Solar and Stellar Astrophysics
I-Band Asymptotic Giant Branch (IAGB) Stars: I. Exploring a New Standard Candle for the Extragalactic Distance Scale
Barry F. Madore, Wendy L. Freedman, Taylor Hoyt et al. (+3 more)
In the I-band color-magnitude diagrams (CMD) of resolved nearby
galaxies, the reddest asymptotic
giant branch (AGB)
stars form a previously unremarked-upon, but nevertheless distinct and easily-identified population of high-luminosity
stars. Hereafter we refer to this population as being comprised of I-Band AGB (IAGB)
stars. Identifying these
stars in the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC) and in NGC4258 (for all three of which there are published
geometric distances) we find that the marginalized luminosity functions are each well approximated by single-peaked Gaussians, having one-sigma dispersions of +/- 0.22 mag, +/- 0.25 mag and +/- 0.24 mag, respectively. The zero points for the modal I-band absolute magnitudes of IAGB
stars are found to be M_I = -4.49 +/- 0.003 mag (stat) in the LMC (4204
stars), M_I = -4.67 +/- 0.008 mag (stat), for the SMC sample (916
stars), and M_I = -4.78 +/- 0.030 mag (stat) for NGC4258 (62
stars). A global average over these three independent calibrations of the IAGB zero point (weighted inversely by squares of their systematic errors) gives <M_I> = -4.65 +/- 0.119 mag (stat) +/- 0.025 (sys). In Paper II we will show the results of applying the IAGB Method to 92
galaxies additional
galaxies resolved by HST, reaching out to distances just short of 10 Mpc.
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All authors Barry F. Madore, Wendy L. Freedman, Taylor Hoyt, In Sung Jang, Abigail Lee, Kayla Owens
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
The initial states of high frequency gravitons
Massimo Giovannini
After distinguishing the role of classical and
quantum inhomogeneities in cosmological backgrounds, we constrain the initial states of the relic gravitons as soon as the different wavelengths of the spectrum cross the comoving Hubble radius, without any reference to earlier timescales. According to this pragmatic perspective the
quantum states with finite energy density at the crossing time consistently affect the two-point functions and the related power spectra. An initial state different from the
vacuum turns out to be marginally permitted in the low frequency range (associated with the largest observable wavelengths that crossed the comoving Hubble radius) while the intermediate and high frequency domains of the spectrum are populated by the gravitons produced from the
vacuum. The non classical correlations are expected to dominate between the kHz and the THz since in this region gravitons are produced
quantum mechanically with a negligible contribution from the initial state.
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Earth and Planetary Astrophysics
Pre-perihelion Volatile Evolution of Interstellar Comet 3I/ATLAS Indicating Significant Contribution from Extended Source in the Coma
Juncen Li, Xian Shi, Man-To Hui et al. (+1 more)
Interstellar comets provide rare opportunities for probing the diversity of refractory and volatile inventory around other
stars. As the second ever interstellar comet, and the third interstellar object, 3I/ATLAS has been the focus of telescopic observations since its discovery in July 2025. Following the previous observations at multi-wavelengths, we present further
radio observations of the 1665/1667 MHz ground-state OH lines and millimeter observations of the CO($J$=1-0) transition at 115.271 GHz that trace the coma $\rm H_2O$ and CO abundances, respectively. We derived OH production rates of $(1.32\pm0.47)\times10^{28}\ \rm s^{-1}$ at 2.27 au and $(1.89\pm0.37)\times10^{28}\ \rm s^{-1}$ at 1.96 au as well as an average CO production rate of $\rm (5.75\pm1.91) \times 10^{27}\, s^{-1}$ between 2.33 and 1.75 au, inferring a CO/$\rm H_2O$ ratio of ($28\pm11\%$). With the mean HCN production rate of $2.5\times 10^{25}\ \rm s^{-1}$ at 2.1 au reported by \citet{2025arXiv251120845R} and \citet{2025arXiv251002817C}, we infer a CO/HCN ratio of ($230\pm76$). By synthesizing water production rates measured with instruments of different apertures, we found that the sublimation from extended source in the coma contributes significantly to 3I's pre-perihelion water measurements, accounting for up to 80% from 3 au to 2 au.
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All authors Juncen Li, Xian Shi, Man-To Hui, Jianchun Shi
High Energy Astrophysical Phenomena
PeV neutrons as origin of separated SS433 TeV signals
D. Fargion, P.G. De Sanctis Lucentini, S. Turriziani et al. (+2 more)
The SS433, a well-known binary system with an internal black hole, have shown since half a century, an inner (a few year light distances) twin precessing jets spirals. These beams are made by
tidal forces while stripping mass from large
stellar companion feeding an inner BH
accretion disk and an orthogonal accelerating twin jet. From it, the
radio, X gamma jet emission. A couple of years ago H.E.S.S
telescope as well as HAWC and LHAASO array detectors, discovered also the surprising signature of an unexpected far twin separated gamma beam at tens TeV energy. At a hundred light years distances from its central source. We suggest that it is the legacy of a past rare eruption, a century ago, of tens PeV (10^16 eV) relativistic twin
neutron beams. Their beta decay in flight at far distances, into
proton,
neutrino and in particular into tens TeV electrons, could feed the observed TeV gamma traces. They are originated by the same secondary tens TeV electrons emitting hard gamma, by Inverse Compton Scattering onto interstellar infrared
photons.
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All authors D. Fargion, P.G. De Sanctis Lucentini, S. Turriziani, M.Y. Khlopov, D. Sopin
High Energy Astrophysical Phenomena
Tracing Fe K X-ray reverberation lag in the energy-resolved spectra of Narrow-line Seyfert 1 galaxy Ton S180
Dilip Kumar Roy, Samuzal Barua, Ranjeev Misra et al. (+2 more)
We report the Fe K relativistic reverberation feature for the first time in the Narrow-line Seyfert\,1
galaxy Ton\,S180. Using a long observation from XMM-Newton we find that the Fe K emission lag peaks at $117\pm49$ s in the lag energy spectrum computed for frequencies $(0.3-8.5) \times 10^{-4}$ Hz. The lag amplitude drops to $22.85\pm14.20$ s as the frequency increases to $(8.5-30) \times 10^{-4}$ Hz. The time-averaged spectrum of the source shows a relatively narrow Fe K line at $\sim6.4$ keV, resulting in black hole
spin to be low ($a=\rm 0.43_{-0.14}^{+0.10}$) found from the reflection modelling. We perform general relativistic transfer function modelling of the lag energy spectra individually. This provides an independent timing-based measure of the
spin at $a=0.30_{-0.17}^{+0.34}$, and black hole mass $M_{\rm BH} = 0.29_{-0.16}^{+0.01}\times10^8M_{\odot}$, comparable to the previous measurement, and height of the corona $h = 2.59_{-0.33}^{+5.17}r_{\rm g}$. Further, we observe that the Fe K lag and the black hole mass fit well in the linear lag-mass relation shown by other Seyfert 1
galaxies.
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All authors Dilip Kumar Roy, Samuzal Barua, Ranjeev Misra, Rathin Sarma, V. Jithesh
High Energy Astrophysical Phenomena
Nonlinear diffusive shock acceleration with upstream escape reproduces DAMPE observations
Han-Xiang Hu, Xing-Jian Lv, Xiao-Jun Bi et al. (+3 more)
We develop a self-consistent nonlinear extension of diffusive shock acceleration that incorporates
cosmic ray (CR) backreaction on the shock precursor together with a physically motivated upstream-escape mechanism that produces an exponential high energy cutoff. The CR pressure gradient decelerates the upstream flow facing the shock wave, generating an extended precursor in which higher
rigidity particles sample a larger cumulative velocity gradient and thereby acquire a progressively harder spectrum. Finite-size/escape effects are modeled by a momentum-dependent loss term, which naturally terminates acceleration and steepens the spectrum near the cutoff. The precursor compression ratio is not imposed as a closure condition but is determined dynamically by requiring consistency between the injection rate inferred from thermal leakage at the subshock and the injection strength demanded by the nonlinear shock modification, with CR-driven wave heating providing stabilizing negative feedback. Applying the model to young
supernova-remnant-like parameters and standard one-zone
Galactic diffusion, we reproduce the main features of the latest DAMPE
proton spectrum: gradual hardening from hundreds of GeV to multi-TeV energies and a subsequent exponential cutoff at tens of TeV. The resulting spectral
evolution follows directly from the competition between precursor-mediated nonlinear feedback and upstream escape.
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All authors Han-Xiang Hu, Xing-Jian Lv, Xiao-Jun Bi, Tian-Lu Chen, Kun Fang, Peng-Fei Yin
Earth and Planetary Astrophysics
Diversities and similarities exhibited by multi-planetary systems and their architectures: II. Radii of singles and multis
Alexandra Muresan, Carina M. Persson and Malcolm Fridlund
The discovered
planets in apparent single-
planet systems (singles) and those in systems with multiple detected
planets (multis) exhibit a rich diversity of physical and orbital properties. We investigate the differences and similarities between 1730 singles and 1522 multis in a catalogue of confirmed transiting
planets orbiting main-sequence
stars with spectral classes ranging from late-M to late-F. After we removed the hot Jupiters, the
planet types and their fractional numbers were similar for the multis and singles hosted by FGK-type
stars. Furthermore, the median radii of both the singles and the multis increase with host
star temperature already from late- to early-type M
dwarfs and further up to F
stars. Our analyses show that the singles are larger on average than the multis in our F, G, K, and M samples. However, after we excluded the hot Jupiters, the radius distributions of the singles and multis orbiting FGK
stars are statistically indistinguishable, particularly at $R < 4\, R_\oplus$. In the FGK sample, we also identified an unexpected and significant overabundance of multis, compared to singles, at radii of $\approx1.4-1.6\, R_\oplus$. For the early- and late-type M samples, our work indicates that the multis are smaller on average than the singles and that the radius distributions of the multis and singles are different, except for the
planets with $R < 4\, R_\oplus$ hosted by early-type M
dwarfs. Nevertheless, these results for the two M samples are inconclusive because the sample sizes of 167 and 101
planets are limited. In conclusion, our analyses reveal that the singles and multis, excluding the hot Jupiters, orbiting FGK
stars are overall consistent with originating from the same underlying population based on their
planet types and radii. This interpretation is, however, not applicable within the region of the overabundance of multis identified in this work.
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Astrophysics of Galaxies
LIGHTS. The Thin Encircling Stellar Stream of NGC 3938
Dennis Zaritsky, Jacob Nibauer, Giulia Golini et al. (+17 more)
We present a
stellar stream found in images of the nearby, nearly face-on, late-type
galaxy, NGC 3938 obtained for the LBT Imaging of
Galactic Halos and
Tidal Structures (LIGHTS) survey that is thin, has very low mean surface brightness ($\langle\mu_g\rangle \approx$ 28.7 mag arcsec$^{-2}$ and $\langle\mu_r\rangle \approx$ 28.1 mag arcsec$^{-2}$), appears to lie nearly on the plane of the sky, and wraps more than half way around a host
galaxy that is otherwise apparently isolated. We estimate that the progenitor had a
stellar mass of $\sim 3.7\times 10^7$ M$_\odot$. Despite an intriguing apparent offset between the centroid of the host
galaxy and the apparent center of the stream orbit, we find that we can reproduce the morphology, including this apparent off-centering, with simple models and standard assumptions about the host (thin disk centered within a canonical spherical dark matter
halo) and the progenitor satellite orbit. We identify a number of detailed features of the stream, such as changes in
curvature and density, that will require more complex models to reproduce. Even this rather simple system provides a rich set of constraints with which to explore the
accretion history and gravitational potential of an otherwise unremarkable late-type
galaxy. Given the depth of the LIGHTS images, this system is an example of the types of
stellar stream that could be found in a majority of nearby
giant galaxies with the 10-year stack of Rubin/LSST data.
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All authors Dennis Zaritsky, Jacob Nibauer, Giulia Golini, Ignacio Ruiz Cejudo, Ignacio Trujillo, Sarah Pearson, Nushkia Chamba, Chen-Yu Chuang, Mauro D'Onofrio, Sepideh Eskandarlou, Sergio Guerra Arencibia, S.Zahra Hosseini-ShahiSavandi, Ouldouz Kaboud, Minh Ngoc Le, Garreth Martin, Mireia Montes, Samane Raji, Javier Román, Nafise Sedighi, Zahra Sharba
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
On the Cuspy Structure of Rotating Wormhole Shadows
Peng Cheng, Ruo-Fan Xu and Peng Zhao
We investigate the shadow cast by a rotating traversable wormhole in the Teo class endowed with a general
redshift function, with particular emphasis on the emergence of cuspy structures. The shadow boundary is the common envelope of two critical orbit families: unstable circular orbits outside the throat and orbits at the throat itself. The formation of cusps, marking the transition between smooth and cuspy shadow boundaries, only becomes possible when the
redshift parameter $\lambda$ is allowed to vary. Moreover, we uncover a universal critical value $\lambda_c$ that signals the onset of the cusp. A phase diagram characterized by the
spin and
redshift parameters reveals four distinct morphologies: smooth, cuspy, ears touching, and throat drowning. The morphology of the wormhole shadow may provide observational diagnostics for the different compact objects in future high-resolution imaging observations.
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Instrumentation and Methods for Astrophysics
In-orbit Demonstration of X-ray Pulsar Navigation with NinjaSat
Naoyuki Ota, Takuya Takahashi, Toru Tamagawa et al. (+26 more)
This study demonstrated the
pulsar navigation capability of the CubeSat X-ray observatory NinjaSat, which is equipped with two Gas Multiplier Counters (GMCs). The GMCs are sensitive to the 2-50 keV energy band and have an effective area of 16 cm^2 per module at 6 keV. We verified the timing accuracy by observing the Crab
Pulsar and confirmed stable timing performance within 100 microseconds. To demonstrate
pulsar navigation, we applied a method that optimizes orbital parameters to maximize the significance of the
pulsar X-ray pulse profile, known as the Significance Enhancement of Pulse-profile with Orbit-dynamics (SEPO) method. We observed the Crab
Pulsar with a total exposure of approximately 100 ks at different epochs and analyzed the data transmitted to the ground. By comparing the optimized orbit with the satellite position derived from Global Positioning System data, we quantitatively evaluated the
navigation performance. The results show that the position component along the Crab line of sight was consistently constrained within approximately 40 km, and the three-dimensional position error ranged from 27 to 370 km depending on the observation epoch. These results demonstrate the feasibility of applying a CubeSat-class X-ray observatory to
pulsar navigation and provide the first experimental verification that the accuracy of the SEPO method depends on the seasonal geometry between the orbital plane and the
pulsar direction.
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All authors Naoyuki Ota, Takuya Takahashi, Toru Tamagawa, Tomoshi Takeda, Teruaki Enoto, Takao Kitaguchi, Wataru Iwakiri, Yo Kato, Masaki Numazawa, Tatehiro Mihara, Hiromitsu Takahashi, Chin-Ping Hu, Yuanhui Zhou, Keisuke Uchiyama, Yuto Yoshida, Syoki Hayashi, Arata Jujo, Sota Watanabe, Amira Aoyama, Satoko Iwata, Kaede Yamasaki, Soma Tsuchiya, Yosuke Nakano, Takayuki Kita, Mayu Ichibakase, Hiroki Sato, Hirokazu Odaka, Tsubasa Tamba, Kentaro Taniguchi
High Energy Astrophysical Phenomena
High Energy Emission from the Galactic Center
Andrea Goldwurm, Maïca Clavel, Stefano Gabici et al. (+1 more)
The center of the
Galaxy is a prominent source in X-rays and gamma-rays. The study of its high-energy (HE) emission is crucial in understanding the physical phenomena taking place in this dense and extreme environment, where the closest supermassive black hole (SMBH) to us, Sgr A*, is lurking nearly invisible, today, in most of the energy spectrum. These phenomena are probably common to other
galactic nuclei and may explain the feedback processes between
nuclear regions and
galaxies, so important for the overall
evolution of the Universe. The
Galactic center HE emission is very complex and consists of both thermal and non thermal radiation produced by compact and extended sources, surrounded by more diffuse components. All these objects and media are interacting with each other in the narrow and dense Central Molecular Zone (CMZ). Some of them also show relevant extensions towards the
Galactic poles, indicating energetic
outflows that seem to link the center to the recently observed large
Galactic polar structures. In spite of the fundamental advances obtained in the last twenty five years with the most sensitive X-ray and gamma-ray observatories, several questions remain open to investigations. We review here the main observational results and the open issues on the high-energy diagnostics of the
Galactic nuclear activity, focusing on processes that take place in the CMZ, and in particular discussing the role of the present and past SMBH activities in powering this region and possibly the whole
Galaxy.
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All authors Andrea Goldwurm, Maïca Clavel, Stefano Gabici, Régis Terrier
High Energy Astrophysical Phenomena
Kinematic Evidence for Open Cluster Origins of Galactic Binary Neutron Stars
Wen-Jie Yu, Lu Zhou, Zhi-Qiang You et al. (+4 more)
We investigate the potential birthplace of
Galactic binary
neutron star (BNS) systems through a kinematic analysis. Using high-precision astrometry from
Gaia DR3, updated
pulsar distances, and Monte Carlo sampling of astrometric errors, we integrate the past trajectories of 11
Galactic BNSs and 167 globular clusters plus 2967 open clusters, to search for past encounters. Our results suggest that BNS origin in globular clusters is unlikely, with low encounter probabilities (e.g., $\lesssim 0.5\%$ for NGC 5139) and requiring excessive ejection velocities. Conversely, our analysis indicates that open clusters are a non-negligible formation channel. Specifically, the double
pulsar J0737$-$3039 shows a $13.9\%$ ($5.4\%$) probability of originating from the young cluster OC 0450 (Theia 58). Based on encounter proximity and time, we argue that Theia 58 is its more plausible birthplace. Our work provides kinematic evidence consistent with an open-cluster origin for a subset of field BNSs.
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All authors Wen-Jie Yu, Lu Zhou, Zhi-Qiang You, Hao Ding, Lu Li, Long Wang, Xing-Jiang Zhu
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Quarkyonic matter and hadron-quark crossover from an ultracold atom perspective
Hiroyuki Tajima, Kei Iida, Toru Kojo et al. (+1 more)
The dense matter equation of state is of great interest due to the recent development of astrophysical observations for
neutron stars. A rapid increase in pressure indicates a continuous crossover from a
hadron phase to a
quark phase without any phase transitions, yet its microscopic mechanism remains elusive. Recently, a peak in the speed of sound and a
baryon momentum-shell structure, which are predicted from a quarkyonic matter picture, have been regarded as key features of the
hadron-
quark crossover. In this work, we explore a field-theoretical framework to describe the
hadron-
quark crossover, drawing an analogy with the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover established in ultracold atomic experiments. Strikingly, a peak in the speed of sound and the
baryon momentum-shell structure can simultaneously be explained by the tripling fluctuation effect arising from a different context of
quantum many-body physics. We demonstrate these properties in a simplified model and provide a microscopic derivation of the quarkyonic matter model within our field-theoretical framework.
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All authors Hiroyuki Tajima, Kei Iida, Toru Kojo, Haozhao Liang
Astrophysics of Galaxies
Effective Magnetic Susceptibility of Dust Grains with Superparamagnetic Inclusions and Implications
Thiem Hoang
Magnetic properties of
dust grains play a fundamental role in their
alignment with ambient
magnetic fields and
magnetic dipole emission. In the radiative torque (RAT) paradigm, superparamagnetic inclusions (SPIs) embedded within
dust grains are expected to significantly enhance
magnetic susceptibility and
alignment efficiency. Previous studies have generally assumed SPIs of a single characteristic size. In this work, we develop an effective superparamagnetism model that explicitly accounts for a power-law size distribution of SPIs. We show that the effective zero-frequency susceptibility can be described by the superparamagnetic susceptibility of uniform-sized inclusions evaluated at the critical blocking size, reduced by a factor $F_{\rm eff}\sim 0.1$. It exhibits a slight increase with
dust temperature $T_{d}$, in contrast to the rapid decrease for the case of single-size SPIs. For rotating grains at angular frequency $\omega$, we identify a characteristic resonance size of SPIs that dominates the
magnetic response, $N_{\rm res} = (T_{d}/T_{\rm act}) \ln (\nu_{0}/\omega)$ with $T_{\rm act}$ activation temperature and $\nu_{0}$ the characteristic attempt frequency of SPIs. The frequency-dependent effective susceptibility is well described by the maximum susceptibility $\chi_{\rm eff}^{\rm max}(\omega)$ at $N_{\rm res}$, reduced by a factor $G_{\rm eff}\sim 0.1$. Unlike models assuming uniform-sized inclusions, we find that the effective susceptibility exhibits a nearly flat spectrum for frequency below $\nu_{0}$, arising from the progressive activation of larger inclusions at lower frequencies. This effective superparamagnetism model based on the SPI size distrbution has important implications for
magnetic grain
alignment,
dust polarization, and
magnetic dipole emission across diverse environments.
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Solar and Stellar Astrophysics
S-PLUS: Beyond Spectroscopy IV. Stellar Parameters and Elemental-abundance Ratios for Six Million Stars from DR4 and First Results for the Magellanic Clouds
Yang Huang, Timothy C. Beers, Kai Xiao et al. (+18 more)
We combine narrow/medium-band filter photometry from the Southern Photometric Local Universe Survey (S-PLUS) DR4 with ultra broad-band filter photometry from
Gaia EDR3 to derive fundamental
stellar parameters ($T_{\rm eff}$, $\log g$, [Fe/H], ages) and elemental-abundance ratios ([C/Fe] and [$\alpha$/Fe]) for 5.4 million
stars in the
Galaxy (4.9 million
dwarfs and 0.5 million
giants), as well as for over 0.7 million red
giant stars in the Large and Small Magellanic Clouds (LMC and SMC). The precisions of the abundance estimates range from 0.05-0.10 dex for
metallicity in the relatively metal-rich range ([Fe/H] $> -1.0$) to 0.10-0.30 dex in the metal-poor regime ([Fe/H] $<-1.0$), 0.10-0.20\,dex for [C/Fe], and 0.05 dex for [$\alpha$/Fe]. The
stellar parameters for LMC and SMC member
stars are somewhat less precise than those from the S-PLUS main survey, primarily because of the effect of high reddening. The use of both
metallicity- and carbon-sensitive filters provides unbiased measurements of both [Fe/H] and [C/Fe], of particular importance for very low-
metallicity ([Fe/H] $< -2.0$)
stars, where carbon enhancement can lead to systematically high estimates of [Fe/H] when only a single
metallicity-sensitive filter is employed. Furthermore, multiple narrow-band filters enable
metallicity estimates down to [Fe/H] $\sim -4.0$ with an accuracy of around 0.3 dex, exceeding the precision typically achieved by low/medium-resolution spectroscopy. This extensive photometric
dataset, combined with the other three
datasets in this series, will serve as a valuable legacy resource for Milky Way and Magellanic Clouds studies.
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All authors Yang Huang, Timothy C. Beers, Kai Xiao, C. Mendes de Oliveira, Felipe Almeida-Fernandes, G.B. Oliveira Schwarz, Young Sun Lee, Jihye Hong, Huiling Chen, Huawei Zhang, Guilherme Limberg, Maiara S. Carvalho, P. K. Humire, André Luiz Figueiredo, Bruno Dias, Alvaro Alvarez-Candal, Marcos Fonseca-Faria, A. Kanaan, T. Ribeiro, W. Schoenell, Silvia Rossi
Cosmology and Nongalactic Astrophysics
VENUS: Strong-lensing model of MACS J1931.8-2635 – revealing the farthest multiply imaged supernova
Joseph F. V. Allingham, Adi Zitrin, Vasily Kokorev et al. (+42 more)
We present a parametric strong-
lensing model for the
galaxy cluster MACS J1931.8-2635 ($z_l = 0.35$), accompanying the detection of the spectroscopically confirmed SN Eos at $z = 5.13$ (Coulter et al. 2026). We identify 10 new multiple-image systems in recent VENUS JWST/NIRCam imaging, so that the model is constrained with a total of 19 robust multiple-image systems – nine of which also have a spectroscopic
redshift. For the point-like source corresponding to SN Eos, our model predicts a total of five images, with the observed radial image pair having a similar magnification of $\mu \simeq 25 - 30$ and a small time delay of $< 5$ days, in agreement with their simultaneous observation. According to the model, the other three predicted images arrived earlier, with time delays of $3.6 \pm 0.7$, $3.4 \pm 0.7$ and $53.9 \pm 10.8$ years prior to the two observed images, and with magnifications of $14.5 \pm 2.9$, $11.9 \pm 2.4$ and $2.2 \pm 0.4$, respectively. The absence of detections at the predicted positions, where the host
galaxy's images are also visible, confirms the transient nature of the source. SN Eos and its host
galaxy are studied in separate articles, and we here focus on the lens model. The final model reaches a very good $r.m.s.$ distance between model and observations of $0.44''$. We present the lens-modeling results, including newly identified systems such as a triply imaged, grand-design spiral
galaxy candidate at $z \simeq 3.65_{-0.09}^{+0.04}$, and discuss the potential of using high-
redshift lensed SNe for cosmography.
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All authors Joseph F. V. Allingham, Adi Zitrin, Vasily Kokorev, Hiroto Yanagisawa, Jose M. Diego, Lukas J. Furtak, Yoshihisa Asada, Dan Coe, David A. Coulter, Seiji Fujimoto, Conor Larison, Masamune Oguri, Justin D. R. Pierel, Fengwu Sun, Marusa Bradac, Pratika Dayal, Paulo A. A. Lopes, Ashish K. Meena, Massimo Pascale, Hollis B. Akins, Franz E. Bauer, Larry D. Bradley, Gabriel Brammer, John Chisholm, Guillaume Desprez, Qinyue Fei, Henry C. Ferguson, Steven L. Finkelstein, Brenda Frye, Miriam Golubchik, Kohei Inayoshi, Yolanda Jimenez-Teja, Anton M. Koekemoer, Ray A. Lucas, Georgios E. Magdis, Nicholas S. Martis, Richard Pan, Johan Richard, Massimo Ricotti, Gregor Rihtarsic, Luke Robbins, William Sheu, Brian Welch, Chris Willott, Rogier A. Windhorst
Cosmology and Nongalactic Astrophysics
Constraining Lorentz Violation using 21cm and CMB Cross Correlations
Bhuwan Joshi, Rahul Kothari and Shyam Chaudhary
Lorentz
symmetry is a fundamental pillar of modern Physics, yet high-energy theories often predict its violation. One potential signature of such a violation is
cosmic birefringence - rotation of the polarization plane of
photons due to Chern-Simons coupling in Maxwell's electrodynamics. This rotation angle, aka birefringence angle, depends upon the distance travelled by the
photon and is thus different for CMB and 21cm
photons. While the rotation angle in CMB, i.e., $\alpha_\mathrm{CMB}$, has been tightly constrained by CMB experiments, the potential of the 21cm cosmological signal to constrain this parameter, as well as constrain $\alpha_\mathrm{21cm}$, remains largely unexplored. In this work, we provide constraints on both these angles by cross-correlating 21cm and CMB signals. Using the Fisher
matrix formalism, we give our forecasts for 21cm experiments, including SKA, HIRAX, and PUMA, and Planck like CMB experiment. We find that best constraints $\sigma_{\alpha_\mathrm{CMB}} \sim 4.4^\circ$ and $\sigma_{\alpha_\mathrm{21cm}} \sim 100^\circ$ are found using $C_\ell^{T_{21} B_\mathrm{CMB}}$ and $C_\ell^{T_{21} B_{21}}$ respectively. Since birefringence hasn't yet been detected in 21cm, we choose the fiducial value $\alpha_\mathrm{21cm}^\mathrm{fid}=0$ assuming the null hypothesis.
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High Energy Astrophysical Phenomena
Pulsar Timing Array in the past decade
Kuo Liu and Siyuan Chen
The past decade has been a transformative period for
pulsar timing arrays (PTAs) and their search for nanohertz gravitational waves (GWs). This progress has been driven by collective advances in instrumentation for
pulsar timing observations, increasingly sophisticated data-analysis techniques, and improved theoretical understanding of the origins of nanohertz GW signals. PTA sensitivity has steadily improved, leading first to progressively more stringent upper limits on the gravitational-wave background (GWB), and subsequently to the identification of a common red-noise process in
pulsar timing data, the first hint of a GWB. In 2023, multiple PTA collaborations reported evidence for the Hellings-Downs correlation, widely regarded as the definitive signature of a GWB. These developments place PTAs on the threshold of a confident GW detection and the opening of a new low-frequency window on the GW Universe. In this article, we present an overview of PTA experiments, with particular emphasis on the rapid progress achieved during this pivotal period for PTA and nanohertz GW science.
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Instrumentation and Methods for Astrophysics
Image instabilities and polarization cross-talk
Roberto Casini and Alfred G. de Wijn
We expand on our previous study of the impact of atmospheric seeing on polarization cross-talk, and show how the formalism that was developed in that work can be applied to treat the case of spatial modulators of polarization. Beside formally demonstrating how the problem of cross-talk is fully eliminated in such devices, we also gain insight on the meaning of polarimetric noise of temporal modulation schemes in the limit of very high modulation frequency. We also describe the problem of spectrograph instabilities, and how the spectral gradients that are naturally associated with a line spectrum feed into the problem of polarimetric errors induced by mechanical vibrations, thermal drifts, and pointing jitter. Finally, we show how this formalism can be used to estimate the contribution of polarization cross-talk to the errors on the elements of the 4$\times$4 Stokes response
matrix, for the purpose of producing realistic error budgets for polarimetric instrumentation.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics
On the modeling and mitigation of interference fringes in polarimetric instrumentation
Roberto Casini and David M. Harrington
Spectral and spatial fringes in polarized light are produced by the interference of transmitted and reflected waves at the interface between materials with different indexes of refraction. These instrumental artifacts can affect the accuracy of optical designs conceived for high-sensitivity spectroscopy and polarimetry. We consider the principal sources of these artifacts and the possible design pathways to mitigate them. In order to do so, we have developed an approximate yet agile treatment of the problem of the transmission and reflection of light in birefringent materials, which fundamentally relies on the assumption of small birefringence of the modeled materials for its implementation. The comparison of our results with those from more rigorous treatments, such as Berreman calculus, thus also serves as a test of the limits of the small-birefringence approximation in optical design applications. The treatment presented in this work is limited to isotropic materials and uniaxial
crystals, which are the most common types of optics employed in polarimetric instrumentation. An extensive set of modeling examples is provided to illustrate the salient characteristics of polarization fringes and their dependence on optical design parameters.
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Instrumentation and Methods for Astrophysics
Optimal polarization modulation and calibration schemes
Roberto Casini, David M. Harrington and Alfred G. de Wijn
We review the algebraic definition of the efficiency of a polarization modulation scheme, which is commonly adopted for
solar and
stellar spectro-polarimetry applications, and generalize it to allow distinct states of the modulation cycle to have arbitrary throughput and different
photon-noise statistics for each state. Such a generalization becomes necessary to model and optimize the polarimetric efficiency of instruments implementing spatial polarization modulation schemes, where different optical paths are assigned to different polarization analysis states, which may be characterized by different throughput values. The proposed algebraic extension also proves essential for introducing a workable concept of the efficiency of a polarization calibration scheme, which can then be used to create a merit function for the optimization of calibration sequences, which take into account the specific characteristics of the polarimetric instrument and of its calibration optics.
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Solar and Stellar Astrophysics
Superhumps and their Relation to the Disk Instability Model
Daisaku Nogami
Since the discovery of superhumps in 1974, these photometric modulations have provided a crucial observational window into disk instabilities in cataclysmic variable
stars, particularly the
tidal instability associated with the 3:1 resonance. Over the past few decades, extensive time-resolved photometry has revealed a rich diversity of superhump-related phenomena, including delayed superhump development, early superhumps in WZ Sge-type
dwarf novae, systematic stage A-B-C
evolution, negative superhumps, and superhumps observed in related systems such as intermediate polars and AM CVn
stars. In this invited review, we summarize key observational advances since the establishment of the thermal-
tidal instability framework, discuss their theoretical interpretations within the disk instability model, and highlight remaining open problems. These developments have been driven by coordinated networks of amateur observers, wide-field robotic surveys, and continuous high-precision space-based photometry from Kepler and TESS. Together, they demonstrate that superhumps remain a powerful probe of disk dynamics, binary parameters, and the interplay between thermal,
tidal, and
geometric effects in
accretion disks.
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Astrophysics of Galaxies
Dense Molecular Clumps with Large Blue Asymmetries: Evidence for Collapse
James M. Jackson, J. Scott Whitaker, Edward Chambers et al. (+11 more)
An analysis of the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey has produced a sample of 27 candidate dense molecular clumps with large collapse motions, as revealed by large “blue” asymmetrical line profiles of the optically thick \hcop\, line. %with respect to the optically thin \nthp\, line. New, more sensitive molecular line observations of this sample, conducted with the Mopra 22-m
telescope, confirm the blue asymmetries in the \hcop\, line profiles, with large, positive values of the asymmetry parameter $A$ ($\bar{A}_{HCO^+} = 0.69\pm0.01$), and positive, but smaller asymmetries in the \hcn\, and \hnc\, lines: ($\bar{A}_{HCN} = 0.35\pm0.01$ and $\bar{A}_{HNC} = 0.28\pm0.01$), as expected for a less optically thick tracer in collapsing clumps. The small, positive mean asymmetry parameters for \cch\, and \htcop, $\bar{A}_{C_2H} = 0.15\pm0.02$ and $\bar{A}_{H^{13}CO^+} = 0.18\pm0.03$, likely indicate slightly optically thick emission for at least some clumps. The hyperfine ratios for \nthp\, are in their optically thin, LTE, values, but for \hcn\ they are not; the $F=1 \to 1$ hyperfine line shows abnormally weak intensities. A simple two-component model shows that self-absorption of the background $F = 1 \to 1$ hyperfine line by the main $F = 2 \to 1$ hyperfine line of a cold, foreground, redshifted cloud can reproduce the observed \hcn\, hyperfine intensities and match the \hcn\, and \hcop\, line profiles. All of these results are consistent with self-absorption of the optically thick lines on the red side of the profile, as expected for collapsing clumps. A simple two-cloud model suggests that this sample represents dense clumps with extreme collapse velocities, $V_{inf} \sim 2.4$ \kms.
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All authors James M. Jackson, J. Scott Whitaker, Edward Chambers, Robert Simon, Cristian Guevara, David Allingham, Philippa Patterson, Nicholas Killerby-Smith, Jacob Askew, Patricio Sanhueza, Ian W. Stephens, Anika Shmiedeke, Jacob Askew, Robert Loughnane
Instrumentation and Methods for Astrophysics
Nonlinearity in H4RG-10 Near-Infrared Detectors at Elevated Temperatures: Characterization and Data-Driven Correction Method
Ryusei Hamada, Gregory Mosby Jr., Shota Miyazaki et al. (+5 more)
We report a newly identified nonlinearity in H4RG-10 near-infrared detectors operating under moderately elevated-temperature conditions (114 K). This component, that potentially arises from illumination-independent defect currents, introduces additional nonlinearity not captured by conventional correction models. To address this issue, we propose a data-driven nonlinearity correction (NLC) method that models the nonlinear behavior of both the classical response and the defect currents, using dual-illumination measurements and a dark exposure. Applied to H4RG-10 detectors on the
PRIME telescope, the method significantly improves signal linearity, especially for pixels with high defect current, while maintaining comparable performance elsewhere. By selecting the optimal correction model per pixel, reliable NLC is achieved across the full array. This study characterizes a nonlinearity intrinsic to H4RG-10 detectors and demonstrates that data-driven post-processing can effectively restore linearity in the presence of large defect currents. Although these effects are unlikely to be significant under nominal operating temperatures, the approach may provide a practical calibration framework for future warm-operation scenarios.
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All authors Ryusei Hamada, Gregory Mosby Jr., Shota Miyazaki, Daisuke Suzuki, Alexander Kutyrev, Joseph Durbak, Yuki Hirao, Takahiro Sumi
Instrumentation and Methods for Astrophysics · Cross-listed from cs.CV
MarsRetrieval: Benchmarking Vision-Language Models for Planetary-Scale Geospatial Retrieval on Mars
Shuoyuan Wang, Yiran Wang and Hongxin Wei
Data-driven approaches like deep learning are rapidly advancing planetary science, particularly in Mars exploration. Despite recent progress, most existing
benchmarks remain confined to closed-set supervised visual tasks and do not support text-guided
retrieval for geospatial discovery. We introduce MarsRetrieval, a
retrieval benchmark for evaluating
vision-
language models for Martian geospatial discovery. MarsRetrieval includes three tasks: (1) paired image-text
retrieval, (2) landform
retrieval, and (3) global geo-localization, covering multiple spatial scales and diverse geomorphic origins. We propose a unified
retrieval-centric protocol to
benchmark multimodal embedding architectures, including contrastive dual-tower encoders and generative
vision-
language models. Our evaluation shows MarsRetrieval is challenging: even strong foundation models often fail to capture domain-specific geomorphic distinctions. We further show that domain-specific fine-tuning is critical for generalizable geospatial discovery in planetary settings. Our code is available at https://github.com/ml-stat-Sustech/MarsRetrieval
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Solar and Stellar Astrophysics
Three-dimensional kink modes in solar coronal slabs: group velocities and their implications for impulsively excited waves
Jing Liu, Bo Li, Mijie Shi et al. (+2 more)
Little
attention has been paid to group velocities of three-dimensional (3D) MHD waves in
solar coronal seismology. This study aims to present a rather comprehensive examination on the group velocities of trapped 3D kink modes in coronal slabs, emphasizing the connection of mode analysis to both mode characterization and impulsively excited 3D kink waves. We work in linear, ideal, pressureless MHD, and take the
equilibrium slab to be symmetrically structured only in one transverse direction. The dispersion relation is numerically solved, with the results understood by making in-depth analytical progress. We address both the transverse fundamental and its first overtone. We develop a three-subgroup scheme for categorizing 3D kink modes on the plane spanned by the axial and out-of-plane wavenumbers. The group ($\vec{v}_{\rm gr}$) and phase velocities ($\vec{v}_{\rm ph}$) sit on the same side of the
equilibrium magnetic field ($\vec{B}_0$) for the “$\vec{B}_0$-same-side A” and “$\vec{B}_0$-same-side F” subgroups, which are further discriminated by the directional similarity of $\vec{v}_{\rm gr}$ and $\vec{B}_0$. The “$\vec{B}_0$-straddling” subgroup is peculiar in that $\vec{v}_{\rm gr}$ and $\vec{v}_{\rm ph}$ lie astride $\vec{B}_0$, a feature that cannot be found for waves in unbounded uniform media in pressureless MHD. This “$\vec{B}_0$-straddling” subgroup pertains to both the fundamental and its overtones. We further place our results in the context of impulsive waves, employing the method of stationary phase to predict the large-time wavefront morphology in the plane of
symmetry of the
equilibrium slab. Wavefronts directed toward $\vec{B}_0$ derive exclusively from “$\vec{B}_0$-straddling” modes, and are confined to narrow sectors.
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All authors Jing Liu, Bo Li, Mijie Shi, Mingzhe Guo, Hui Yu