High Energy Astrophysical Phenomena
Multi-Wavelength Identification of a Luminous Mid-Infrared Supernova Powered by Circumstellar Interaction with Binary-Driven Pre-supernova Mass Loss
Kohki Uno, Kishalay De, Geoffrey Mo et al. (+6 more)
Terminal mass-loss in massive
stars is commonly reconstructed from observations of circumstellar interaction in core-collapse
supernovae (CCSNe); however, such signatures can be easily missed depending on the phase when they appear. In this paper, we present a multi-wavelength study of SN\,2022yyz, a nearby CCSN selected by its luminous late-time mid-infrared (MIR) excess in NEOWISE at $> 500$ days after the discovery. Classified as a Type II SN at discovery, it reached a peak bolometric luminosity of $1.3^{+0.7}_{-0.4}\times10^{43}$ erg s$^{-1}$ before fading away with a light-curve drop at $\sim 300$ days. We present late-time HST/WFC3 ultraviolet (UV) imaging and Keck/LRIS spectroscopy at $\sim 1200$ days, which reveal clear signs of circumstellar-medium (CSM) interaction via a UV excess consistent with a strong MgII contribution and a flat-topped H$\alpha$ profile. We show that the bolometric light curve and the late-time UV luminosity can be explained using a semi-analytic CSM interaction model involving a broken power-law density profile: with $\sim 2.7~M_\odot$ of nearby, dense CSM within a radius of $\sim 10^{16}$ cm surrounded by wind-like outer CSM with a mass-loss rate of $\sim 10^{-4} {\rm ~M_\odot~yr}^{-1}$. The broken density profile indicates $\gtrsim 100\times$ mass-loss rate enhancement starting a few hundred years before explosion, pointing to a possible common-envelope ejection in a binary system. Despite being overlooked for follow-up at such proximity, our results demonstrate that IR photometric selection methods provide a powerful way of mapping terminal mass-loss in massive
stars - laying the groundwork for the Roman Space
Telescope surveys.
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All authors Kohki Uno, Kishalay De, Geoffrey Mo, Viraj Karambelkar, Kaitlyn Shin, Christoffer Fremling, Jesper Sollerman, Daichi Hiramatsu, Jacob E. Jencson
Cosmology and Nongalactic Astrophysics
Inductive Biases in Field-Level Cosmological Inference from Galaxy Catalogs
James O. Baldwin, Shy Genel and Francisco Villaescusa-Navarro
We perform field-level likelihood-free inference of the matter density parameter $\Omega_m$ from simulated
galaxy catalogs using machine learning models with differing inductive biases. Using hydrodynamic simulations from CAMELS, we examine how observable choice and architecture govern cosmological information extraction. We consider
galaxy positions and line-of-sight peculiar velocities, separately and jointly, and compare permutation-invariant Deep Sets, implemented with either multilayer perceptrons (MLPs) or Kolmogorov-Arnold Networks (KANs), to graph neural networks (GNNs), which explicitly encode spatial relations. We test in-distribution and out-of-distribution (OOD) performance across simulations with different subgrid
galaxy-formation prescriptions. Deep Sets infer $\Omega_m$ from velocities alone with mean relative errors of approximately $18\%$ in-distribution and $\sim25\%$ OOD, with KANs and MLPs achieving comparable performance. In contrast, the same set-based approach does not yield useful $\sigma_8$ predictions in either in-distribution or cross-suite tests. Adding positions does not improve Deep Sets, while GNNs infer $\Omega_m$ with mean relative errors of about $10\%$ in-distribution and $10$–$17\%$ OOD. These results indicate that peculiar velocities provide the dominant source of $\Omega_m$ information for set-based models in this setting, while spatial information is most effectively used by architectures that explicitly encode
galaxy-
galaxy relations. Because the velocity inputs are exact simulated peculiar velocities, applications to survey data will require validation under realistic velocity-measurement noise, selection effects, and survey geometry.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Space-Based Lock-In Determination of Newton's Gravitational Constant
Ulrich D. Jentschura
Inspired by a recent ground-breaking space-based measurement of Newton's gravitational constant, we outline a proposal for a general layout of an optimized space-based approach that combines the advantages of a largely disturbance-free environment with lock-in techniques, null coordinates and the method of covariances. The method of covariances, and cross-covariances, is used for an optimized statistical analysis of data originating from two distinct experimental channels. One of two distinct measurement channels relies on an approximately constant acceleration in the gravitational field of static sources masses, while the second channel involves a lock-in measurement based on test and source masses with oscillating coordinates. Conceivable mission parameters are analyzed in terms of the optimum scale for the source masses and launch capabilities of currently available space launch systems. A candidate location for a largely disturbance-free position in geostationary orbit is identified.
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Earth and Planetary Astrophysics
Detecting White Dwarf Exoplanets in the Roman Era
Zifan Lin and Tansu Daylan
White dwarfs (WDs) provide an unparalleled opportunity for detecting and characterizing
exoplanets because of the large
planet-to-
star size ratio. However, only one transiting WD
exoplanet is confirmed to date, and occurrence rate constraints remain loose because the rapid transits and weak phase curve modulations of WD
exoplanets require high-precision, high-cadence photometry. The Galactic Bulge Time Domain Survey (GBTDS) of the Nancy Grace Roman Space
Telescope will provide exactly this by observing thousands of WDs at 12.1-minute cadence. The expected WD
exoplanet yield of this survey is not yet quantified. Here, we predict the GBTDS WD
exoplanet yield over its first three high-cadence seasons, through both transiting and non-transiting (phase curve) channels. We run Monte Carlo detection probability simulations over a grid of
planet radius, orbital period, and host properties for a Besançon synthetic population of WDs. Jupiter-sized
planets dominate the transit yield, with a period-averaged effective survey size of $\overline{N}_\mathrm{eff}\approx8$, requiring an underlying occurrence rate of $\overline{\eta}_1\approx12\%$ for one expected detection, followed by $\overline{N}_\mathrm{eff}\approx2.6$ ($\overline{\eta}_1\approx38\%$) for Neptune-sized and $\overline{N}_\mathrm{eff}\approx1.8$ ($\overline{\eta}_1\approx55\%$) for sub-Neptune-sized
planets. Source blending is the major observational challenge in the crowded GBTDS fields, removing $\approx95\%$ of the raw predicted yield. Phase curve provides marginal detections, adding at most $\approx4\%$ to the transit yield. A null detection by GBTDS would constrain $\eta_\mathrm{WD}$ to $< 28\%$ for Jupiter-sized
planets at $95\%$ confidence. GBTDS will deliver the first WD
exoplanet occurrence-rate constraints beyond the solar neighborhood and identify
prime targets for future characterization.
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Earth and Planetary Astrophysics
Earth-Projected Clustering of Historical Optical Transients in the Palomar Observatory Sky Survey-I (POSS-I)
Stephen Bruehl, Beatriz Villarroel, Hichem Guergouri et al. (+2 more)
Palomar Observatory Sky Survey-I (POSS-I) images obtained before the launch of Sputnik contain
star-like point sources consistent with sub-second flashes that are absent from all subsequent observations. The nature and origin of these transients remain poorly understood. Based on models suggesting they are in geosynchronous orbit, we estimated the latitude/longitude over which POSS-I transients appeared. From a
dataset of 107,875 POSS-I transients, we selected a subset with high probability of representing real objects based on a machine learning model. Two independent approaches were used to test whether transients non-randomly grouped over specific locations (hotspots). Based on comparing transient numbers in discrete 5{\deg} x 5{\deg} Earth-projected regions to numbers randomly expected in these same regions, 16 statistically-significant hotspots were identified. Separately, two-step cluster analysis identified 6 highly-distinct hotspots (silhouette value = 0.70). The two methods identified several similar hotspots not attributable to POSS-I survey biases: 1) Pacific ocean west of southern Mexico/Central America, 2) southern Gulf of Mexico, 3) southwestern US (Sedona, AZ, White Sands, NM regions). Transients accounting for reported transient-nuclear testing associations displayed location specificity, with exclusively Pacific transient locations during Pacific nuclear testing and primarily southwestern US locations during Nevada testing. Findings hint at intriguing POSS-I transient characteristics.
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All authors Stephen Bruehl, Beatriz Villarroel, Hichem Guergouri, Brian Doherty, Alina Streblyanska
Astrophysics of Galaxies
JWST Spectra Conclusively Show an Excess of Neutral Gas Outflows in Quiescent Galaxies at z=2-5
Rion Oh, Gourav Khullar, Arianna S. Long et al. (+15 more)
Galaxies exhibit a broad range of
star formation activity, from actively
star-forming to quiescent systems. Yet, the mechanisms responsible for the rapid shutdown and continued suppression of
star formation remain poorly understood, particularly for the quiescent
galaxies recently uncovered by JWST at $z>3$. Neutral gas outflows provide a direct tracer of gas removal and regulation in quiescent
galaxies. We therefore present a NaID $\lambda\lambda5891,5897$ absorption–line stacking analysis of 274
galaxies at $z=2$–5 drawn from the DAWN JWST Archive (DJA) and the EMBER JWST program, using JWST/NIRSpec medium-resolution grating spectroscopy and NIRCam photometry. NaID absorption is detected in all quiescent
galaxy stacks spanning $z=2$–5, providing the first statistical evidence that neutral gas outflows are a ubiquitous feature of quiescent
galaxies in the early Universe. Compared to the non-quiescent
galaxy stacks, the quiescent stacks show mass loading factors higher by 2–4 dex, with mass outflow rates $\dot{M}_{\rm out} \sim 9$–$30\,M_\odot\,{\rm yr}^{-1}$ elevated by $\sim0.5$–$1$ dex and outflow velocities $v_{\rm out} \sim 310$–$570\,{\rm km\,s}^{-1}$ higher by a factor of $\sim2$. The extreme mass loading factor values and declining
star formation histories strongly indicate that these outflows cannot be driven by current
star formation alone. In the statistically reliable quiescent
redshift bins at $2 \leq z < 3$ and $3 \leq z < 4$, the elevated $[\mathrm{N\,II}]/\mathrm{H}\alpha$ and $[\mathrm{O\,III}]/\mathrm{H}\beta$ ratios are consistent with a possible AGN contribution, suggesting that non-stellar feedback may play a role in sustaining quiescence in
galaxies at these epochs.
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All authors Rion Oh, Gourav Khullar, Arianna S. Long, Julissa Sarmiento, Hollis B. Akins, Caitlin M. Casey, Yingjie Cheng, Andreas L. Faisst, Maximilien Franco, Ghassem Gozaliasl, Micheaela Hirschmann, Erini Lambrides, Jacqueline E. McCleary, Tiara Anderson, David C. Andrews, Dylan Berry, Nguyen Binh, Elaine Gammon
Astrophysics of Galaxies
Characterization of Orbits in Bars in Disc Galaxies Using Fourier Frequencies
A. Silva-Castro, I. Puerari and D. Valencia-Enríquez
Bars are among the most prominent dynamical structures in disc
galaxies, yet their long-term
evolution and the orbital families that sustain them remain only partially understood. In this work, we introduce a new methodology based on frozen potentials combined with
Fourier analysis of particle trajectories to identify regular and sticky orbits in self-consistent $N$-body simulations. This approach allows us to isolate particles belonging to the $x_1$ family, directly associated with the bar, and the $x_2$ family, linked to a secondary perpendicular structure. Tracking these orbits across multiple snapshots enables us to quantify the time
evolution of key bar properties, including its mass fraction, semi-axes, and density profile. Compared with established used diagnostics, our method provides the closest match to the temporal behaviour of the
Fourier bar-strength parameter $A_2$, while offering a direct dynamical interpretation and full three-dimensional characterization that
Fourier-based approaches cannot provide. Our analysis further reveals that the indices $n_x$, $n_y$, and $n_z$ describing the bar density distribution are anisotropic and rarely equal to the canonical $n=2$ assumed in Ferrers profiles, highlighting the limitations of standard analytical approximations. We also find strong correlations between bar growth, orbital chaoticity, and angular momentum redistribution, with the bar acting both as a sink and as a driver of angular momentum transfer. A comparison between the two models analysed shows that rapidly forming bars are weaker and less stable than those that grow more gradually. Altogether, our methodology provides a robust framework for linking orbital structure to the dynamical
evolution of barred
galaxies.
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High Energy Astrophysical Phenomena
Evolution of Main Sequence Stars Transferring Mass to a Supermassive Black Hole
Andrey Sandomirsky, Re'em Sari, Aleksandra Olejak et al. (+1 more)
We consider main-sequence
stars orbiting close to a supermassive black hole (SMBH), which are potential gravitational wave (GW) sources for LISA if their orbital periods are of the order of an hour. At such a short orbital period, mass transfer from the
star to the SMBH occurs. The
evolution of the semi-major axis and GW frequency depends on the
evolution of the stellar mass and radius. We use MESA to study
stars that transfer mass to SMBHs similar to Sagittarius A* starting on the zero-age main sequence (MS). We identify 4 evolutionary phases. (I)
Stars initially with mass $>2 M_\odot$ remain on the MS as their mass and radius decrease. (II) Below $2 M_\odot$, the separation is sufficiently small so that the GW timescale is too short for the
stars to maintain thermal
equilibrium. They evolve adiabatically off the MS and shrink rapidly as they lose their high-
entropy envelope. (III) Below $0.5-1 M_\odot$, depending on the initial mass, the uniform low-
entropy core is exposed and
stars expand adiabatically. (IV) Below $0.15-0.4 M_\odot$, the thermal and GW timescales become comparable, and
stars cool and shrink while maintaining this balance. Overall, mass transfer causes the orbit to expand, slowing down the orbital
evolution and leading to GW emission at lower frequencies making the GW signal harder to detect. If located around Sagittarius A*, mass transferring
stars spend most of the time relatively close to the LISA sensitivity curve, with maximal SNR reaching around 600 during the transition between stages II and III.
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All authors Andrey Sandomirsky, Re'em Sari, Aleksandra Olejak, Selma E. de Mink
Solar and Stellar Astrophysics
Cycle Variation in the Occurrence of Great Soft X-ray Solar Flares
V.N. Obridko, M.M. Katsova and D.D. Sokoloff
Powerful nonstationary processes such as
flares and coronal mass ejections are detected mainly near the solar cycle maxima. However, the analysis of the great
flares since 1975, when the GOES monitoring started, leads us to more precise conclusions. We have traced the latitudinal distribution of X-class
flares and their dependence on the phase of the cycle throughout four cycles. Besides, we compared directly their positions with the
magnetic field structure. It was found that the relatively weak X4–7
flares occur at relatively high latitudes (15 – 20 degrees), where two waves of activity converge, one moving toward the equator and the other, the wave of the following cycle, directed poleward. Such events are observed almost constantly 1 – 2 years before the cycle maximum. At the same time, the number of the powerful X-ray
flares increases sharply during the maximum phase, but the greatest X10
flares are observed at the beginning of the decline phase, where wave interactions still persist, and throughout the decline phase. Note that they are virtually absent during the cycle growth phase. Thus, we conclude that the greatest X-ray
flares begin to appear 1 – 2 years before the maximum number of sunspots in the overlapping phase, when different kinds of activity waves coexist on the Sun at relatively high latitudes, and, then, continue to appear at the boundary, which separates the wave of local fields and the poleward wave of the following cycle.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Perturbations of Charged Black Holes with Higher-Order Interactions
Oleksandr S. Stashko, Roman A. Konoplya and Mark P. Hertzberg
We study linear gravitational perturbations and the corresponding quasinormal-mode spectra of electrically and magnetically charged black holes in the presence of higher-order corrections to the Einstein-
Hilbert action. In particular, we consider a four-derivative interaction that couples the Riemann tensor to the electromagnetic field strength in the unique (Horndeski) combination that preserves second-order equations of motion. We provide a comprehensive analysis of the stability conditions. We numerically confirm the absence of exponentially growing modes throughout the physically admissible region of parameter space where the theory remains free of pathologies. We then investigate in detail the properties of the quasinormal-mode spectra and identify several distinctive features induced by the higher-order interaction.
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Astrophysics of Galaxies
TDCOSMO XXX: Spatially resolved kinematics of the deflectors in time-delay lens systems B1608+656 and SDSSJ1206+4332 from JWST-NIRSpec observation
Pritom Mozumdar, Shawn Knabel, Anowar J. Shajib et al. (+3 more)
We present spatially resolved stellar kinematics of the deflector
galaxies in two time-delay lens systems, B1608+656 and SDSS J1206+4332, measured from JWST NIRSpec integral field spectroscopy. B1608+656 is a quadruply imaged
quasar lensed by a pair of tidally interacting
galaxies, the primary deflector (G1) and a close companion (G2), for which we quantified G2's tidal influence on G1 and define a criterion identifying the region where this perturbation is negligible and standard Jeans-equation modeling remains valid. SDSS J1206+4332 is a doubly imaged
quasar whose extended host
galaxy is itself quadruply imaged by a foreground massive
galaxy (G0), accompanied by a fainter perturber (G1). For both systems, we report the first spectroscopic
redshift and velocity dispersion measurements of the perturber
galaxies. For G2 in B1608+656, we measure {\sigma}_v = 188 +/- 7 (stat.) +/- 2 (sys.) km/s at z = 0.6307, identical to the
redshift of the main deflector G1. For G1 in SDSS J1206+4332, we find {\sigma}_v = 100 +/- 21 (stat.) +/- 2 (sys.) km/s at z = 0.7403, slightly lower than the primary deflector G0. The resolved velocity maps of both primary deflectors show clear rotation signatures and we visually classify them as fast or regular rotators. The data products will be made publicly available and will be combined with time delays, lens models, and line-of-sight convergence to measure cosmological parameters in the upcoming TDCOSMO 2026 milestone publication.
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All authors Pritom Mozumdar, Shawn Knabel, Anowar J. Shajib, Tommaso Treu, Michele Cappellari, Aymeric Galan
Earth and Planetary Astrophysics
Beyond Pebble Isolation: Diverse Pathways to Giant Planet Formation Across Stellar and Orbital Scales
Lorenzo Peerani, Sho Shibata and Ravit Helled
Context. Giant
planet formation requires reaching crossover mass, i.e., when the mass of the gaseous envelope becomes equal to the mass of the core, within the disc's lifetime. The formation process depends critically on the orbital distance and stellar mass. Aims. We simulate
planet formation via pebble
accretion up to crossover mass around stellar hosts with masses of 0.1-1.5 Msun, considering a range of formation locations, with and without Type I migration. Methods. We use a modified version of MESA that couples pebble
accretion, gas
accretion, and disc
evolution. Results. We find that cold/warm Jupiters form, whereas in-situ formation fails at short orbital separations: viscous heating raises the isolation mass enough to assemble adequate cores, but the accompanying high disc's temperature prevents cooling and suppresses gas giant formation. This supports migration-based explanations for the origin of hot Jupiters. At large orbital distances, crossover can be reached before pebble isolation mass. This is possible due to efficient envelope contraction in the cold, low-opacity outer disc. Inferred core masses at crossover range between 0.7 and 20 M_Earth. Conclusions. Pebble
accretion accommodates multiple formation pathways. Giant
planets can also have very small cores. Overall, different formation conditions significantly influence planetary growth and can explain the diversity in compositions and internal structures observed in the
exoplanet population.
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Cosmology and Nongalactic Astrophysics
A Finely-Binned Measurement of the Connected Even-Parity Galaxy 4-Point Correlation Function of DESI Year 1 Luminous Red Galaxies
William Ortolá Leonard, Alex Krolewski, Zachary Slepian et al. (+46 more)
We present the connected even-parity
galaxy 4-Point Correlation Function (4PCF) of DESI Year 1 (Y1) Luminous Red
Galaxies (LRGs). This is one of the first measurements of the connected 4PCF on data, and shows a clear detection at $\sim$12 to 17$\sigma$ in the full-sky analysis. We test the robustness of the signal by varying three factors: hemisphere (north vs. south),
redshift range (either the full range $0.4 < z < 1.1$ or the higher-number-density interval $0.4 < z < 0.8$), and sample completeness (the full sample vs. only the most complete regions within the number density-motivated cut). Finally, we cross-correlate different patches that are spatially well-separated, and thus should have largely independent noise. This approach, at leading order, is able to remove mismatch between the covariance
matrix of the data and that of the mocks; however, in certain cases at the cost of sensitivity. We find $\sim$15$\sigma$ evidence for an even-parity 4PCF in this approach. Overall, the studies of the 4PCF presented here probe sensitively any mismatch between mock catalogs and data, and also open up the prospect of fitting a model, constraining cosmological parameters and
galaxy biases, and searching for Baryon Acoustic Oscillation (BAO) features.
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All authors William Ortolá Leonard, Alex Krolewski, Zachary Slepian, Alessandro Greco, Simon May, J. Aguilar, S. Ahlen, O. Alves, A. Aviles, F. Beutler, D. Bianchi, D. Brooks, A. Carnero Rosell, T. Claybaugh, A. de la Macorra, Biprateep Dey, S. Ferraro, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, G. Gutierrez, K. Honscheid, D. Huterer, M. Ishak, S. Juneau, T. Karim, R. Kehoe, D. Kirkby, O. Lahav, M. Landriau, L. Le Guillou, M. Manera, A. Meisner, R. Miquel, J. A. Newman, E. Paillas, W. J. Percival, F. Prada, I. Pérez-Ràfols, C. Ravoux, R. Ruggeri, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, J. H. Silber, M. Siudek, G. Tarlé, B. A. Weaver
Instrumentation and Methods for Astrophysics
The future of high-resolution UV spectroscopy: Science with a UV Échelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission
Annalisa De Cia, David Cont, Kevin Heng et al. (+39 more)
High-resolution UV spectroscopy serves a diversity of science cases, from small bodies to
planets,
stars, and
galaxies, but is currently limited to the Hubble Space
Telescope and bright targets. Major advances require increasing sensitivity by at least one order of magnitude. Here we present the UV science cases for PEGASUS (
Planets, Earths,
Galaxies, And
Stars UV Spectrograph), a UV Échelle high-resolution spectrograph concept, with $R = \lambda/\delta\lambda \sim 100\,000$ (full range 10 000-140 000) and covering 90–400 nm, with a foreseen extension to at least 800 nm. PEGASUS is ideally suited for the Habitable Worlds Observatory (HWO), enabling transformative science across the UV/optical wavelength ranges. PEGASUS will be unique in high sensitivity (effective area) and high spectral resolution – an uncharted territory – as well as robustness, thanks to the simplicity of its design. Its UV science cases include: I) Formation and
evolution of
planets and their habitability: properties of
exoplanets and atmospheres, protoplanetary disks, Solar System bodies; II) Stellar lives and deaths at their extremes: the first
stars and the origin of the elements, compact and massive
stars,
Supernovae; III) Gas and metals in the baryon cycle of
galaxies: the interstellar, circumgalactic, and intergalactic medium and their roles in
galaxy growth. These are essential for the Astro Decadal 2020 Survey, Voyage 2050, and HWO. While this paper focuses on high-impact science enabled by UV high-resolution spectroscopy, PEGASUS will extend into the optical regime and lower spectral resolution, making it a multi-purpose, widely used, workhorse spectrograph for HWO.
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All authors Annalisa De Cia, David Cont, Kevin Heng, Boris Gänsicke, Frank Grupp, Ralf Bender, Helena Lamprecht, Frances H. Cashman, Hsiao-Wen Chen, Valentina D'Odorico, Kevin France, Andrew Fox, Jens Hoeijmakers, Masahiro Ikoma, Wynn Jacobson-Galán, Sean D. Johnson, Mansi Kasliwal, Shingo Kameda, Varsha Kulkarni, Carlo F. Manara, Antonija Oklopčić, Cyrielle Opitom, Lidia Oskinova, Anna F. Pala, Ian U. Roederer, P. Christian Schneider, Peter Scicluna, Daniel E. Welty, Sascha Zeegers, Abel de Burgos Sierra, Miriam García, Avery Kim, Christina Konstantopoulou, Roberto Maiolino, Daniel Pauli, Tanita Ramburuth-Hurt, Philipp Richter, Andreas A.C. Sander, Tomer Shenar, Sergio Simón-Díaz, O. Grace Telford, Anna Velichko
Solar and Stellar Astrophysics
Chromospheric and Transition Region Responses of activities at the base of Coronal Plumes
Biswanath Malaker, Vishal Upendran and Durgesh Tripathi
We present the identification of the co-spatial and co-temporal small scale jets – sometimes also named as jetlets – at the base of the coronal hole plume associated with chromospheric and transition region (TR) flows. We identified 19 jets with coordinated observations recorded on March 19, 2016 using the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS). Our analysis of \ion{Si}{4} 1393.7~Å line suggests blueshifts mostly in the range of 10 to 33~km~s$^{-1}$, but few less than -10~km~s$^{-1}$, while analysis of co-spatial \ion{Mg}{2}~h~&~k lines show both blueshifts and
redshifts in the range of {–}9 to 17~km~s$^{-1}$. We observed highly asymmetric, enhanced intensity in \ion{Si}{4} line during these events. The upflows observed in transition region through \ion{Si}{4} is strongly correlated with chromospheric downflows observed in \ion{Mg}{2}. We interpret these results as a signature of interchange reconnections creating bi-directional flows – giving rise to upflows (downflows) in transition region (chromosphere).
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High Energy Astrophysical Phenomena
cuDART: a GPU-accelerated ray tracing code for generating synthetic observations of relativistic astrophysical sources
Henry Whitehead, Emma L. Elley and Christoper N. Everett
The generation of synthetic observations is required to compare simulations of astrophysical phenomena with real sources. We present a new open-source toolkit cuDART which allows meshed simulation data to be rapidly rendered into synthetic observations of optically thin emission, automatically accounting for a range of relativistic and
geometric effects such as Doppler boosting. Unlike previous visualisation schemes which generally consider a single snapshot in time, cuDART is capable of accounting for the finite time delay across astrophysical distances by rendering data from multiple simulation epochs simultaneously. We demonstrate how failing to account for a finite light time delay can result in synthetic observations with incorrect observed motion, morphologies and fluxes. The code does not require a static pattern frame for integration, relaxing standard assumptions required for analytical observational estimates. The rendering processes is accelerated through hardware (using GPUs) and software (using the 3D differential digital analyser
algorithm), allowing for rapid generation of observations from a large number of viewing orientations. In this paper we describe the physical motivation, document the code operation and test the output against theoretical relativistic and
geometric expectations. cuDART is publicly available via GitHub and documented using ReadTheDocs.
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Earth and Planetary Astrophysics
A Stellar-Type Dependence in the Rocky and Volatile Composition of Small Exoplanets
Ji Wang, Caroline Dorn and Komal Bali
We investigate the rocky and volatile composition of small
exoplanets by modeling the population-level distribution of densities using a mixture framework that links interior structure models to observable quantities. We analyze three complementary samples spanning different stellar environments: the Luque & Pallé M-dwarf sample, the DACE M-dwarf sample, and the DACE FGK sample. We consider a log-normal parameterization, which captures a characteristic core mass fraction (CMF) and the intrinsic dispersion to describe a single rocky population. The single rocky population inference suggests a higher CMF for small
planets around FGK
stars than those around M
stars by $\sim$16% (7-11 $\sigma$ depending on sample selection). We also consider a power-law parameterization, which probes clustering near compositional boundaries at CMF=0.32. The power-law parameterization provides an alternative interpretation: 89.9% to 97.0% of the
planets around FGK
stars are rocky whereas up to 61.6% (ranging from 4.1% to 61.6%) of
planets around M
stars are rocky. In addition, we find that volatile mass fractions are highly concentrated. For example, to describe the DACE M-dwarf sample using a mixture of rocky, water-rich, and gas-rich
planets, we find that more than 99.5% gaseous
planets have an atmospheric mass fraction (AMF) $\lesssim 0.01\%$, and more than 55.4% (82.7%) gaseous
planets have a water mass fraction (WMF) $\lesssim 0.1\%$ ($\lesssim 1\%$). These results suggest that while volatile-bearing
planets are common, their composition and prevalence depend strongly on stellar environment, and their volatile inventories are tightly constrained by formation and evolutionary processes.
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High Energy Astrophysical Phenomena
Electromagnetic Emission and Orbital Evolution of Eccentric Supermassive Black Hole Binaries in Retrograde Disks
David ONeill, Mark J. Avara, Christopher Tiede et al. (+3 more)
Circumbinary disks around supermassive black hole binaries (SMBHBs) are expected to form across a broad range of inclinations, with retrograde configurations potentially a common occurrence. Here we present the first grid-based hydrodynamical simulations of retrograde circumbinary disks around eccentric SMBHBs, solving an energy equation that balances viscous and shock heating against blackbody radiative cooling. We investigate different initial disk Mach numbers $\mathcal{M}_a \in \{10, 20, 40\}$ and consider binary eccentricities $e_\mathrm{b}\in[0.0,\,0.8]$, finding that multiple stable states exist for the same binary eccentricity and Mach number. These states differ by the sense of rotation of their minidisks; both retrograde ($\downarrow\downarrow$), both prograde ($\uparrow\uparrow$), or one of each ($\uparrow\downarrow$), a property set by the initial conditions. Our findings indicate that each state produces qualitatively distinct orbital
evolution: $\downarrow\downarrow$ and $\uparrow\downarrow$ minidisks drive circular inspirals whereas $\uparrow\uparrow$ minidisks drive eccentric inspirals with potentially observable eccentricity in the LISA band. We measure the electromagnetic emission produced by the disk, finding that a binary of mass $M_\mathrm{b}=8\times10^6\mathrm{M}_\odot$ at
redshift $z=1$ would be detectable by both current and upcoming optical and UV instruments. We demonstrate that the time- and azimuthally-averaged disk profiles are well described by 1D models, which naturally set a cavity radius within which angular momentum transport is dominated by Reynolds stresses rather than viscosity.
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All authors David ONeill, Mark J. Avara, Christopher Tiede, Daniel J. DOrazio, Zoltan Haiman, Andrew MacFadyen
High Energy Astrophysical Phenomena
Free Neutron Decay in Kilonova Ejecta: X-ray/UV Flashes with Non-Thermal Effects
Daniel Brethauer, Daniel Kasen, Smaranika Banerjee et al. (+2 more)
Neutron star-bearing compact-object mergers can create a kilonova, a transient powered by the radioactive decay of material synthesized via rapid
neutron capture ($r$-process). During the merger, a fraction of the ejecta is launched at high speeds ($\gtrsim$ 0.4c) that can lead to
neutrons evading capture onto seed
nuclei, resulting in free
neutrons. The free
neutrons then decay and inject additional energy that power early-time ($\lesssim$1 day) emission. Here, using Sedona, we present a grid of the first non-local thermodynamic
equilibrium and frequency-dependent opacity radiative transfer simulations to predict early X-ray/UV/optical emission from free
neutron decay that span the expected theoretical range of free
neutron mass, mixing with $r$-process material, and extent of the high-velocity ejecta tail. The emission can be characterized by an SED that rapidly shifts from X-rays of $\sim\rm{few} \times10^{41}-10^{42}$ erg s$^{-1}$ in the first $\sim$ minutes to a far-UV and near-UV peak on the timescale of $\sim$ minutes to hours, followed by enhanced optical and IR emission for sufficiently large free
neutron masses. The properties of the free
neutron ejecta are most distinguishable, in principle, at extreme-UV and far-UV wavelengths, with SED peak flux and wavelength determined by the maximum velocity of the ejecta and the mixing. In the far-UV and near-UV, free
neutron ejecta masses as small as 10$^{-7}$ M$_\odot$ exhibit a unique bump compared to
neutron-free models, demonstrating the importance of upcoming UV missions like UVEX and ULTRASAT to constraining the nucleosynthetic environment of
neutron star mergers.
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All authors Daniel Brethauer, Daniel Kasen, Smaranika Banerjee, Raffaella Margutti, Ryan Chornock
Cosmology and Nongalactic Astrophysics
JZ-FMM: GPU-native differentiable N-body simulations with the Fast Multipole Method
Jens Stücker and Oskar Foldal
N-body simulations are an essential tool for modelling the
evolution of gravitating systems. Differentiable N-body simulations allow solving complicated reconstruction problems by connecting observations of evolved systems to simple informative priors on their initial conditions. While so far most reconstruction efforts focus on mildly non-linear large scale dynamics, the internal dynamics of
galaxies and clusters should exhibit rich information about their formation. The exploration of reconstruction possibilities in this highly non-linear regime naturally requires highly performant differentiable N-body simulations with small scale forces. Here, we present JZ-FMM, a GPU-native differentiable implementation of the fast multipole method for N-body simulations. We show that the GPU oriented design of tree structure, dual tree traversal and multipole translation operators improves performance over established CPU-native and hybrid N-body codes by notably more than an order of magnitude. Further, we show that gradients can be evaluated efficiently and accurately so that JZ-FMM can be used as an essential building block in future field-level reconstruction efforts. We apply the new code to the reconstruction problem of a tidally stripped satellite to show that deeply non-linear problems can indeed be solved efficiently with simulation gradients, although appropriate care must be taken to navigate the complicated optimization landscape.
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Astrophysics of Galaxies
Little Dots: the ULX Analogy
Andrew King
I consider recent observations of the Little Dots (LDs) observed in high–
redshift ($z\sim 7$)
galaxies. I have suggested that the central black holes in these objects are probably fed mass at very super–Eddington (factors $\sim 50$) rates. In physical terms, this idea makes them supermassive analogues of the (stellar–mass) ultraluminous X–ray sources (ULXs), whose hard X–ray emission is strongly anisotropic (`beamed'). In this paper I argue that the recent discovery of extended rest–frame hard X–ray ionization cones from an LD gives strong quantitative support to this view, as its geometry is what one would expect from a ULX–like object viewed not along one of its X–ray beams, but instead `from the side', very similar to the extreme Galactic system SS433. This in turn agrees in quantitative terms with recent suggestions that LDs resemble supermassive versions of SS433–like systems. I emphasize that in contrast, the rest–frame soft X–ray emission from LDs must be roughly isotropic, and presumably power the
torus emission observed from these
galaxies.
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Astrophysics of Galaxies
Exploring the AGN population in protoclusters: results from the TNG300 simulation and comparison with observations
A. Traina, F. Vito, A. Pillepich et al. (+7 more)
In this work, we investigate the physical properties and
cosmic evolution of
galaxies and AGN in a sample of 280 protoclusters identified in the TNG300 simulation, selected to end up in $z = 0$ clusters with $M_{200, \rm c} > 10^{14} \, {\rm M_{\odot}}$. Our goal is to provide the first statistical view of AGN activity enhancement in a uniformly defined sample of overdense environments, and to identify the physical mechanisms driving it. We identify protoclusters as the progenitors of present-day
galaxy clusters through merger-tree reconstruction and compare their
galaxy and AGN populations with a control sample of field
galaxies across the
redshift range $0 \leq z \leq 6$. We investigate
galaxy and SMBH demographics, AGN fractions, bolometric luminosity functions, and the SMBH
accretion rate density, consistently applying homogeneous selection criteria in all environments. We find that TNG300 protoclusters host systematically more massive
galaxies and SMBHs than the field by up to $1 \, {\rm dex}$ at all
redshifts, with signatures of accelerated
galaxy evolution already visible at $z \sim 3-4$. The AGN fraction increases with stellar mass in both environments and, at fixed host-
galaxy stellar mass, is broadly consistent between protoclusters and field
galaxies, indicating no strong environmental triggering of SMBH
accretion. However, when analysed as a function of
redshift, protoclusters exhibit a significant enhancement of AGN activity (by a factor $> 2$), particularly at high luminosities and early
cosmic times. We show that this enhancement primarily arises from differences in the stellar-mass distributions of
galaxies in overdense regions, where massive systems assemble earlier than in the field. Consistently, protoclusters dominate the bright end of the AGN bolometric luminosity function and contribute up to $\sim 50\%$ of the total SMBH
accretion rate density at $z \sim 6$.
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All authors A. Traina, F. Vito, A. Pillepich, A. Kapahtia, O. Cucciati, R. Gilli, F. Arrigoni-Battaia, C. Vignali, M. N. Isla Llave, V. L. Cavicchi
Earth and Planetary Astrophysics
The ALMA View of the Edge-on Gomez's Hamburger System: A Highly-Dynamic, Asymmetric Protoplanetary Disk Reveals the Earliest Phases of Giant Planet Formation
Charles J. Law, Jensen Lawrence, Richard Teague et al. (+18 more)
Chemical tracers provide some of the strongest observational signatures of ongoing
planet formation and localized dynamical perturbations in protoplanetary disks. In particular, sulfur-bearing molecules are predicted to be enhanced in regions of shock heating, ice sublimation, and gravitational instability. Here, we present high-angular-resolution ($\approx$0.$^{\prime\prime}$2) Atacama Large Millimeter/submillimeter Array observations of $^{12}$CO J=3-2, $^{13}$CO J=3-2, CS J=7-6, and SO J$_{\rm N}$=8$_8$-7$_7$ toward the large, edge-on Gomez's Hamburger ('GoHam'; IRAS 18059-3211) disk. We detect a narrow, one-sided arc of SO emission that peaks near a previously-identified gas over-density, suggesting localized heating around an early-stage giant protoplanet or disk fragment. The edge-on geometry of GoHam enables us to place this chemical signature in the broader context of the disk gas and dust structure. To do so, we map the vertical distribution of molecular gas relative to millimeter- and (sub)-micron-sized dust, identify a pronounced north-south continuum asymmetry, and detect non-Keplerian $^{12}$CO and $^{13}$CO emission indicative of a disk wind. We also derive a dynamical stellar mass of 2.2 $\pm$ 0.5 M$_{\odot}$ and a revised dust-extinction-map-based distance of 139 $\pm$ 24 pc, which places GoHam in the outskirts of the Scorpius-Centaurus association. Together, these observations reveal a highly dynamic disk in which localized sulfur chemistry may trace one of the earliest observable stages of wide-separation giant
planet formation.
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All authors Charles J. Law, Jensen Lawrence, Richard Teague, Zhe-Yu Daniel Lin, Romane Le Gal, Kristina Monsch, Gordian Edenhofer, Hans Baehr, Edwin A. Bergin, L. Ilsedore Cleeves, Anne Dutrey, Coralie Foucher, Stéphane Guilloteau, Thomas J. Haworth, Thomas Henning, John D. Ilee, Marija R. Jankovic, Kamber R. Schwarz, Ilaria Pascucci, Dmitry Semenov, Ke Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Cosmological Collider Signals From a Triangle Loop
Zhehan Qin and Zhong-Zhi Xianyu
Triangular loop signals appear frequently in cosmological
collider models but their analytical forms remain unknown due to multiple technical challenges. Here, we determine for the first time the leading analytical cosmological
collider signals generated by a massive scalar triangle loop in inflationary bispectrum and trispectrum. Combining a directional cutting rule with partial Mellin-Barnes representations, we obtain both the local and nonlocal trispectrum signals in a soft limit and derive the leading signal in the squeezed bispectrum. Remarkably, all these signals are reproduced by the corresponding bubble diagram with a single effective pinched coupling. Signals beyond leading order and cases with arbitrary internal masses,
spins, and interactions can be generated within the same framework. Our approach also provides a systematic route to extracting analytical loop signals from general cosmological correlators.
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High Energy Astrophysical Phenomena
Dispersion Measure Variability in Fast Radio Bursts from Photoionization
Brian D. Metzger
Magnetars became favored engines of fast
radio bursts (FRBs) following the discovery of a luminous
radio burst coincident with a hard X-ray
flare from a Galactic magnetar. Several repeating FRB sources exhibit time-variable rotation measures and compact, spatially coincident persistent
radio emission, consistent with energetic-particle nebulae confined by young
supernova ejecta. Secular changes in the dispersion measure (DM) of repeating FRBs have also been observed, offering a complementary probe of their local environments; for example, the DM of FRB 121102 rose until 2019 before declining in recent years. Although rising DM
evolution has been attributed to shock ionization, shocked ejecta can cool efficiently through metal-line emission and recombine, especially if mixed with cooler gas. Here we argue that DM variations of the observed magnitude and timescale instead arise from changes in the ionization state of
supernova ejecta irradiated by X-rays from a time-variable central engine. The dominant rapidly variable contribution comes from the dense, weakly ionized shell swept up by the expanding nebula, whose ionization and recombination times are shorter than those of the more extended ejecta. The model predicts that enhanced FRB activity should be accompanied by rising DM, with a response smoothed over the ionization/recombination time and superposed on a slower secular decline from ejecta expansion. In FRB 121102, the DM maximum occurred close to the burst-rich 2018-2019 activity episodes. If the recently reported renewed activity is sustained, its DM decline should flatten and may reverse into a fresh rise over the coming years.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Ruling out matter-induced bumps in black-hole effective potentials
Matteo Della Rocca, Romeo Felice Rosato and Paolo Pani
Matter fields localized around black holes can produce small secondary bumps in the effective potentials governing black-hole perturbations, potentially leading to quasinormal-mode spectral instabilities and late-time echoes. Considering physically motivated models of anisotropic fluids surrounding a spherically symmetric black hole, we show that the appearance of such a secondary bump is accompanied by either singular matter profiles or divergent characteristic speeds in the fluid. These features indicate that the corresponding matter configurations are unphysical. We further demonstrate that a secondary bump in the effective potential does not necessarily imply the existence of additional light rings in the spacetime.
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Astrophysics of Galaxies
Chasing Cosmic Reionization: An Extremely Faint Highly Magnified Source at $z=5.66$ with high $\xi_{\rm ion}$
Sofía Rojas-Ruiz, Matteo Messa, Eros Vanzella et al. (+5 more)
We present JWST NIRSpec IFU spectroscopic measurements of one of the faintest (M$_{UV}>-13.6$) known ionizing sources at $z=5.66$, dubbed Small And Lensed Source Arc, SALSA. This source is highly magnified ($\mu>100$) by the
lensing galaxy cluster Abell 2744, providing a unique opportunity to investigate the physical properties of faint sources in the Epoch of Reionization. We characterize SALSA's nebular emission using rest-frame UV and optical emission lines and investigate the relationship between its ionizing efficiency, nebular excitation, and chemical enrichment. We robustly detect H$\alpha$ emission and use it to predict the H$\beta$ flux assuming negligible dust attenuation. We also measure the [OIII]$\lambda$5007 emission and estimate oxygen abundance resulting in a high R3 index $2.82_{-0.25}^{+0.34}$ and relatively low
metallicity $\mathrm{12+log(O/H)}= 7.43\pm0.09$. SALSA presents a high ionizing production efficiency log$(\xi_{ion})=25.49_{-0.08}^{+0.09}$ Hz erg $^{-1}$, consistent with theoretical models from very massive
stars and constant
star formation rate, and a high Ly$\alpha$ escape fraction $f_{\mathrm{esc}}^{\mathrm{Ly}\alpha}=0.39\pm0.14$. These properties place SALSA among the most extreme
star-forming sources known at this epoch.
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All authors Sofía Rojas-Ruiz, Matteo Messa, Eros Vanzella, Tommaso Treu, Pietro Bergamini, Giorgia Di Rosa, Marco Lombardi, Piero Rosati
Astrophysics of Galaxies
Deus Ex Statistica: A Statistical Solution to the binary-binary Outcome of the Chaotic, Non-Hierarchical Four-Body Problem
Yoav Zack, Hagai B. Perets and Yonadav Barry Ginat
We present an analytical, statistical solution to the binary-binary (2+2) outcome of the chaotic non-hierarchical four-body problem. The solution is based on the density-of-states formulation pioneered by J. J. Monaghan. The method skips the computationally expensive integration of the equations of motion, and instead samples the outcome from the chaotic phase-space, subject to conservation of energy, momentum, and angular momentum. From the joint distribution, we extract marginal distributions of several key parameters using Monte-Carlo integration, and numerically verify them by comparing to an identical ensemble of scattering experiments produced by the FEWBODY code. From the comparison, we identify a regime not represented by the density-of-states formulation: the hard binary regime, where one binary is much harder then the four-body energy scale, and the system acts as an effective three-body system. We hypothesize that at this regime the system's probability distribution spreads over an effective reduced three-body chaotic phase space. The process of transfer from four-body to three-body phase-space is still not understood, and represents the next natural extension of density-of-states methods.
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Earth and Planetary Astrophysics
The GAPS programme at TNG LXXVIII. Phase-resolved detection of multiple atomic species in the atmosphere of KELT-20b/MASCARA-2b
F. Biassoni, F. Borsa, L. Fossati et al. (+15 more)
Among the different classes of
exoplanets, ultra-hot Jupiters represent
prime laboratories for atmospheric characterisation. With an
equilibrium temperature of ~2300 K, KELT-20b/MASCARA-2b (HD 185603 b) is a well-studied ultra-hot Jupiter, for which several atomic species have already been detected in both transmission and emission spectroscopy. Nevertheless, important open questions remain regarding the completeness of the chemical inventory and the interpretation of spurious aliasing signals that may mimic genuine atmospheric signatures. In addition, asymmetries in the detected signals across transits can encode valuable information on the spatial structure and dynamics of the planetary atmosphere. In this work, we analyse seven transits of KELT-20b/MASCARA-2b observed with the high-resolution spectrograph HARPS-N at the Telescopio Nazionale Galileo. We apply the cross-correlation function technique to a large set of atomic and ionic species, accounting for aliasing effects that can lead to false detections. We confirm previous detections of HI, NaI, MgI, CrI, FeI, and FeII, and tentatively detect CrII. We further report new detections of KI, CaI, VI, MnI, and BaII, and a tentative detection of PrI in the planetary atmosphere. By performing a phase-resolved analysis and splitting the transit into pre- and post-mid-transit phases, we investigate longitudinal variations in the detected signals. For several species, we observe a double-peaked structure in the Kp-Vsys maps, notably in CaI, VI, CrI, and FeI, consistent with absorption arising from two distinct atmospheric limbs of the
planet.
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All authors F. Biassoni, F. Borsa, L. Fossati, M.C. D'Arpa, A.S. Bonomo, G. Guilluy, T. Zingales, D. Sicilia, A. Sozzetti, M. Rainer, M. Basilicata, I. Carleo, R. Cosentino, R. Claudi, P. Giacobbe, A. Harutyunyan, L. Malavolta, L. Mancini
Astrophysics of Galaxies
Overmassive No More: The Case for Little Red Dots Hosting Black Hole Seeds as Massive as Single Supermassive Stars
Wendy Q. Sun, Rohan P. Naidu, Hanpu Liu et al. (+17 more)
Little Red Dots (LRDs) display singular properties unlike any known class of AGN or
galaxies, motivating novel mass
estimators for their central engines. Inspired by their similarities to stellar phenomena, here we interpret the LRD continuum as being produced by a pseudo-photosphere. We fit tailored stellar atmosphere models to host-subtracted LRD central engines ("black hole
stars," BH*s) represented by stacks of $117$ objects. Typical BH* continuum spectra are well fit by models in a narrow range of temperatures ($T_{\rm eff}\approx4200-4800$ K), with bolometric luminosities $\approx10^{43-45}$ erg s$^{-1}$, implying pseudo-photospheric radii $\approx700-2000$ au. Based on these parameters, we explore four different approaches to deriving BH* masses: 1) using the surface
gravity from atmosphere models; 2) appealing to the resemblance to super-Eddington phenomena; 3) approximating the escape velocity from the outflowing material; and 4) exploiting the lack of variability to bound the dynamical time. For the typical BH*, all of these methods yield remarkably consistent masses of $\approx10^{4-5}\,M_\odot$, implying a highly super-Eddington luminosity of $L_{\rm{bol}}/L_{\rm{Edd}}\sim5-50$. These mass estimates place BH*s within the scatter of the local scaling relation between black hole mass and host
galaxy stellar mass, providing a self-consistent alternative to "overmassive" black holes that lie $2-3$ dex above it. Crucially, our derived masses are consistent with BH*s arising from single supermassive
stars (SMSs), whose masses cannot exceed $\approx10^{5-6}\,M_\odot$ due to general relativistic instabilities. Furthermore, for our derived $L_{\rm bol}/L_{\rm Edd}$, the sharp cutoff of the LRD luminosity function matches the maximum theoretical mass of an SMS. With LRDs, we may therefore be directly observing the birth of heavy black hole seeds.
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All authors Wendy Q. Sun, Rohan P. Naidu, Hanpu Liu, Anna de Graaff, Jenny E. Greene, Jorryt Matthee, Chris Ashall, John Chisholm, Anna-Christina Eilers, Qinyue Fei, Kasper E. Heintz, Daichi Hiramatsu, Vasily Kokorev, Joel Leja, Zhaoran Liu, Priyamvada Natarajan, Pascal A. Oesch, Robert A. Simcoe, Alberto Torralba, Andrea Weibel