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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 30 July

Astrophysics of Galaxies

SDSS-V Local Volume Mapper (LVM): The Integrated Light and Internal Rotation of Omega Centauri

Maximilian Häberle, Dmitry Bizyaev, Alina Boecker et al. (+34 more)

The SDSS-V Local Volume Mapper (LVM) is a wide-field integral field spectroscopic survey of the Southern Milky Way plane, the Magellanic Clouds, and nearby Local Group galaxies. We use Early Science observations of the whole body of the nearest nuclear cluster, Omega Centauri, to extend the LVM beyond its primary interstellar-medium science case. The wide LVM field allows us to precisely map $\omega$ Cen's line-of-sight rotation out to $\sim 3r_{HL}$ or $15^\prime$, reaching a maximum value of $(8.4 \pm 0.8)$ km s$^{-1}$ at $r \approx 4.7^\prime$. Within the central region, comparisons with existing VLT MUSE oMEGACat data show explicitly that the unresolved-light signal is dominated by a small number of bright stars, with an effective sample size of only $\sim$12 per resolution element. Using Gaia DR3 as an external reference, we verify that the SDSS-V's LVM reduction pipeline recovers integrated stellar fluxes to 1-4 % across six magnitudes of surface brightness. Our resulting total spectrum of $\omega$ Cen is one of the highest S/N integrated spectrum for any globular or nuclear star cluster. We use it to test four widely-used SSP template libraries against resolved age-metallicity ground truth from oMEGACat. All templates recover an old, metal-poor population. But, even at S/N $\sim$1300, the inferred mean ages and mean [Fe/H] vary by $\sim$7 Gyr and $\sim$0.4 dex, respectively, across libraries and wavelength ranges, reflecting a systematic floor for integrated-light studies of old multi-population systems.
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All authors Maximilian Häberle, Dmitry Bizyaev, Alina Boecker, Callie Clontz, Bruno Dias, Antoine Dumont, Evgeniya Egorova, Anja Feldmeier-Krause, José G. Fernández-Trincado, Pablo García, Thomas M. Herbst, Thomas Hilder, Hector Javier Ibarra-Medel, Amy M. Jones, Ralf Klessen, Nick Konidaris, Kathryn Kreckel, Alejandra Z. Lugo-Aranda, Alfredo Mejía-Narváez, Nadine Neumayer, Hans-Walter Rix, Alexandre Roman-Lopes, Sebastián Sánchez, Saroon Sasi, Anil Seth, Amrita Singh, Peter Smith, Rodolfo de J. Zermeño, Zixian Wang, Guillermo A. Blanc, Joel R. Brownstein, Niv Drory, Oleg Egorov, Evelyn J. Johnston, Ivan Katkov, Juna A. Kollmeier, Sorya Lambert

Cosmology and Nongalactic Astrophysics

Ab Initio Cosmological Simulations: From Inflation to Present-Day Structure Formation

Drew Jamieson, Angelo Caravano and Eiichiro Komatsu

The cosmic web preserves a record of the physics that shaped the universe in its earliest moments, the period of exponential expansion known as cosmic inflation. However, if inflation involves significant nonlinear interactions, there are no direct theoretical predictions for the resulting cosmic web. We present the first simulation of the entire history of the universe, from deep in the inflationary epoch to the present-day cosmic structure. Applying this to axion-U(1) inflation, we find that early-universe interactions enhance small-scale structure at high redshift, imprinting the matter power spectrum and the mass function of dark matter halos with signatures of a modified primordial curvature power spectrum and non-Gaussianity. These signatures make high-redshift galaxy surveys, 21-cm observations, and line-intensity mapping promising probes of inflationary physics. More broadly, this ab initio approach provides a novel framework for mapping the signatures of nonlinear inflationary dynamics onto observable cosmic structures across cosmic time.
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Cosmology and Nongalactic Astrophysics

Local bandpower diagnostics for the hemispherical power asymmetry in CMB E-mode polarization

Robert A Lynch

We present local bandpower diagnostics that test whether a candidate dipolar modulation in E-mode polarization data originates in the cosmic microwave background (CMB) itself rather than in noise or systematics. The target is the hemispherical power asymmetry (HPA), one of the most persistent large-scale anomalies in the CMB temperature field; polarization offers an independent probe of its origin, but at Planck sensitivity the polarized sky is noise-dominated. Local power is estimated in overlapping patches on the masked sky, with E-to-B leakage corrected through standard pseudo-$C_\ell$ deconvolution, and dipole directions are fitted independently to the two Planck half-mission maps, which share the same sky but carry independent noise. Tight directional agreement indicates a CMB-level signal, although it cannot distinguish a real modulation from a chance CMB fluctuation. Applied to Planck PR3 Commander data at $\ell = 15$-$40$, the half-mission directions are separated by $8.7^\circ$, a closer agreement than in any of the 300 isotropic simulations ($p < 0.33\%$), and lie near the temperature HPA axis. The coherence appears only in EE, vanishes without leakage correction, and is corroborated by a cross-spectrum check. LiteBIRD, with substantially higher polarization sensitivity, is a natural next application.
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Solar and Stellar Astrophysics

Averaging Effects on the Solar Wind Alfven Mach Number: Implications for Switchbacks and Alfven Transition

Joshua Goodwill, Subash Adhikari, Francesco Pecora et al. (+10 more)

Averaging techniques in solar wind measurements have been a longstanding subject of debate. Using Parker Solar Probe (PSP) observations from encounters 1 to 19, we investigate how averaging timescales influence the characterization of turbulent properties across the Alfvenic transition. We compute the rolling mean Alfven Mach number over various averaging intervals, which are then analyzed against switchbacks, magnetic fluctuation energy, and correlation time. We find that the distribution of subAlfvenic intervals is relatively insensitive to judiciously-chosen averaging scales. In contrast, magnetic fluctuation energies increase systematically with larger averaging window, while maintaining a consistent profile across the Alfven transition. We further show that the effective magnetic correlation time decreases with decreasing heliocentric distance and MA, reaching values of several minutes approaching MA =1. These results demonstrate the importance of choosing physically meaningful backgrounds for turbulence parameters, such as the correlation scales, and their impacts on characterizing the solar wind.
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All authors Joshua Goodwill, Subash Adhikari, Francesco Pecora, Rayta Pradata, Jiaming Wang, Sujan Prasad Gautam, Manuel E. Cuesta, Orlando Romeo, David Ruffolo, Panisara Thepthong, Peera Pongkitiwanichakul, Rohit Chhiber, William H. Matthaeus

Astrophysics of Galaxies

Fishing for Jellyfish Galaxies: Exploring ram-pressure stripping with crowd science

C. Bellhouse, Y. L. Jaffé, J. P. Crossett et al. (+13 more)

Aims: We present the first results of Fishing for Jellyfish Galaxies, a pilot citizen-science project using Zooniverse to identify galaxies undergoing ram-pressure stripping (RPS). Methods: Volunteers visually inspected colour images of late-type galaxies from the Dark Energy Camera Legacy Survey, from a sample of 49,703 galaxies selected within $4 \times R_{500}$ of clusters and groups, restricted to galaxies brighter than 19th magnitude in the g and r bands, and with a minimum half-light radius of 2 arcseconds, to aid classification. We detail our data processing, including debiasing classifications and optimising vote-fraction thresholds to maximise completeness and purity, calibrated against a ground-truth set of pre-labelled galaxies. Results: Our final catalogue contains 6739 jellyfish candidates (6621 new), 5430 merger candidates, and 29,729 undisturbed galaxies, with 3910 jellyfish exhibiting prominent tail-like morphologies. We find that the fraction of RPS candidates rises from ~10% in galaxy groups to ~20-30% in massive clusters, confirming the findings of previous studies carried out on smaller samples. For the subset of our RPS candidate sample with spectroscopic data, we measure a median clustercentric velocity 53% higher than the general cluster population, consistent with galaxies in early stages of accretion into the cluster. They are also typically late-type blue galaxies with elevated star-formation rates, in agreement with expectations. These results demonstrate that citizen scientists can reliably identify galaxies that undergo environmental processes. We provide the initial release of 37,599 visually classified galaxies as a resource for future studies of galaxy transformation in clusters.
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All authors C. Bellhouse, Y. L. Jaffé, J. P. Crossett, S. L. McGee, Ignacio Quiroz, C. Dulcien, R. Smith, B. M. Poggianti, B. Vulcani, V. Sampaio, A. Werle, N. Tomicić, A. Müller, N. Akerman, A. Ignesti, A. Khoram

Solar and Stellar Astrophysics

Cataclysmic variables from Gaia XP spectra: The Gaia emission-line magnitude (GEM) diagram

Ilkham Galiullin, Vladislav Dodon, Antonio C. Rodriguez et al. (+1 more)

Gaia DR3 opens a new window for the census of Galactic stellar populations in all-sky surveys, specifically for identifying cataclysmic variables (CVs). While the majority of CVs are distributed below the main sequence on the Gaia HR diagram, identifying them among dominant background stellar populations remains a significant challenge. Here, we present the Gaia Emission-line Magnitude (GEM) diagram - a tool designed to isolate CV candidates from background stars located below the main sequence. Using Gaia photometric data and low-resolution BP/RP (XP) spectra, we construct the GEM diagram by plotting the extinction-corrected absolute magnitude ($M_{G0}$) against the pseudo-equivalent width of the H$\alpha$ line ($pgEW_{H\alpha}$), which is computed via a Gaussian line-profile approximation. We find that known CVs and major stellar background populations, including white dwarfs, hot subdwarfs, and white dwarf-main sequence binaries, occupy distinct regions on the GEM diagram, reflecting both their physical properties and the low-resolution nature of the Gaia XP spectra. We define an empirical selection line on the GEM diagram to separate true H$\alpha$-emitting CVs from background contaminants. As a proof of concept, we apply the GEM diagram to a Gaia volume-limited sample within 250 pc ($G<17.5$ mag) distributed below the main sequence, recovering known CVs. Additionally, we identify three new CV candidates whose accreting nature is supported by archival X-ray data and optical variability. Compared to traditional optical color-based selection techniques, the GEM diagram uses Gaia's low-resolution spectra for initial target identification in all-sky surveys. This provides a more reliable framework for the statistical selection of CV candidates prior to ground-based spectroscopic follow-up and can be scaled to future Gaia data releases to map Galactic emission-line star populations.
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All authors Ilkham Galiullin, Vladislav Dodon, Antonio C. Rodriguez, Askar Sibgatullin

Astrophysics of Galaxies

Changing-Look AGNs from DESI. VI. Host Galaxies

Shengxiu Sun, Linhua Jiang, Wei-Jian Guo et al. (+2 more)

Changing-look (CL) AGNs trace rapid changes in nuclear activity, but their connection to host galaxy properties remains unclear. We present a study of the host galaxies of 105 CL AGNs previously selected by comparing DESI and SDSS data. We apply a two-epoch spectrophotometric decomposition to the DESI and SDSS spectra of the 105 objects. Meanwhile, HSC images are used to constrain their varying AGN components and non-varying stellar population components. We find that 79 of the 105 (75.2%) CL AGN hosts are quiescent galaxies, and 31/105 (29.5%) also show post-starburst signatures. We focus on 82 CL AGNs with extended host emission in the HSC images and compare them with extended quasars at similar redshift and stellar mass. Their star formation activity, Balmer absorption, and quiescent fractions are broadly consistent with those of the comparison quasars, although post-starburst hosts are more common among the CL AGNs. Our CL AGNs with extended host emission are more often quiescent than those with compact morphology, but this difference is not apparent after matching in redshift and stellar mass. The $\mathrm{O\, \small II}$ and $\mathrm{O\, \small III}$ narrow lines show no population-wide response to the continuum and broad line changes, consistent with the slower response expected from the narrow line region. Together, these results favor changes in the central supermassive black hole accretion rate as the main origin of the CL transitions.
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All authors Shengxiu Sun, Linhua Jiang, Wei-Jian Guo, Sarah E. I. Bosman, Zhiwei Pan

Astrophysics of Galaxies

Quiescent Host Galaxies of Extended Quasars Revealed by Spectrophotometric Decomposition

Shengxiu Sun, Linhua Jiang, Zhiwei Pan et al. (+27 more)

Previous works of low-redshift quasar host galaxies have focused on compact quasars and found that their host galaxies are mainly star-forming galaxies. Here we present a study of host galaxies for quasars with extended morphologies in ground-based optical images. We select a sample of more than 1000 type 1 quasars at redshift $0.1<z<1$ that are classified as extended objects by DESI. Combining high-resolution spectra from DESI and high-quality images from Subaru HSC, we develop a spectrophotometric decomposition technique to iteratively decompose each quasar into an AGN component and its host galaxy. The technique can effectively break the degeneracy between the AGN and host components and capture the host spectral features. Our results show that the host galaxies of most quasars have low star-formation rates (SFRs) and low specific SFRs, indicating that they are quiescent galaxies. Many of them exhibit prominent post-starburst features with the existence of significant old stellar populations. These properties are quite different from the nature of compact quasars with star-forming host galaxies. In addition, the relation between the black hole mass and stellar mass for our sample is broadly consistent with the canonical local relations. This work is complementary to the previous studies and suggests that the host galaxies of low-redshift quasars are more diverse than what was thought.
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All authors Shengxiu Sun, Linhua Jiang, Zhiwei Pan, Małgorzata Siudek, Mar Mezcua, Gaocheng Yin, Swayamtrupta Panda, Wei-Jian Guo, Steven Ahlen, David Brooks, Todd Claybaugh, Axel de la Macorra, Peter Doel, Enrique Gaztañaga, Gaston Gutierrez, Theodore Kisner, Andrew Lambert, Martin Landriau, Aaron Meisner, Ramon Miquel, John Moustakas, Ignasi Pérez-Ráfols, Eusebio Sanchez, David Schlegel, Michael Schubnell, Hee-Jong Seo, David Sprayberry, Gregory Tarlé, Benjamin Alan Weaver, Rongpu Zhou

Solar and Stellar Astrophysics

The s-process at Subsolar Metallicity: Insights from High-Resolution Infrared Spectroscopy of Magellanic Cloud Planetary Nebulae

N. C. Sterling, M. G. Stephenson, Harriet L. Dinerstein et al. (+8 more)

We present observations of 12 Magellanic Cloud planetary nebulae (PNe) obtained with the high-resolution near-infrared spectrometer IGRINS on Gemini South. In 10 targets we detect multiple neutron(n)-capture elements that can be synthesized by the s-process during the preceding asymptotic giant branch (AGB) phase, including the widely-observed species Se and Kr, and first detections of Rb, Cd, and Te in extragalactic PNe. The derived abundances significantly expand the inventory of trans-iron element abundance determinations from PNe in subsolar metallicity stellar populations. Seven targets exhibit s-process enrichments relative to the metallicity references O and Ar, with abundances elevated by factors of up to ~40-50 for Te and Kr. We compare these results with AGB nucleosynthesis predictions, using a machine-learning algorithm to find the best-fitting Monash, FRUITY, and NuGrid models. For five of the PNe, Monash and FRUITY models with 2-4 solar masses and metallicities from 1/3 solar to near-solar match the observations well, although the Monash models more successfully fit the largest Kr enhancements. NuGrid models predict smaller s-process enrichments than observed, but the limited number of available models makes it difficult to assess their ability to reproduce the observed abundances. We were unable to find models that provide good fits to three other enriched PNe, including the most metal-poor objects in our sample. These comparisons address uncertainties in mass loss, convection, and other mixing mechanisms during the late evolution of low- and intermediate-mass stars, and improve the accuracy of s-process yields of AGB stars, which are key parameters for modeling galactic chemical evolution.
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All authors N. C. Sterling, M. G. Stephenson, Harriet L. Dinerstein, A. Yagüe-López, Kyle F. Kaplan, J. Beaumont, Maria Lugaro, Amanda I. Karakas, Umberto Battino, J. García-Rojas, Samuel M. H. Erben

Instrumentation and Methods for Astrophysics

End-to-end differentiable retrieval of molecular spectra using hydrodynamics, chemistry, and radiative transfer

T. Grassi, G. Vermariën, J.E. Pineda et al. (+3 more)

We aim to reproduce observed molecular line emission using a pipeline that couples hydrodynamics, chemistry, and radiative transfer, capable of simultaneously optimizing all relevant physical and chemical parameters. We developed an end-to-end differentiable Jax pipeline consisting of a custom hydrodynamical code, a modified version of the differentiable chemical code Carbox, and a custom radiative transfer code. We tested the framework using controlled synthetic data. We demonstrate that the framework can recover the parameters of hydrodynamical shock models directly from molecular line spectra and optimize selected chemical reaction rate coefficients through gradient-based optimization. The differentiable formulation enables efficient optimization of the coupled physical and chemical model while preserving the full time-dependent evolution.
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All authors T. Grassi, G. Vermariën, J.E. Pineda, S. Spezzano, S. Bovino, P. Caselli

Cosmology and Nongalactic Astrophysics

A Simulation Based Inference Approach to Modelling of Type Ia Supernova Populations

B. Popovic, M. Grayling, M. O'Callaghan et al. (+8 more)

Type Ia Supernovae (SNe Ia) are prominent cosmological probes, utilising a standardisation process to reduce their observed scatter to $\sim0.15$ mag. A growing number of models seek to explain this remaining intrinsic scatter, based on a diversity of dust properties and possible connections to the progenitor systems. Inference of new models has been limited due to the cost of simulations and attendant complexity. Here, we present Stjörnumál, a simulation based inference pipeline to infer intrinsic and extrinsic parameters of SNe Ia, an upgrade to previous SN Ia modelling attempts with SALT, e.g. Dust2Dust. Stjörnumál provides fast and accurate posterior inference via Neural Posterior Estimation, integrated model comparison with Neural Ratio Estimation, and overall significant speed and quality-of-life upgrades. We fit the Dark Energy Survey (DES) 5-year SN sample, finding good agreement with previously-published dust model parameters for DES5YR. We test 7 models of SN Ia behaviour, finding that more data is needed to break degeneracies between $R_V$ models, but sufficient to evidence ($\log(10)~\textrm{Bayes Factor} = +1.9$, $f_{\rm mix} = 0.8$) against two populations of SNe Ia at high-redshift. We employ a combination of frequentist $\chi^2$ metrics and Bayesian model comparison to make model determinations, finding neither are sufficient on their own to properly compare models. For our nominal model, we find a smaller $\Delta R_V = 0.8$ for our nominal model than previous SALT-based attempts. We test our model for consistency against our assumed cosmology, and find our results are robust to $|\Delta w| < 0.10$. The code is publicly available at https://github.com/bap37/Stjornumal, and presents an opportunity to flexibly and rapidly test potential models of SNe Ia scatter in a common framework.
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All authors B. Popovic, M. Grayling, M. O'Callaghan, B. M. Boyd, K. Mandel, P. Wiseman, B. Carreres, N. Shiamtanis, D. Scolnic, E. Charleton, Y. Murakami

High Energy Astrophysical Phenomena

Deep Learning-Based Classification and Analysis of Pulsar Candidates in Fermi-LAT Unassociated Sources

C. Pozo González, R. López-Coto, J. Méndez-Gallego et al. (+1 more)

The Large Area Telescope (LAT) has revolutionized our understanding of the high-energy sky, yet approximately one-third of the sources in the Fourth Fermi-LAT Source Catalog (4FGL) remain unassociated. Conventional machine learning, such as Decision Trees, often treat spectral features as independent tabular entries, neglecting the sequential topological information inherent in the Spectral Energy Distribution (SED). We aim to classify unassociated Fermi-LAT sources by exploiting the intrinsic shape of their spectra and variability features, avoiding the use of galactic coordinates as training features. Our primary objective is to generate a high-confidence list of PSRs candidates, further distinguishing between Young Pulsars (YPs) and Millisecond Pulsars (MSPs). We developed a hierarchical deep learning framework based on a 1D Convolutional Neural Network (1D-CNN), named TabularResCNN. This architecture treats the spectral data from the 4FGL catalog, allowing the model spectral shape. The classification is performed in two stages: first discriminating between AGNs and PSRs, and subsequently categorizing PSRs into YPs and MSPs. We implemented a cost-sensitive learning strategy to handle class imbalance and utilized Grad-CAM techniques to ensure the physical interpretability of the model's decisions. Applying this framework to 2563 unassociated sources, we identified 1136 AGNs and 202 high-confidence PSR candidates (166 YPs, 36 MSPs), increasing the pulsar population by more than 60%. They exhibit strong astrophysical consistency: YPs are confined to the Galactic plane, MSPs show a broader vertical distribution, and AGNs are isotropic. Furthermore, we identified 5 out of 5 PSRs recently confirmed by FAST. The proposed 1D-CNN framework isolates PSRs candidates based on intrinsic spectral and temporal properties, minimizing spatial bias.
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All authors C. Pozo González, R. López-Coto, J. Méndez-Gallego, E. de Oña Wilhelm

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

Natural Phantom Crossing from Axion-WIMP Interactions

Cédric Delaunay, Seung J. Lee, Yuan Yin et al. (+1 more)

We construct a technically natural model in which thermal dark matter (DM) interacts with axion dark energy (DE) and produces an apparent late-time crossing of the phantom divide. A direct axion coupling to weakly-interacting massive particles (WIMPs) would ordinarily radiatively destabilize the ultralight axion potential. We avoid this issue through $N$ fermion species related by a cyclic $\mathbb{Z}_N$ symmetry, which projects the leading Coleman-Weinberg potential onto the exponentially suppressed $N$th harmonic. Although the microscopic theory preserves $\mathbb{Z}_N$, the axion-dependent WIMP masses generate unequal equilibrium abundances that freeze-out imprints on the cosmological relic state, thereby breaking the symmetry spontaneously. The resulting relic distribution retains a memory of the initial axion value and generates an unsuppressed finite-density potential that holds the field fixed at early times. As the WIMP density dilutes, the axion rolls toward the minimum of its confining potential, transferring energy from DE to DM at late times. An observer assuming separately conserved components then infers an effective equation of state that crosses below $-1$, without ghosts or violation of the null-energy condition. We present an illustrative cosmological solution with a DESI-like phantom crossing and percent-level suppression of structure growth, and discuss the implications of the WIMP multiplicity and relic distribution for DM searches.
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All authors Cédric Delaunay, Seung J. Lee, Yuan Yin, Bingrong Yu

Solar and Stellar Astrophysics

A New Sirius-like System at Only 21 Parsecs: An Elusive White Dwarf Companion to the Nearby K-dwarf HD 38230

Alexander Venner, Logan A. Pearce, Qier An et al. (+6 more)

White dwarfs are among the rarest and faintest stars found in the solar neighbourhood and are therefore persistently challenging to detect. Whereas the Gaia mission has vastly expanded our knowledge of isolated white dwarfs, limited contrast sensitivity means that white dwarfs companions to much brighter solar-type stars are easily missed, leaving a subset of white dwarfs in "Sirius-like systems" that can only be discovered via high-contrast imaging. Here we report the discovery of a white dwarf companion to the nearby K0V star HD 38230 (HIP 27207). The companion, HD 38230 B, was originally detected with Keck/NIRC2 observations taken as part of the TRENDS high-contrast imaging survey, was detected by Gaia without an astrometric solution, and was independently observed using Lick/ShaneAO and Palomar/PHARO in the literature. Combining these multiple imaging detections spanning 6 years, we demonstrate that HD 38230 B is a gravitationally bound companion and has photometry consistent only with a white dwarf. Our analysis of the binary orbit, combining relative astrometry with over 25 years of precise radial velocity observations and Hipparcos-Gaia astrometry, results in strong constraints on the $P$ = $1390^{+310}_{-200}$ year orbit despite the short observational span, and provides a precise dynamical mass of $M_B$ = $0.71^{+0.06}_{-0.05}$ $M_\odot$ for the white dwarf. At 21 pc, this is the 11th-nearest Sirius-like system known to date, highlighting residual incompleteness in the local white dwarf census.
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All authors Alexander Venner, Logan A. Pearce, Qier An, Clémence Fontanive, Elisabeth C. Matthews, Kyle Franson, Justin R. Crepp, Hai Fu, Timothy D. Brandt

Earth and Planetary Astrophysics

Atmospheric Signatures of Common Envelope Evolution in White Dwarf Planets

Sydney Jenkins, Andrew Vanderburg, James Mang et al. (+4 more)

The majority of confirmed exoplanets orbit within 1 au of a main-sequence (MS) star. When their stellar hosts evolve off the MS, many of these planets will be engulfed and destroyed, creating empty "forbidden" zones around the stars as they evolve to their final state as a white dwarf (WD). However, several confirmed and candidate WD planets have been found within this forbidden zone. Two formation scenarios have been proposed to explain the existence of these close-in planets: high-eccentricity migration and common envelope evolution (CEE). There are currently few observational tests to distinguish between these pathways. In this study, we investigate whether CEE could leave a detectable atmospheric signature. Using Modules for Experiments in Stellar Astrophysics (MESA) models, we simulate an engulfed planet inspiraling into an AGB star, and allow the planet to accrete mass via Bondi-Hoyle-Lyttleton accretion. Assuming a range of planet masses (1$-$13 M$_{\mathrm{Jup}}$) and accretion efficiencies (0.01$-$1.0), we find that the planet can accrete up to 48% of its initial mass in the most extreme Eddington-limited scenario. Because this accreted material is enriched in hydrogen and helium, we expect it to decrease the planet's bulk metallicity. Using simulated emission spectra, we find that CEE can increase thermal emission by up to 9.0% for a cool planet such as WD 1856 b. For lower accretion efficiencies (0.01$-$0.5), thermal emission increases between 0.1$-$3.6%. This signature may be observable in the most favorable cases, providing a potential new probe for investigating the dynamical history of close-in planets around WDs.
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All authors Sydney Jenkins, Andrew Vanderburg, James Mang, Juliette Becker, Caroline V. Morley, Melinda Soares-Furtado, Ricardo Yarza

Astrophysics of Galaxies

Misaligned or chaotic? A strong break of axial symmetry in the local LRD J1025 revealed with VLT/FORS2 spectropolarimetry

Francesco D'Eugenio, Gabriele Pezzulli, Roberto Maiolino et al. (+18 more)

Little Red Dots (LRDs) are compact active galactic nuclei (AGN) with unusual spectral energy distributions and broad Balmer emission, candidate signposts of rapid black-hole growth. We present VLT/FORS2 optical linear spectropolarimetry of the closest known LRD, SDSS J102530.29+140207.3, at z=0.1. In total light, we detect spatially extended narrow-H$\alpha$ emission, probably tracing the host galaxy. We measure a nearly grey continuum polarisation $p_{\rm cont}=1.53\pm0.04$(rand.)$\pm$0.20(syst.) per cent, while broad H$\alpha$ is less polarised, $p_{\rm H\alpha}=0.58-0.84$ per cent. We rule out polarisation by Milky Way dust and dilution by an unpolarised line. The polarised continuum with a depolarised line resembles local Seyfert-1 nuclei and favours a single dominant source over multi-source explanations. After Stokes-continuum subtraction, broad H$\alpha$ shows no blue-to-red swing, but there is a significant (48$\pm$4)$^\circ$ continuum-to-line offset in polarisation angle. This implies a break of axial symmetry inside this object, posing interesting geometrical challenges to all existing LRD models and frameworks. We discuss different possible origins of this symmetry break and possible paths to discriminate between them with future observations.
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All authors Francesco D'Eugenio, Gabriele Pezzulli, Roberto Maiolino, Alessandro Marconi, Xihan Ji, Cristina Ramos Almeida, Andrea Ferrara, Piero Madau, Xiaojing Lin, José A. Acosta-Pulido, Fuyan Bian, Matilde Brazzini, Zheng Cai, Stefano Carniani, Xiaohui Fan, Ignas Juodžbalis, Robert G. Pascalau, Jan Scholtz, Charlotte Simmonds, Fengwu Sun, Sandro Tacchella

High Energy Astrophysical Phenomena

Peering through the dip: IXPE unveils the extended scattering environment of GX 13+1

Alessandro Di Marco, Fabio La Monaca, Luigi Stella et al. (+17 more)

Neutron star low-mass X-ray binaries feature complex accretion geometries, often including an accretion disk corona or disk winds. Here, a study of the highly inclined dipping source GX 13+1, using coordinated observations from the IXPE, NuSTAR, and Swift-XRT, is presented; this is the first time that such a campaign was conducted to monitor its periodic dip. Our analysis reveals significant variations in polarimetric properties tracking the dip. At the center of the dip, the polarization degree reaches a maximum of ${\sim}$9% (at more than $8\sigma$ confidence level). This is accompanied by a highly significant polarization angle rotation of roughly 60$^\circ$ when passing from the dip to the subsequent off-dip state. Furthermore, the dip state exhibits energy-dependent polarization. By modeling the polarization during the periodic dip, we constrain the geometry of the scattering medium. In the scenario of an oblate extended accretion disk corona (ADC), an equatorial radius at least 1.5 times its polar radius is needed with $\tau{\sim}0.3$. Alternatively, the results can be modeled as scattering in a disk wind with a most probable electron density of $1.3\times10^{14}$ cm$^{-3}$ and an opening angle near 40$^\circ$, corresponding to an optical depth of ${\sim}0.2$. The obtained results highlight the crucial role of X-ray polarimetric data to unveil the geometry of the extended scattering environment surrounding the accretion disks, advancing our understanding of neutron star low-mass X-ray binaries.
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All authors Alessandro Di Marco, Fabio La Monaca, Luigi Stella, Anagha P. Nitindala, Alexandra Veledina, Anna Bobrikova, Eleonora Veronica Lai, Alessandro Papitto, Maura Pilia, Juri Poutanen, Daniele Rogantini, Matteo Bachetti, Maria Cristina Baglio, Caterina Ballocco, Ettore Del Monte, Wei Deng, Giulia Illiano, Vladislav Loktev, Sara Motta, Fei Xie

Astrophysics of Galaxies

Searching for Population III stars with line intensity mapping cross-correlations

Sahil Hegde, Guochao Sun, Julian B. Muñoz et al. (+1 more)

Decades of searches for Population III stars in individual galaxies have yielded a few potential candidates, but a statistically robust characterization of the demographics of the first stars in the lowest-mass systems remains elusive. Line intensity mapping (LIM), an observational technique that measures fluctuations in the aggregate emission from the entire galaxy population — including the faintest sources — offers an alternative strategy that is especially well-suited for the Pop III era. With the recent launch of SPHEREx and the rapid development of a number of complementary LIM studies, we are poised to place some of the first LIM constraints on sites of star formation at high-redshift. In this work, we expand an analytical model for LIM power spectra, Zeus21/oLIMpus, to include Pop III stars and the emission lines identified as diagnostic signatures of star formation with a low-metallicity, top-heavy IMF, such as H$\alpha$ and HeII. We introduce a flexible framework to estimate the measurement uncertainties associated with instrument and survey configurations, and apply these to study LIM signatures of the first stars in mock surveys carried out with SPHEREx and potential next-generation instruments. We quantify the sensitivity of the LIM signal to variations in Pop II and III parameters and forecast joint limits that can be placed on the Pop III star formation efficiency (SFE) and IMF shape with SPHEREx. We find that next-generation instruments will be necessary to comprehensively survey the Pop III theoretical landscape — both with respect to `classical' and `exotic' Pop III models — and identify design improvements that will enable such studies. Finally, we carry out a Fisher analysis to characterize synergies between SPHEREx and JWST, suggesting that joint constraints on the Pop III SFE and extensions to conventional Pop III models may be within reach.
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All authors Sahil Hegde, Guochao Sun, Julian B. Muñoz, Steven R. Furlanetto

Cosmology and Nongalactic Astrophysics

Single Frequency CMB Foreground Removal with Inter-scale Machine Learning

Helen Shao, Fiona McCarthy, Blake D. Sherwin et al. (+2 more)

Accurate measurements of Cosmic Microwave Background (CMB) B-mode polarization, a key probe of inflationary physics, are hindered by complex Galactic dust foregrounds. Traditional foreground removal with Internal Linear Combination (ILC) fully preserves the primordial signal but requires multi-frequency data and is limited to two-point statistics. We present a novel way to estimate and remove foregrounds at single frequency using signal-preserving machine learning that leverages inter-scale correlations. Using the DustFilaments simulations, we train CNNs to reconstruct large-scale foregrounds ($\ell < 200$) from small-scales ($\ell > 200$). We quantify the effectiveness of foreground removal with the residual foreground power, $f_{\rm{resid}}$, which gives the fraction of foreground power remaining after removal. Predictions using only small-scale $B$-modes achieve $f_{\rm{resid}}\simeq 0.704$, while adding temperature and $E$-modes decreases it to $f_{\rm{resid}} \simeq 0.376$. These results are still higher than the spatial ILC, which leverages multi-frequency data at Simons-Observatory-like frequencies. However, a hybrid network that uses both multi-frequency and inter-scale correlations attains $f_{\rm{resid}}=4.71\times10^{-4}$ when using $B$-mode inputs alone, and $3.62\times10^{-4}$ when using temperature and $E/B$-mode inputs. This network achieves a residual power of $\sim 7\times$ lower than ILC, while inheriting ILC's signal-preserving property. This is $\sim 2$–$3\times$ lower than a network that only uses multi-frequency inputs, demonstrating that correlations across scale are not redundant with correlations across frequency and that our techniques are complementary to multi-frequency foreground removal. However, this is achieved only for DustFilments and network generalization across simulations remains a key challenge for robust ML-based foreground removal. (abridged)
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All authors Helen Shao, Fiona McCarthy, Blake D. Sherwin, Miles Cranmer, Carlos Hervias-Caimapo

Cosmology and Nongalactic Astrophysics

Understanding constraints on primordial mass black holes made of dark matter using fast radio bursts

Surajit Kalita, Shruti Bhatporia and Amanda Weltman

In recent decades, a multitude of modified gravity theories have been proposed to address a variety of cosmological and astrophysical problems. While many of these theories remain viable, observational constraints on their parameters are increasingly stringent. Fast Radio Bursts (FRBs), in particular, have emerged as powerful probes of cosmology and fundamental physics. This study investigates the implications of a generic modified gravity theory for gravitational lensing by FRBs. By analyzing the dataset of CHIME/FRBs, we constrain the fraction of dark matter composed of primordial black holes within this theoretical framework. Furthermore, we demonstrate that modified gravity introduces a screening effect on gravitational lensing, analogous to the scattering effect of plasma on light rays.
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High Energy Astrophysical Phenomena

A Four-dimensional Model-agnostic Probe into the Astrophysical Origins of Binary Black Hole Subpopulations

Anarya Ray and Vicky Kalogera

There is strong evidence of multiple binary black hole~(BBH) subpopulations in the cumulative gravitational wave catalog by the LIGO-Virgo-KAGRA collaboration that likely originate through distinct evolutionary channels. The astrophysical interpretation of this complex underlying population is subject to theoretical uncertainties in treatments of binary stellar evolution, core collapse, and host environments. Due to a lack of robust predictions and the sheer diversity of plausible features, strongly modelled population analyses often lead to prior-driven conclusions. On the other hand, flexible alternatives are often difficult to scale in higher dimensions, which can lead to a loss of critical information on astrophysically meaningful correlations. In this Letter, we present the first data-driven reconstruction of the joint four-dimensional distribution of BBH primary masses, mass ratios, effective inspiral and effective precessing spin parameters, which yields novel model-agnostic constraints on the astrophysical origins of BBH subpopulations. We characterize four distinct subpopulations spanning different ranges of BBH masses and report new correlations in these specific mass ranges that are beyond the reach of strongly modeled parametrizations and lower-dimensional data-driven frameworks. Our results unveil novel insights into the abundances of specific subchannels of isolated binary evolution, dynamical assembly, and hierarchical mergers across various mass ranges in the astrophysical BBH population.
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Cosmology and Nongalactic Astrophysics

Cosmo-SPINN: Fuzzy Dark Matter Simulations with Physics-Informed Generative Networks

Ashutosh Kumar Mishra, Emma Tolley and Nicolas Cerardi

Generative machine learning models have recently emerged as powerful tools for producing cosmological simulations. However, many existing emulators do not explicitly enforce the underlying physical dynamics governing cosmological evolution, often leading to artifacts and poor adherence to the evolution equations. In this work, we present a physics-informed generative U-Net framework for fuzzy dark matter (FDM) that addresses two complementary tasks: (i) the evolution of cosmological fields from initial conditions to an arbitrary cosmological scale factor and (ii) the super-resolution of FDM simulations at a specified cosmological scale factor. Our model incorporates a physics-informed loss function that explicitly enforces consistency with the underlying Schrödinger-Poisson (SP) dynamics during training. For the evolution task, we find that the inclusion of this physics-based loss significantly improves the quality of the predicted simulations, even when only a small amount of training data is available. Using only 20% of the training data, the model accurately reproduces the target simulations in a 1 $h^{-1}$ Mpc box. Furthermore, the framework generalizes effectively across previously unseen realizations of the initial conditions. For the super-resolution task, we present, for the first time, a generative super-resolution model trained on FDM simulations obtained by solving the full SP equations, considering both single and multiple realizations of the initial conditions and analyzing the role of the physics-informed loss in each case. Our approach enables modern generative modeling of cosmological simulations while maintaining physical consistency and substantially reducing generative artifacts.
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Instrumentation and Methods for Astrophysics

Laboratory demonstration of low order wavefront control using light reflected off the vortex coronagraph

Clarissa R. Do Ó, Kane Sjoberg, Luke Lamitina et al. (+4 more)

The Astro2020 Decadal Survey identified exoplanet imaging as a high priority for the Habitable Worlds Observatory (HWO), which must image and characterize exo-Earths at contrasts of $1\times10^{-10}$. The vector vortex coronagraph (VVC) is a leading architecture for this task owing to its small inner working angle and high throughput. Using light reflected from the VVC for wavefront sensing and control provides a potential path to improving robustness to residual wavefront errors and minimizing contrast degradation. Here we present the first laboratory demonstration of a low order wavefront sensing and control (LOWFS) tip-tilt loop operating on light reflected from a VVC, carried out on the High Contrast and Spectroscopy Testbed (HCST) at Caltech's Exoplanet Technology Laboratory. The demonstration is enabled by HCST's upgrade to CATKit2, a service-oriented framework in which we implement phase retrieval, electric field conjugation (EFC), and the LOWFS loop as concurrent routines. Our phase retrieval reduces the science camera wavefront error from 71.6 to 7.9 nm RMS, a $>$9$\times$ improvement. Over a 12 hour open loop run, we find that PSF drift is strongly correlated with bench temperature ($r>0.88$). Closing the tip-tilt loop suppresses drift below 1 Hz by more than two orders of magnitude and holds pointing to $<0.005~\lambda/D$. Run concurrently with EFC, the closed loop maintains a dark hole contrast of $\sim$5$\times10^{-8}$ over one hour, whereas in open loop a drift of $\sim$0.2–0.4 $\lambda/D$ degrades contrast by more than an order of magnitude. These results establish reflected light sensing off a VVC as a viable foundation for future wavefront control architectures in high contrast coronagraphy.
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All authors Clarissa R. Do Ó, Kane Sjoberg, Luke Lamitina, Susan Redmond, Dimitri Mawet, Jorge Llop-Sayson, Siria Alicata

Astrophysics of Galaxies

Characterizing the disruption of Böotes III: a missing link in the Galactic halo?

Jaclyn Jensen, Daniel A. Boyea, Alan W. McConnachie et al. (+14 more)

The Böotes III (Boo3) dwarf galaxy has long been suspected of being the progenitor of Styx, a ~50{\deg}-long stellar stream that was simultaneously discovered in the same region of sky. Boo3's diffuse morphology, large velocity dispersion, small pericenter, and excess of candidate stars at large radii suggest it is undergoing active tidal disruption. A link to Styx is therefore logical; however, a clear connection between these structures has not yet been clearly demonstrated. Here, we re-examine the Boo3-Styx association by searching for Boo3's tidal debris using a combination of Gaia-selected members, new CaHK narrow-band imaging with CFHT/MegaCam, and stellar tracer catalogues of blue horizontal branch and red giant branch stars. We also conduct a broad search for a putative stream using matched filter techniques applied to SDSS DR17 and DELVE DR2. Despite our extensive search, we find no observational evidence directly linking Boo3 to Styx. Furthermore, our results suggest that either Boo3's extended substructure is too diffuse to be detected with current data, or that its particular orbit may have erased a coherent tidal signature. Boo3 thus remains an enigmatic system, and exemplifies the need for spectroscopic follow-up to properly disentangle the nature between this faint Milky Way satellite and nearby stream.
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All authors Jaclyn Jensen, Daniel A. Boyea, Alan W. McConnachie, Raphaël Errani, Akshara Viswanathan, Nicolas Martin, Zhen Yuan, Guillaume F. Thomas, Julio F. Navarro, Kim A. Venn, Pascale Jablonka, Khyati Malhan, Anya Dovgal, Simon E.T. Smith, Gustavo E. Medina, Thomas de Boer, Gregory S.H. Paek

Cosmology and Nongalactic Astrophysics

Axion Inflation with a Massive Abelian Gauge Field

Ricardo Z. Ferreira, Alessio Notari and José Jaime Terente Díaz

An axial coupling between an inflaton and an Abelian gauge field can trigger the tachyonic amplification of one gauge-field helicity. For a massless vector, modes with physical momentum $k/a\sim |\xi|H$ are enhanced by approximately $\exp(\pi|\xi|)$, and sufficiently efficient production can provide substantial friction for the homogeneous inflaton. We extend this mechanism to a vector of mass $m$. The instability is present only for $|\xi|>\bar m\equiv m/H$, and in the heavy regime the mode amplitude scales as $\exp[\pi(|\xi|-\bar m)]$. Because the amplified modes remain well inside the Hubble radius when $\bar m\gg1$, their contribution to long-wavelength curvature perturbations $\zeta$ is power-law suppressed at fixed background backreaction. In the weak-backreaction regime we obtain a spectrum ${\cal P}^{\rm id}_{\zeta} \propto \bar m^{-w}$, with $w \sim 2$, while including the gauge-induced friction of scalar perturbations gives the scaling ${\cal P}^{\rm id}_{\zeta}\propto \bar{m}^{-s}$, with $s$ between three and four. These estimates indicate that ${\cal P}^{\rm id}_{\zeta}\lesssim 10^{-9}$ on CMB scales should be compatible with gauge field backreaction for $\bar{m}$ larger than order a few hundred. We test the analytical mode functions and backreaction estimates with the first lattice simulations based on a massive-vector extension of the Pencil Code, including simulations in the strongly backreacting regime.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

LISA Reconstruction Landscape for Metastable Cosmic Strings

Satyabrata Datta and Rome Samanta

We study reconstruction of stochastic gravitational-wave backgrounds from metastable cosmic strings with the Laser Interferometer Space Antenna (LISA). In the vacuum-tunneling benchmark, the network decays via zero-temperature nucleation of monopole pairs on the string worldsheet. Initially following cosmic-string scaling, loop production is suppressed after a decay time linked to efficient loop breaking and network collapse. This finite lifetime imprints an infrared tail and a transition toward a stable-string-like high-frequency plateau. Using synthetic LISA data with instrumental noise and unresolved astrophysical foregrounds, we perform Bayesian analysis in the $(G\mu,\kappa_{\rm CS})$ parameter space. We map detectability, uncertainties, correlations, and localization to distinguish background detection from parameter reconstruction. Reconstruction is governed by lifetime-dependent spectral features in the LISA band. When LISA samples the transition between tail and plateau, data contain amplitude and shape information, enabling recovery of string tension and metastability scale. Posteriors may remain correlated, reflecting an amplitude–lifetime trade-off, yet occupy a small parameter region. By contrast, featureless spectra constrain only limited parameter combinations or become prior dominated. High-SNR plateau-like spectra can retain partial sensitivity to $\kappa_{\rm CS}$ through residual lifetime dependence even when the transition is not prominent. Finally, we assess sensitivity to Galactic foreground modeling by comparing a flexible template with a reduced tanh template. Our results show where LISA can move beyond detection to probe the lifetime of the underlying string network.
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Cosmology and Nongalactic Astrophysics

Dark Matter Constraints from Small-Scale Cosmic Structure

Ethan O. Nadler, Keir K. Rogers and Alex Drlica-Wagner

Small-scale cosmic structure provides a powerful test of the fundamental nature of dark matter (DM). A wide range of DM models impact matter clustering on small scales, including warm, fuzzy, and (self-)interacting DM. In these scenarios, DM physics such as free-streaming, wave interference, and self/Standard Model interactions alter the abundance and internal structure of DM halos. Cosmological and astrophysical probes of nonlinear structure—including dwarf galaxies, strong lensing, the Lyman-$\alpha$ forest, stellar streams, and high-redshift galaxies—are therefore sensitive to these effects. Here, we review DM constraints provided by small-scale structure, focusing on observables that probe scales smaller than $\sim 1~\mathrm{Mpc}$, which define the frontier of current measurements. We summarize how these constraints have been translated to limits on microphysical DM models, and we discuss key modeling uncertainties and observational systematics. Finally, we highlight the growing importance of probe combination and simulation-based inference for this field, and we overview upcoming observational facilities that will sharpen small-scale structure tests of DM physics.
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Instrumentation and Methods for Astrophysics

Upgrading LBTI/NOMIC with a quadruple annular groove phase mask and GeoSnap detector for imaging nearby, habitable-zone exoplanets

Kevin Wagner, Manny Montoya, Steve Ertel et al. (+32 more)

The Large Binocular Telescope Interferometer (LBTI)'s Nulling-Optimized Mid-Infrared Camera (NOMIC) is among the most capable thermal-infrared imaging systems available for high-contrast, high-angular-resolution astronomical observations. Here we describe two in-progress upgrades to LBTI/NOMIC: (1) the design, fabrication, and installation of a quadruple annular groove phase mask (Q-AGPM) coronagraph, and (2) the installation of a 13 micron-cutoff Teledyne GeoSnap array. The Q-AGPM is the first coronagraph to be installed within NOMIC and one of the first optimized for N-band (~11 micron) observations. It places four annular groove phase masks on a single diamond substrate so that, in the LBTI dual-aperture imaging mode, each of the two telescope beams can be chopped between a pair of masks without loss of observing efficiency. The GeoSnap array will replace NOMIC's original AQUARIUS array, delivering higher quantum efficiency, larger well depth, faster and more linear readout, and freedom from the excess low-frequency noise that requires aggressive chopping. Together these upgrades substantially improve the achievable contrast and sensitivity at small angular separations. We also present a high-contrast Fizeau imaging sequence obtained with LBTI's new FFTCam fringe tracker, which confirms the interferometric gain over a single aperture through injection/recovery tests: relative to an equal-time single aperture exposure, the S/N = 3 contrast is a factor of ~2-4 deeper across 0.2-1 arcsec, spanning the contrast- and background-limited regimes. Finally, we describe the role of the upgraded LBTI/NOMIC instrument within the Breakthrough Watch program at the University of Arizona, which aims to perform the deepest observations yet of the habitable zones of the nearest single Sun-like stars.
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All authors Kevin Wagner, Manny Montoya, Steve Ertel, Jarron Leisenring, Pontus Forsberg, Samuel Ronayette, Andre Wong, Mikael Karlsson, Olivier Absil, Denis Defrère, Markus Kasper, Jordan Stone, Dániel Apai, Laird Close, Jamie Dietrich, Ewan Douglas, Jamie Drew, Olivier Durney, Marina Fetisova, Kyran Grattan, Olivier Guyon, Jacob Isbell, Sebastián Jorquera, Petri Karvinen, Markku Kuittinen, Hervé Le Coroller, Jared Males, Brittany Miles, Dillon O'Reilly, Eric Pantin, Sascha P. Quanz, Eckhart Spalding, Vivek Vijayakumar, Zach Werber, S. Pete Worden

High Energy Astrophysical Phenomena

Spinning down neutron-star merger remnants with the Tayler-Spruit dynamo: Global simulations reveal the formation of massive disks and neutron-rich ejecta

Harry Ho-Yin Ng and Elias R. Most

Magnetic-field amplification and angular momentum (AM) transport critically shape the secular evolution, lifetime, and electromagnetic signatures of binary neutron-star merger remnants. While the magnetorotational instability can operate in the outer negative-shear regions of the neutron-star remnant and accretion disk, the positive-shear, stably stratified core may instead be susceptible to the Tayler-Spruit dynamo. We present the first global, long-term general-relativistic neutrino-radiation magnetohydrodynamics simulations of a neutron-star merger remnant incorporating the unresolved Tayler-Spruit dynamo through a new mean-field dynamo subgrid prescription. Our axisymmetric simulations starting from a realistic merger remnant show that the Tayler-Spruit dynamo is primarily active in high-latitude regions of the remnant core. The resulting Maxwell stresses redistribute AM on a spin-down timescale of a few hundred milliseconds, substantially flattening the core rotation profile and transferring mass and AM from the outer remnant into the disk. This produces a more massive, extended, and strongly magnetized disk with a low electron fraction, leading to substantially more neutron-rich ejecta. Our results demonstrate that currently unmodelled Tayler-Spruit dynamo action can qualitatively alter the rotational evolution, collapse prospects, disk formation, and multi-messenger signatures of long-lived neutron-star merger remnants.
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High Energy Astrophysical Phenomena

Search for gravitational waves associated with high-energy neutrinos detected by IceCube during the third observing run of LIGO-Virgo

Matthias Vereecken, Matteo Pracchia, Kara Merfeld et al. (+3 more)

We search for generic gravitational-wave transients associated with high-energy neutrinos detected by the IceCube Neutrino Observatory during the third Observing Run (O3) of Advanced LIGO, Advanced Virgo, and KAGRA. We perform an unmodeled, targeted search, which is sensitive to gravitational-wave signals weaker than those reported in real time or in the gravitional-wave transient catalog, and can thus uncover coincidences missed by typical neutrino follow-up searches. We find no statistically significant gravitational-wave signal and set lower bounds on the distance of possible gravitational-wave sources for different emission models.
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All authors Matthias Vereecken, Matteo Pracchia, Kara Merfeld, Iara Tosta e Melo, Wasim Javed, Patrick Sutton