Solar and Stellar Astrophysics
Visual Orbits of Spectroscopic Binaries with the CHARA Array. V. HD 210763 and HD 221950
Kathryn V. Lester, Josephine Singleton, Alexandra M. Twomey et al. (+16 more)
We present the visual orbits and dynamical masses of two longer period spectroscopic binary
stars, HD 210763 and HD 221950, using long baseline interferometry with the CHARA Array and high resolution spectroscopy with the APO 3.5 m and CTIO 1.5 m
telescopes. By combining the astrometric and radial velocity observations, we solve for the full, three-dimensional orbits and determine the
stellar masses to within 0.5% uncertainty and the distance to within 0.2% uncertainty. For HD 210763, we found component masses of M1 = 1.748 Msun and M2 = 1.492 Msun. For HD 221950, we found masses of M1 = 1.098 Msun and M2 = 1.031 Msun. We then estimate the effective temperature and radius of each component
star through disentangling and spectral energy distribution analyses. We compare the observed
stellar parameters to the predictions of the
stellar evolution models and estimate the system ages. The primary component of HD 210763 is at the end of the main sequence while the secondary component is on the main sequence, providing a tight age constraint for this system at 1.6 Gyr. Both components of HD 221950 are still on the main sequence with an age of 3.76 Gyr. These systems have longer orbital periods, beyond the
tidal circularization limit, and therefore are better proxies for single
stars and tests of
stellar evolution models than short period, eclipsing systems.
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All authors Kathryn V. Lester, Josephine Singleton, Alexandra M. Twomey, Viktoria Sargent, Sally V. Shepherd, Douglas R. Gies, Gail H. Schaefer, Cyprien Lanthermann, Jeremy Jones, Katherine Shepard, Narsireddy Anugu, Claire L. Davies, Todd J. Henry, Hodari-Sadiki Hubbard-James, Wei-Chun Jao, Stefan Kraus, John D. Monnier, Leonardo A. Paredes, Benjamin R. Setterholm
Earth and Planetary Astrophysics
Kick Velocities and Mass Function of Free-Floating Planets from Dynamical Ejection in Hierarchical Three-Body Systems
Hugh Kramer and Stefano Profumo
Free-floating
planets (FFPs), also known as rogue
planets, are sub-
stellar objects that travel through the
Galaxy unbound to any host
star. Their velocity distribution carries information about the dynamical channel that released them from their birth systems, while their mass distribution encodes the underlying abundance of
planets available for ejection. We present a suite of direct $N$-body simulations of hierarchical three-body systems consisting of a
Solar-mass host
star, a massive
giant perturber, and a lighter
planet treated in the restricted three-body regime. We vary the mass of the ejected
planet, the mass of the
giant perturber, the light
planet's semi-major axis, and the eccentricities of both
planets, measuring the asymptotic ejection velocity $v_\infty$ and the finite-radius ejection speed $v_{\rm kick}$ at the first accepted ejection output. The ejected body's mass has little effect on the outcome over four orders of magnitude, confirming the test-particle limit. By contrast, the
giant-
planet mass sets the ejection scale and time, following the secular scaling $t_{\rm ejec}\propto M_J^{-1}$. The eccentricities mainly affect the high-velocity tail rather than the median: a higher light-
planet eccentricity extends the kick ceiling to $\sim23$ km/s, while a highly eccentric
giant can yield rare kicks near $80$ km/s via pericentre-enhanced slingshot encounters. We interpret these trends with a semi-analytic framework based on Hill-scale scattering, the Tisserand parameter, and an eccentricity-dependent upper envelope for slingshot energy exchange, and discuss how the ejection velocities map onto the
Galactic FFP velocity dispersion and how the mass function sets the microlensing timescale distribution relevant for Roman and Euclid.
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Instrumentation and Methods for Astrophysics
Fast, low noise, megapixel detector and readout systems for future X-ray astronomy missions
Sven Herrmann, Peter Orel, Tanmoy Chattopadhyay et al. (+22 more)
Next-generation strategic X-ray astronomy missions will require the simultaneous achievement of high angular resolution, large effective collecting area, and wide-field imaging with large-format focal plane detectors. Realizing the associated science objectives–ranging from precision measurements of bright point sources to the detection and characterization of faint diffuse emission-places stringent and, in some cases, competing requirements on detector performance. In particular, high frame rates are necessary to mitigate
photon pile-up in observations of bright sources and to reduce contamination from particle-induced background in measurements of low surface brightness structures. At the same time, these instruments must preserve excellent soft X-ray response, which places tight constraints on read noise and on the fidelity of event characterization. State-of-the-art X-ray charge-coupled devices (CCDs) approach many of the key performance metrics required for these missions, but readout speed remains a primary limitation. Addressing this gap requires readout architectures that scale to high channel count, sustain high pixel throughput, and preserve the low-noise characteristics needed for soft X-ray sensitivity.
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All authors Sven Herrmann, Peter Orel, Tanmoy Chattopadhyay, Haley R. Stueber, Jill Juneau, Abigail Y. Pan, Kevan Donlon, Declan O'Neill, Gregory Prigozhin, Eric D. Miller, R. Glenn Morris, Tonya L. Peshel, Artem Poliszczuk, Beverly LaMarr, Catherine E. Grant, Christopher Leitz, Steven W. Allen, Sebastian Albrecht, Marshall W. Bautz, Michael Cooper, Ajay Dakshinamurthy, Matthew Heine, Anna Schweingruber, Keith Warner, Daniel Wilkins
Astrophysics of Galaxies
Tracing luminous infrared galaxy populations through cluster evolution in a cosmological mock redshift survey
Norma Araceli Nava-Moreno, Alfredo Montaña, Itziar Aretxaga et al. (+2 more)
We present GARDENS-Wide, a new 100 square degree mock
redshift survey of the dusty
star-forming
galaxy population based on the MultiDark-Planck 2 dark-matter
halo simulation. The mock reproduces observed multiwavelength number counts at 500 $\mu$m, 1.1, 1.4 and 2.0 mm. The large simulated area enables us to identify gravitationally bound systems, trace their assembly histories, and quantify the
redshift evolution of their
galaxy content and structural extent. We find strong
evolution in the fractional contribution of
galaxy populations within cluster progenitors.
Star-forming
galaxies account for ~35 per cent of members at low
redshift, increasing to 60-65 per cent at $z\sim2$ and declining to ~20 per cent by $z\sim5$. LIRGs contribute ~20-40 per cent, peaking near $z\sim2$, while ULIRGs remain subdominant and HyLIRGs are rare. We measure proto-cluster radii as the maximum 3D comoving distance from the central
halo to the most distant member
halo. Proto-clusters contract significantly over
cosmic time, from >20 comoving Mpc at high
redshift to a few Mpc at $z\sim0$. ULIRGs become increasingly centrally concentrated at $z>1.5$ in rich proto-clusters. We provide observational predictions for the TolTEC Large-Scale Structure survey.
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All authors Norma Araceli Nava-Moreno, Alfredo Montaña, Itziar Aretxaga, Aldo Rodríguez-Puebla, Vladimir Avila-Reese
Instrumentation and Methods for Astrophysics
A new NASA Pioneer: the Globe Orbiting Soft X-ray Polarimeter (GOSoX)
Herman L Marshall, Sarah N T Heine, Alan Garner et al. (+16 more)
The Globe Orbiting Soft X-ray Polarimeter (GOSoX) is a spectropolarimeter for the soft X-ray band. GOSoX is based on the Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX), a NASA-funded sounding rocket payload. Like REDSoX, GOSoX consists of Wolter I X-ray optics from NASA/MSFC, critical-angle transmission (CAT) gratings made at MIT, and multilayer (ML) coated mirrors from LBNL that polarize the X-rays. Colleagues at U. Tübingen will adapt commercially available sCMOS sensors for the focal plane. The grating dispersion is matched to the lateral grading of ML mirrors set at 45\deg. GOSoX can measure polarization across the entire 0.2-0.4 keV band with a spectral resolution E/dE $\sim$100. Minimum detectable polarizations (MDPs) of 3-10% are expected for over a dozen targets in a one-year mission. The mission was selected by NASA for launch in 2030.
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All authors Herman L Marshall, Sarah N T Heine, Alan Garner, Sean Gunderson, Hans M Guenther, Ralf K Heilmann, Stephen Bongiorno, Eric M Gullikson, Andrea Santangelo, Chris Tenzer, Ruth Kelly, Silvia Zane, Roberto Taverna, Roberto Turolla, Michela Negro, Rozenn Boissay-Malaquin, Luigi Gallo, Honghui Liu, Swati Ravi
Solar and Stellar Astrophysics
New Spatially Resolved Observations of Betelgeuse from the VLA and ALMA: Evidence for Atmospheric Perturbations from a Close Companion
L. D. Matthews, A. K. Dupree, A. M. S. Richards et al. (+1 more)
We present new spatially resolved observations of the red supergiant Betelgeuse ($\alpha$ Orionis) at seven frequencies: 22 GHz ($\lambda$1.36cm); 44 GHz ($\lambda$6.8mm); 107 GHz ($\lambda$2.8mm); 136 GHz ($\lambda$2.2mm); 224 GHz ($\lambda$1.3mm); 338 GHz ($\lambda$0.89mm); and 485 GHz ($\lambda$0.62mm) using the Karl G. Jansky Very Large Array and the Atacama Large Millimeter/submillimeter Array. These observations (spanning 2021-2026) enable a characterization of the mean brightness temperature ($T_B$), shape, and
symmetry of the
star's extended atmosphere. At 22 GHz and 44 GHz $T_B$ has increased following the historic lows observed in 2019, just prior to the Great Dimming of late 2019/early 2020. We find that $T_B$ peaks at a larger projected radius ($r\sim2.7R_{\star}$) compared with measurements prior to 2016, consistent with a possible
evolution in the atmospheric density profile. In addition we find a systematic decrease in $T_B$ from $\approx3500$K at $\sim2.7R_{\star}$ to $T_{B}\approx$2220K at $\sim1.2R_{\star}$, confirming a previously reported temperature minimum between the photosphere and chromosphere. At all observed frequencies $T_B$ is lower than temperatures inferred from ultraviolet measurements at comparable radii, indicating the continued presence of cooler
plasma ($T\le T_{\rm eff}$) mixed with the warmer chromospheric material. The new measurements yield a global spectral index $\alpha=1.35\pm$0.03, with no evidence for a change in $\alpha$ over more than two decades in frequency. Recently, evidence of a close-in companion to Betelgeuse has been reported, with an orbital separation $r\sim2.3R_{\star}$. We have identified a correlation between the ellipticity of Betelgeuse, as obtained from
radio measurements, and the companion's orbital phase. The results are consistent with periodic perturbations of the atmosphere by the companion.
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All authors L. D. Matthews, A. K. Dupree, A. M. S. Richards, W. R. F. Dent
Instrumentation and Methods for Astrophysics
Single-Photon Counting CMOS Detectors for the Habitable Worlds Observatory
Edwin Alexani, Justin P. Gallagher and Donald F. Figer
The Habitable Worlds Observatory (HWO) is NASA's current New Great Observatory concept. HWO will observe the universe to search for life beyond Earth. It will need unprecedented instrument stability and detector performance. However, no single detector technology currently satisfies HWO's demanding specifications. Complementary metal-
oxide-
semiconductor (CMOS) single-
photon counting detectors (SPCDs) are excellent candidates for further development, as they already satisfy several specifications for HWO. We report the results of a characterization program for 9.4 Mpixel CMOS SPCDs. We measure a dark current of 0.0005 e-/s/pixel, a read noise of 0.19 e-/pixel, a peak
quantum efficiency of 88% at 485 nm, negligible crosstalk and persistence, and we present conversion gain measurements. The detector satisfies several key HWO performance requirements, including deep sub-electron read noise and low dark current, while additional development is required in ultraviolet
quantum efficiency and full mission qualification. We include a simulated low-flux observation using characterization results, along with a roadmap for developing CMOS SPCDs to satisfy HWO specifications, especially at UV wavelengths.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.hist-ph
The orientation of historic churches in Las Palmas de Gran Canaria and its surroundings: preliminary results
Alejandro Gangui, Jose Ricra, Joaquin Pallares et al. (+1 more)
We present preliminary results of the analysis of the precise spatial orientation of colonial Christian churches located in the city of Las Palmas, capital of the island of Gran Canaria (Spain), and its surroundings. Our sample consists of 27 churches, 15 of which belong to the city proper while the rest are situated within roughly 12 km away inland. Most of these churches were constructed between the first decades after the Castilian conquest of the island, and the end of the 19th century. In our analysis we examine whether these orientations respond to calendrical coincidences, to the main features of the landscape, or whether the standard tradition was followed regarding the orientation of the churches' apses eastwards. We find that no church in the sample is oriented towards points of the horizon on which the Sun rises on the day of the patronal feasts. Furthermore, we find no correlation between the global orientation pattern and the orography of the island which, near the local prominent Guiniguada ravine, could have been an important factor at the time of the construction of the churches. What we do find is that most of the orientations fit within the
solar range, mainly to the east but also with a few historic churches oriented towards the west, while less than 20% have astronomical declinations outside of this range. In the statistical analysis, the declination histogram for the sample shows a pattern where the apses of the churches point consistently to the north of due east. This might signal constructions that were oriented to the rising Sun on dates close to Easter. We briefly discuss the implications these findings may have for a future study of the rest of Gran Canaria, which includes several dozens of historic churches scattered throughout the valleys, slopes, and volcanic calderas of the island.
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All authors Alejandro Gangui, Jose Ricra, Joaquin Pallares, Juan Antonio Belmonte
High Energy Astrophysical Phenomena
Structural quasi-universality in highly magnetized differentially rotating neutron stars
Pratul Manna and Surajit Kalita
Universal relations among macroscopic properties of
neutron stars provide a powerful framework to probe their internal structures while minimizing uncertainties associated with the equation of state (EoS). Although such relations have been extensively studied for uniformly rotating
stars, their extension to differentially rotating and strongly magnetized configurations is relatively less explored. We systematically investigate
equilibrium configurations for a wide range of EoSs, rotation profiles, and
magnetic field strengths with XNS numerical simulation code. For sequences with fixed angular momentum, we analyze the dependence of normalized moment of inertia on compactness. We establish a generalized quasi-universal relation between the moment of inertia and compactness that remains remarkably insensitive to the underlying EoS across uniformly rotating, differentially rotating, and strongly magnetized toroidal configurations. For sequences with fixed angular momentum, the normalized moment of inertia exhibits a quasi-universal dependence on compactness, with deviations primarily due to
magnetic field strength and degree of differential rotation. We derive analytic expressions for these dependencies, enabling a unified phenomenological model applicable over a wide range of
stellar configurations. As astrophysical applications, we quantify the systematic bias in magnetar luminosity estimates and the rotational kinetic energy of post-merger remnant of GW170817. These results extend quasi-universal relations beyond the standard assumptions of uniform rotation and weak magnetization, providing a robust framework for interpreting observations of highly magnetized and differentially rotating
neutron stars, and enabling more reliable constraints on their astrophysical properties.
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Solar and Stellar Astrophysics
The Bimodal Mass Ratio Distribution of the Hyades
Henri M.J. Boffin
The distribution of
stellar mass ratios, q, in binary systems provides critical insights into the dynamical history and
star-formation processes of open clusters. Here, I re-evaluate the recently published mass ratio distribution (MRD) of a sample of spectroscopic binaries in the Hyades cluster, which was based on
stellar positions in colour-magnitude diagrams. I demonstrate that the mass ratios derived in that work are statistically inconsistent with a random distribution of orbital inclinations. Furthermore, several systems yielded non-physical results. By applying a Richardson-Lucy deconvolution to the spectroscopic mass functions and assuming a random distribution of inclinations, I re-derive the MRD for this sample, showing that it is statistically different from a uniform distribution. I further find a significant dependence on the primary mass: systems with lower-mass primaries exhibit a peak near q~1, whereas more massive primaries show a distribution heavily skewed toward low mass ratios (q~0.15). These findings highlight the potential pitfalls of photometric mass ratio derivations and underscore the need for further verification with future data releases such as
Gaia DR4.
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High Energy Astrophysical Phenomena
The Indian Pulsar Timing Array Data Release 2: III. Search for a Stochastic Gravitational Wave Background
Hemanga Tahbildar, Kunjal Vara, Mayuresh Surnis et al. (+28 more)
We present the first independent search for an isotropic
stochastic gravitational wave background in the second data release of the Indian
Pulsar Timing Array, comprising of 27 millisecond
pulsars monitored simultaneously in two frequency bands with the upgraded
Giant Metrewave
Radio Telescope over a maximum 7.2 year baseline. Building on a comprehensive single
pulsar noise analysis, we search for a common uncorrelated red noise process within a
Bayesian inference framework and with the noise-marginalized optimal statistics, and we test the robustness of the result through per-
pulsar dropout analyses and
solar-wind exclusion cuts. Leaving the spectral index free, we recover a broad amplitude posterior, $\log_{10} A_{\rm CURN} = -13.71^{+1.06}_{-3.28}$, with an unconstrained spectral index $\gamma_{\rm CURN} = 2.98^{+3.62}_{-2.70}$ and a Savage-Dickey Bayes factor of $2.5$ for a common red process over the no signal model. The optimal-statistic signal to noise ratios for the monopole, dipole, and Hellings-Downs correlations are all consistent with zero. Fixing the spectral index to $\gamma = 13/3$, the value predicted by an idealized toy model in which the background is sourced by a population of supermassive black hole binaries in circular orbits evolving purely under leading-order gravitational radiation reaction, we place a $95\%$ upper limit on the common-process amplitude of $A_{\rm GWB} < 3.4\times10^{-14}$, stable across
solar elongation cuts of $10^\circ$, $20^\circ$, and $30^\circ$. This limit lies approximately an order of magnitude above the amplitudes reported by other, longer-running
pulsar timing array experiments. We also demonstrate through simulated
datasets with the addition of simple chromatic and achromatic noise components that it will take at least a 10 year baseline to start recovering the common red noise signal.
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All authors Hemanga Tahbildar, Kunjal Vara, Mayuresh Surnis, Churchil Dwivedi, Bhal Chandra Joshi, Sharika Dhakappa, Aman Srivastava, Shantanu Desai, Abhimanyu Susobhanan, Adya Shukla, Himanshu Grover, P. Arumugam, Manjari Bagchi, Neelam Dhanda Batra, Manoneeta Chakraborty, Shaswata Chowdhury, Debabrata Deb, A. Gopakumar, Sushovan Mondal, Kuldeep Meena, K Nobleson, Avinash Kumar Paladi, Arul Pandian B, Kaustubh Rai, Prerna Rana, Shubhit Sardana, Vidit Singh, Jaikhomba Singha, Keitaro Takahashi, Pratik Tarafdar, Zenia Zuraiq
High Energy Astrophysical Phenomena
Gamma-ray and radio populations of millisecond pulsars in globular clusters
Hannah Lawson and Duncan R. Lorimer
The populations of millisecond
pulsars (MSPs) across the Milky Way's globular cluster (GC) system serve as powerful diagnostics of
neutron star evolution in a variety of dense
stellar environments. Using properties of 118
Galactic GCs, we performed Monte Carlo simulations of their gamma-ray fluxes observed by
Fermi. We compared two luminosity models: a 3D fundamental plane (model A) and a lognormal distribution (model B). Both models reproduce the observed gamma-ray fluxes and mirror the scaling law with the GC
stellar encounter rate established for low-mass X-ray binaries and
radio MSPs. Due to its lower average gamma-ray luminosities, model B predicts a 6-7 times larger MSP population ($5150^{+720}_{-710}$) than model A ($770\pm60$). Furthermore, both models accurately predict a population-wide expectation of roughly three clusters whose aggregate gamma-ray emission is dominated by a single bright MSP. Invoking a
radio-to-gamma-ray luminosity scaling ($L_r \sim 3.5 \times 10^{-7} L_{\gamma}$), we find that model B predicts a mean
radio pseudoluminosity ($\log L_{\rm pseudo} \sim -1.6$) that is fainter than canonical
pulsars. This result is consistent with recent evidence attributing the apparent faintness of
Galactic MSPs to
geometric effects. In contrast, model A implies an intrinsically brighter population ($\log L_{\rm pseudo} \sim -0.3$) that lacks a clear physical basis and is inconsistent with the results found for
Galactic pulsars. The larger underlying population of faint millisecond
pulsars predicted by model B could be probed by sensitive surveys with emerging
radio facilities to further constrain the evolutionary pathways of MSPs.
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Solar and Stellar Astrophysics · Cross-listed from gr-qc
On Modeling Anisotropic Quark Stars: The Role of Anisotropy in Radial Oscillation Spectra
G. Panotopoulos
We model the compact object Cen X-3, which is considered to be a good strange
quark star candidate of known mass and radius, incorporating a negative anisotropic factor, and we compute the frequencies of the ten lowest radial oscillation modes. We introduce the anisotropy in three different manners and investigate its impact on the spectra.
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Earth and Planetary Astrophysics
Rings in the Sky: Orbital Data Centres and Potential Impacts to Astronomy and the Sky
Aaron C. Boley, Samantha M. Lawler and Hanno Rein
Megaconstellations of orbital data centres (ODCs) have the potential to fundamentally change the sky without a concerted mitigation effort. Potential changes include producing large coherent structures that would be visible during twilight and some portions of the night, as well as produce persistent infrared and
radio source regions. We investigate the potential sky impacts of three ODC designs, as proposed by three companies. While more companies have proposed to launch megaconstellations of ODCs, other potential operators are expected to use the same design principles as presented here. These systems would produce large ring structures with each ring passing through the sky twice a day. The largest impacts are expected to occur during winter, where ring structures could be seen sweeping through otherwise dark skies. The confinement of the rings' orbital nodes will play a large role in determining whether the rings will be dense arcs in the sky or will produce sky-wide interference. The rings will persist throughout the day in polar regions, with the potential to interfere with polar science initiatives. Such structures will further have societal implications for high-latitude communities. We use simplified brightness models, which compare well with more detailed calculations, to show that brightness mitigation and/or hard limits on satellite numbers will be essential for preventing a future that has more visible satellites in the sky than visible
stars during certain times of night.
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Cosmology and Nongalactic Astrophysics
Weak-lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: III. A precision cosmological sample enabled by optical confirmation
I-Non Chiu, Kai-Feng Chen, Masamune Oguri et al. (+9 more)
We develop fCAMIRA (forced-mode CAMIRA), a tool for optical cluster confirmation, and apply it to a sample of 129 weak-
lensing (WL) shear-selected
galaxy clusters identified in aperture-mass maps obtained from the Hyper Suprime-Cam Subaru Strategic Program Three-Year (HSC-SSP Y3) weak-
lensing data. fCAMIRA is built upon the CAMIRA cluster-finding
algorithm and relies on a red-sequence (RS)
galaxy model that is calibrated in a data-driven way. The RS model adopts the
metallicity-luminosity relation measured in this work using X-ray-selected clusters up to
redshift $z\approx1.3$, followed by the calibration of color offsets using large spectroscopic samples. With the RS model, we build two types of
galaxy richness maps, one obtained with a spatial filter matched to a typical cluster size of $R=0.8\,h^{-1}\,\mathrm{Mpc}$ and the other obtained with a fixed angular-size filter identical to that used in constructing the WL aperture-mass maps. The fCAMIRA
algorithm utilizes these two richness maps, identifies all optical counterpart candidates along the line of sight of each shear-selected cluster, and measures the cluster photometric
redshift from the highest-ranked counterpart. The ranking is determined by the fractional
lensing contribution $f_{\mathrm{lens}}$ of each candidate. Using available spectroscopic cluster
redshifts, we quantify the mean bias and scatter in the cluster photometric
redshifts at levels of approximately 0.005 and 0.008, respectively, demonstrating excellent photometric-
redshift performance. We compare the fCAMIRA photometric
redshifts with estimates from direct positional cross-matching and find that approximately 8% of the total sample exhibits
redshift discrepancies greater than 0.15. This outlier fraction is primarily attributed to projection effects, leading to the misidentification of the optical counterparts. (abridged)
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All authors I-Non Chiu, Kai-Feng Chen, Masamune Oguri, Satoshi Miyazaki, Surhud More, Atsushi J. Nishizawa, Nobuhiro Okabe, Ken Osato, Naomi Ota, Tomomi Sunayama, Sut-Ieng Tam, Keiichi Umetsu
Astrophysics of Galaxies
Molecular absorption lines toward the Galactic ISM detected at 89 GHz with VLBI
Keisuke Nakashima, Hiroshi Imai and Youngjoo Yun
As the first step to explore the
Galactic foreground interstellar medium (ISM) with high angular resolution, we investigated the detectability of molecular absorption lines with very long baseline interferometry (VLBI). This paper reports our first observations of HCO+ J=1-0 and HCN J=1-0 molecular absorption lines toward four extragalactic compact
radio sources with the Korean VLBI Network (KVN). HCO+ absorption lines were detected in all directions and HCN absorption lines in three directions. All of these detections, except for two HCO+ detections, are reported here for the first time with VLBI. We find that the column density ratio N(HCN)/N(HCO+) obtained with VLBI is consistent with the trend established from observations with connected-element interferometers, demonstrating the feasibility of future VLBI studies of molecular absorption.
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Astrophysics of Galaxies
Cloud Scale Star Formation and Gas Scaling Relations in the Milky Way
Alphesunny Sarkar, Tapas Baug, Ariful Hoque et al. (+2 more)
We investigate cloud-scale
star formation in the Milky Way using a sample of 45 molecular clouds (sizes of $5-240$ pc) in the inner
Galactic plane, spanning heliocentric distances of $1.1-14.4$ kpc. Masses of these clouds are derived from $^{12}$CO and $^{13}$CO emission, while
stellar masses are estimated using the young
stellar object (YSO) population. The studied molecular clouds have masses ranging from $\sim10^{3}$ to $2.3\times10^{6}$ $\rm M_\odot$, with
star formation efficiencies (SFE) up to 0.33. We find a tight, nearly linear scaling of the
star formation rate (SFR) with the cloud mass, indicating that more massive clouds form proportionally more
stars. The SFE, however, shows a declining trend with cloud mass. The relation between the
star formation rate surface density ($\Sigma_{\rm SFR}$) and gas surface density ($\Sigma_{\rm gas}$) exhibits substantial cloud-to-cloud scatter, indicating that the canonical Kennicutt–Schmidt law is not strongly recovered at the scale of individual molecular clouds. Incorporating the cloud free-fall time ($\rm t_{ff}$) into the
star formation scaling relation highlights its important role in regulating
star formation, although the observed relations suggest that the
star formation efficiency per free-fall time is not universal. In particular, the SFE decreases with increasing gas mass available per free-fall time. We discuss the implications of our results in the context of recent theoretical models of molecular cloud
evolution and
star formation.
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All authors Alphesunny Sarkar, Tapas Baug, Ariful Hoque, Suchetana Chatterjee, Chayan Mondal
Instrumentation and Methods for Astrophysics
Enhancing the sensitivity of next-generation X-ray imaging detectors with artificial intelligence and advanced event reconstruction algorithms
D. R. Wilkins, A. Poliszczuk, A. Y. Pan et al. (+11 more)
Advanced
algorithms incorporating artificial intelligence and machine learning (AI/ML) enhance the sensitivity of X-ray imaging detectors and the scientific capabilities of future X-ray missions. In orbit, current instruments are limited in their sensitivity by (1) the instrumental background, induced by
cosmic rays which produce signals that can be confused for genuine, astrophysical X-rays, and (2) the ability to reconstruct the detected
photon events, degrading the
quantum efficiency and energy resolution at the lowest energies, where much discovery space resides. We report on the development of prototype
algorithms designed to operate on the raw frame-level data to provide improved identification of particle-induced background events and enhanced energy reconstruction. These
algorithms consider the contextual information from all signals in a frame, and are built upon physics-motivated models of charge
diffusion and signal generation within the detector. Using high fidelity simulations, we show that following recent developments, prototype ML
algorithms can reduce the unrejected particle background by up to 68 per cent compared with traditional filtering methods when operated in an aggressive mode suitable for source detection in imaging surveys, or up to 40 per cent in a conservative mode designed to prioritize accurate measurements of the spectrum. We find that next-generation event reconstruction
algorithms improve the sensitivity and energy resolution of CCD-like detectors at event energies below 1keV, and can aid in background filtering, and reduce the impact of
photon pile-up. We present new laboratory data that demonstrates the performance of the
algorithm on the MIT-LL CCID-93 CCD detector. Together with the capabilities of next-generation high-speed, low-noise detectors, these
algorithms can satisfy the requirements for future X-ray flagship missions.
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All authors D. R. Wilkins, A. Poliszczuk, A. Y. Pan, L. Sajkov, S. W. Allen, M. Heine, C. E. Grant, M. W. Bautz, T. Chattopadhyay, K. Donlon, S. Herrmann, B. LaMarr, E. D. Miller, P. Orel
High Energy Astrophysical Phenomena
Alex Rojewski and Cecilia Lunardini
Gravitational waves originating from unresolved sources, or
stochastic gravitational wave backgrounds (SGWBs), carry precious information about the physics underlying their diverse sources, and represent an important target for future experimental searches. Here, we model the SGWB due to core collapse
supernovae. Using an extensive collection of state-of-the-art, three-dimensional, multi-second
supernova simulations, we characterize the two main components of this background: one at $f \sim 10^{-2} - 1$ Hz, due to anisotropic
neutrino emission (the gravitational wave
memory); the other at $f \gtrsim 10^{2}$ Hz, from the near-core matter dynamics. We find that the
memory component offers the best prospects of detection, as its characteristic peak at $f\sim 0.1$ Hz is within the reach of future space-born detectors. At the peak, the energy density might be comparable to that of backgrounds from slow roll inflation and from possible cosmological relics, thus potentially impacting searches of these important signals.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Determination of the Angular Momentum of Radiated Gravitons, Scalars, and Dark Photons from Binary Orbits
Arpan Hait and Subhendra Mohanty
We compute the energy and angular momentum radiated by compact binaries through gravitational waves, scalar and vector fields, using the field-theoretic approach. We observe that each emitted graviton carries away an angular momentum of $\dot{J}/\dot {N}\simeq 2\hbar$, not only for elliptical orbits (as has already been pointed out by Page [arXiv:2409.00305]) but also for
hyperbolic orbits. We extend the analysis to scalar and vector radiation and find that the angular momentum carried by each emitted
quantum of radiation is approximately $\hbar$, i.e., $\dot{J}/\dot{N}\simeq \hbar$ for both types of radiation. We demonstrate that the radiated energy and angular momentum of binary systems can be determined from the
evolution of the orbital angular frequency and the eccentricity of the quasi-Kepler orbit. However, a gauge-invariant decomposition of the angular momentum carried by the emitted particles into the
spin and orbital components is not possible.
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Astrophysics of Galaxies
Galaxy-LRD Strong Lenses: A Missing Population?
Zizhao He, Nan Li, Simon Dye et al. (+2 more)
The physical nature of Little Red Dots (LRDs) remains uncertain, although these abundant, compact, and red sources may offer important insights into early black-hole growth and
galaxy formation. Strong gravitational
lensing can magnify LRDs and spatially resolve their internal structure, thereby helping to discriminate among competing physical scenarios. However, no
galaxy-scale strongly lensed LRD has yet been securely confirmed. To predict the abundance of such systems in current and future surveys and to guide dedicated searches, we present the first
benchmark estimate of the detectable population of
galaxy-scale lensed LRDs by combining literature-based LRD source models with a population of foreground early-type
galaxy deflectors. Our Monte Carlo simulation spans $50~{\rm deg}^{2}$ and contains 270,713 LRDs and 5,460,841 deflectors. We predict idealized surface densities of $10.70\pm3.76~{\rm deg}^{-2}$ for doubles and $0.64\pm0.69~{\rm deg}^{-2}$ for quads. After accounting for the JWST point-spread function and survey limiting magnitudes, the detectable surface densities decrease to $3.70\pm1.89~{\rm deg}^{-2}$ and $0.52\pm0.58~{\rm deg}^{-2}$, respectively. For the de-duplicated $0.66~{\rm deg}^{2}$ footprint covered by COSMOS-Web, PRIMER-UDS, PRIMER-COSMOS, CEERS, JADES GOODS-S, and JADES GOODS-N, for which the reported limiting depths are combined through area-weighted averaging in flux space, the predicted probabilities of detecting no systems are $8.6\%$ for doubles and $70.8\%$ for quads.
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All authors Zizhao He, Nan Li, Simon Dye, Xinzhong Er, Fuwen Shu
Astrophysics of Galaxies
The Fornax Cluster VLT Spectroscopic Survey - V. Mass modelling of the BCG NGC 1399 out to 150 kpc
Avinash Chaturvedi, Nicola R. Napolitano, Michael Hilker et al. (+7 more)
NGC 1399, the bright central
galaxy of the Fornax cluster, hosts an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer
halo, about 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (~150 kpc), using a comprehensive radial velocity catalogue of GCs, combining data from the Fornax cluster VLT spectroscopic survey (FVSS) with prior measurements from the literature. Applying spherical Jeans equations, we performed dispersion-kurtosis modelling of NGC 1399's GC kinematics to derive its mass profile and GC orbital anisotropy. We also investigated the impact of including intra-cluster GCs in the mass modelling, selected based on spatial segregation and a velocity $\sigma$-clipping method. Our findings indicate that both cusp-like (NFW) and core-like (Burkert)
halos can reproduce the observed kinematics of GCs. Including the intra-cluster GCs in the mass modelling yields broadly consistent mass profiles for both
halo types, with the full GC sample giving a virial mass of log $\log M_{\rm vir} = 13.81 \pm 0.09~M_{\odot}$ for the NFW
halo, slightly higher than the value inferred for the Burkert
halo. Regardless of the dark matter
halo profile adopted, we observe that the intra-cluster GCs exhibit radial anisotropy in the outskirts, especially among the blue, metal-poor GCs. These results suggest that GCs in NGC 1399's outer
halo are influenced by an additional
halo component associated with the
galaxy cluster potential. The radial anisotropy observed in these outer-
halo GCs provides strong dynamical evidence supporting their
accretion from external sources, consistent with prior photometric and spectroscopic studies of GCs. This study highlights the importance of including intra-cluster GCs in dynamical mass modelling to fully account for the contribution of dark matter to the cluster gravitational potential.
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All authors Avinash Chaturvedi, Nicola R. Napolitano, Michael Hilker, Katja Fahrion, Sabine Thater, Glenn van de Ven, Michele Cantiello, Chiara Spiniello, Maurizio Paolillo, Tadeja Veršič
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Abundant production of scalars and axions from phase transition bubble expansion
Isabel Garcia Garcia, Gaurang Ramakant Kane, John March-Russell et al. (+1 more)
We revisit aspects of particle production during cosmological first-order phase transitions, and show that the expansion of true-
vacuum bubbles can be a copious source of particle production. Specifically, for a massive
spin-0 field linearly coupled to the bubble profile, spherical bubbles expanding even at constant radial velocity efficiently produce particles until the local-rest-frame radius of
curvature of the bubble wall exceeds the particle Compton wavelength – contrary to the expectation that walls moving at constant speed cannot radiate. We compute the momentum spectrum of the produced particles for both accelerated and constant-velocity expansion histories, identify the regimes of coherent and incoherent production, quantify the validity of the perturbative treatment, and show that this mechanism can parametrically dominate other production processes of feebly coupled particles, including freeze-in. Our results apply to many models of light, feebly coupled particles studied in the literature, providing new sources of dark radiation and dark matter. In particular, a first-order deconfinement-confinement transition in a hidden Yang-Mills sector can abundantly produce
axion-like particles, leading to dark radiation and/or dark matter signatures over large regions of parameter space.
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All authors Isabel Garcia Garcia, Gaurang Ramakant Kane, John March-Russell, Andrea Paolini
High Energy Astrophysical Phenomena
AT 2022csn: A Photometrically Peculiar Optical/UV Tidal Disruption Event in a Type II AGN
Yael Dgany, Iair Arcavi, Grisha Zeltyn et al. (+18 more)
The emission mechanism and host
galaxy preference of optical/UV
tidal disruption events (TDEs) are still not entirely understood. We present observations of the TDE AT 2022csn, which is one of the most distant (d_L~726 Mpc) and luminous (L_peak=2.487^(+0.073)_(-0.067)*10^(44) erg/s) optical/UV TDEs observed to date. Although it is a spectroscopically normal H+He TDE, it shows some photometric peculiarities, exhibiting a pronounced double-peaked light curve (with peaks separated by 18.30 pm 2.84 days in the g-band), and lying in the low-temperature and large-radius end of the optical/UV TDE population. The host
galaxy of AT 2022csn shows evidence for a significant starburst within the last ~Gyr consistent with other optical/UV TDEs, but also narrow emission lines that place it within the Type II AGN region of the BPT diagram. Interaction between the TDE and a pre-existing AGN
accretion disk might explain the peculiar photometric properties. However, it is puzzling that a TDE would be visible in a Type II AGN, where according to the AGN unification picture the central region around the supermassive black hole is obscured. We suggest a few scenarios to reconcile this. AT 2022csn together with AT 2019ahk, which shows similar properties, may belong to a new subset of low-temperature, high-radius TDEs in
galaxies with Type II AGN emission features.
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All authors Yael Dgany, Iair Arcavi, Grisha Zeltyn, Sebastian Gomez, Daichi Hiramatsu, Benny Trakhtenbrot, Megan Newsome, Dalya Baron, Craig Pellegrino, Jamison Burke, Nadejda Blagorodnova, David Jones, Gerard-Garcia Moreno, Erez A. Zimmerman, Asaf Horowicz, Avishay Gal-Yam, Mariusz Gromadzki, Edo Berger, Sara Faris, D. Andrew Howell, Harsh Kumar
Instrumentation and Methods for Astrophysics
The Research Impact of the Jodrell Bank Observatory and Other Facilities affected by the UK Science Funding Cuts in 2025
Rommulus Francis Lewis, Amruth Alfred and Hetansh Shah
The United Kingdom Research and Innovation body and the Science and Technology Facilities Council recently announced funding cuts to facilities at the Jodrell Bank Observatory, specifically the e-MERLIN network of
radio telescopes as well as a few other facilities across the world like the James Clerk Maxwell
Telescope. These funding cuts have been extremely disturbing to the Astronomical community, as is evident from widespread news coverage about these cuts. Here we present a short analysis of the research impact e-MERLIN and the other affected facilities had in 2025 from a
dataset consisting of every Astrophysics paper submitted to the arXiv during the year. This serves to help members of the community and all stakeholders make better sense of the research output of the facilities that are not being prioritised under the new budget.
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Solar and Stellar Astrophysics
Something new under the Sun: A magnetically driven CH/CN anti-correlation
Y. Momany, L. Monaco, S. Villanova et al. (+11 more)
Spectroscopic monitoring surveys have shown that the
magnetic cycle alters the photospheric structure of the Sun, perturbing the formation of molecular lines. In parallel, the study of Globular Clusters has remained centred on the multiple
stellar populations conundrum, a phenomenon defined-most notably-by the anti-correlation between CH and CN molecular bands, serving to distinguish between first-population and second-population
stars. We systematically monitored the behaviour of the CH and CN molecular bands as a function of the
solar magnetic cycle. We demonstrate that the disc-integrated
solar spectrum exhibits a distinct CH/CN anti-correlation driven by the
magnetic cycle. Our results suggest that the spectroscopic and photometric anomalies defining the multiple populations conundrum may be physically linked to a differential spectral response to varying degrees of surface
magnetic coverage.
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All authors Y. Momany, L. Monaco, S. Villanova, S. Zaggia, I. Saviane, L. Girardi, G. Volpato, G. Costa, N.R. Landin, I. Yegorova, M. Montalto, M. Dima, F. R. Herpich, F. Almeida-Fernandes
Astrophysics of Galaxies
Discovery of the Distant, Ultra-Faint Milky Way Satellite Aquarius IV with the Vera C. Rubin Observatory Early Data Preview 2
William Cerny, Aashay Pai, Alex Drlica-Wagner et al. (+16 more)
We present the discovery of Aquarius IV (Rubin J2201$-$0234) – the first ultra-faint Milky Way satellite to be identified using data from the Vera C. Rubin Observatory. This system was detected at $\sim$8$\sigma$ significance using Rubin Early Data Preview 2 (EDP2) photometry and independently confirmed at $\sim$6$\sigma$ significance in archival Dark Energy Camera imaging. Jointly fitting its morphology and distance, we find that Aquarius IV is a low-luminosity ($M_V=-1.9^{+0.6}_{-1.0}$), compact ($r_{1/2} = 19^{+4}_{-6}$ pc; $r_h = 0.60^{+0.14}_{-0.17}$ arcmin)
stellar system in the outer
Galactic halo ($D_{\odot} = 109^{+6}_{-8}\ \mathrm{kpc}$). Its
stellar population is consistent with an ancient, metal-poor
stellar isochrone ($\tau = 13$ Gyr, $Z=0.0001$). These properties closely resemble those of the smallest and faintest confirmed ultra-faint
dwarf galaxies, though a globular cluster classification is not ruled out. Given the small number of detected member
stars in Rubin EDP2, deeper imaging and spectroscopy will be critical for determining the properties and classification of Aquarius IV at higher confidence.
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All authors William Cerny, Aashay Pai, Alex Drlica-Wagner, Andrew B. Pace, Peter S. Ferguson, Marla Geha, Chin Yi Tan, Sasha Campana, Jeffrey L. Carlin, Denija Crnojević, Alexander P. Ji, Guilherme Limberg, Pol Massana, Sidney Mau, Gustavo E. Medina, Burçin Mutlu-Pakdil, Joanna D. Sakowska, Nora Shipp, Guy S. Stringfellow
Instrumentation and Methods for Astrophysics
SDSS-V Local Volume Mapper (LVM): Dithered Data Cube Reconstruction with 3dcubegen
H. J. Ibarra-Medel, A. Z. Lugo-Aranda, R. de J. Zermeño et al. (+16 more)
The Sloan Digital Sky Survey V (SDSS-V) Local Volume Mapper (LVM) is conducting an unprecedented wide-field integral field spectroscopic survey of the Milky Way, the Magellanic Clouds, and nearby
galaxies using a strategy based on multiple dithered observations to achieve full spatial coverage, improved spatial sampling, and enhanced spectral depth. However, the scientific exploitation of these observations requires a robust methodology to combine the individual row-stacked spectra (RSS) into homogeneous three-dimensional data cubes. In this work, we present 3DCubeGen, a flexible and scalable reconstruction tool designed to combine multiple LVM dithers while preserving flux and propagating uncertainties. The method enables the coaddition of large
datasets, improving the signal-to-noise ratio, enhancing spatial resolution, and increasing sensitivity to faint emission features, following and extending approaches previously implemented in integral field surveys such as CALIFA. We apply 3DCubeGen to a large set of LVM observations, including the Large and Small Magellanic Clouds and nearby
galaxies, combining thousands of dithers corresponding to millions of spectra. The resulting data products demonstrate significant improvements in spatial sampling and spectral depth, enabling detailed studies of the ionised gas,
stellar populations, and kinematics across extended regions. 3DCubeGen provides a robust and scalable solution for LVM data cube reconstruction and represents a key tool for exploiting the scientific potential of the SDSS-V Local Volume Mapper.
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All authors H. J. Ibarra-Medel, A. Z. Lugo-Aranda, R. de J. Zermeño, Sebastián F. Sánchez, Lesly Castañeda-Carlos, J. Eduardo Méndez-Delgado, K. Kreckel, Roeland P. van der Marel, R. Orozco-Duarte, Aida Wofford, Castalia Alenka Negrete, Irene Cruz-González, Carlos G. Román-Zúñiga, Guillermo A. Blanc, Evelyn J. Johnston, Ivan Katkov, Alfredo J. Mejía-Narváez, Tony Wong, Oleg V. Egorov
High Energy Astrophysical Phenomena
Generation of Correlated Time Series for X-ray Astronomy Applications
Seth Rowan Larner, Michael A. Nowak and Jörn Wilms
Cross-spectral methods have become essential for studying
accretion physics in X-ray binaries and active
galactic nuclei, where coherence and phase lag measurements constrain physical models and reveal variability components invisible in power spectra alone. Recent multi-Lorentzian fitting techniques have uncovered new quasi-periodic features through joint analysis of power spectra and cross-spectra, but testing these methods requires synthetic data with realistic statistical properties. We present an
algorithm for generating pairs of time series with arbitrary power spectra, coherence functions, and phase lag profiles. The method extends existing methods by decomposing the dependent time series into coherent and incoherent components, where the coherent part is constructed through a complex transfer function applied to a reference series. We derive the transfer function and normalization required to preserve target spectral shapes while achieving specified cross-spectral properties. We obtain approximate analytic expressions for the variance of coherence and phase lag
estimators and construct the approximate covariance
matrix relating these quantities to the underlying power and cross-spectra. When fitting models jointly to power and cross-spectra, these correlations must be incorporated into the likelihood. We apply the method to a two-Lorentzian model with component-specific phase lags and demonstrate close agreement between input models and generated power spectra, coherence function, and phase lag profile across four decades in frequency.
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Earth and Planetary Astrophysics
Orbital-Period Determination As an Indispensable Tool to Study the Pedigree of a Sungrazing Comet
Zdenek Sekanina
Among some 4500 Kreutz sungrazers known, the orbital period has been established to better than about +/-20 years only for C/1882 R1, C/1963 R1, C/1965 S1, C/2011 W3, and C/2026 A1. I describe solutions to a range of intriguing problems involving the orbital-period determination. A helpful, but computer-intensive routine is a detailed investigation of derived orbital periods as a function of the last observation used, which allows one to filter out effects of activity (the case of C/2026 A1) or
nuclear fragmentation (the case of C/1965 S1) and thereby reliably evaluate the time of the previous perihelion, a cornerstone in the quest for a sungrazer's pedigree. Experience shows that only very massive objects, such as the original
nucleus of C/1882 R1 or its main fragment B are immune to effects of this kind. Different problems are presented by a sungrazer whose
nucleus falls apart shortly after perihelion (the case of C/2011 W3) or by one observed only after perihelion (the case of C/1963 R1). The documented high sensitivity of the derived orbital period to minor perturbations of a sungrazing comet's motion is exploited to advantage when the standard approach does not work or yields inconclusive results.
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