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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 4 November

Cosmology and Nongalactic Astrophysics

Supernova Classification using the Recurrent Neural Network in the CSST Ultra-Deep Field Survey

Minglin Wang, Yan Gong, Dejia Zhou et al. (+1 more)

We study supernova (SN) classification using the Recurrent Neural Networks (RNNs) within the Chinese Space-station Survey Telescope Ultra-Deep Field (CSST-UDF) photometric survey and explore the improvements in cosmological constraints. We simulate Type Ia supernovae (SNe Ia) and core-collapse supernovae (CCSNe) using SNCosmo with SALT3 SN Ia model and CCSN templates, and apply the SuperNNova (SNN) program for classification. Our study indicates that the SNN combined with the Joint Light-curve Analysis cuts can enhance the purity of the CSST-UDF SN Ia sample up to over 99.5% with 2,193 SNe Ia and 4 CCSNe, which can significantly increase the reliability of the cosmological constraints. The method based on the Bayesian Estimation Applied to Multiple Species with Bias Corrections framework is used to correct the SN Ia magnitude bias caused by the selection effect and CCSN contamination, and the Markov Chain Monte Carlo (MCMC) method is employed for cosmological constraints. We find that the accuracy of the constraints on the matter density $\Omega_{\rm M}$ and the equation of state of dark energy parameter $w$ can achieve 14% and 18%, respectively, assuming the flat $w$CDM model. This result is comparable to current surveys relying on spectroscopic confirmation. Our results indicate that our data analysis method is effective, and the CSST-UDF SN photometric survey is a powerful tool to explore the expansion history of the Universe.
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All authors Minglin Wang, Yan Gong, Dejia Zhou, Xuelei Chen

Solar and Stellar Astrophysics

Mass ratio estimates for overcontact binaries using the derivatives of light curves. II. Systems with deep eclipses

Shinjirou Kouzuma

This is the second paper that proposes a simple method for estimating mass ratios using the derivatives of light curves for overcontact binaries. In the first paper (Kouzuma 2023, ApJ, 958, 84) , we presented a method to estimate the mass ratios for systems exhibiting a double-peak feature in the second derivatives of their light curves around eclipses. This second paper focuses on overcontact systems that are not addressed in the first paper, that is, systems lacking a double peak in the second derivative. A sample of synthetic light curves for overcontact binaries consists of 89670, covering a parameter space typical of overcontact systems. On the basis of a recent study that proposed a new classification scheme using light-curve derivatives up to the fourth order, the sample light curves were classified. We found that time intervals between two local extrema in the derivatives are associated with the mass ratio in systems that exhibit a high degree of eclipse obscuration. Using regression analysis for the identified associations, we derived empirical formulae to estimate the mass ratio and its associated uncertainty. The application of our proposed method to real overcontact binary data demonstrated its effectiveness in providing reliable estimates for both values.
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Solar and Stellar Astrophysics

The nature of ASASSN-24fw's occultation: modelling the event as dimming by optically thick rings around a sub-stellar companion

Sarang Shah, Jonathan P. Marshall, Carlos del Burgo et al. (+12 more)

ASASSN-24fw is a main-sequence F-type star that experienced a rapid and long-lasting dimming event beginning in late 2024 and continuing until mid 2025. Its pre-dimming spectral energy distribution shows a persistent infrared excess with a fractional luminosity of approximately 0.5 percent. We model this excess using a two-component blackbody fit and find dust components with temperatures of about 1070 K and 390 K. Archival light curves indicate that ASASSN-24fw was photometrically stable prior to the event, suggesting that the dimming is caused by an external occulting body rather than intrinsic stellar variability. The event lasted about 275 days and exhibits a distinctive flat-bottomed profile of nearly 200 days, unlike most long-duration occultation events reported in the last decade. We analyze the light curve and spectra obtained during dimming to study the properties of both the star and the occulting material. A parametric light-curve model reveals multiple ingress phases, consistent with variations in the density and structure of the obscuring material. A second transit model favors an occulting body consistent with a gas giant or brown dwarf with a minimum mass of about 3.4 Jupiter masses and surrounded by an extended circumplanetary disk or rings of radius roughly 0.17 au. Near-infrared spectra taken during dimming show enhanced infrared excess and spectral features consistent with a late-type companion, approximately M8. We also detect variable H-alpha emission, suggesting evolving gas and dust in the occulting structure. Imaging from LCOGT identifies a nearby object within 3 arcsec, likely a bound companion at a projected separation of about 3000 au. Systems like ASASSN-24fw appear rare, and continued follow-up will help constrain the nature of the occulting body and the circumstellar environment.
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All authors Sarang Shah, Jonathan P. Marshall, Carlos del Burgo, Gergely Hajdu, Isabel Rebollido, Bogumił Pilecki, Ashish Mahabal, Mansi M. Kasliwal, Viraj Karambelkar, Matthew J. Graham, Stanislav G. Djorgovski, Daniel Stern, Sascha T. Zeegers, Bacham Eswar Reddy, Ciska Kemper

High Energy Astrophysical Phenomena

Characterising EP241107a: Multiwavelength Observations of an Einstein Probe-detected Fast X-ray Transient

D. Eappachen, A. Balasubramanian, Vishwajeet Swain et al. (+12 more)

Fast X-ray Transients (FXTs) represent a new class of highly luminous transients in soft X-rays ($\sim$0.3-10 keV) associated with violent astrophysical processes. They manifest as short, singular flashes of X-ray photons with durations lasting from minutes to hours. Their origin remains unclear, and they have been associated with various progenitor mechanisms. The newly launched X-ray survey, Einstein-Probe (EP), is revolutionising this field by enabling the discovery and immediate follow-up of FXTs. Here we present the multiwavelength observations of EP-discovered FXT EP241107a and the discovery of its radio counterpart. Comparison of the optical and radio observations of EP241107a and its host properties with other extragalactic transients suggests a gamma-ray burst (GRB) origin. Through our afterglow modelling, we infer the GRB jet properties for EP241107a, yielding a jet of the isotropic-equivalent kinetic energy $E_{\mathrm{K,iso}} \sim10^{51}$ erg, with a half opening angle $\theta_{c}$ $\approx$15$^{\circ}$, viewed at an angle of $\theta_{\rm obs}$~$\approx$9$^{\circ}$. We also evaluate EP241107a in the landscape of both EP-discovered FXTs as well as the FXTs discovered from Chandra, XMM-Newton, and Swift-XRT.
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All authors D. Eappachen, A. Balasubramanian, Vishwajeet Swain, G. C. Anupama, D. K. Sahu, V. Bhalerao, T. Ahumada, I. Andreoni, Sudhanshu Barway, J. Carney, J. Freeburn, M. M. Kasliwal, Tanishk Mohan, A. C. Rodriguez, G. Waratkar

Astrophysics of Galaxies

Anisotropy ansatz for the Jeans equations: oblate galaxies

Leonardo De Deo, Luca Ciotti and Silvia Pellegrini

In the solution of the Jeans equations for axisymmetric galaxy models the “$b$-ansatz" is often adopted to prescribe the relation between the vertical and radial components of the velocity dispersion tensor, and close the equations. However, $b$ affects the resulting azimuthal velocity fields quite indirectly, so that the analysis of the model kinematics is usually performed after numerically solving the Jeans equations, a time consuming approach. In a previous work we presented a general method to determine the main properties of the kinematical fields resulting in the $b$-ansatz framework before solving the Jeans equations; results were illustrated by means of disk galaxy models. In this paper we focus more specifically on realistic ellipsoidal galaxy models. It is found that how and where $b$ affects the galaxy kinematical fields is mainly dependent on the flattening of the stellar density distribution, moderately on the presence of a Dark Matter halo, and much less on the specific galaxy density profile. The main trends revealed by the numerical exploration, in particular the fact that more flattened systems can support larger $b$-anisotropy, are explained with the aid of simple ellipsoidal galaxy models, for which most of the analysis can be conducted analytically. The obtained results can be adopted as guidelines for model building and in the interpretation of observational data.
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Solar and Stellar Astrophysics

A Comprehensive Study of the Physical and Geometrical Characteristics of the Close Visual Binary System HIP 45571

Motasem J. Alslaihat, Hatem S. Widyan, Mashhoor A. Al-Wardat et al. (+3 more)

In this paper, we estimated the physical and geometrical characteristics of the visually close binary stellar system Hip 45571, using Al-Wardat's method for analyzing binary and multiple stellar systems. We estimated the physical properties of the components of the system for the four measured parallax given by Gaia and Hipparcos, which gives a dynamical mass sum ranges between 2.43 and 2.52 solar mass using the new orbital parameters following Tokovinin's dynamical method. The method used is a spectrophotometrical computational technique that employs Kurucz plane-parallel line-blanketed model atmospheres for single stars. These model atmospheres are used to construct the synthetic spectral energy distributions (SED) of each component and for the entire system. To ensure the method's accuracy, we apply the fit between synthetic and observational photometry under different filters, including the recently published Gaia DR3 measurements. The positions of the components on the H-R diagram and the evolutionary tracks were used to estimate their masses and ages. We found that the system consists of 2.24 Gyr two F2.5 IV and F3.5 IV subgiant components with T_eff_A= 6800, T_eff_B= 6700, logg=4.19 m/s^2, logg=4.33 m/s^2, R_A=1.77 R_sun, R_B=1.34 R_sun, L_A=6.01 L_sun, L_B=3.25 L_sun and Z=0.011. Depending on the masses estimated by Al-Wardat's method, a new parallax value of 28.72+-0.30 mas was obtained. Which lies between the values given by DR2 and DR3. This research underscores the importance of precision and reliability in employing these methods and measurements in a dynamic context, deepening our understanding of such stellar systems.
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All authors Motasem J. Alslaihat, Hatem S. Widyan, Mashhoor A. Al-Wardat, Awni M. Kasawneh, Diala M. Taneenah, Abdullah M. Hussein

Solar and Stellar Astrophysics

The Arizona-Montréal spectroscopic survey of hot subluminous stars

M. Latour, E. M. Green, M. Dorsch et al. (+6 more)

Hot subdwarf B (sdB) and O (sdO) type stars are evolved helium-burning objects that lost their hydrogen envelope before the helium flash when their progenitors were close to the tip of the red giant branch. They populate the extreme horizontal branch (EHB) in the Hertzsprung-Russell diagram (HRD). Using the high-quality, homogeneous spectra of 336 hot subluminous star candidates from the Arizona-Montréal Spectroscopic Survey, we aim to improve our understanding of the atmospheric and stellar properties of hot subdwarf stars. We used large grids of model atmospheres to fit the observed spectra and derived their atmospheric parameters: effective temperature (Teff), surface gravity, and helium abundance. The model grids were further utilized to fit the spectral energy distribution of each star and the $Gaia$ parallax was used to compute the stellar parameters radius, luminosity, and mass. We detected helium stratification in six sdB stars with Teff around 30 kK, making them good candidates for also showing $^3$He enrichment in their atmospheres. The mass distributions of H-rich sdBs and sdOs are similar and centered around 0.47 $\text{M}_\odot$, consistent with the canonical formation scenario of helium ignition under degenerate conditions. Among the H-rich hot subdwarfs, we found no difference between the mass distributions of close binaries and apparently single stars. The He-sdOs have a significantly wider mass distribution than their H-rich counterparts, with an average mass of about 0.78 $\text{M}_\odot$. This strongly favors a merger origin for these He-rich objects. We identified a small number of candidate low-mass ($<$0.45$ \text{M}_\odot$) sdBs located below the EHB that might have originated from more massive progenitors. Finally, we identified more than 80 pulsating stars in our sample and found these to fall into well-defined $p$- and $g$-mode instability regions.
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All authors M. Latour, E. M. Green, M. Dorsch, V. Van Grootel, P. Chayer, S. Charpinet, U. Heber, S. K. Randall, X.-Y. Ma

Solar and Stellar Astrophysics

Recalibration of the Landolt UBVRI Standard Stars and the Generation of 5.4 Million New UBVRI Standard Stars using LAMOST and Gaia

Bowen Huang, Haibo Yuan, Kai Xiao et al. (+1 more)

We present an independent validation and recalibration of the Landolt 2013 (celestial equator and $\delta \sim -50^\circ$) and 2016 ($\delta \sim -50^\circ$) standard stars in the Johnson $UBV$ and Kron-Cousins $RI$ systems, using tens of thousands of XPSP data from the BEst STar (BEST) database. Our analysis reveals an overall zero-point offset between the 2016 and 2013 datasets. We further identify zero-point offsets for each standard field, ranging from 5 – 14 mmag across all $UBVRI$ bands, with correlations between offsets in different bands. Additionally, we confirm the spatial structures up to 7 – 10 mmag in the $BVRI$ bands. We also find that spatial structures are similar across bands for the same field, and similar across different fields for the same band. These similarities may arise from the averaged flat-fields from each observing run. The recalibrated results are consistent with the XPSP data within 48 mmag in the $U$ band, 11 mmag in the $B$ band, and 5 – 6 mmag in the $VRI$ bands in the brightness $G<16$. Furthermore, based on stellar atmospheric parameters from LAMOST DR12 and Gaia DR3 photometry, along with the XPSP data, we derive temperature- and extinction-dependent extinction coefficients for the $UBVRI$ bands as well as a LAMOST & Gaia-based catalog of 5.4 million standard stars in the $UBVRI$ bands, for which the U-band photometry of the vast majority of sources exhibits significantly higher precision than XPSP. The recalibrated Landolt standard stars and LAMOST & Gaia-based standard stars will be available on the BEST website (https://nadc.china-vo.org/data/best/) and (https://doi.org/10.12149/101704).
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All authors Bowen Huang, Haibo Yuan, Kai Xiao, Ruoyi Zhang

Solar and Stellar Astrophysics

Dynamical Masses and Radiative Transfer Modeling of HD 698: a Be Binary in Evolutionary Transition

Ilfa A. Gabitova, Alex C. Carciofi, Tajan H. de Amorim et al. (+13 more)

We present a detailed analysis of the early post-mass-transfer binary HD 698 (V742 Cas) combining high-resolution optical spectroscopy, long-baseline interferometry, and radiative-transfer modeling. Counter-phased radial-velocity curves yield a circular orbit with P=55.927+/-0.001 d and component masses M_Be=7.48+/-0.07 M_sun and M_comp=1.23+/-0.02 M_sun. The Be primary is traced by broad H alpha wings, while narrow metallic absorption lines arise from a slowly rotating companion. The interferometric separation implies a dynamical distance of 888+/-5 pc. The spectral energy distribution is reproduced with E(B-V)=0.321+/-0.016 and a viscous decretion disk of base density rho_0~5x10^-12 g cm^-3 at r=R_eq, declining radially as rho(r)~r^-n with n=3.0. The companion is luminous and inflated, with T_eff=10.0(+0.2,-0.1) kK, R_comp=13.1+/-0.2 R_sun, and log(L/L_sun)=3.19, contributing significantly to the flux (L_comp/L_Be~0.3). Spectral line mismatches further suggest a hydrogen-poor, CNO-processed atmosphere, consistent with a stripped-envelope star. HD 698 thus adds to the emerging class of Be+bloated OB binaries, capturing a brief post-mass-transfer phase when the donor remains spectroscopically detectable prior to the subdwarf stage.
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All authors Ilfa A. Gabitova, Alex C. Carciofi, Tajan H. de Amorim, Mark Suffak, Anatoly S. Miroshnichenko, Sergey V. Zharikov, Amanda C. Rubio, Steve Danford, Alicia N. Aarnio, Peter Prendergast, Richard J. Rudy, Richard C. Puetter, R. Brad Perry, Aldiyar T. Agishev, Nadezhda L. Vaidman, Serik A. Khokhlov

Solar and Stellar Astrophysics

Nominal thresholds for good astrometric fits, and prospects for binary detectability, for the full extended Gaia mission

F. Guerriero, Z. Penoyre and A. G. A. Brown

The full extended Gaia mission spans slightly over 10 years, whilst the current data releases represent only a fraction of it, 34 months in Gaia's third data release (DR3). The longer baseline improves the quality of astrometric fits, lowering the noise floor and making consistently bad fits (e.g., due to binarity) more apparent. In this paper, we use simulated binaries from the Gaia Universe Model to examine the long-term astrometric behaviour of single stars and stellar binaries. We calculate nominal upper limits on the spread of goodness of astrometric fits for well-behaved single stars. Specifically, for the RUWE parameter, for upcoming DR4 ($\rm RUWE_{lim}=1.15$) and DR5 ($\rm RUWE_{lim}=1.11$), using the full mission nominal scanning law. These can be used to identify poor astrometric fits and can flag potential binary systems. We show the increase in the number and type of binaries detectable through RUWE. With our updated RUWE thresholds, the number of detectable short-period binaries increases by 5-10% with each subsequent data release, suggesting detections may be possible for orbital periods down to days. The number of detectable long-period systems increases by 10-20%, with periods up to 100 years, causing significant deviations in low and moderate-eccentricity binaries. Very eccentric systems with much longer periods (thousands of years) can still be detected if they pass through periapse during the observing window. Finally, we compare our results to the analytic estimate for the spread in UWE, which we predict from a $\chi$-distribution moderated by the number of observations. These agree with our inferred population limits but suggest that we may be biased by a small number of poorly sampled systems. In regions of the sky that are more frequently observed, lower limits could be employed, potentially bringing even more binaries above the threshold for detectability.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th

General relativistic study of $f$-mode oscillations in neutron stars with gravitationally bound dark matter

Pinku Routaray

A comprehensive investigation of nonradial oscillations in neutron star (NS) admixed with gravitationally bounded dark matter (DM) is carried out within the framework of full general relativity. The relativistic mean field (RMF) formalism is employed to illustrate the hadronic equation of state (EOS), while a physically motivated, gravitationally captured, non-uniform fermionic Higgs-portal DM component is incorporated to model DM-admixed NS. The DM distribution is characterized by two free parameters: $\alpha M_\chi$, an effective control parameter that combines the DM concentration and the DM candidate mass, and $\beta$, a steepness parameter controlling the DM density distribution. The quasi normal mode (QNM) characteristics such as fundamental ($f$) mode frequency and its corresponding gravitational-wave (GW) damping time ($\tau$) is calculated for DM-admixed NS by solving the general relativistic perturbed equations involving axial as well as polar modes. The study demonstrates how the inclusion of DM distribution modifies the $f$-mode frequency and enhances the damping rate, reflecting a stronger coupling between matter and spacetime perturbations. Considering DM effects, the correlation analysis among DM model parameters, NS observables and QNM characteristics also carried out. Analytic fits for the $f-C-\tau$ and $f-\Lambda -\tau$ relations are constructed and calibrated for DM-admixed NS models. Building upon asteroseismic universal relations (URs), multimessenger constraint from the GW170817 event is employed by mapping the tidal deformability $\Lambda_{1.4}$ into the $(f_{1.4},\tau_{1.4})$ space, thereby providing observational bounds on the oscillation properties of canonical DM-admixed NS model.
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High Energy Astrophysical Phenomena

ELAIS-N1 deep field uGMRT Band-2: constraints on diffuse Galactic synchrotron emission power spectrum

Rashmi Sagar, Abhirup Datta, Arnab Chakraborty et al. (+13 more)

We present high sensitivity, low radio frequency continuum observations of the ELAIS-N1 field with 32 hours of observations of the uGMRT Band-2 ($120-250$ MHz) covering $5.86\,\text{deg}^2$ area, achieving a central off-source RMS noise of $237\,\mu\mathrm{Jy}/\mathrm{beam}$ with a resolution of $11.45''$ at the central frequency of 183 MHz. A radio source catalogue of 1027 sources statistically matches with similar observations at different frequencies within the sensitivity range of the uGMRT. The calibrated data is further used to characterise the dominant foreground, the Diffuse Galactic Synchrotron Emission (DGSE), in angular scale and frequency regime. We derived the angular power spectrum (APS) of DGSE in two ways: image-based estimator (i-APS) and visibility-based Tapered Gridded Estimator (TGE; hereafter as t-APS). We assess the characteristics of DGSE with a power-law form of $C_{\ell} = A({1000}/{\ell})^{\beta}$. Combining data from Band-2 and earlier Band-3 observations, we derived a spectral variation of $C_{\ell}$ in the form of $C_{\ell} = A{\nu^{-2{\alpha}}}{\ell^{-{\beta}}}$. Our result indicates a spectral break at $\nu = 230\,{\pm}\,5$ MHz, corresponding to a synchrotron age of $t_\text{syn} = 106\,{\pm}\,1$ Myr for the cosmic-ray electrons (CRe). This break result suggests a low-energy cutoff in the CRe population, leading to spectral curvature at low frequencies. Using both of the techniques, i-APS and t-APS, we find that the mean spectral index $\alpha$ and power-law index $\beta$ are consistent within the frequency range $120-500$ MHz.
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All authors Rashmi Sagar, Abhirup Datta, Arnab Chakraborty, Nirupam Roy, Akriti Sinha, Aishrila Mazumder, Prasun Dutta, Kh. Md. Asif Elahi, Kanan K. Datta, Samir Choudhuri, Somnath Bharadwaj, Srijita Pal, Anshuman Tripathi, Suman Majumdar, Tirthankar Roy Choudhury, Sk. Saiyad Ali

Solar and Stellar Astrophysics

Data-driven Radiative Magnetohydrodynamics Simulations with the MURaM Code: Coronal Heating and Dynamics in an Emerging Active Region

Feng Chen

We present the application of the data-driven branch of the MURaM code, which follows the evolution of the active region 11640 over 4 days starting from 2012 December 30 at 12:00 UT and reproduces many key coronal extreme-ultraviolet (EUV) emission features seen in remote sensing observations. Radiative magnetohydrodynamic (MHD) simulations that account for sophisticated energy transport processes, such as those in the real corona, have been extended with the ability to use observations as time-dependent boundaries such that the models follow the evolution of actual active regions. This opens the possibility of a one-to-one model of a target region over an extensive time period. We use a hybrid strategy that combines fast-evolving idealized zero-$\beta$ models that capture the evolution of the large-scale active region magnetic field over a long time period and sophisticated radiative MHD models for a shorter time period of interest. The synthesized EUV images illustrate the formation of coronal loops that connect the two sunspots or fan out to the domain boundary. The model reveals in three-dimensional space fine structure in the coronal heating and plasma properties, which are usually concealed behind the EUV observables. The volumetric heating rate in bright coronal loops is proportional to $\mathbf{B}^{2}$. The emission-measure-weighted line-of-sight velocity, which represents the Doppler shift of a spectral line forming in a certain temperature range, reveals vigorous dynamics in plasma at different temperatures and ubiquitous MHD waves, as expected in the real solar corona.
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Cosmology and Nongalactic Astrophysics

Redshift-dependent Distance Duality Violation in Resolving Multidimensional Cosmic Tensions

Zhihuan Zhou, Zhuang Miao, Rong Zhang et al. (+3 more)

In this work, we investigate whether violations of the distance-duality relation (DDR) can resolve the multidimensional cosmic tensions characterized by the $H_0$ and $S_8$ discrepancies. Using the Fisher-bias formalism, we reconstruct minimal, data-driven $\eta(z)$ profiles that capture the late-time deviations required to reconcile early- and late-Universe calibrations. While a constant DDR offset preserves the Pantheon-inferred matter density $\Omega_m = 0.334 \pm 0.018$–leaving its inconsistency with the Planck best-fit $\Lambda$CDM model and weak-lensing surveys unresolved–a time-varying DDR substantially reduces cross-dataset inconsistencies and improves the global fit, yielding $\Delta\chi^2 \simeq -10$ relative to $\Lambda$CDM when the SH0ES prior is excluded. This result suggests that the $\Omega_m$ discrepancy may represent indirect evidence for a time-varying DDR. A hybrid scenario combining a time-dependent DDR with a phantom-like dark energy transition achieves the most consistent global reconciliation, reducing the tension with DES-Y3 measurements to below $2\sigma$. These findings indicate that a mild DDR violation, coupled with evolving dark energy, offers a coherent pathway toward jointly addressing the $H_0$ and $S_8$ tensions.
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All authors Zhihuan Zhou, Zhuang Miao, Rong Zhang, Hanbing Yang, Penghao Fu, Chaoqian Ai

Astrophysics of Galaxies · Cross-listed from gr-qc

Signatures of a Schwarzschild-like Black Hole Immersed in Dark Matter Halo

Akshat Pathrikar

Astrophysical black holes are often surrounded by dark matter, which can influence their dynamics and observational signatures. In this work, we study a Schwarzschild-like black hole immersed in a Dehnen-type $(1,4,2)$ dark matter halo and analyse scalar, electromagnetic, and gravitational perturbations in this spacetime. We compute quasinormal modes (QNMs) using the Wentzel-Kramers-Brillouin (WKB) approximation method with Padé approximants, investigate particle motion and photon trajectories, and use black hole shadow observations to place constraints on the halo parameters. We further examine the greybody factors associated with Hawking radiation for different perturbation spins. This combined analysis aims to understand how dark matter environments may affect black hole oscillations, radiation properties, and the corresponding observational signatures.
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Astrophysics of Galaxies

Hierarchical Structure and Self-gravity in the Rosette Molecular Cloud

Suziye He, Yuehui Ma, Hongchi Wang et al. (+6 more)

We analyze the hierarchical structure in the Rosette Molecular Cloud (RMC) using $^{13}$CO J=1-0 data from the Milky Way Imaging Scroll Painting (MWISP) survey with a non-binary Dendrogram algorithm that allows multiple branches to emerge from parent structures. A total of 588 substructures are identified, including 458 leaves and 130 branches. The physical parameters of the substructures, including peak brightness temperature ($T_{\rm peak}$), brightness temperature difference ($T_{\rm diff}$), radius ($R$), mass ($M$), velocity dispersion ($\sigma_v$), and surface density ($\Sigma$), are characterized. The $T_{\rm peak}$ and $T_{\rm diff}$ distributions follow exponential functions with characteristic values above $5\sigma_{\rm RMS}$. The statistical properties and scaling relations, i.e., $\sigma_v$-$R$, $M$-$R$, and $\sigma_v$-$R\Sigma$ relations are in general consistent with those from traditional segmentation methods. The mass and radius follow power-law distributions with exponents of 2.2-2.5, with slightly flatter slopes for substructures inside the HII region. The velocity dispersion scales weakly with radius ($\sigma_v \propto R^{0.45\pm 0.03}$, $r = 0.58$), but shows a tighter correlation with the product of surface density and size ($\sigma_v \propto (\Sigma R)^{0.29\pm 0.01}$, $r = 0.73$). Self-gravitating substructures are found across scales from $\sim$0.2 to 10 pc, and nearly all structures with peak brightness above 4 K are gravitationally bound ($\alpha_{\rm vir} < 2$). The fraction of bound structures increases with mass, size, and surface density, supporting the scenario of global hierarchical collapse (GHC) for the evolution of molecular clouds, in which molecular clouds and their substructures are undergoing multiscale collapse.
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All authors Suziye He, Yuehui Ma, Hongchi Wang, Renjie Shen, Miaomiao Zhang, Chong Li, Zhenyi Yue, Xiangyu Ou, Xuepeng Chen

Instrumentation and Methods for Astrophysics

ASTROFLOW: A Real-Time End-to-End Pipeline for Radio Single-Pulse Searches

Guanhong Lin, Dejia Zhou, Jianli Zhang et al. (+20 more)

Fast radio bursts (FRBs) are extremely bright, millisecond duration cosmic transients of unknown origin. The growing number of wide-field and high-time-resolution radio surveys, particularly with next-generation facilities such as the SKA and MeerKAT, will dramatically increase FRB discovery rates, but also produce data volumes that overwhelm conventional search pipelines. Real-time detection thus demands software that is both algorithmically robust and computationally efficient. We present Astroflow, an end-to-end, GPU-accelerated pipeline for single-pulse detection in radio time-frequency data. Built on a unified C++/CUDA core with a Python interface, Astroflow integrates RFI excision, incoherent dedispersion, dynamic-spectrum tiling, and a YOLO-based deep detector. Through vectorized memory access, shared-memory tiling, and OpenMP parallelism, it achieves 10x faster-than-real-time processing on consumer GPUs for a typical 150 s, 2048-channel observation, while preserving high sensitivity across a wide range of pulse widths and dispersion measures. These results establish the feasibility of a fully integrated, GPU-accelerated single-pulse search stack, capable of scaling to the data volumes expected from upcoming large-scale surveys. Astroflow offers a reusable and deployable solution for real-time transient discovery, and provides a framework that can be continuously refined with new data and models.
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All authors Guanhong Lin, Dejia Zhou, Jianli Zhang, Jialang Ding, Fei Liu, Xiaoyun Ma, Yuan Liang, Ruan Duan, Liaoyuan Liu, Xuanyu Wang, Xiaohui Yan, Yingrou Zhan, Yuting Chu, Jing Qiao, Wei Wang, Jie Zhang, Zerui Wang, Meng Liu, Chenchen Miao, Menquan Liu, Meng Guo, Di Li, Pei Wang

Cosmology and Nongalactic Astrophysics

Weak-Lensing Analysis of the Galaxy Cluster Abell 85: Constraints on the Merger Scenarios of Its Southern Subcluster

Soojin Kim, Kim HyeongHan, Wonki Lee et al. (+3 more)

Abell 85 is a nearby (z=0.055) galaxy cluster that hosts a sloshing cool core, a feature commonly reported in relaxed clusters. However, the presence of multiple past and ongoing mergers indicates that it is an active node within the Abell 85/87/89 complex. We present a weak gravitational lensing (WL) analysis using Subaru Hyper Suprime-Cam imaging data to understand its assembly history by investigating the dark matter components of the substructures. Our mass reconstruction resolves three substructures associated with the brightest cluster galaxy (main), the southern (S) subcluster, and the southwestern (SW) subcluster, with WL peak significances of $> 6\sigma$, $> 5\sigma$, and $> 4\sigma$, respectively. The location of these mass peaks are consistent with those of the member galaxies. We estimate the masses of the main cluster ($M_{200c,main} = 2.91 \pm 0.72 \times 10^{14}\ M_\odot$) and the S subcluster ($M_{200c,S} = 1.23 \pm 0.52 \times 10^{14}\ M_\odot$) by fitting a multi-halo Navarro-Frenk-White profile. This $\sim$2:1 mass ratio indicates that the system is undergoing a major merger that is actively shaping the current dynamical state of Abell 85. Incorporating X-ray observations, we discuss the merger phase of the S subcluster and further examine the star-forming activity along the putative filament extending southeast of Abell 85.
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All authors Soojin Kim, Kim HyeongHan, Wonki Lee, Jong-In Park, Myungkook James Jee, Ho Seong Hwang

High Energy Astrophysical Phenomena

Magnetic-type Love number differentiating quark stars from neutron stars

Kenji Fukushima, Josuke Minamiguchi and Tomoya Uji

The quark star (QS) is a hypothetical and yet undiscovered stellar object, and its existence would mark a paradigm shift in research on nuclear and quark matter. Although compactness is a well-known signature for distinguishing between two branches of QSs and neutron stars (NSs), some QSs can overlap with NSs in the radius-mass plane. To manifest their evident differences, we investigate the tidal properties of QSs and NSs. We then find that the magnetic-type Love number is a robust indicator for differentiating between QSs and NSs, whereas the electric-type one is insufficient when QSs and NSs have similar masses and radii. Finally, we show that gravitational waves from binary star mergers can, in principle, be sensitive to differences between QSs and NSs.
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Astrophysics of Galaxies

Stellar Birth Radii in the LMC: Insights into Chemodynamics, Radial Migration, and Star Formation Across the Disk

Yuxi Lu, Bethany Garver, David L. Nidever et al. (+4 more)

The LMC and SMC are interacting dwarf galaxies that offer a valuable testbed for studying the effects of galactic mergers. We investigate the chemodynamic history of the LMC in the context of its interaction with the SMC by inferring stellar birth radii, first validated on a hydrodynamical simulation tailored to reproduce their interaction history. Using inferred birth radii and stellar ages, we identify signatures of dynamical and chemical evolution across the LMC disk. We find that the LMC's metallicity gradient steepened around 5, 3, and 1 Gyr ago, coinciding with enhanced star formation (SF) episodes. These events exhibit distinct spatial patterns – initially concentrated in the inner disk at 5 Gyr, expanding outward by 3 Gyr, and becoming widespread with renewed central activity at 1 Gyr – likely reflecting changes in spin alignment between the interacting disks if the enhancements of SF tracks the pericenter passages of the SMC to the LMC. The inferred radial migration strength of the LMC shows notable enhancements at 0.5, 2, and 5 Gyr. The most $\alpha$-enriched stars form 2-3 Gyr ago at birth radii of 2-4 kpc, the only epoch when star formation is broadly distributed across the disk. Finally, unlike the Milky Way, the LMC lacks a clear [$\alpha$/M]-[Fe/H] bimodality. This is likely due to its more centrally concentrated star formation during these periods, compared to the MW's more extended outer-disk star formation enhancements. These findings place strong constraints on the LMC's assembly history and its interaction with the SMC.
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All authors Yuxi Lu, Bethany Garver, David L. Nidever, Joshua T. Povick, Nicolás Garavito-Camargo, Maria-Rosa L. Cioni, Danny Horta

High Energy Astrophysical Phenomena

Search for Diffuse Supernova Neutrino Background with 956.2 days of Super-Kamiokande Gadolinium Dataset

K. Abe, S. Abe, Y. Asaoka et al. (+245 more)

We report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3~MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with $22,500\times956.2$$~\rm m^3\cdot day$ exposure. %$22.5{\rm k}\times956.2$$~\rm m^3\cdot day$ exposure. Starting in the summer of 2020, SK introduced 0.01% gadolinium (Gd) by mass into its ultra-pure water to enhance the neutron capture signal, termed the SK-VI phase. This was followed by a 0.03% Gd-loading in 2022, a phase referred to as SK-VII. We then conducted a DSNB search using 552.2~days of SK-VI data and 404.0~days of SK-VII data through September 2023. This analysis includes several new features, such as two new machine-learning neutron detection algorithms with Gd, an improved atmospheric background reduction technique, and two parallel statistical approaches. No significant excess over background predictions was found in a DSNB spectrum-independent analysis, and 90% C.L. upper limits on the astrophysical electron anti-neutrino flux were set. Additionally, a spectral fitting result exhibited a $\sim1.2\sigma$ disagreement with a null DSNB hypothesis, comparable to a previous result from 5823~days of all SK pure water phases.
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All authors K. Abe, S. Abe, Y. Asaoka, M. Harada, Y. Hayato, K. Hiraide, K. Hosokawa, T. H. Hung, K. Ieki, M. Ikeda, J. Kameda, Y. Kanemura, Y. Kataoka, S. Miki, S. Mine, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Noguchi, G. Pronost, K. Sato, H. Sekiya, R. Shinoda, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takemoto, H. Tanaka, T. Yano, Y. Itow, T. Kajita, R. Nishijima, K. Okumura, T. Tashiro, T. Tomiya, X. Wang, P. Fernandez, L. Labarga, D. Samudio, B. Zaldivar, C. Yanagisawa, E. Kearns, L. Wan, T. Wester, B. W. Pointon, J. Bian, B. Cortez, N. J. Griskevich, Y. Jiang, M. B. Smy, H. W. Sobel, V. Takhistov, A. Yankelevich, J. Hill, M. C. Jang, S. H. Lee, D. H. Moon, R. G. Park, B. S. Yang, B. Bodur, K. Scholberg, C. W. Walter, A. Beauch'ene, E. Le Bl'evec, O. Drapier, A. Ershova, M. Ferey, Th. A. Mueller, A. D. Santos, P. Paganini, C. Quach, R. Rogly, T. Nakamura, J. S. Jang, R. P. Litchfield, L. N. Machado, F. J. P. Soler, J. G. Learned, K. Choi, S. Cao, L. H. V. Anthony, N. W. Prouse, M. Scott, Y. Uchida, V. Berardi, N. F. Calabria, M. G. Catanesi, N. Ospina, E. Radicioni, A. Langella, G. De Rosa, G. Collazuol, M. Feltre, M. Mattiazzi, L. Ludovici, M. Gonin, L. P'eriss'e, B. Quilain, S. Horiuchi, A. Kawabata, M. Kobayashi, Y. M. Liu, Y. Maekawa, Y. Nishimura, R. Akutsu, M. Friend, T. Hasegawa, Y. Hino, T. Ishida, T. Kobayashi, M. Jakkapu, T. Matsubara, T. Nakadaira, Y. Oyama, A. Portocarrero Yrey, K. Sakashita, T. Sekiguchi, T. Tsukamoto, N. Bhuiyan, G. T. Burton, F. Di Lodovico, J. Gao, T. Katori, R. Kralik, N. Latham, R. M. Ramsden, H. Ito, T. Sone, A. T. Suzuki, Y. Takeuchi, S. Wada, H. Zhong, J. Feng, L. Feng, S. Han, J. Hikida, J. R. Hu, Z. Hu, M. Kawaue, T. Kikawa, T. Nakaya, T. V. Ngoc, R. A. Wendell, S. J. Jenkins, N. McCauley, A. Tarrant, M. Fan`i, M. J. Wilking, Z. Xie, Y. Fukuda, H. Menjo, Y. Yoshioka, J. Lagoda, M. Mandal, J. Zalipska, M. Mori, J. Jiang, K. Hamaguchi, H. Ishino, Y. Koshio, F. Nakanishi, T. Tada, T. Ishizuka, G. Barr, D. Barrow, L. Cook, S. Samani, D. Wark, A. Holin, F. Nova, S. Jung, J. Yoo, J. E. P. Fannon, L. Kneale, M. Malek, J. M. McElwee, T. Peacock, P. Stowell, M. D. Thiesse, L. F. Thompson, H. Okazawa, S. M. Lakshmi, E. Kwon, M. W. Lee, J. W. Seo, I. Yu, Y. Ashida, A. K. Ichikawa, K. D. Nakamura, S. Goto, H. Hayasaki, S. Kodama, Y. Kong, Y. Masaki, Y. Mizuno, T. Muro, K. Nakagiri, Y. Nakajima, N. Taniuchi, M. Yokoyama, P. de Perio, S. Fujita, C. Jes'us-Valls, K. Martens, Ll. Marti, K. M. Tsui, M. R. Vagins, J. Xia, M. Kuze, S. Izumiyama, R. Matsumoto, R. Asaka, M. Ishitsuka, M. Sugo, M. Wako, K. Yamauchi, Y. Nakano, F. Cormier, R. Gaur, M. Hartz, A. Konaka, X. Li, B. R. Smithers, S. Chen, Y. Wu, B. D. Xu, A. Q. Zhang, B. Zhang, H. Adhikary, M. Girgus, P. Govindaraj, M. Posiadala-Zezula, Y. S. Prabhu, S. B. Boyd, R. Edwards, D. Hadley, M. Nicholson, M. O'Flaherty, B. Richards, A. Ali, B. Jamieson, C. Bronner, D. Horiguchi, A. Minamino, Y. Sasaki, R. Shibayama, R. Shimamura

Solar and Stellar Astrophysics

A robust method for identifying Be stars in the LAMOST Data Release 11 based on Deep-learning approach

Lei Tan, Hui Deng, Ying Mei et al. (+4 more)

Be stars are rapidly rotating B-type stars that exhibit Balmer emission lines in their optical spectra. These stars play an important role in studies of stellar evolution and disk structures. In this work, we carried out a systematic search for Be stars based on LAMOST spectroscopic data. Using low-resolution spectra from LAMOST DR11, we constructed a data set and developed a classification model that combines long short-term memory networks and convolutional neural networks , achieving a testing accuracy of 97.86%. The trained model was then applied to spectra with signal-to-noise ratios greater than 10, yielding 55,667 B-type candidates. With the aid of the MKCLASS automated classification tool and manual verification, we finally confirmed 40,223 B-type spectra. By cross-matching with published H{\alpha} emission-line star catalogs, we obtained a sample of 8298 Be stars, including 3787 previously reported Be stars and 4511 newly discovered. Furthermore, by incorporating color information, we classified the Be star sample into Herbig Be stars and Classical Be stars. In total, we identified 3363 Classical Be stars and 35 Herbig Be stars. The B-type and Be star catalogs derived in this study, together with the code used for model training, have been publicly released to facilitate community research.
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All authors Lei Tan, Hui Deng, Ying Mei, Huanbin chi, Yixing Chen, Tianhang Liu, Feng Wang

Cosmology and Nongalactic Astrophysics

Reconstruction of dark energy using DESI DR2

Xue Zhang, Yin-Hao Xu and Yu Sang

Using a model-independent Gaussian process (GP) method to reconstruct the dimensionless luminosity distance $D$ and its derivatives, we derive the evolution of the dimensionless Hubble parameter $E$, the deceleration parameter $q$, and the state parameter $w$ of dark energy. We utilize the PantheonPlus, SH0ES, and Gamma Ray Burst (GRB) data to derive the dimensionless luminosity distance $D$. Additionally, we employ observational $H(z)$ data (OHD) and baryon acoustic oscillations (BAO) from Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) to obtain the first derivative of the dimensionless luminosity distance $D^{'}$. To obtain the reconstructed $D$ and $D^{'}$, we utilize the fiducial value from each dataset, with particular emphasis on the varying $H_0$. According to the reconstruction results obtained from PantheonPlus+SH0ES+GRB+OHD and PantheonPlus+SH0ES+GRB+OHD+DESI data, we find that $E$ are consistent with the predictions of the $\Lambda$CDM model at a $2\sigma$ confidence level within the redshift range of $z<2$. However, the reconstruction results for $q$ exhibit deviations from the $\Lambda$CDM model in the range of $z<0.3$. Furthermore, we observe that the mean value of $w$ exhibits evolving behavior, transiting from $w < -1$ to $w > -1$ around $z_{\rm wt}=0.464^{+0.235}_{-0.120}$. Combining data from DESI DR2 can slightly enhance the accuracy of our constraints.
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Astrophysics of Galaxies

Characterizing the astrometric quality of AGNs in Gaia-CRF3

Shilong Liao, Qiqi Wu, Ye Ding et al. (+2 more)

Active Galactic Nuclei (AGNs), owing to their great distances and compact sizes, serve as fundamental anchors for defining the celestial reference frame. With about 1.9 million AGNs observed in Gaia DR3 at optical precision comparable to radio wavelengths, Gaia provides a solid foundation for constructing the next-generation, kinematically non-rotating optical reference frame. Accurate assessment of systematic residuals in AGN astrometry is therefore crucial. In this talk, we analysed the parallaxes and proper motions of Gaia DR3 AGNs to characterize systematic errors and their correlations with various physical and observational properties. A subset of Gaia-CRF3 AGNs exhibits significant astrometric offsets, mainly arising from dual or lensed quasars whose structural variations induce photocenter jitter, mimicking parallax and proper motion. Such sources must be carefully excluded from reference frame construction. To this end, we introduce an astrometric quality index for each source to quantify its astrometric reliability. The results reveal a strong correlation between lower quality index values and increasing errors in position, proper motion, and parallax, demonstrating that the proposed index provides an effective metric for selecting high-fidelity AGNs as primary reference sources.
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All authors Shilong Liao, Qiqi Wu, Ye Ding, Qi Xu, Zhaoxiang Qi

Cosmology and Nongalactic Astrophysics

Exploring One-point Statistics in HERA Phase I Data: Effects of Foregrounds and Systematics on Measuring One-Point Statistics

Honggeun Kim, Jacqueline N. Hewitt, Nicholas S. Kern et al. (+61 more)

Measuring one-point statistics in redshifted 21 cm intensity maps offers an opportunity to explore non-Gaussian features of the early universe. We assess the impact of instrumental effects on measurements made with the Hydrogen Epoch of Reionization Array (HERA) by forward modeling observational and simulation data. Using HERA Phase I observations over 94 nights, we examine the second (m2, variance) and third (m3) moments of images. We employ the DAYENU-filtering method for foreground removal and reduce simulated foreground residuals to 10% of the 21 cm signal residuals. In noiseless cosmological simulations, the amplitudes of one-point statistics measurements are significantly reduced by the instrument response and further reduced by wedge-filtering. Analyses with wedge-filtered observational data, along with expected noise simulations, show that systematics alter the probability distribution of the map pixels. Likelihood analysis based on the observational data shows m2 measurements disfavor the cold reionization model characterized by inefficient X-ray heating, in line with other power spectra measurements. Small signals in m3 due to the instrument response of the Phase I observation and wedge-filtering make it challenging to use these non-Gaussian statistics to explore model parameters. Forecasts with the full HERA array predict high signal-to-noise ratios for m2, m3, and S3 assuming no foregrounds, but wedge-filtering drastically reduces these ratios. This work demonstrates conclusively that a comprehensive understanding of instrumental effects on m2 and m3 is essential for their use as a cosmological probe, given their dependence on the underlying model.
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All authors Honggeun Kim, Jacqueline N. Hewitt, Nicholas S. Kern, Joshua S. Dillon, Kai-Feng Chen, Zhilei Xu, Eleanor Rath, Vincent MacKay, Tyrone Adams, James E. Aguirre, Rushelle Baartman, Adam P. Beardsley, Gianni Bernardi, Tashalee S. Billings, Judd D. Bowman, Richard F. Bradley, Philip Bull, Jacob Burba, Steven Carey, Chris L. Carilli, David R. DeBoer, Eloy de Lera Acedo, Matt Dexter, Nico Eksteen, John Ely, Aaron Ewall-Wice, Nicolas Fagnoni, Steven R. Furlanetto, Kingsley Gale-Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Bryna J. Hazelton, Jack Hickish, Daniel C. Jacobs, Joshua Kerrigan, Piyanat Kittiwisit, Matthew Kolopanis, Adam Lanman, Paul La Plante, Adrian Liu, David H. E. MacMahon, Lourence Malan, Cresshim Malgas, Keith Malgas, Bradley Marero, Zachary E. Martinot, Andrei Mesinger, Mathakane Molewa, Miguel F. Morales, Tshegofalang Mosiane, Steven G. Murray, Hans Nuwegeld, Aaron R. Parsons, Nima Razavi-Ghods, James Robnett, Peter Sims, Craig Smith, Hilton Swarts, Nithyanandan Thyagarajan, Pieter van Wyngaarden, Haoxuan Zheng

High Energy Astrophysical Phenomena

A Face-on Accretion Disk Geometry Revealed by Millimeter-wave Periodicity in Sgr A$^*$

Kazuki Yanagisawa, Tomoharu Oka, Ryo Ariyama et al. (+3 more)

We analyzed 77 epochs of Atacama Large Millimeter/submillimeter Array (ALMA) archival data to investigate flux variability in Sagittarius A$^*$ (Sgr A$^*$), the supermassive black hole at the Galactic Center. Among these, we identified a rare but unusually clear and coherent ~52-minute sinusoidal modulation at 230 GHz, with a statistical significance exceeding 5{\sigma}. Modeling with a Doppler-boosted hotspot scenario yields an orbital radius of ~4 Schwarzschild radii and a disk inclination of 8$^\circ$ (or 172$^\circ$), providing the first direct millimeter wavelength constraint on the inner accretion flow geometry. This nearly face-on inclination is in good agreement with previous constraints from GRAVITY and EHT observations. These findings provide robust, independent evidence that millimeter-wave periodicity can directly probe the innermost accretion flow geometry, offering a powerful complement to variability studies at infrared and X-ray wavelengths.
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All authors Kazuki Yanagisawa, Tomoharu Oka, Ryo Ariyama, Kazuki Yanagihara, Yuhei iwata, Mikiya M. Takahashi

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

Dark Matter Freeze-in from a $Z^\prime$ Reheaton

Avirup Ghosh, Alexei H. Sopov and Raymond R. Volkas

We consider the Standard Model (SM) extended by a secluded $U(1)_D$ gauge sector encompassing a Dirac fermion ($\chi$) dark matter (DM), an abelian gauge boson $Z^\prime$ and a SM-singlet complex-scalar field $\Phi$, whose radial component drives cosmic inflation. When the Higgs portal coupling is small, the $Z^\prime$ then acts as a “reheaton”, dominating the energy budget of the Universe before finally yielding the SM bath, with reheating temperature $< O(10)$ TeV, through the gauge portal interaction. We explore the possibility that DM freezes-in via non-thermal $Z^\prime$ decays before reheating ends, giving rise to substantial viable parameter space. We account for non-perturbative effects, relevant during the initial stages of reheating, using lattice simulations. We additionally show how the cosmological gravitational wave (GW) background produced by preheating and inflation allow for a direct probe of the reheating mechanism.
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Astrophysics of Galaxies

An Extremely Luminous Flare Recorded from a Supermassive Black Hole

Matthew J. Graham, Barry McKernan, K. E. Saavik Ford et al. (+17 more)

Since their discovery more than 60 years ago, accreting supermassive black holes in active galactic nuclei (AGN) were recognized as highly variable sources, requiring an extremely compact, dynamic environment. Their variability traces to multiple phenomena, including changing accretion rates, temperature changes, foreground absorbers, and structural changes to the accretion disk. Spurred by a new generation of time-domain surveys, the extremes of black hole variability are now being probed. We report the discovery of an extreme flare by the AGN J224554.84+374326.5, which brightened by more than a factor of 40 in 2018. The source has slowly faded since then. The total emitted UV/optical energy to date is $\sim10^{54}$ erg, i.e., the complete conversion of approximately one solar mass into electromagnetic radiation. This flare is 30 times more powerful than the previous most powerful AGN transient. Very few physical events in the Universe can liberate this much electromagnetic energy. We discuss potential mechanisms, including the tidal disruption of a high mass $(>30\, M_\odot)$ star, gravitational lensing of an AGN flare or supernova, or a supermassive (pair instability) supernova in the accretion disk of an AGN. We favor the tidal disruption of a massive star in a prograde orbit in an AGN disk.
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All authors Matthew J. Graham, Barry McKernan, K. E. Saavik Ford, Daniel Stern, Matteo Cantiello, Andrew J. Drake, Yuanze Ding, Mansi Kasliwal, Mike Koss, Raffaella Margutti, Sam Rose, Jean Somalwar, Phil Wiseman, S. G. Djorgovski, Patrik M. Veres, Eric C. Bellm, Tracy X. Chen, Steven L. Groom, Shrinivas R. Kulkarni, Ashish Mahabal

Instrumentation and Methods for Astrophysics

Thermal and Electrical Properties of Prototype Readout Components for CMB-S4

Wilber Dominguez, Darcy R. Barron, Zeeshan Ahmed et al. (+11 more)

CMB-S4 is the fourth-generation ground-based cosmic microwave background project, designed to probe the early universe and cosmic inflation. CMB-S4 would achieve its science goals in part by dramatically increasing the number of transition edge sensor (TES) bolometer detectors on the sky. The detector readout system for CMB-S4 is time-division multiplexing (TDM) with a two-stage Superconducting Quantum Interference Device (SQUID) system. To accommodate the large increase in detectors, the size of our camera increases, placing physical constraints on the readout, its wiring, and its power dissipation. Therefore, to optimize readout performance, we need to balance competing design considerations such as thermal load and bandwidth. We present results characterizing the thermal and electrical performance of prototype components, including wiring and SQUID arrays for CMB-S4, and discuss the impact on overall system performance.
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All authors Wilber Dominguez, Darcy R. Barron, Zeeshan Ahmed, Amy N. Bender, Sandra Diez, Malcolm Durkin, Tristan A. Eggenberger, Gunther Haller, Shawn W. Henderson, Katherine Hewey, Johannes Hubmayr, Christopher Rooney, Robinjeet Singh, Michael Vissers

Cosmology and Nongalactic Astrophysics

Measurement of angular cross-correlation between the cosmological dispersion measure and the thermal Sunyaev–Zeldovich effect

Ryuichi Takahashi, Kunihito Ioka, Masato Shirasaki et al. (+1 more)

The dispersion measures (${\rm DMs}$) from fast radio bursts (FRBs) and the thermal Sunyaev–Zeldovich (tSZ) effect probe the free-electron density and thermal pressure, respectively, in the intergalactic medium (IGM) and the intervening galaxies and clusters. Their combination enables disentangling the gas density and temperature. In this work, we present the first detection of an angular cross-correlation between the ${\rm DMs}$ and the Compton $y$ parameter of the tSZ effect. The theoretical expectation is calculated using the halo model $\texttt{HMx}$, calibrated with hydrodynamic simulations. The observational cross-correlation is measured over angular separations of $1^\prime$–$1000^\prime$ using the ${\rm DMs}$ from $133$ localized FRBs and the $y$-maps from the Planck satellite and the Atacama Cosmology Telescope (ACT). We detect a positive correlation with amplitudes of $\mathcal{A}=2.01 \pm 0.50$ ($4.0 \sigma$) for Planck and $\mathcal{A}=1.23 \pm 0.82$ ($1.5 \sigma$) for ACT, where $\mathcal{A}=1$ corresponds to the theoretical prediction of the Planck 2018 $\Lambda$CDM cosmology. Assuming an isothermal gas, the measured amplitude implies an average electron temperature of $\approx 2 \times 10^7 \, {\rm K}$. The correlation is highly sensitive to the matter clustering parameter $\sigma_8$ and to baryon feedback, and its dependence on other cosmological and astrophysical parameters – such as the ionized fraction and the Hubble constant – differs from that of the ${\rm DM}$ alone. This suggests that future joint analyses of the ${\rm DMs}$ and the tSZ effect could help break degeneracies among these parameters.
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All authors Ryuichi Takahashi, Kunihito Ioka, Masato Shirasaki, Ken Osato