Astrophysics of Galaxies
Detection of a triple nucleus in the Wolf-Rayet composite Sy 2 galaxy NGC 6764
Jochen Heidt, Francisco Pozo Nuñez, Nina Mackensen et al. (+2 more)
We report adaptive-optics Ks-band imaging of the composite Seyfert 2 and Wolf-Rayet
galaxy NGC 6764 (D = 32 Mpc), obtained with LUCI/SOUL at the Large Binocular
Telescope. The
nucleus resolves into three compact sources with pairwise projected separations of 0.07-0.20 arcsec, corresponding to 11.0-30.9 pc. All three have indistinguishable H, Ks, H2, and Br-gamma colours, so photometry alone cannot separate
accretion from
star formation. The system is consistent with a Seyfert
nucleus and two
star-forming regions, but a dual or triple AGN cannot be excluded. In the latter case, the separations would be two orders of magnitude smaller than in any confirmed or candidate AGN triplet reported to date. Diffraction-limited near-infrared integral-field spectroscopy is required to establish the nature of each component.
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All authors Jochen Heidt, Francisco Pozo Nuñez, Nina Mackensen, Magdalena Vukojevic, David Thompson
Solar and Stellar Astrophysics
SPIRITS 19q: Dust Production by a Subsolar-metallicity Carbon-rich Wolf-Rayet Star in NGC 2403
Sam Rose, Ryan M. Lau, Jacob E. Jencson et al. (+20 more)
We present JWST/NIRSpec IFU observations of SPIRITS 19q, the highly dust-producing carbon-rich (WC) binary candidate located in a subsolar-
metallicity region of the nearby spiral
galaxy NGC 2403. The observations, taken in April of 2024, confirm the association of a dusty outburst observed in 2019 by the Spitzer Space
Telescope with an early-type WC
star. Using models from the Potsdam Wolf-Rayet (PoWR) LMC model grid we find that the WC
star of SPIRITS 19q likely has an especially high mass-loss rate ($\gtrsim$ 10$^{-4}$ $M_{\odot}$ yr$^{-1}$). From the flux peak of the IR transient as measured by Spitzer/IRAC as well as constraints on dust composition and size from the JWST spectrum, we estimate a total dust mass formed in the outburst of 6.6 $\pm$ 0.4 $\times$ 10$^{-6}$ $M_{\odot}$. Assuming a minimum orbital period of 12 years, this corresponds to a period-averaged dust production rate of $\lesssim$ 5.5 $\times$ 10$^{-7}$ $M_{\odot}$ yr$^{-1}$. These observations suggest that even a single WC system can contribute to the dust budget at subsolar
metallicities, and that such systems are an important source of carbonaceous dust grains in the early universe.
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All authors Sam Rose, Ryan M. Lau, Jacob E. Jencson, Mansi M. Kasliwal, Andreas A.C. Sander, Howard E. Bond, Michael F. Corcoran, Izumi Endo, Matthew J. Hankins, Olivia C. Jones, Viraj R. Karambelkar, Astrid Lamberts, Thomas Madura, Anthony F.J. Moffat, Patrick W. Morris, Takashi Onaka, Michael E. Ressler, Noel D. Richardson, Christopher M. P. Russell, Itsuki Sakon, J. Sanchez-Bermudez, Gerd Weigelt, Peredur M. Williams
Solar and Stellar Astrophysics
Age Discrepancy in Three Galactic Cepheid Binaries
Sashwat Prasadh, Hilding R. Neilson and Nancy Remage Evans
SV Per, RW Cam, and KN Cen are Galactic classical Cepheids found in binary systems along with B-type companions. Each system exhibits an “apparent age discrepancy", where the Cepheid appears significantly younger than its companion. We compute stellar
evolution tracks using the MESA code and compare them with these
stars on the Hertzsprung-Russell diagram to estimate the masses and the corresponding ages. We find that, for two of the systems, the companions appear to be between 1.5 times to double the age of the Cepheids, suggesting that the Cepheids may be rejuvenated merger products of two main-sequence
stars that have since evolved. We find that the third system KN Cen is consistent with single
star evolution when we reevaluate ultraviolet observations and find that the companion is hotter than previously measured. We test this idea using the MESA code for each system by evolving a single
star model and rapidly accreting mass on the main sequence to emulate a merger, and then continuing the
evolution until the model is consistent with the parameters of the Cepheids. The results are consistent with the hypothesis that the Cepheids were originally merger products. We conclude with a discussion of potential observational tests of the merger hypothesis.
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Earth and Planetary Astrophysics
An Upper Limit on Turbulent Viscosity in the Circumjovian Nebula
Konstantin Batygin and Fred C. Adams
Circumplanetary disks are open, dynamic systems sustained by a meridional circulation that draws gas and dust from the parent nebula along nearly polar streamlines, and ultimately returns some of this material through a viscously driven, in-plane outflow. In such a disk, the water ice line acts as a site of solid-mass accumulation: inward-drifting icy solids sublimate interior to the ice line, the resulting vapor is advected outward by the gas, and recondensation beyond the ice line resets the material to a small Stokes number. The operation of this drift-mediated loop requires the fragmentation-limited Stokes number of the mass-dominant icy aggregates to exceed the
equilibrium Stokes number at which the radial drift of solids reverses. Because the former scales inversely with the Shakura-Sunyaev viscosity parameter $\alpha$ while the latter is directly proportional to it, this requirement yields a compact upper bound on the vigor of
turbulence in the satellite-forming region. Adopting an actively heated, steady-state circumjovian disk truncated at the tidal radius, we find a marginal bound of $\alpha\lesssim 10^{-3}$ for an icy-particle fragmentation threshold of $v_f\simeq1\,{\rm m\,s^{-1}}$ - appropriate for cold ice with sticking properties similar to silicate dust. This bound scales linearly with $v_f$, reaching $\alpha\lesssim5\times10^{-3}$ for more adhesive, warm ice ($v_f\simeq5\,{\rm m\,s^{-1}}$). The bound carries no explicit dependence on the disk's mass flux, and is set entirely by the local thermal state, pressure gradient, and geometry of the circumjovian nebula.
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Astrophysics of Galaxies
Formation of Heavy Seed Black Holes and Little Red Dots-like Compact Clusters in Metal-enriched Star-forming Regions
Sunmyon Chon, Shingo Hirano, Ke-Jung Chen et al. (+1 more)
The origin of supermassive black holes (SMBHs) in the early Universe remains uncertain. While the classical direct-collapse scenario requires pristine gas exposed to intense Lyman-Werner (LW) radiation, recent JWST observations suggest that early growing BHs may reside in compact, metal-enriched environments. We investigate early BH formation using a cosmological radiation-hydrodynamic simulation that self-consistently follows the formation and
evolution of rapidly accreting supermassive
stars (SMSs). We find that intense LW radiation develops in clustered
star-forming regions; by the time the first heavy seed forms, the mass-weighted internal intensity has reached $J_{21}\sim1000$. Most seeds form in weakly metal-enriched gas with [Z/H]$\sim-3$ to $-2$, because the strongest LW fields occur in regions already enriched by previous stellar feedback. All
halos above $10^9M_\odot$ in our zoom-in region host a BH more massive than $10^5M_\odot$. We construct stellar spectra using MIST/PHOENIX libraries for normal
stars and $6000~\mathrm{K}$ blackbody spectra for bloated SMSs. Five of eight massive clusters with stellar masses larger than $10^6~M_\odot$ exhibit intrinsically V-shaped spectra similar to those of Little Red Dots (LRDs). In the most prominent cases, luminous SMSs dominate the red optical emission, although Balmer breaks in normal stellar populations also contribute. We also identify off-center LRD-like systems in our simulation resembling those recently reported in strongly lensed observations. Our results suggest that heavy-seed formation, compact-cluster formation, and LRD-like continuum emission are linked outcomes of clustered, weakly metal-enriched, strongly irradiated environments.
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All authors Sunmyon Chon, Shingo Hirano, Ke-Jung Chen, Volker Springel
Earth and Planetary Astrophysics
Accelerating Chemical Kinetics for Exoplanet Atmospheres using Neural Networks
Isaac Malsky, Xi Zhang, Tiffany Kataria et al. (+5 more)
Observations increasingly reveal the coupled radiative, chemical, and dynamical processes that shape
exoplanet atmospheres. Interpreting these atmospheres requires models that can capture this complexity. However, multidimensional models remain fundamentally limited by computational cost, and answering key questions requires simulating the governing physical mechanisms at speeds classical methods cannot achieve. As a result, models often rely on simplifying approximations, such as
equilibrium chemistry, even when those assumptions miss important effects. There is a pressing need for fast and accurate chemical kinetics solvers to model planetary atmospheres. Here we present a machine learning local-box chemical kinetics solver for
exoplanet atmospheres using a residual flow-map architecture. We demonstrate that this surrogate model is several orders of magnitude faster than a classical solver, achieving microsecond-scale inference while retaining percent-level accuracy. The surrogate model covers a parameter space that spans $T=300$-$3000$ K, $P=10^{-6}$-$10^{4}$ bar, $\Delta t=10^{-3}$-$10^{8}$ s, and compositions ranging from $10^{-2}$ to $10^{3}$ times solar in both C/O ratio and
metallicity. Our model outperforms several commonly used machine learning architectures and performs robustly under the extreme stiffness characteristic of atmospheric chemistry. The machine learning framework presented here is a flexible and efficient approach to emulating state-to-state flow-map problems that commonly arise in numerical simulations.
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All authors Isaac Malsky, Xi Zhang, Tiffany Kataria, Matthew Graham, Ziyu Huang, Boris Bonev, Shang-Min Tsai, Elspeth K.H. Lee
Solar and Stellar Astrophysics
The Formation of Very Close Binary Stars
Maxwell Moe
The majority of very close binaries (orbital periods P < 5 days) are in triples. Previous studies surmised that the tertiary hardened the inner binary via Kozai-Lidov cycles coupled with tidal friction. Alternatively, the trend could be due to a common origin, e.g., more massive molecular cores and protostellar disks are more likely to fragment twice into a triple and harden the inner binary to very short periods via disk migration. Disk migration occurs during the embedded Class I protostellar phase while secular
evolution with a tertiary occurs on much longer timescales. To determine the dominant migration mechanism, I accurately measure the very close binary fractions of both late-type and early-type primaries in
star-forming environments. After combining five surveys, the late-type Class II/III T Tauri very close binary fraction is F_VCB = 2.1_{-0.5}^{+1.0}%, which is consistent with the measurement for late-type field main-sequence
stars (1.7% +/- 0.1%). More than 85% of very close late-type binaries hardened via disk migration during the Class I protostellar phase. I next measure the OGLE-III eclipsing binary (EB) fractions of young massive
stars in the LMC. The very close EB fractions of massive young stellar objects (YSOs; F_VCEB = 8.3_{-3.2}^{+4.9}%), OB
stars near massive YSOs (4.7% +/- 0.8%), and OB
stars in small, young H II regions (6.4% +/- 1.5%) are consistent with each other and the measurement for OB
stars in slightly older clusters (4.7% +/- 0.3%). More than 90% of very close massive binaries hardened via disk migration during the embedded protostellar phase.
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Earth and Planetary Astrophysics
Where planetary solids survive sublimation around young and hot white dwarfs
Dimitri Veras, Keiji Ohtsuki, Rafael Martinez-Brunner et al. (+2 more)
All observed planetary systems orbiting single white dwarfs have lived through the hot stellar transition from an asymptotic giant branch
star. In this post-nebular transition period, the initial conditions for planetary system
evolution throughout white dwarf cooling are established. The hottest ($\gtrsim$ 20,000 K) and youngest ($\lesssim$ 20 Myr-old) white dwarf planetary system host
stars differ significantly from their canonical older and colder counterparts by failing to support solid body accumulation in the immediate vicinity (a few $R_{\odot}$) of the white dwarf. Here, we analyse the likely locations of both solid-body survival and the sublimated gaseous content during this pivotal epoch, and the consequences. We find that (i) reservoirs of iron-rich, rocky and water-rich asteroids of radius $R$ that later observably enrich, or pollute, the white dwarf need to remain parked for the first tens of Myr of white dwarf cooling beyond critical distances of (16 au)$\times(1 {\rm km}/R)^{1/2}$ (for iron), (30 au)$\times(1 {\rm km}/R)^{1/2}$ (for rock) and (130 au)$\times(1 {\rm km}/R)^{1/2}$ (for snow), (ii) sublimation acts much more quickly than radiatively-driven orbital drifts from Poynting-Robertson drag or the Yarkovsky effect, and (iii) although large asteroids ($R \approx$ 10-1000 km) that are kicked on highly eccentric orbits around newly born white dwarfs could survive sublimation, they may fragment into debris which will sublime before the white dwarf cools. These results support, but do not necessitate, dynamical origin scenarios of polluted white dwarfs that feature delayed gravitational instability subsequent to the host
star's asymptotic giant branch phase at Kuiper Belt-like distances, and beyond.
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All authors Dimitri Veras, Keiji Ohtsuki, Rafael Martinez-Brunner, Takato Nishio, Ryo Tamon
Instrumentation and Methods for Astrophysics
The Canadian Galactic Emission Mapper (CGEM): A Cosmic Microwave Foreground Experiment
Parham Zarei, Pedro Villalba-González, Mandana Amiri et al. (+12 more)
The Canadian Galactic Emission Mapper (CGEM) is a 4-meter single-dish
radio telescope located at the Dominion
Radio Astrophysical Observatory (DRAO) in Penticton, Canada. CGEM is designed to map polarized Galactic synchrotron emission across the entire northern sky at 8-10 GHz with 1 MHz frequency resolution and 0.5 degree angular resolution. Its goal is to obtain high-fidelity, low-noise maps of polarized Galactic synchrotron radiation, at frequencies where synchrotron dominates, in order to provide a reliable template for CMB B-mode foreground cleaning. We will show on sky performance of CGEM's single-pixel azimuthally-symmetric
telescope, its coherent, dual-polarized radiometer, and show maps made from commissioning data from the first few months of operation.
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All authors Parham Zarei, Pedro Villalba-González, Mandana Amiri, Charles L. Bennett, Guinevere Berg, Mark Halpern, Gary Hinshaw, Gordon Lacy, Joshua MacEachern, Thomas J. Rennie, Shuyu van Kerkwijk, Bruce Veidt, Janet Weiland, Don Wiebe, Edward J. Wollack
Astrophysics of Galaxies · Cross-listed from gr-qc
A Fast and Scalable Transformer Pipeline for Binary Black Hole Detection
Chayan Chatterjee, Abigail Petulante, Haowei Fu et al. (+3 more)
With the projected increase in the detection rate of compact-binary coalescences in the coming decade, there is critical need to develop fast, robust, and scalable alternatives to matched filtering for gravitational-wave searches.
Transformer models have revolutionized natural
language and audio processing but their application to gravitational-wave astronomy is still largely unexplored. In this work, we introduce \castor, a
transformer-based coincident search pipeline for detecting binary black hole gravitational-wave signals from Advanced LIGO detectors. One of the major features of our model is that it allows the false-alarm rate to be estimated via time slides cheaply without requiring repeated evaluations of the neural network. We evaluate \castor\ on
datasets from the Machine-Learning Gravitational-Wave Search Challenge (MLGWSC-1) and on approximately five months of real O3b observing strain. When tested on
benchmark datasets, \castor\ ranks among the most sensitive machine-learning pipelines and successfully recovers the majority of confident events from the GWTC-3 catalog that lie within its training range. We also
benchmark \castor\ against another
transformer architecture, GW-Whisper, a domain-adaptation of OpenAI's audio foundation model. We find that \castor\ substantially outperforms the repurposed audio model in sensitivity and also reduces the computational cost of background estimation by a factor of 20. Our results demonstrate a highly practical, scalable approach for deep-learning gravitational wave searches and empirical background estimation for future observing runs.
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All authors Chayan Chatterjee, Abigail Petulante, Haowei Fu, Yang Hu, Roy Lau, Karan Jani
Solar and Stellar Astrophysics
Direct Measurement of Polar Coronal Hole-like Solar Wind in its Acceleration Phase
Samuel T. Badman, Yeimy J. Rivera, Michael L. Stevens et al. (+38 more)
The early
evolution of fast polar coronal hole (PCH) solar wind remains largely unconstrained by in situ measurements. In March 2025, Parker Solar Probe (Parker) at its closest approach of 9.86 Solar Radii ($R_\odot$) measured outflow from a large equatorial coronal hole (ECH) which was also measured at 1\,au and at intermediate distances by Solar Orbiter (also near its perihelion). At 1\,au the stream properties are consistent with PCH properties established by Ulysses. The stream was measured by Parker substantially below the Alfvén surface, with
proton temperatures in excess of 2\,MK and a speed at $\sim$10\,$R_\odot$ which was only $\sim$60% of its asymptotic value. The Solar Orbiter data indicates that the acceleration is largely complete by 60~$R_{\odot}$. Spherically-polarized fluctuations in the stream are observed to develop from near-transverse and small-angle at Parker to full reversal “switchbacks” at Solar Orbiter. Comparison of the implied acceleration profile to historical doppler-dimming measurements suggests that the stream's low coronal acceleration is similar to that of PCH flows. Consistent with previous work, this acceleration requires significantly more energy than can be provided by the observed thermal pressure gradients, with a significant contribution likely from the abundant Alfvénic fluctuation energy observed at Parker. These observations provide unique constraints on models of the radial
evolution of the fastest solar wind, and indicate that these wind streams experience gradual, steady acceleration over their first few tens of solar radii of
evolution.
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All authors Samuel T. Badman, Yeimy J. Rivera, Michael L. Stevens, Mari Paz Miralles, Steven R. Cranmer, Andrea Verdini, Lynn B. Wilson III, Xiangyu Wu, Georgios Nicolaou, Jean-Baptiste Dakeyo, Kai Jaffarove, Tamar Ervin, Dominic S. Payne, Michael Terres, Kristopher G. Klein, Jasper S. Halekas, Sujan Prasad Gautam, William H. Matthaeus, Riddhi Bandyopadhyay, Srijan Bharati Das, Tatiana Niembro, Christopher J. Owen, Rungployphan Kieokaew, Ali Rahmati, Orlando M. Romeo, Federico Fraschetti, Marco Velli, Lorenzo Matteini, Kristoff W. Paulson, Lidiya Ahmed, Stuart D. Bale, Phyllis Whittlesey, Marc Pulupa, Nour E. Raouafi, Timothy S. Horbury, Jean Morris, Helen O'Brien, Roberto Livi, Davin E. Larson, Adam J. Finley, Philippe Louarn
Solar and Stellar Astrophysics
A Data-Driven Model for $r$-Process Production Patterns
Chen-Qi Li, Yong-Zhong Qian, Axel Gross et al. (+1 more)
Using the elemental abundances in 68 metal-poor (MP)
stars, we present a data-driven model for $r$-process production patterns covering Sr to U. We show that essentially all the $r$-process patterns in those and other test
stars can be adequately explained as mixtures of Patterns 1 and 2, which provides theoretical insights into the empirical categories of limited-$r$, $r$-I, and $r$-II
stars. We carry out an extensive survey of the yield templates produced by parametric $r$-process calculations. We propose that Pattern 2 may be dominated by a single template and points to regularity in $r$-process production by a subset of
neutron star mergers (NSMs), while Pattern 1 is the average superposition of multiple templates and reflects production by other NSMs and perhaps also some magneto-rotational
supernovae. We raise possible systematic issues with abundance ratios for elements measured in different ionization states, and highlight the need for examining the Os, Ir, and Pt measurements for HD~122563, which is dominated by Pattern 1 with a prominent Pt peak in our model. If this result is confirmed, the meaning of the limited-$r$ category requires drastic revision. Further measurements of a wider range of $r$-process elements in a larger sample of MP
stars are critical to test and improve our model.
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All authors Chen-Qi Li, Yong-Zhong Qian, Axel Gross, Zewei Xiong
Solar and Stellar Astrophysics
TESS Observations of Seven Newly Identified High-amplitude $\delta$ Scuti Stars
Chenglong Lv, Ali Esamdin, Amir Hasanzadeh et al. (+3 more)
We report seven newly identified high-amplitude $\delta$ Scuti (HADS)
stars. Among them, two
stars (TIC 30977864 and TIC 387379145) exhibit pure radial pulsation without the excitation of non-radial modes. TIC 30977864 is classified as a double-mode HADS
star, while the other four
stars potentially show triple-mode HADS behavior. TIC 112682462 and TIC 255603395 closely resemble RR Lyrae
stars based on their light curves, position in the period-luminosity diagram, and the period-ratio diagram. However, without spectral observations, it is challenging to ascertain whether these two
stars are HADS or RR Lyrae
stars. TIC 281695001 exhibits a fundamental frequency amplitude smaller than that of the first overtone, suggesting the presence of intriguing phenomena that necessitate further analysis. We analyzed the relationship between
metallicity and period using data provided by Netzel & Smolec. The
metallicities of the 176
stars display a broad distribution ranging from -2.0 dex to 0.5 dex, with periods spanning 0.05 to 0.20 days. This random distribution of
metallicities may contribute to the dispersion observed in the $P_1/P_0$ ratio. To derive more accurate conclusions, future spectroscopic observations of a larger sample of HADS
stars are crucial. These observations will provide precise rotational velocities and more accurate determinations of
metallicities.
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All authors Chenglong Lv, Ali Esamdin, Amir Hasanzadeh, Shuguo Ma, TaoZhi Yang, Rivkat Karimov
Solar and Stellar Astrophysics
Statistical analysis of asteroseismic indices and stellar parameters of TESS-observed $\delta$ Scuti stars
C. Lv, A. Esamdin, A. Hasanzadeh et al. (+4 more)
We analyze the statistical properties and asteroseismic indices of delta Scuti
stars observed during TESS Cycle 4. Using 2 minute cadence photometry and
Fourier analysis, we identified 765 delta Scuti
stars in Sectors 40-55, including 179 objects with low-resolution stellar parameters from LAMOST. We examined the distributions of their pulsation and stellar parameters using values from the TESS Input Catalog and LAMOST. Most targets lie within the classical instability strip, follow the period-luminosity relation, and show periods, amplitudes, temperatures, surface gravities, and luminosities consistent with delta Scuti
stars. For the LAMOST subsample, we estimated the large frequency separation ($\Delta\nu$), $\nu_{\rm max}$, and $\nu({\rm Amax})$ using an empirical relation and a two-dimensional autocorrelation method. We also derived relations among these asteroseismic indices. This catalog provides a useful sample for future studies of the internal structure and
evolution of delta Scuti
stars.
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All authors C. Lv, A. Esamdin, A. Hasanzadeh, M. Ghazinejad, J. Pascual-Granado, G. M. Mirouh, R. Karimov
Solar and Stellar Astrophysics
Discovery and Characterization of Three New High-amplitude delta Scuti Stars from TESS Observations
Chenglong Lv, Ali Esamdin, J. Pascual-Granado et al. (+5 more)
We report the discovery and detailed analysis of three new high-amplitude {\delta} Scuti (HADS)
stars, TIC 408074920, TIC 189714989, and TIC 34137913, identified from Transiting
Exoplanet Survey Satellite short-cadence observations.
Fourier analysis reveals dominant radial modes accompanied by rich harmonic structures in all three
stars, confirming their HADS classification. In addition, TIC 189714989 exhibits clear symmetric side peaks around the radial harmonics, indicative of amplitude and/or phase modulation. Broadband spectral energy distribution (SED) fitting constrained by Gaia DR3 parallaxes provides independent estimates of the stellar effective temperatures and radii. These are compared with results from stellar evolutionary and seismic modeling based on MESA and GYRE. For two targets, the SED-derived and seismic radii are mutually consistent, while TIC 408074920 displays a significant discrepancy, plausibly attributable to the different sensitivities of the two methods and additional systematic effects. These findings highlight the diversity of amplitude variability among classical HADS and emphasize the importance of the long-term monitoring that future missions such as PLATO will allow in order to explore the underlying physical mechanisms of this variability.
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All authors Chenglong Lv, Ali Esamdin, J. Pascual-Granado, Guojie Feng, Haozhi Wang, Rivkat Karimov, Bolkin Juraev, Shuhrat A. Ehgamberdiev
Astrophysics of Galaxies
ELVES-Dwarf. II. A Systematic Search for Satellite Systems of Dwarf Galaxies in the Local Volume
Jiaxuan Li, Jenny E. Greene, Shany Danieli et al. (+7 more)
We present the Exploration of Local VolumE Satellites of Dwarf
Galaxies (ELVES-Dwarf) survey, a systematic census of satellite systems around dwarf hosts in the Local Volume. Our final sample comprises 39 predominantly isolated hosts with stellar masses $10^{7}<M_\star<10^{10}\,M_\odot$, including 32 hosts searched uniformly in this work and 7 drawn from the literature. We search for satellite candidates within the projected virial radius of each host using $155~\mathrm{deg}^2$ of Legacy Surveys imaging data. We determine satellite membership using surface brightness fluctuation distances from Subaru/HSC, Magellan/IMACS, and Gemini/GMOS imaging, supplemented by literature TRGB distances and radial velocities. From 207 candidates, we confirm 39 satellites with $M_\star>10^5\,M_\odot$ around the 39 hosts. Above our fiducial completeness threshold of $M_\star\gtrsim10^{5.7}\,M_\odot$ and within the projected virial radius, 21 hosts have no confirmed satellites, 10 have one, six have two, and two have four, revealing substantial host-to-host scatter in satellite abundance. Overall, the observed satellite abundances and stellar mass functions are broadly consistent with predictions from the cosmological simulation TNG50 and
galaxy formation models calibrated using Milky Way satellites. The projected radial distribution of the satellites is also consistent with theoretical expectations and with satellite populations around Milky Way-mass hosts. In contrast, the quenched fraction of satellites around dwarf hosts is substantially lower than around Milky Way-mass hosts, suggesting that environmental quenching is less efficient in dwarf
halos. ELVES-Dwarf provides the first large, homogeneous, distance-confirmed sample of satellites around dwarf hosts and establishes a foundation for understanding
galaxy formation and
evolution in less-dense environments.
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All authors Jiaxuan Li, Jenny E. Greene, Shany Danieli, Scott G. Carlsten, John Moustakas, Marla Geha, Masayuki Tanaka, Fangzhou Jiang, Ping Chen, Sufia Birmingham
Earth and Planetary Astrophysics
Three-dimensional circumplanetary flows in a PDS 70c-inspired system: hydrodynamic simulations with FARGO3D and analysis with FARGOpy
Alejandro Murillo-Gonzalez, Jorge I. Zuluaga and Matias Montesinos
The detection of circumplanetary material around the forming
planet PDS~70c provides a valuable setting for studying three-dimensional gas
accretion during giant-
planet formation. We present three-dimensional hydrodynamic simulations with FARGO3D for a locally isothermal protoplanetary disk, adopting system-motivated stellar, orbital, and disk parameters and planetary masses of $2$, $4$, and $8,M_{\rm Jup}$, all above the local thermal mass. The locally isothermal prescription provides a controlled prescribed-temperature limit that isolates the hydrodynamic organization of the flow, without modeling self-consistent thermal
evolution or radiative observables. Gas enters the planetary environment through meridional flows from the upper disk layers and streams near the midplane. With increasing planetary mass, the flow changes from a vertically extended, envelope-like configuration to a more compact and stratified circumplanetary structure. The inferred CPD radius increases from $R_{\rm CPD}\simeq0.31$ to $0.40,R_{\rm Hill}$, while the flow remains sub-Keplerian, reaching $v_\phi/V_{K,p}\sim0.79$–$0.85$. Most enclosed gas mass lies within a few tenths of the Hill radius, whereas the outer Hill sphere is dominated by anisotropic inflow, outflow, and recirculation. The analysis was performed with FARGOpy, a Python post-processing framework developed in this work to reconstruct three-dimensional fields, compute integrated fluxes, and characterize circumplanetary kinematics from FARGO3D outputs. This study therefore provides both a hydrodynamic baseline for a PDS~70c-like environment and a reproducible framework for analyzing three-dimensional FARGO3D simulations.
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Astrophysics of Galaxies
Accretion-disk sizes in two quasars with interferometrically resolved broad-line regions at $z=2.3$ and $z=4.0$
Francisco Pozo Nuñez, Eduardo Bañados, Swayamtrupta Panda et al. (+3 more)
We present the first direct comparison between
accretion-disk (AD) and broad-line region (BLR) sizes in
quasars at z > 2, combining continuum reverberation mapping with interferometric BLR constraints from
GRAVITY and
GRAVITY+. Using medium-band photometric monitoring with the MPG/ESO 2.2 m
telescope, we measure inter-band continuum lags in SDSS J092034.17+065718.0 at z = 2.33 (J0920) and SMSS J052915.80-435152.0 at z = 3.96 (J0529), among the most luminous
quasars known (Lbol ~ 10^48 erg s^-1). These are currently the only two
quasars at z > 2 with spatially resolved BLRs and dynamical black-hole masses from interferometry. We detect significant continuum lags in both
quasars, increasing monotonically with wavelength. The inferred UV disk sizes are RAD = 4.35 +0.78/-0.91 light-days for J0529 and RAD = 3.15 +0.50/-0.48 light-days for J0920. For J0920, accreting at lambda_Edd ~ 7-20, the disk size is consistent with standard thin-disk expectations despite its super-Eddington regime. For J0529, the disk size agrees with thin-disk predictions using the single-epoch black-hole mass, but implies disk inflation by a factor of a few if the
GRAVITY+ dynamical mass, an order of magnitude lower, is adopted. UV continuum disk sizes therefore provide an independent physical scale constraining black-hole mass and
accretion-rate models, particularly where BLR kinematics are dominated by outflows. The interferometric BLR sizes reveal pronounced radial hierarchies, with RBLR/RAD ~ 270 for J0529 (Hbeta) and ~115 for J0920 (Halpha). The successful lag detections at Lbol ~ 10^48 erg s^-1 show that continuum reverberation mapping remains feasible for the most luminous systems, opening a path to larger samples with surveys such as the Vera C. Rubin Observatory's LSST.
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All authors Francisco Pozo Nuñez, Eduardo Bañados, Swayamtrupta Panda, Amit Kumar Mandal, Bozena Czerny, Jochen Heidt
Instrumentation and Methods for Astrophysics
The Hopkins Ultraviolet Telescope: A Historical and Personal Retrospective
William P. Blair
This manuscript documents the inception and development of the Hopkins Ultraviolet
Telescope (HUT) project, which was a component of the Astro Observatory payload that flew on two Spacelab shuttle missions in the 1990s. The discussion places the HUT project in the context of the times and highlights the importance of its acceptance by NASA in 1980 to the growth and development of astrophysics at the Johns Hopkins University. Personal recollections from the author, including a detailed description of the real time flight operations during each mission, provides an insiders view. The document includes a link to an online historical archive of supporting materials compiled in support of this effort.
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Earth and Planetary Astrophysics
A JWST transiting survey of FGK stellar limb darkening: empirical evidence for quadratic laws and atmospheric model comparisons
David K. Sing, Joshua D. Lothringer, Jeff A. Valenti et al. (+11 more)
We present a study of stellar limb-darkening using JWST transit observations of seven
exoplanets orbiting FGK host
stars, spanning 4200-6800 K. The wide wavelength coverage and high S/N of NIRISS/SOSS and NIRSpec/PRISM enable precise constraints on the wavelength-dependent limb-darkening. Using
Bayesian model selection, we find that the quadratic limb-darkening law is statistically preferred over higher-order laws for most FGK
stars, recovers consistent intensity profiles for $>$95% of the stellar disk area, and introduces a minimal bias in the derived transit depths of only $\sim$14 ppm (1$\sigma$) for 6/7 targets. This contrasts with previous studies relying on stellar models. We compare the empirically derived quadratic coefficients to predictions from the PHOENIX, MPS-ATLAS, MURaM, and Stagger stellar atmosphere grids. We introduce a quadratic limb-darkening parameterization in terms of limb intensity ($\ell$) and
curvature at mid-$\mu$ ($\delta$), finding that empirical FGK limb darkening is generally more linear than models predict ($\delta \lesssim 0.1$). We identify wavelength-independent offsets between data and model quadratic coefficients, minimized by adopting $\mu_{\rm min} = 0.2$ in intensity calculations; we attribute this in part to models overpredicting limb-darkening near the limb where the plane-parallel approximation breaks down. For spherical PHOENIX models, we derive a $\mu$ rescaling method using a $\tau = 1$ photospheric radius. With these corrections, residual offsets are minimized and all stellar models achieve statistically acceptable fits. We provide recommended limb-darkening offset priors for use in JWST transit analyses, enabling more accurate constraints on
exoplanet transmission spectra while accounting for residual stellar model uncertainties.
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All authors David K. Sing, Joshua D. Lothringer, Jeff A. Valenti, Natalie H. Allen, Katherine A. Bennett, Carlos Gascón, Mei Ting Mak, Patrick McCreery, Sagnick Mukherjee, Lakeisha M. Ramos Rosado, Stephen P. Schmidt, Kevin B. Stevenson, Daniel P. Thorngren, Le-Chris Wang
Instrumentation and Methods for Astrophysics
Simulation and development of astrophotonic H-band nulling beam combiner for the CHARA Array
Samantha G. Morrison, Pradip Gatkine and Michael P. Fitzgerald
Nulling interferometry is a promising method for direct detection and characterization of faint stellar companions such as
exoplanets and faint binary sources. The dominant constraint on instrument performance is instability noise from vibrations, thermal expansions, and other systematic sources. Photonic instruments have footprints of a few centimeters and enable advanced light control architectures. Astrophotonic implementations can include active phase control via Mach-Zehnder interferometers (MZIs) to actively minimize residual optical path errors at the location of beam combination. The compact size of photonic chips also makes them a promising solution for space-based applications such as the upcoming Habitable Worlds Observatory. The Center for High Angular Resolution Astronomy (CHARA) Array is equipped with the world's longest baseline in the near-infrared at 330 meters long. CHARA therefore has the most sensitive angular resolution in the near-infrared. A nuller at CHARA would have access to a novel parameter space essential for
exoplanet discovery and characterization. The first step in preparing a nulling beam combiner for CHARA is to develop compelling, realistic, and well-defined science cases. Simulation suites quantify the technical requirements to reach such science goals in their respective complex systems. The CHARA Array Response Model (CHARM) is the first-ever simulator built specifically for CHARA, opening up new pathways for instrument simulation. CHARM is a flexible simulation tool of an H-band, self-calibrated astrophotonic nulling beam combiner with active phase control for the CHARA Array. In this paper, we present an update on the development of our photonic nulling beam combiner for CHARA. We include early results from CHARM, demonstrating that the photonic nuller has the potential to detect and characterize a wide range of bright stellar companion systems.
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Instrumentation and Methods for Astrophysics
Flux jump correction in the QUBIC TES data pipeline
Belen Costanza, Lucas Merlo Azzolina, Claudia G. Scoccola et al. (+20 more)
Flux jumps occur in the readout electronics of Transition Edge Sensor (TES) detectors coupled to Superconducting
Quantum Interference Devices (SQUIDs), as a consequence of the periodic transfer function of SQUIDs in the superconducting regime. These events manifest as discontinuities in the Time Ordered Data (TOD) and can significantly degrade the quality of the measured signals. In this work, we present an automated pipeline to identify and correct flux jumps in the calibration data of the QUBIC (Q & U Bolometric Interferometer for Cosmology) instrument, designed to measure the B-mode polarization of the
Cosmic Microwave Background (CMB). Using data from multiple observation campaigns, we characterize the statistical properties of flux jumps and compare them with expectations based on the electronic configuration of the instrument. The proposed pipeline successfully corrects these events, allowing the recovery of affected data and enabling their use in subsequent CMB analysis.
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All authors Belen Costanza, Lucas Merlo Azzolina, Claudia G. Scoccola, Nahuel Miron Granese, Elia Battistelli, Jean-Christophe Hamilton, Michel Piat, Damien Prele, Steve Torchinsky, Ismail Bekkaoui, Alessandro Coppolecchia, Paolo De Bernardis, Sofia Ferazzoli, Massimo Gervasi, Luca Gomez, Sabrina Marwede, Silvia Masi, Youssef Moulane, Alessandro Paiella, Mathias Regnier, Gustavo Romero, Federico Sanchez, Ivan Queirolo
Solar and Stellar Astrophysics
A Probabilistic Framework for Incorporating Helioseismic Far-Side Active Regions into SFT Models
Bibhuti Kumar Jha, Lisa A. Upton, K. D. Leka et al. (+5 more)
Surface Flux Transport (SFT) models are routinely used to model the Sun's photospheric
magnetic field and provide inner boundary conditions for coronal and heliospheric models, yet they remain fundamentally limited by the lack of direct information about flux emergence on the far side of the Sun. To address this, we develop a framework for incorporating helioseismic images of far-side active regions (HIFAR), into the Advective Flux Transport (AFT) model. Using near-simultaneous
magnetic flux maps (HIFARM) inferred from HIFAR, and STEREO/EUVI 304 A observations from 2010 May 13 to 2014 August 18, we develop a logistic regression model to estimate the probability that a helioseismic detection corresponds to an AR based on descriptors of
magnetic flux, field strength, and location. The model achieves a precision of 0.93 for active region (AR) detections at a probability threshold of 0.73, selected to reject 90% of "ghost" ARs. We also derive an empirical scaling relationship between HIFARM and AFT flux to place HIFARM on the AFT flux scale and demonstrate that the framework reproduces the flux
evolution of ARs consistent with near-side observations over multiple solar rotations. At the global scale, we find that conventional near-side-driven AFT simulations underestimate the total unsigned
magnetic flux by ~10-20% of the Sun's total
magnetic flux budget. The probabilistic AR detection model and the complete framework developed in this work provide a practical pathway for incorporating helioseismic far-side ARs into SFT models, a step toward realistic modeling of full-Sun
magnetic field.
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All authors Bibhuti Kumar Jha, Lisa A. Upton, K. D. Leka, Ruizhu Chen, Junwei Zhao, Shea Hess Webber, Ignacio Ugarte-Urra, Kiran Jain
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Radiative Corrections and Reheating in Supergravity Models of Inflation
John Ellis, Tony Gherghetta, Kunio Kaneta et al. (+2 more)
We consider the effects of radiative corrections in Starobinsky-like models of inflation, concentrating on models of inflation formulated in N=1 no-scale supergravity. Inflaton couplings to matter fields are necessary for reheating and these have an impact on loop corrections to the inflaton potential. Whilst corrections due to the supergravity couplings of the inflaton to Standard Model (MSSM) fields are negligible, we use Planck data to obtain interesting constraints on GUT bilinear couplings, vevs, and gauge
boson masses that could be sharpened by future CMB measurements.
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All authors John Ellis, Tony Gherghetta, Kunio Kaneta, Wenqi Ke, Keith A. Olive
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Gravitational waves from core collapse of rotating very-massive stars: 3D numerical relativity computation
Alan Tsz-Lok Lam, Masaru Shibata and Sho Fujibayashi
We numerically study the collapse of rotating, very-massive stellar cores with masses of $\approx 200$, $300$, $500$, and $1100M_\odot$ into black holes using both axisymmetric and three-dimensional (3D) numerical relativity. Our results indicate that when the dimensionless
spin of the resulting black hole exceeds 0.8, a massive disk consistently forms around it. These massive, compact disks, carrying more than about 10% of the black hole's mass, are prone to non-axisymmetric deformations that trigger gravitational-wave bursts with frequencies around 10-50 Hz. Such waves could be detected by the Einstein
Telescope and
Cosmic Explorer, even from sources a few Gpc away. We also summarize the gravitational-wave signals from axisymmetric collapse, which tend to have lower amplitudes and higher frequencies than those caused by non-axisymmetric instabilities.
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Astrophysics of Galaxies
The gradual decline of Ly$\alpha$ visibility in the CANDELS fields: evidence for the combined effects of galaxy evolution and reionization
L. Napolitano, L. Pentericci, A. Ferrara et al. (+35 more)
We investigate the
evolution of Ly$\alpha$ visibility and the physical properties of Ly$\alpha$ emitters (LAEs) across the five CANDELS fields using publicly available JWST/NIRSpec PRISM spectroscopy. Our catalog comprises 3446 spectroscopically confirmed sources at 4 $\leq $ z < 14.2, including 3361
star-forming
galaxies (SFGs), of which 539 are robust (S/N > 3) LAEs. We measure the fraction of LAEs with EW$_0$ > 25A (X$_{\mathrm{Ly\alpha}}$) and trace its
redshift evolution in two UV luminosity bins, namely -20.25 < M$_{\mathrm{UV}}$ < -18.75 and -21.75 < M$_{\mathrm{UV}}$ < -20.25. Within the fainter-UV range, X$_{\mathrm{Ly\alpha}}$ increases from z = 5 to z = 6 at 3$\sigma$ significance and subsequently declines toward higher
redshifts with a significant monotonic trend at z > 6. We also investigate the physical properties of both LAEs and the full SFG population. We find that the stellar mass, UV slope $\beta$, stellar reddening, SFR,
metallicity, sSFR, and burstiness of LAEs remain approximately stable with
redshift. The only exception is the mass-weighted age which decreases with increased
redshift. Conversely, the properties of the full SFG population evolve significantly, progressively approaching the region of
galaxy-property space occupied by LAEs as
redshift increases. This suggests that
galaxy evolution may enhance the intrinsic production and escape of Ly$\alpha$
photons toward earlier epochs. We argue that this effect should be accounted when inferring the
evolution of the neutral hydrogen content of the IGM from the observed visibility of Ly$\alpha$ emission. To this end, we employ a physically motivated framework based on the Attenuation-Free Model, jointly accounting for
galaxy evolution and IGM attenuation. Our observations favor reionization histories that proceed gradually over scenarios characterized by a rapid increase in the
cosmic neutral hydrogen fraction.
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All authors L. Napolitano, L. Pentericci, A. Ferrara, M. Llerena, M. Dickinson, A. Calabrò, S. L. Finkelstein, R. Begley, P. Arrabal Haro, A. Arroyo-Polonio, B. E. Backhaus, D. Bevacqua, A. Bhagwat, M. Bischetti, M. Castellano, S.-J. Chang, E. R. Cueto, V. D'Odorico, C. T. Donnan, M. Galbiati, G. Gandolfi, M. Giavalisco, M. Hirschmann, J. Kartaltepe, A. M. Koekemoer, K. K. Knudsen, R. A. Lucas, S. Mascia, L. Paquereau, B. Pérez-Díaz, C. Piscitelli, R. Rana, P. Santini, A. J. Taylor, E. Taylor, R. Tripodi, S. M. Wilkins, L. Y. A. Yung