang Li, Xi-Jing Wang, Kai Liao

Astrophysics of Galaxies

The internal kinematics of local young stellar associations. Identifying correlations among age, expansion, rotation, and shear

J. Olivares, N. Miret-Roig and P.A.B. Galli

Context. The local (<200 pc away) young (<50 Myr old) stellar associations (LYSA) provide fundamental evidence for the study of the star formation process in the local neighbourhood. Aims. We aim at exploring robust statistical correlations in the internal kinematics of LYSAs and of these with age. Methods. We analyse a public data set containing the linear velocity field parameters and expansion ages of 18 LYSAs. We identify the most robust correlations using frequentist and Bayesian methods. Results. Among the 45 correlations, we identify only four that passed both frequentist and Bayesian criteria, with these four related to radial motions in the Galactic Z direction. We hypothesise several origins for these four correlations and identify the gravitational potential of the Galactic disk as the most likely driving element. It imprinted the observed motions in the parent molecular clouds, and once the stars were formed, it also damped these motions on a timescale shorter than the LYSAs' ages. Conclusions. The internal kinematics of local young stellar associations contain fundamental information about the star-formation process that is not fully addressed by star-formation theories, in particular, rotation and shear. Although the Galactic potential appears to be the driving force of these correlations, we urge the theoretical community to provide predictions about the internal motions of expansion, rotation, and shear of stellar associations.
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Friday 2 January

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

From the Wavefunction of the Universe to In-In-Correlators: A Perturbative Map to All Orders

Gonzalo A. Palma

Both the Wavefunction of the Universe and the Schwinger-Keldysh in-in formalism are central tools for analyzing primordial cosmological observables, such as equal-time correlation functions. While their conceptual equivalence is well established, a systematic and explicit map between their diagrammatic expansions has remained elusive. In this article, I construct such a map by analyzing the relation between the two frameworks at the diagrammatic level. I show that diagrams contributing to correlation functions in the Wavefunction of the Universe approach can be uniquely reorganized into Schwinger-Keldysh diagrams. This correspondence holds to all orders in perturbation theory, including arbitrary numbers of interaction vertices and loops.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Cosmological redshift of a Schwarzschild-de Sitter black hole: Towards estimating the Hubble constant

Deborah Villaraos, Alfredo Herrera-Aguilar, Mehrab Momennia et al. (+1 more)

In this work we estimate the parameters of several astrophysical black holes hosted at the core of active galactic nuclei by studying the kinematics of test objects in their accretion disk. First, we derive expressions for the redshift and blueshift of photons emitted by a massive particle circularly orbiting a Schwarzschild-de Sitter black hole, and detected by a distant receding observer. The frequency-shift depends on the mass and distance of the black hole, the orbital radius of the photon source, as well as the Hubble constant, directly relating these quantities to astrophysical observables, namely, the redshift and the angular position of the emitting particle on the sky. We apply for the first time this theoretical model, which accounts for the universe expansion through the Schwarzschild-de Sitter metric, to real astrophysical systems using megamaser galaxies within the Hubble flow, namely UGC 3789, NGC 5765b, NGC 6264, NGC 6323, and CGCG 074-064. Bayesian inference based on Markov Chain Monte Carlo methods is employed to estimate the mass-to-distance ratio, the product of the Hubble constant with the distance, and the black hole angular position. Additionally, by assuming a Gaussian prior on the Hubble constant, the mass, distance, and the Hubble constant are also estimated. Furthermore, we find that cosmic expansion is embedded in the gravitational contribution of the frequency-shift within this spacetime metric. Therefore, our results introduce a general relativistic framework that accounts for cosmic expansion and differs from the standard empirical Hubble law.
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All authors Deborah Villaraos, Alfredo Herrera-Aguilar, Mehrab Momennia, Ulises Nucamendi

Instrumentation and Methods for Astrophysics

Real-Time Multi-Mode Post-Merger Gravitational Wave Detection using Convolutional Neural Networks: Methodology Development for Third-Generation Detectors

Roo Weerasinghe

The detection and characterization of post-merger gravitational wave signals from binary neutron star mergers remains challenging with current ground-based detectors. We present a convolutional neural network framework designed for real-time detection and multi-mode frequency extraction of post-merger signals, achieving an inference latency of 3.0 ms and a frequency accuracy of 48.6 Hz on the direct-comparison subsets (53 Hz on the comprehensive test set). The framework is validated on realistic LIGO O4 detector noise including authentic GravitySpy glitch morphologies, demonstrating ROC AUC of 0.999999 and 99.998% detection efficiency at 1% false alarm rate. These exceptional performance metrics arise from an aggressive training augmentation strategy that exposes the network to artificially challenging conditions, enabling robust generalization to our synthetic O4 detector noise model. We compare performance against a simplified matched filtering baseline using Lorentzian templates (23x more accurate despite a 4.7x computational overhead) and Bayesian parameter estimation (1.2 million times faster), establishing complementary trade-offs in the analysis landscape. While current O4 sensitivity limits post-merger detections to ~20 Mpc (~1 detection per century), this methodology provides essential infrastructure for third-generation detectors (Einstein Telescope, Cosmic Explorer) where post-merger detection will become routine with annual detection rates exceeding 100 events. Our validation framework identifies expected behavior in uncertainty scaling that reflects realistic training constraints rather than idealized Fisher information limits, demonstrating honest assessment practices for machine learning applications in gravitational wave astronomy.
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High Energy Astrophysical Phenomena · Cross-listed from hep-th

Graviton Photoproduction by a Kerr-Newman Black Hole with Worldline EFT

Qinyuan Zheng

We present the first computation of the gauge-invariant, long-wavelength scattering amplitude for the graviton photoproduction by a Kerr-Newman black hole through $\mathcal{O}\big((\omega m)^2\big)$, or correspondingly $\mathcal{O}(S^2)$, and to linear order in $G$, using the worldline effective field theory. We show that electromagnetic interactions can be introduced consistently into the spinning worldline theory while preserving spin gauge invariance. We also derive the full angular dependence of the conversion cross section through $\mathcal{O}(S^2)$, and demonstrate that the relevant Wilson coefficients at this order are fixed entirely by matching the electromagnetic and gravitational multipole moments to the Kerr-Newman solution. This result provides a benchmark for future analyses of coupled gravitoelectromagnetic scattering in spinning, charged compact-object backgrounds.
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High Energy Astrophysical Phenomena

Spectral Analysis of the 2019 and 2022 Outbursts of SAX J1808.4-3658

Katherine Bruce, Sachiko Tsuruta, Andrew C. Liebmann et al. (+1 more)

The accreting millisecond pulsar SAX J1808.4-3658 went into outburst from July to November in 2019 and August to October in 2022, which were observed by NICER and NuSTAR. In this paper, we first present the light curve for both outbursts using NICER data. Several thermonuclear bursts occurred during these outbursts. We analyze the evolution of the spectra of two thermonuclear bursts that took place during the 2019 NuSTAR observation. We proceed by analyzing the combined broad-band spectrum using NICER and NuSTAR for the first time for this source. We jointly modeled the combined quiescent spectra of both outbursts with a self-consistent reflection component. In our best-fit model, we find evidence of reflection, consistently constrain the inclination to 72\deg$^{+1\deg}_{-4\deg}$\, considering this reflection, and identify a 1 keV feature during persistent emission.
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All authors Katherine Bruce, Sachiko Tsuruta, Andrew C. Liebmann, Marcus Teter

Instrumentation and Methods for Astrophysics

thornado+Flash-X: A Hybrid DG-IMEX and Finite-Volume Framework for Neutrino-Radiation Hydrodynamics in Core-Collapse Supernovae

Eirik Endeve, Vassilios Mewes, J. Austin Harris et al. (+15 more)

We present neutrino-transport algorithms implemented in the toolkit for high-order neutrino-radiation hydrodynamics (thornado) and their coupling to self-gravitating hydrodynamics within the adaptive mesh refinement (AMR)-based multiphysics simulation framework Flash-X. thornado, developed primarily for simulations of core-collapse supernovae (CCSNe), employs a spectral, six-species two-moment formulation with algebraic closure and special-relativistic observer corrections accurate to $O(v/c)$, and uses discontinuous Galerkin (DG) methods for phase-space discretization combined with implicit-explicit time stepping. A key development is a nonlinear neutrino-matter coupling algorithm based on nested fixed-point iteration with Anderson acceleration, enabling fully implicit treatment of collisional processes, including energy-coupling interactions such as neutrino-electron scattering and pair production. Coupling to finite-volume (FV) hydrodynamics is achieved with a hybrid DG-FV representation of the fluid variables and operator-split evolution in Flash-X. The implementation is verified using basic transport tests with idealized opacities and relaxation and deleptonization problems with tabulated microphysics. Spherically symmetric CCSN simulations demonstrate accuracy and robustness of the coupled scheme, including close agreement with the CCSN simulation code Chimera. An axisymmetric CCSN simulation further demonstrates the viability of DG-based neutrino transport for multidimensional supernova modeling within Flash-X. thornado's neutrino-transport solver is GPU-enabled using OpenMP offloading or OpenACC, and all CCSN applications included in this work use the GPU implementation. Together, these results establish a foundation for future enhancements in physics fidelity, numerical algorithms, and computational performance, for increasingly realistic large-scale CCSN simulations.
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All authors Eirik Endeve, Vassilios Mewes, J. Austin Harris, M. Paul Laiu, Ran Chu, Steven A. Fromm, Anthony Mezzacappa, O. E. Bronson Messer, W. Raphael Hix, Stephen W. Bruenn, Eric J. Lentz, Klaus Weide, Christian Y. Cardall, Ann S. Almgren, Anshu Dubey, Sean M. Couch, Philipp Moesta, Donald E. Willcox

Instrumentation and Methods for Astrophysics

Website with interactive visualization of multivariate astronomical time series

M. Volkov, M. Demianenko, D. Matveev et al. (+2 more)

Light curves represent astronomical time series of flux measured across one or more photometric bands. With the rapid growth of large-scale sky surveys, time-domain astronomy has become an essential area of modern astrophysical research. Interactive visualization of extensive light-curve datasets plays a key role in exploring transient phenomena and in planning large follow-up campaigns. In this work, we introduce two web-based platforms designed for interactive light-curve visualization: Fulu, for transient event studies, and VALC, for investigations of low-mass active galactic nuclei (AGNs). These tools provide a user-friendly interface for examining, comparing, and interpreting vast collections of astronomical light curves, supporting scientific discovery.
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All authors M. Volkov, M. Demianenko, D. Matveev, K. A. Grishin, I. V. Chilingarian

Earth and Planetary Astrophysics

A comprehensive study of the relations between the properties of planetary systems and the chemical compositions of their host stars

Luan Ghezzi, Ellen Costa-Almeida, Verónica Loaiza-Tacuri et al. (+1 more)

The giant planet-metallicity correlation revealed that planetary formation depends on the stellar properties. There is growing evidence that it is also valid for smaller hot planets, but it is not clear whether elements other than iron also influence the properties of planetary systems. To investigate this, we determined the abundances of 13 chemical elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni and Cu) for a sample of 561 Kepler exoplanet-hosting stars using high-resolution Keck/HIRES spectra. We find that stars in systems having only large or hot planets are enriched in some elements relative to those having only small or warm planets, respectively, with this signature being related to the underlying stellar metallicity. This Kepler sample is composed of stars belonging to the Galactic low- and high-$\alpha$ sequences, corresponding to the chemical thin and thick disks. Our results reveal that stars enhanced in $\alpha$-elements may facilitate the formation of large planets in metal-poor environments although the iron abundance is still a limiting factor. We also investigated chemical abundances as a function of elemental condensation temperatures and found that there is a diversity of slopes regardless of the exoplanetary systems hosted by the star. We confirmed that the Sun is depleted in refractory elements relative to the solar twins in our sample, all of which host a diversity of exoplanets, suggesting that this depletion is caused by processes not related to planet formation.
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All authors Luan Ghezzi, Ellen Costa-Almeida, Verónica Loaiza-Tacuri, Katia Cunha

Astrophysics of Galaxies

GA-NIFS: AGN activity in a Ly{\alpha} emitter within a triple-AGN system anchored by a passive galaxy at z=3

Michele Perna, Santiago Arribas, Mahmoud Hamed et al. (+15 more)

Massive quenched galaxies at z>3 challenge models of early galaxy evolution, as their rapid formation and abrupt quenching require efficient feedback, often linked to active galactic nuclei (AGN). The quiescent galaxy GS10578 at z=3.1 is a key example of this population. Previous JWST/NIRSpec IFU data revealed an AGN outflow and uncovered a compact pair of AGN separated by ~5 kpc. In addition, VLT/MUSE spectroscopy has identified a third AGN candidate at a projected distance of ~30 kpc, associated with a luminous Lya emitter (LAE2) characterised by high-ionisation UV lines, although rest-frame optical diagnostics were not previously available. We aim to confirm the nature of LAE2 using rest-frame optical diagnostics enabled by new JWST data, and to characterise the physical and ionisation properties of both LAE2 and a distinct nearby Lya emitter (LAE1) that lacks any detectable continuum counterpart. We analyse new NIRSpec IFU observations targeting the optical nebular lines of LAE1 and LAE2, complemented with MUSE data, as part of the GA-NIFS project. We extract integrated and spatially resolved spectra, construct emission-line maps, and use standard diagnostic diagrams to determine ionisation sources and kinematics. LAE2 exhibits line ratios fully consistent with an embedded AGN. Its optical lines display a clumpy morphology and irregular kinematics on sub-kpc scales. Except for Lya, LAE1 remains undetected in all nebular lines and in JWST imaging. The similarity of the LAE1 and LAE2 Lya profiles in both velocity and flux suggests that LAE1 traces resonantly scattered emission rather than in-situ star formation. Our analysis reveals that the environment of GS10578 contains both multi-black-hole activity and gas structures on tens-of-kpc scales, offering new insights into how feedback and satellite interactions influence the late evolutionary stages of quenched massive galaxies.
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All authors Michele Perna, Santiago Arribas, Mahmoud Hamed, Francesco D'Eugenio, J. Andrew Bunker, Stefano Carniani, Stéphane Charlot, Roberto Maiolino, Bruno Rodríguez Del Pino, Hannah Übler, Torsten Böker, Elena Bertola, Giovanni Cresci, Isabella Lamperti, Giacomo Venturi, Michele Ginolfi, Montserrat Villar Martín, Sandra Zamora

Astrophysics of Galaxies

Widespread Extended [CII] Emission in High-Redshift Galaxies: Insights from the FIRE-2 Cosmological Zoom-in Simulations

Lun-Jun Liu, Guochao Sun, Andreas L. Faisst et al. (+2 more)

Recent ALMA observations reveal diffuse [CII] emission ("[CII] halos") extending to $\sim 10\,$kpc in galaxies at $4 < z < 6$. These measurements provide new insights into high-redshift galactic ecosystems and processes that drive metal enrichment on inner circumgalactic scales. To better understand the nature of [CII] halos, we analyze a suite of high-redshift FIRE-2 simulations at $5 \leq z \leq 6$ in the stellar mass range of $10^{9}$–$10^{10.5}\,M_{\odot}$. By post-processing these simulations with three-dimensional dust radiative transfer and photoionization modeling, we generate synthetic images of [CII] and UV continuum emission, from which we extract one-dimensional surface brightness profiles. Our results reproduce both the galaxy-integrated and spatial distribution of [CII] and UV emission, capturing in particular the more extended profile of [CII] emission. Comparing the time evolution of [CII] halos with bursty star formation histories of the simulated galaxies, we find that [CII] emission becomes more spatially extended following the decline of star formation rate in recent starburst episodes. This implies a strong correlation between extended [CII] emission and bursty star formation, consistent with a key role for star formation-driven outflows in producing [CII] halos – though the kinematics of [CII]-emitting gas suggest that inflows and turbulent motions are also significant contributors. We also find a modest contribution from satellite galaxies to extended [CII] emission. Our framework can be readily applied to predict the observability of [CII] halos at higher redshifts and extended to create spatially resolved synthetic observations of other important emission lines, such as [OIII] and H$\alpha$.
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All authors Lun-Jun Liu, Guochao Sun, Andreas L. Faisst, Claude-André Faucher-Giguère, Adam Lidz

Instrumentation and Methods for Astrophysics

Inflight performance and future improvements for the INtegral Field Ultraviolet Spectrographic Experiment, the first far ultraviolet integral field spectrograph

Alex Haughton, Emily M. Witt, Brian T. Fleming et al. (+9 more)

Integral field spectroscopy allows for spectral mapping of extended sources in a time efficient manner. An integral field unit (IFU) in the ultraviolet on Habitable Worlds Observatory (HWO) could be used to quickly map extended objects like supernova remnants or galaxies and their surroundings, but there are technical challenges to an ultraviolet IFU. The INtegral Field Ultraviolet Spectrographic Experiment (INFUSE), a sounding rocket project, is the first static configuration far ultraviolet integral field spectrograph. INFUSE features an f/16, 0.49m Cassegrain telescope and a 26-element image slicer feeding 26 replica holographic gratings, with spectra imaged by the largest cross-strip microchannel plate detector flown in space. The first launch of INFUSE occurred from White Sands Missile Range on October 29th, 2023, and demonstrated spectral multiplexing, successfully detecting ionizing gas emission in the XA region of the Cygnus Loop. INFUSE will launch again in fall 2025 to observe NGC 2366, a local analog for Green Pea type galaxies, with several enhancements including a xenon-enhanced lithium fluoride + aluminum coated grating, testing the leading flight coating for HWO for the first time. The INFUSE IFU is designed as a pathfinder for a potential IFU mode on HWO, enabling rapid 3D spectroscopy of extended sources.
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All authors Alex Haughton, Emily M. Witt, Brian T. Fleming, Alex Sico, Michael J. Kaiser, M.S. Oey, Grace Halferty, Dmitry Vorobiev, Kevin France, Takashi Sukegawa, Oswald Siegmund, Adrian Martin

Solar and Stellar Astrophysics · Cross-listed from hep-ph

Is the Conventional Picture of Coherence Time Complete? Dark Matter Recoherence

Chaitanya Paranjape, Gilad Perez, Wolfram Ratzinger et al. (+1 more)

The local solar gravitational potential forms a basin for ultralight dark matter (ULDM), with discrete energy levels. Even if barely populated, it introduces a new characteristic timescale in DM dynamics. This necessitates a generalization of the notion of coherence time. We find that, at long times, the phenomenon of recoherence emerges, whereby a subcomponent of ULDM exhibits a formally divergent coherence time. The fact that this generalized coherence time can significantly exceed the naive estimate implies an enhanced sensitivity for dark matter searches that accumulate data over extended observation periods.
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All authors Chaitanya Paranjape, Gilad Perez, Wolfram Ratzinger, Somasundaram Sankaranarayanan

High Energy Astrophysical Phenomena

Ultra Heavy Cosmic Rays from Magnetars

Anirudh Patel, Rebecca Diesing and Brian Metzger

Matter ejected from the neutron star crust during a magnetar giant flare will undergo $r$-process nucleosynthesis during decompression. Ultra heavy ions ($Z \gg 26$) can be accelerated to cosmic ray energies by the reverse shock as the ejecta decelerates by interacting with the ambient environment. We investigate the contribution of magnetars to the local ultra heavy cosmic ray flux using semi-analytic Galactic transport calculations, demonstrating that they may be significant contributors throughout Galactic history depending on the giant flare rate and ion acceleration efficiency. Although neutron star mergers inject orders of magnitude more energy into cosmic rays, they rarely occur within the spallation-limited propagation horizon for ultra heavy species, reducing their local contributions. As compared to lighter nuclei which are dominantly accelerated by supernovae, the SuperTIGER experiment has presented tentative evidence for a distinct contribution to the cosmic ray abundances near and above the first $r$-process peak ($Z \approx 35\text{--}56$). We argue that current abundance data are consistent with either a magnetar giant flare or neutron star merger origin for these species. Measurements with single element resolution through the third $r$-process peak, expected from the upcoming TIGERISS experiment, may discriminate between these sources for the heaviest cosmic rays.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

On Cosmological Correlators at One Loop

Guilherme L. Pimentel and Tom Westerdijk

We study equal-time in-in correlators of massless scalar fields in flat space at one loop. Using the time-ordered decomposition of correlators together with a cosmological analogue of the Baikov representation, we systematically construct relatively simple loop integrals and make manifest why, in this setting, loop corrections to correlators are simpler than those of wavefunction coefficients. As benchmark examples, we analyse the bubble and triangle diagrams. The bubble exhibits a UV divergence that can be removed by a local counterterm, while the triangle yields a finite result, which we evaluate explicitly in terms of dilogarithms using an integral transform for the Laplacian Green's function. We classify the kinematic singularities of these diagrams using Landau analysis, identifying novel types of singular behaviour, and validate this analysis against the explicit results. Finally, we derive a factorisation property of one-loop cosmological correlators at singular kinematics, relating them to flat-space loop amplitudes and lower-point tree-level correlators.
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Earth and Planetary Astrophysics

Observable Metal Pollution in Main-Sequence Stars: Simulations of Rocky Planets Engulfed by Stars in the $0.5$ to $1.4$ M$_\odot$ Range

Kaitlyn T. Lane, Alexander P. Stephan, Melinda Soares-Furtado et al. (+2 more)

The engulfment of planets by their host stars is an expected outcome of various dynamical processes and has been invoked to explain a variety of observed stellar properties, such as rapid rotation, chemical abundance abnormalities, and other transient phenomena. Recent observations support engulfment as the cause of such signatures; however, many engulfment process details remain uncertain. Here, we present a model for determining the chemical signatures produced due to the pollution of main sequence stars by rocky planets, a common engulfment scenario due to the high frequency of observed short-period rocky exoplanets. A key novel element of our model is that we calculate the gradual evaporation of the planet due to drag interactions with the stellar envelope, which can lead to observable pollution on the stellar surface even if the bulk of the planet is only destroyed below the star's outer convective zone. Our results indicate that rocky planet pollution is most easily measurable for stars in the $1.0$ to $1.4$ M$_\odot$ range and that elements such as aluminium, calcium, and vanadium, in addition to lithium, are most suited to detect pollution. We predict that it is also possible to differentiate between the engulfment of one large planet versus several small planets, for the same total pollution mass, for some stellar hosts. We find that rocky planet engulfment events generally take years to decades for most stars. Our results can guide future observational campaigns that may search for sites of past or current engulfment events.
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All authors Kaitlyn T. Lane, Alexander P. Stephan, Melinda Soares-Furtado, Keivan G. Stassun, Ricardo Yarza

High Energy Astrophysical Phenomena

The Emission and Suppression of Line Features in Luminous Transients

Olivia Aspegren and Daniel Kasen

Featureless optical and ultraviolet (UV) spectra are a puzzling signature to emerge from recent observations of luminous fast blue optical transients (LFBOTs) and some tidal disruption events (TDEs). We describe the landscape of source and gas properties that are expected to form H, He I and He II emission lines, and map spectral types to the parameter space of luminosity and system radius. Using one-dimensional radiative transfer calculations, we show that high source luminosities ($L > 10^{44}\,\rm erg~s^{-1}$) and compact ejecta radii ($r < 10^{14}\,\rm cm$) produce featureless spectra due to the high temperature and ionization state of the emitting medium. Intermediate luminosities and moderately compact systems can generate He II-dominated spectra, while lower luminosities and more extended atmospheres result in conspicuous H and He I emission. Large expansion velocities ($v \geq 0.1c$) can further broaden lines such that they blend into the continuum. Featureless UV spectra may require even more extreme ionization environments or velocities to suppress the many intrinsically strong metal lines at those wavelengths. Applying this framework to understand the absence of features observed in LFBOTs and featureless TDEs, we find that under the optically thick, quasi-thermal conditions considered here, non-homologous, compact outflows are likely necessary for featurelessness to persist in optical and UV spectra.
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Astrophysics of Galaxies

Mapping the Distorted Dark Matter Distribution of the LMC-SMC System Prior to Milky Way Infall with Basis Function Expansions

Hayden R. Foote, Himansh Rathore, Gurtina Besla et al. (+6 more)

The SMC orbits within the LMC's dark matter (DM) halo in a $\sim$1:10 mass-ratio encounter. The LMC:Milky Way (MW) interaction is also $\sim$1:10, and is expected to perturb the MW's DM distribution. However, no framework exists to quantify the severity of these perturbations over multiple pericenters and longer periods of time, such as the LMC-SMC interaction history. We construct basis function expansions of a high-resolution N-body simulation of the Clouds interacting in isolation and analyze their DM distributions at an epoch approximating the time of their infall to the MW. Our goal is to quantify how the Clouds distort each other's DM distributions without the MW. The LMC halo's response to the SMC includes a $\sim 20$ kpc long dynamical friction wake and the displacement of the LMC's density center during each SMC pericenter, which produces two overdensities in the LMC halo (at $\sim$60 and $\sim$100 kpc) at MW infall. The SMC's tidal radius at infall is just $\sim4$ kpc, at which point the SMC has lost two-thirds of its initial DM mass to the LMC. The distortions to the Clouds' halos produce a highly asymmetric acceleration field. Accurate orbit integration in the LMC-SMC system must account for the time-dependent shapes of both halos. The SMC-induced perturbations in the LMC DM halo resemble the MW-LMC system, and persist over multiple SMC pericenters. We conclude that 1:10 satellite-host encounters induce characteristic deformations in both DM halos across host-mass scales, with implications for merger rates and tests of DM models.
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All authors Hayden R. Foote, Himansh Rathore, Gurtina Besla, Nicolás Garavito-Camargo, Ekta Patel, Michael S. Petersen, Martin D. Weinberg, Facundo A. Gómez, Chervin F. P. Laporte

Solar and Stellar Astrophysics

JWST observations of three long-period AM CVn binaries: detection of the donors and hints of magnetically truncated disks

Kareem El-Badry, Antonio C. Rodriguez, Matthew J. Green et al. (+1 more)

We present JWST/NIRSpec high-cadence infrared spectroscopy of three long-period, eclipsing AM CVn binaries, Gaia14aae, SRGeJ0453, and ZTFJ1637. These systems have orbital periods of 50-62 minutes and cool donors that are undetectable in the optical. The data cover a wavelength range of 1.6-5.2 $\mu$m at resolution $R=1000-2000$. We obtained 150-200 spectra of each system over two orbits, split between the G235M and G395M gratings. All three systems show strong, double-peaked He I emission lines dominated by an accretion disk. These lines are nearly stationary but contain radial velocity (RV) variable sub-components that trace stream-disk interactions. In Gaia14aae and SRGeJ0453, we detect two Na I doublets in emission whose RVs track the irradiated face of the donor, marking the first direct detection of the donors of long-period AM CVns. No absorption lines from the donors are detected, implying that the IR excesses observed in many long-period AM CVns primarily trace disks, not donors. The He I emission profiles in all systems lack high-velocity wings and show no emission beyond $\approx 1500,\rm km,s^{-1}$. The morphology of the disk eclipses and Doppler tomograms are best reproduced by models in which the disk is truncated well outside the white dwarf and only material at $r \gtrsim 0.07,R_{\odot}$ contributes to the disk emission. We interpret this as possible evidence of magnetized white dwarf accretors. For plausible mass transfer rates, the truncation radii imply surface magnetic fields of $B = 30-100$ kG, consistent with recent constraints based on X-ray periodicity. The absence of cyclotron humps out to 5 $\mu$m rules out stronger MG-level fields. We make the data from the program publicly available to the community.
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All authors Kareem El-Badry, Antonio C. Rodriguez, Matthew J. Green, Kevin B. Burdge

High Energy Astrophysical Phenomena

Probabilistic modeling of Cherenkov emission from particle showers

Ian Crawshaw, Tianlu Yuan, Emre Yildizci et al. (+2 more)

Subatomic particles can interact with target nuclei in matter or decay in flight, and an individual high-energy particle can induce a particle shower composed of numerous, lower-energy secondaries. These particle showers broadly exhibit universality across diverse media, including air, water, ice, and other materials, with their development governed by the Standard Model. Full Monte Carlo simulation of particle showers, where each secondary is individually tracked and propagated, can be a computational challenge to perform at scale. Experiments thus resort to parametrized approximations when efficient simulation becomes necessary. Here, we construct distributions of parameters capable of describing the Cherenkov light yield from particle showers in ice or water. Sampling from the distributions allows for a much improved description of event-to-event fluctuations, in amplitude and shape, along the shower axis. Including these effects is essential for a more accurate simulation of signal and background events in current and next-generation neutrino telescopes.
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All authors Ian Crawshaw, Tianlu Yuan, Emre Yildizci, Lu Lu, Anatoli Fedynitch

High Energy Astrophysical Phenomena

XRISM finds the Changing-Look AGN NGC 1365 in an extended low state: A dense, highly ionized outflow obscures the central source

Fatima Zaidouni, Erin Kara, Peter Kosec et al. (+21 more)

We present the first XRISM/Resolve observations of the active galactic nucleus, NGC 1365, obtained in 2024 February and July. NGC 1365 is known for rapid transitions between Compton-thick and Compton-thin states, along with strong absorption from a highly ionized wind. During our observations, the source is found in a persistent low-flux state, characterized by a decrease in hard-X-ray luminosity and significant line-of-sight obscuration. In this state, XRISM/Resolve reveals clear Fe\,xxv and Fe\,xxvi absorption lines together with, for the first time in this source, corresponding emission lines. These features may arise either from reemission from a photoionized wind (P Cygni profile) or from collisionally ionized gas associated with outflow-driven shocks in the interstellar medium. We estimate the wind launch radius to be approximately $10^{16}~\mathrm{cm}$ ($\sim 10^4 R_{\mathrm{g}}$), consistent with the location of the X-ray broad-line region. We also resolve a broadened Fe K$\alpha$ line by $\sigma \sim 1300$ km s$^{-1}$ placing it at similar scales to the wind, consistent with radii inferred from disk-broadening models and the variability of the Fe K$\alpha$ broad line. The similarity of the Fe K$\alpha$ profile to the H$\beta$ wing and broad Pa$\alpha$ width indicates that the X-ray-emitting region is likely cospatial with the optical/IR broad-line region and originates from the same gas.
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All authors Fatima Zaidouni, Erin Kara, Peter Kosec, Ehud Behar, Richard Mushotzky, Michael Koss, Anna Juráňová, Elias Kammoun, Laura W. Brenneman, Joheen Chakraborty, Ken Ebisawa, Megan E. Eckart, Andrew C. Fabian, Yasushi Fukazawa, Javier A. García, Liyi Gu, Megan Masterson, Shoji Ogawa, Takashi Okajima, Stéphane Paltani, Daniele Rogantini, Yuichi Terashima, Brian J. Williams, Satoshi Yamada

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

Dark Dimension Right-handed Neutrinos Confronted with Long-Baseline Oscillation Experiments

Ai-Yu Bai, Auttakit Chatrabhuti, Yin-Yuan Huang et al. (+2 more)

Right-handed neutrinos are naturally induced by dark extra dimension models and play an essential role in neutrino oscillations. The model parameters can be examined by the long-baseline neutrino oscillation experiments. In this work, we compute the predicted neutrino oscillation spectra within/without extra dimension models and compare them with the experimental data. We find that the neutrino data in the T2K and NOvA experiments are compatible with the standard neutrino oscillation hypothesis. The results set the stringent exclusion limit on the extra dimension model parameters at a high confidence level. The derived constraints on dark dimension right-handed neutrinos are complementary to those results from the collider experiments and cosmological observations.
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All authors Ai-Yu Bai, Auttakit Chatrabhuti, Yin-Yuan Huang, Hiroshi Isono, Jian Tang

Earth and Planetary Astrophysics

Callisto's Nonresonant Orbit as an Outcome of Circum-Jovian Disk Substructure

Teng Ee Yap and Konstantin Batygin

The Galilean moons of Io, Europa, and Ganymede exhibit a 4:2:1 commensurability in their mean motions, a configuration known as the Laplace resonance. The prevailing view for the origin of this three-body resonance involves the convergent migration of the moons, resulting from gas-driven torques in the circum-Jovian disk wherein they accreted. To account for Callisto's exclusion from the resonant chain, a late and/or slow accretion of the fourth and outermost Galilean moon is typically invoked, stalling its migration. Here, we consider an alternative scenario in which Callisto's nonresonant orbit is a consequence of disk substructure. Using a suite of N-body simulations that self-consistently account for satellite-disk interactions, we show that a pressure bump can function as a migration trap, isolating Callisto and alleviating constraints on its timing of accretion. Our simulations position the bump interior to the birthplaces of all four moons. In exploring the impact of bump structure on simulation outcomes, we find that it cannot be too sharp nor flat to yield the observed orbital architecture. In particular, a "Goldilocks" zone is mapped in parameter space, corresponding to a well-defined range in bump aspect ratio. Within this range, Io, Europa, and Ganymede are sequentially trapped at the bump, and ushered across it through resonant lockstep migration with their neighboring, exterior moon. The implications of our work are discussed in the context of uncertainties regarding Callisto's interior structure, arising from the possibility of non-hydrostatic contributions to its shape and gravity field, unresolved by the Galileo spacecraft.
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Cosmology and Nongalactic Astrophysics

Dynamical Dark Energy Imprints in the Lyman-Alpha Forest

Diego Garza, Brant Robertson, Piero Madau et al. (+7 more)

The nature of dark energy (DE) remains elusive, even though it constitutes the dominant energy-density component of the Universe and drives the late-time acceleration of cosmic expansion. By combining measurements of the expansion history from baryon acoustic oscillations, supernova surveys, and cosmic microwave background data, the Dark Energy Spectroscopic Instrument (DESI) Collaboration has inferred that the DE equation of state may evolve over time. The profound implications of a time-variable, “dynamical" DE (DDE) that departs from a cosmological constant motivate the need for independent observational tests. In this work, we use cosmological hydrodynamical simulations of structure formation to investigate how DDE affects the properties of the Lyman-Alpha “forest” of absorption features produced by neutral hydrogen in the cosmic web. We find that DDE models consistent with the DESI constraints induce a spectral tilt in the forest transmitted flux power spectrum, imprinting a scale- and redshift-dependent signature relative to standard Lambda-CDM cosmologies. These models also yield higher intergalactic medium temperatures and reduced Lyman-Alpha opacity compared to Lambda-CDM. We discuss the observational implications of these trends as potential avenues for independent confirmation of DDE.
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All authors Diego Garza, Brant Robertson, Piero Madau, Nick Gnedin, Matthew W. Abbruzo, Evan Schneider, Reuben D. Budiardja, James B. White III, Robert Caddy, Bruno Villasenor

Instrumentation and Methods for Astrophysics

Unlocking the Future of X-Ray Polarimetry with IXPE: Lessons Learned and Next Steps

Paolo Soffitta, Enrico Costa, Ettore Del Monte et al. (+7 more)

This paper discusses issues encountered during the early development of the instrument on the Imaging X-ray Polarimetry Explorer (IXPE), a NASA ASI Small Explorer mission launched on 9 December 2021. IXPE has observed about 100 sources, yielding meaningful polarimetry for most of them. An on-board calibration system mitigated most non-ideal detector behaviors during operations. Data from the on-board polarized and unpolarized X-ray sources are routinely ingested by the flight pipeline to correct the instrument response in a manner transparent to users. Based on its scientific return and payload health, the IXPE mission has been extended through 2028. The lessons learned are informing the design of next-generation X-ray polarimetry missions, as discussed elsewhere in these conferences.
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All authors Paolo Soffitta, Enrico Costa, Ettore Del Monte, Alessandro Di Marco, Sergio Fabiani, Riccardo Ferrazzoli, Fabio La Monaca, Fabio Muleri, Alda Rubini, Alessio Trois