High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quantum black hole ringdown
Konstantinos Topaloglou, Elena Cuoco and Roberto Casadio
The ringdown of a black hole following a merger is a potential candidate for revealing the signatures of
quantum gravity in the emerging gravitational waves. In
quantum theory, black holes are expected to have a discrete area and energy spectrum, which conflicts with the classical notion of an horizon that absorbs all infalling perturbations. We propose that the
quantum black hole dissipates the energy it cannot absorb by emitting “soft” gravitons that carry away the energy difference between the energy of the infalling perturbation and the
quantum transition energy. We find that the ringdown spectrum is consequently enriched with low-frequency components, and that there exists a weak low-frequency flux that persists for a timescale much longer than the ringdown itself.
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High Energy Astrophysical Phenomena
The Galactic Black Hole mass distribution
L S. Rocha, N. Pires, L. M. de Sá et al. (+8 more)
The population of extragalactic black holes has been significantly expanded and better understood since the first detection of gravitational waves. Over the past decade, approximately 290 events have been confirmed to involve at least one black hole. In contrast, the galactic black hole population has grown at a much slower pace, with only 42 systems possessing mass estimates, while the vast majority remain as candidates. In this work, we present the first update of a
Bayesian analysis of the mass distribution of galactic black holes since 2011, previously based on a sample of 15 low-mass X-ray binaries and 5 high-mass X-ray binaries. Our update includes 28 low-mass X-ray binaries, 6 high-mass X-ray binaries, 7 detached binaries and 1 isolated black hole, also present in the living catalog CatNoir which we introduce. We apply a
Bayesian framework using five parametric models – Gaussian, two-Gaussian, log-normal, power-law, and decaying exponential – and compare their performance in fitting the observed data. Furthermore, we inspect the effect of removing model-dependent systems from the sample. Our results suggest that the power law better describes the Combined sample, while the Gaussian is preferred for the LMXB-only sample, closely followed by the two-Gaussian and log-normal. We derive the $1\%$-
quantile of the preferred model's posterior predictive distribution to access information about the lower mass gap. For the Combined and LMXB Samples, we find $M_{1\%} > 4.06\,M_\odot$ and $M_{1\%} > 2.56\,M_\odot$ (at $90\%$ C.I.), respectively. The LMXB result allows for the existence of a sparsely populated Gap, instead of a completely empty one.
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All authors L S. Rocha, N. Pires, L. M. de Sá, B. B. Martins, L. G. Barão, G. R. C. Sampaio, D. V. Rodrigues, R. M. G. Takahashi, M. G. B. de Avellar, J.E. Horvath, A. Bernardo
Solar and Stellar Astrophysics
Reconstruction of pretelescopic and early telescopic solar activity cycles from auroral records
Kristof Petrovay, Laura G. Magyar and Hisashi Hayakawa
The historical record of low-latitude aurorae is essentially a poorly sampled record of the largest space weather events (SWEs). Its use for the identification of individual solar cycles is hindered by the low event rate and by the fact that the solar cycle profile of the occurrence of SWEs does not closely follow the variation of sunspot numbers. Based on recent studies of the solar cycle dependence of the occurrence rates of large SWEs, here we construct Monte-Carlo simulations of a large number of activity cycles to identify the optimal procedure to infer the characteristics of underlying solar cycles from the sparse record. We find that a reliable reconstruction of the cycle phase ($>90$% of reconstructed minima corresponding to actual minima within $\pm 2$ years) is possible whenever the long-term mean event rate (annual mean number of space weather events resulting in low-latitude auroral sightings) reaches or exceeds a value around 3. This condition is found to be satisfied during most of the the Early Modern Active Period (EMAP), a century-long period of normal solar activity between the Spörer and Maunder Minima. For the numbering of solar cycles in the EMAP we introduce the "telescopic era", where T$n$ denotes the $n$th cycle from the first telescopically observed cycle, T$0$, ongoing in 1610. Using our optimal procedure we reconstruct a series of 8 solar activity cycles from T$-5$ to T$2$ (1560-1640). Earlier cycles starting from 1540 can be reconstructed with a somewhat lower degree of reliability. Comparing our results with radionuclide-based reconstructions and sunspot observations we find a good overall correspondence, with the exception of the last cycle before the Maunder Minimum.
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Instrumentation and Methods for Astrophysics
A compact time-domain reduced order quadrature for gravitational wave inspirals with non-stationary noise
Benjamin Zhang, Kris Pardo and Bence Bécsy
We develop the first time-domain reduced order quadrature for gravitational waves in the early inspiral period, motivated by the need for
dataset compression in the presence of gaps, uneven sampling, and dense covariance
matrices. A single reduced basis with 1290 elements can represent inspirals from supermassive black hole binary sources with chirp masses between $10^7-10^{10}$ $M_\odot$, but in the presence of non-stationary noise $\sim 1290^2$ reduced order quadrature weights must be stored. We are able to reduce the stored weights by a factor of two by partitioning our parameter space by GW frequency, with relative waveform/likelihood accuracies remaining below $10^{-5}$/$10^{-3}$ after partition. Finally, we point out that heterodyning can be combined with reduced order methods with no loss in accuracy. Our reduced order quadrature makes inspiral searches in the time domain feasible for both
pulsar timing arrays and relative stellar astrometry.
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Earth and Planetary Astrophysics · Cross-listed from cs.CG
The optimal-transport cartogram: world population as a Brenier map
Philipp Bogdan
A contiguous cartogram is a map whose area is proportional to a quantity such as population. The defining condition, that the Jacobian determinant of the deformation equals the density, is one equation for two unknown functions, so every cartogram method adds a tie-breaker, usually implicitly. Optimal transport makes the tie-breaker explicit: among all density-equalising maps of the frame onto itself, take the one that moves the population least in the mean-square sense. By Brenier's
theorem that map is the gradient of a convex potential, so it has no local rotation anywhere and cannot fold. We compute this map for the world population of 2025 on a 4096 by 4096 Mercator grid (10 km
cells) from the GHS-POP raster, using the fixed-point Monge-Ampère iteration of Benamou, Froese and Oberman with spectral Poisson solves, continuation in the population share and an ocean-only buffer, on a laptop GPU. Against a Gastner-Newman
diffusion cartogram of the same density we find the same transport cost to within 0.4 per cent and density errors of a few per cent for both, but a median local rotation of 8.8 degrees for
diffusion against 0.01 for transport, and a median anisotropy of 6.30 against 3.93. The construction extends to local refinement, by transporting a city's 100 m population onto the area measure the global map assigns to it, and to a semi-discrete counterpart: 8,192 Laguerre
cells of 1.00 million people each. Code, data provenance and every figure's inputs are public.
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Cosmology and Nongalactic Astrophysics
A comprehensive assessment of weak-lensing inferred circular velocity profiles of isolated galaxies
Sri Devaki Meduri and Shantanu Desai
We fit the circular velocity data, derived from weak
lensing observations of isolated
galaxies selected from the KiDS survey in four baryonic mass bins, using three different dark matter profiles. These include NFW, Burkert, and pseudo-isothermal profile. We find that the NFW and Burkert profiles cannot adequately fit the circular velocity data for all the four baryonic mass bins, whereas only the pseudo-isothermal profile can fit the data for all the four bins.
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Astrophysics of Galaxies
The New Dark Matter Density Profile from JWST JADES Galaxies
Aritra Sanyal and Farook Rahaman
We present the first dark matter density profile derived directly from James Webb Space
Telescope JADES Data Release~3 NIRSpec observations of $N = 587$
galaxies spanning the
cosmic noon epoch $1.5 \leq z \leq 3.5$. From each NIRSpec G235M/G395M spectrum we extract the H$\alpha$ emission-line velocity dispersion $\sigma_{\rm ha}$, stack
galaxies in four
redshift bins of $\Delta z = 0.5$, and reconstruct representative group rotation curves within the General Theory of Relativity. Fitting the four-parameter modified exponential model and deriving the exact GTR energy density, we reduce the profile to a compact $[2/3]$ Padé approximant with all coefficients determined in closed form from JWST observations. The profile is cusp-free, fully analytic, and
redshift-dependent. Energy conditions, causality, and orbital stability are all satisfied. Most strikingly, the central density $\rho(0)$ varies by less than $15\%$ across $z = 1.5$–$3.5$ despite a $35\%$ decline in the asymptotic rotation velocity, revealing a universal dark matter core saturation density at
cosmic noon decoupled from baryonic
evolution.
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Astrophysics of Galaxies
Recovering turbulent velocity statistics from noisy integral-field spectroscopy
J. García-Vázquez, William J. Henney and S. Jane Arthur
Turbulence plays a critical role in the
evolution of H II regions, yet recovering its statistical properties from observations remains challenging, particularly when centroid velocities are affected by instrumental noise. We present a methodology for recovering the second-order velocity structure function from intermediate spectral-resolution integral-field spectroscopy and apply it to VLT MUSE observations of the Orion Nebula. The plane-of-sky velocity field is characterized by fitting a simple parametric model to the observed structure function, allowing the turbulent velocity variance, correlation length, power-law slope, and noise level to be estimated simultaneously. We investigate the trade-off between instrumental noise and spatial resolution through systematic spatial binning and validate the recovered turbulent parameters against previously analyzed high spectral-resolution KPNO echelle observations. We find that spatial binning improves the empirical structure function provided that the bin size remains below approximately $0.05 r_0$, while the fitted model recovers consistent turbulent parameters across all binning levels. The MUSE results agree closely with those from the KPNO data, demonstrating that intermediate-resolution integral-field spectroscopy can recover reliable
turbulence statistics despite its relatively poor velocity resolution. We also identify modest but systematic differences in the turbulent properties traced by emission lines of different ionization potential, reflecting the
geometric and ionization structure of the nebula. Our methodology provides a robust framework for extracting turbulent velocity statistics from noisy integral-field spectroscopic observations.
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Cosmology and Nongalactic Astrophysics
Measuring the spatio-temporal variation of fundamental physical constants using the OH sum rules
Renzhi Su and Minfeng Gu
In this paper, we introduce a method to constrain the variation of fundamental physical constants predicted by grand unified theories. This approach utilizes OH sum rules, which exhibit different forms depending on the physical conditions of the OH gas. Employing a least-squares technique, we can directly derive the relative velocity offsets among four OH lines in each ground state. This circumvents the need for spectral profile fitting, which is often unfeasible for spectra with complex profiles. Moreover, this method remains robust even when portions of the spectra are contaminated by
radio frequency interference (RFI). Applying this method to a Galactic source G035.1+0.5, we obtained a stringent constraint of $\Delta X/X=(-1.8\pm5.1)\times10^{-6} $, where $X=\mu^{-1}\alpha^{2}g_{p}^{0.54}$. This method is expected to play a crucial role in extracting fundamental physics from large
datasets of upcoming Square Kilometre Array (SKA)
telescope.
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Solar and Stellar Astrophysics
Investigating Variability in Long-lived Protoplanetary Disks (>10 Myr) using NEOWISE
Gregory Mathews Ben, Jessy Jose and Jesús Hernández
We present the mid-infrared variability study of 120 long-lived disk candidates (ages 10-100 Myr) and 13 confirmed "Peter Pan" disks using NEOWISE to constrain the longevity of dynamic disk processes beyond the standard 10 Myr dispersal threshold. We identified 32 sources exhibiting significant variability by combining
stochastic flux metrics and the Stetson $J$ index. The majority of these variables belong to the 10-25 Myr age range, suggesting a sharp decline in disk brightness variability after 25 Myr. Morphologically, the variability is characterized by irregular fluctuations with mean amplitudes of $\Delta W2 \approx 0.5$ mag, consistent with variable extinction or inner disk warping induced by embedded planetesimals. We also report a strong correspondence between mid-infrared and optical variability for the Peter Pan disks, with all 9 mid-IR variables confirmed as optical variables in the literature. Our findings reveal a population of 23 new long-lived disk candidates that retain active, gas-rich environments, supporting the existence of a rarefied class of systems that survive well into the debris disk era.
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Solar and Stellar Astrophysics
Investigating r-Process Diversity in Mildly Metal-Poor Stars Using the Th II 5989 Angstrom Line
Kurumi Furutsuka and Satoshi Honda
The origin of the heaviest elements remains a fundamental mystery, with the "actinide-boost" (Thorium overabundance) serving as a critical diagnostic of r-process nucleosynthesis conditions. While this diversity is well documented in extremely metal-poor (EMP)
stars, its frequency in the mildly metal-poor (MMP) regime ($-2.0 < $ [Fe/H] $< -0.5$) is poorly constrained due to blending issues in the commonly used 4019 angstrom line. We present a systematic abundance analysis of mildly metal-poor
stars, exploiting the relatively unblended Th II 5989 angstrom line. High-dispersion spectra were obtained using the 1.5 m
telescope at Gunma Astronomical Observatory with GAOES, complemented by archival data from the Subaru
Telescope/HDS retrieved via SMOKA. We successfully detected Th in 32 out of 42 sample
stars. Our analysis demonstrates that the 5989 angstrom line is a useful diagnostic for Th abundance measurements in cool red giants. The mean [Th/Eu] ratio remains nearly constant over the MMP
metallicity range, suggesting that progressive homogenization of the interstellar medium during Galactic chemical
evolution would reduce abundance variations inherited from individual r-process events, or the dominant r-process events may share similar initial Th/Eu production ratios. While the [Th/Eu] ratio is nearly constant overall in the MMP regime, its dispersion appears to increase toward the metal-rich end of this regime and reaches approximately 1 dex near solar
metallicity. This behavior may reflect the combined effects of variations in the initial Th/Eu production ratios of the progenitor objects, the mixing of r-process products in the interstellar medium, and the radioactive decay of Th over stellar lifetimes.
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Cosmology and Nongalactic Astrophysics
Consistent treatment of flavour-specific neutrino self-interactions in cosmology
Gabriela Barenboim, Marco Drewes and Isabel M. Oldengott
We study the impact of flavour-specific
neutrino self-interactions on the CMB anisotropy spectrum and consistently take into account
neutrino mixing. Starting from the
neutrino quantum kinetic equations, we derive the
neutrino Boltzmann hierarchies for the
neutrino mass states. Our work shows that most scenarios of flavour-specific
neutrino self-interactions are well approximated by a combined fluid approach. In practice, this implies that existing CMB bounds on the effective
neutrino coupling are weakened by a factor $\sqrt{2}$ for scenarios in which only two
neutrino flavours interact (irrespective of which flavours). If only one
neutrino flavour interacts the bounds are weaker by a factor $\sqrt{6}$, with the only caveat that the combined fluid approach is less reliable for only $\nu_e$ interacting.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Frequency shift in gravitational lensing by Kerr metric
Samaneh Sarbaz and Sohrab Rahvar
In this study, we calculate the relative frequency shift ($\Delta \nu / \nu$) caused by gravitational
lensing resulting from the transverse motion of a spinning lens described by the Kerr metric \cite{Kerr:1963ud}. While the effect of transverse velocity on the frequency shift has previously been investigated using the Schwarzschild metric \cite{Rahvar_2020,10.1093/mnras/stae1938}, extending this to the Kerr metric provides a new window for measuring the transverse velocity of a lens or its
spin parameter, a parameter often subject to degeneracy in gravitational microlensing observations. Recent microlensing observations have revealed black holes as viable
lensing candidates \cite{2022ApJ...933...83S}. Since spinning black holes form naturally from stellar
evolution, astrophysical black hole lenses are best described by the Kerr metric. Furthermore, recent observations of supermassive black holes at the centers of
galaxies provide an ideal laboratory for testing the observational effects of the Kerr metric by measuring the frequency shifts of lensed sources.
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Solar and Stellar Astrophysics
Multi-Instrument Analysis of NOAA AR 12781: Coupling Surface Evolution of the AR with Its In-Situ Solar Wind Signatures
Dharanesh Palaniappan and Khagendra Katuwal
Understanding the relationship between photospheric
magnetic flux
evolution and coronal emission remains an important problem in heliophysics. We investigate the decay of NOAA Active Region 12781 from 7 to 11 November 2020 using observations from the Solar Dynamics Observatory (SDO). Coronal emission was measured from the Atmospheric Imaging Assembly (AIA) 193\~Å images, while the photospheric signed and unsigned
magnetic flux was derived from Helioseismic and
Magnetic Imager (HMI) observations of the FeĨ 6173\~Å line. The unsigned
magnetic flux and mean 193\~Å intensity showed a strong inverse relationship, with Pearson and Spearman correlation coefficients of $r\_p=-0.771$ and $r\_s=-0.758$, respectively. During the five-day decay phase, the unsigned
magnetic flux decreased by 36.54\% from its maximum value, while the coronal emission increased by 21.96\%. We also compared the remote-sensing observations with near-Earth solar-wind and interplanetary
magnetic-field measurements from the OMNI database using an estimated propagation delay. The results show that the coronal emission did not vary directly with the photospheric
magnetic flux during the decay of AR\~12781. The possible association with the solar wind is discussed cautiously because a direct source connection cannot be established from the time-delay estimate alone.
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Instrumentation and Methods for Astrophysics
Consistency and precision of very long baseline interferometry source coordinate time series
X.-X. Zhang, N. Liu, S. B. Lambert et al. (+18 more)
Coordinate time series of extragalactic
radio sources from very long baseline interferometry observations are widely used to evaluate source positional stability, select stable sources for celestial reference frames, assess reference-frame axis stability, and investigate source-related astrometric variability. Their external consistency, realistic errors, and relation to processing strategies and analysis configurations remain to be investigated. We aim to compare coordinate time series solutions from different analysis centers and investigate how processing strategies and configurations contribute to their differences. We collected eight solutions from seven analysis centers and selected 496 common sources after data selection, reference-frame
alignment, and extraction of common observing sessions. Inter-solution differences were characterized with pairwise positional offsets and correlation analysis, and realistic positional errors with the N-cornered-hat (NCH) method and bootstrap resampling. Most solutions have median weighted root mean square (WRMS) values of a few hundred microarcseconds $(\mathrm{\mu as})$, and the median NCH-derived precision is about 200-300 $\mathrm{\mu as}$ in right ascension and 250-400 $\mathrm{\mu as}$ in declination. Solutions with similar strategies, software, or source constraints show higher consistency, with more similar WRMS values, stronger correlations, and closer precision estimates. Consistency is affected not only by the global or independent mode distinction but also by detailed analysis configuration. NCH-derived precision depends on declination, being poorer in the southern sky, and stabilizes with more observing sessions. Processing strategies and configurations introduce marginal differences; solutions remain generally consistent. Inter-solution comparisons independently estimate realistic
stochastic errors beyond formal errors.
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All authors X.-X. Zhang, N. Liu, S. B. Lambert, K. Le Bail, H. Krásná, O. Titov, M. Karbon, T. Nilsson, Z. Zhu, J.-C. Liu, I. N. Huda, J. Yang, X.-P. Cheng, B.-W. Sohn, F.-C. Shu, X. He, Z.-W. Wang, Z.-Y. Zhang, H.-F. Yu, J. Yao, D.-D. Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A Unified Numerical Study of Axion Stars: From the Nonrelativistic Regime to General Relativity
Parisa Arabameri, Paola Arias, Francisco Colipí-Marchant et al. (+1 more)
Axion-
star mass-radius relations are commonly computed using different orders of relativistic approximation, making it important to determine where these descriptions remain reliable. We perform a unified numerical comparison of
axion-
star ground-state configurations in the Newtonian Schrödinger-Poisson description, first- and second-order relativistic effective field theories, and the full Einstein-Klein-Gordon system for a real scalar field. Using the same attractive quartic self-interaction in all four descriptions, we scan $|\widetilde{\lambda}|=(M_{\rm Pl}/f_a)^2$ and determine the maximum masses and corresponding enclosed-mass radii. All descriptions recover the common large-$|\widetilde{\lambda}|$ dilute-
star scaling, while substantial differences appear at weak and moderate coupling. The relativistic EFTs interpolate systematically between the Newtonian and full-GR results. For part of the maximum-mass sequence where $\max|\phi|/f_a=O(1)$, we test the temporal-harmonic and potential truncations explicitly in full GR. The higher-harmonic expansion shows rapid convergence, while restoring the complete single-cosine potential changes the maximum mass only at the percent level and $R_{95}$ at the several-percent level. Together with the systematic convergence of the relativistic EFT descriptions toward full GR, these results show that the large weak-coupling departure from the Schrödinger-Poisson prediction reflects the breakdown of the nonrelativistic structural description. Our results provide a systematic
benchmark for determining when Newtonian, relativistically corrected, or fully general-relativistic descriptions are required for
axion-
star structure. The numerical implementation used in this work is available in the
Axion Star Solvers repository at https://github.com/Parisa-Arabameri/AxionStar.
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All authors Parisa Arabameri, Paola Arias, Francisco Colipí-Marchant, Enrico D. Schiappacasse
High Energy Astrophysical Phenomena
Examining Temporal Characteristics of GCRs in the AMS-02 era
Cheng-Rui Zhu, Yu-Lu Liu, Mei-Juan Wang et al. (+3 more)
The energy spectra of Galactic
cosmic rays (GCRs) serve as critical probes of their astrophysical origins and propagation mechanisms through the interstellar medium. Among the key physical processes shaping the observed spectra, solar modulation, driven by turbulent heliospheric
magnetic fields and the variability of the solar wind, plays a dominant role in modifying GCR fluxes within the inner heliosphere. The recent release of time-dependent flux measurements for He, Li, Be, B, C, N, and O by AMS-02 provides unprecedented precision to investigate solar modulation phenomena. In this study, we demonstrate that Li, Be, B, C, N, and O
nuclei exhibit solar modulation parameters consistent with those of
protons (p) and He within a modified force-field approximation (FFA) framework incorporating rigidity-dependent modulation potentials. By positing that GCRs with the same charge-sign sharing the solar modulation parameters, we further forecast daily fluxes of Ne, Mg and Si from 2011 to 2020.
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All authors Cheng-Rui Zhu, Yu-Lu Liu, Mei-Juan Wang, Tian-Hao Li, Yi-Hua Zhu, Kai-Kai Duan
Instrumentation and Methods for Astrophysics
A Two-Stage Physically Grounded Optical Design Framework with Application to a Multi-Channel Focal Reducer
M. R. Najera, J. Herrera, Esteban Luna et al. (+1 more)
We present a two-stage optimization framework that formalizes classical optical design strategies within a reproducible computational workflow. Starting point designs are constructed from paraxial and third-order models, providing optically consistent initial configurations. These configurations are refined through a physically grounded residual merit function evaluated by exact ray tracing, followed by RMS-based image refinement. Applied to a multi-channel astronomical focal reducer, the methodology provides a structured transition from aberration-based modeling to numerical optimization while preserving physically interpretable intermediate stages. By
embedding classical optical design principles into an open computational pipeline, the approach reduces reliance on heuristic initial conditions and improves the reproducibility and interpretability of the design process.
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All authors M. R. Najera, J. Herrera, Esteban Luna, Erika Sohn