High Energy Astrophysical Phenomena
Radio emission from beyond the light cylinder in millisecond pulsars
Michael Kramer and Simon Johnston
A striking aspect of the
radio profiles of many millisecond
pulsars (MSPs) is that they consist of components separated from each other by regions lacking in emission. We devise a technique for determining "disjoint" from "contiguous" components and show that 35% of MSPs have disjoint components as opposed to only 3% of the slow
pulsar population. We surmise that the
pulsars with these disjoint components show evidence for both emission above the polar cap and from the current sheet beyond the light cylinder (LC), co-located with gamma-ray emission. For some of the
radio MSPs only the LC emission is being observed. It is our contention that almost all of the current population of gamma-ray MSPs show evidence for co-located
radio emission. A simple
geometric explanation allows the presence (or not) of LC emission and the relationship (or not) between the gamma-ray and
radio profiles to be determined. The LC components have frequently very high polarization and typically flat position-angle traverses thus helping to explain the difficulties in determining the geometry of MSPs. In cases where the geometry can be determined the values broadly align with expectations. In this picture, the number of potentially detectable
radio MSPs is higher than previously thought, although the actual detectability of LC components depends on their luminosity function. A mechanism is required to produce coherent
radio emission far from the
stellar surface. These ideas have implications for our understanding of the populations of
radio-loud and
radio-quiet rotation-powered millisecond
pulsars, and may have implications for the long-term timing stability of some of these sources.
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Cosmology and Nongalactic Astrophysics
Radiative-Corrected Higgs Inflation in Light of the Latest ACT Observations
Jureeporn Yuennan, Farruh Atamurotov and Phongpichit Channuie
Recent measurements from the Atacama Cosmology
Telescope (ACT), particularly when combined with DESI
baryon acoustic oscillation data, have reported a scalar spectral index $n_s$ slightly higher than that inferred by Planck~2018, suggesting a mild tension with the predictions of standard inflationary attractor models. In this work, we revisit the
quantum-corrected
Higgs inflation scenario within the framework of a non-minimally coupled scalar field theory. Starting from the one-loop effective action, we incorporate radiative corrections through the anomalous scaling parameter ${\bf A_I}$ and derive analytic expressions for the inflationary observables $n_s$ and $r$ in the Einstein frame. Our analysis demonstrates that
quantum corrections naturally shift $n_s$ toward higher values while keeping the tensor-to-scalar ratio $r$ suppressed. For ${\cal N} = 60$, the model predicts $n_s \simeq 0.9743$ and $r \simeq 5.4\times10^{-3}$, in excellent agreement with the latest ACT+DESI (P-ACT-LB) data and fully consistent with the Planck~2018 limit $r < 0.036$. The derived constraint $4.36\times10^{-10} < \lambda/\xi^{2} < 10.77\times10^{-10}$ confirms the robustness of the
quantum-corrected
Higgs framework and indicates that near-future CMB polarization experiments such as CORE, AliCPT, LiteBIRD, and CMB-S4 will be able to probe the predicted parameter space with high precision.
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Earth and Planetary Astrophysics
Line shapes of the Na/K resonance line profiles perturbed by H2 at extreme density
N. F. Allard and J. F. Kielkopf
Collision broadening by molecular hydrogen of sodium and potassium is one of the major broadening mechanisms in the atmospheres of brown
dwarf stars and
exoplanets at an effective temperature of about 1000K. The accurate computation of line profiles from collision broadening at high density requires use of a
Fourier transform of the autocorrelation function inside the model atmosphere code. We strongly warn that use of Lorentzian profiles at a high perturber density neglects radiation during close collisions and may lead to erroneous conclusions.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.CL
Adaptive and Multi-Source Entity Matching for Name Standardization of Astronomical Observation Facilities
Liza Fretel, Baptiste Cecconi and Laura Debisschop
This ongoing work focuses on the development of a methodology for generating a multi-source mapping of astronomical observation facilities. To compare two entities, we compute scores with adaptable criteria and Natural
Language Processing (NLP) techniques (Bag-of-Words approaches, sequential approaches, and surface approaches) to map entities extracted from eight semantic artifacts, including Wikidata and astronomy-oriented resources. We utilize every property available, such as labels, definitions, descriptions, external identifiers, and more domain-specific properties, such as the observation wavebands, spacecraft launch dates, funding agencies, etc. Finally, we use a Large
Language Model (LLM) to accept or reject a mapping suggestion and provide a justification, ensuring the plausibility and
FAIRness of the validated synonym pairs. The resulting mapping is composed of multi-source synonym sets providing only one standardized label per entity. Those mappings will be used to feed our Name Resolver API and will be integrated into the International Virtual Observatory Alliance (IVOA) Vocabularies and the OntoPortal-Astro platform.
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High Energy Astrophysical Phenomena
Convolution and Graph-based Deep Learning Approaches for Gamma/Hadron Separation in Imaging Atmospheric Cherenkov Telescopes
Abhay Mehta, Dan Parsons, Tim Lukas Holch et al. (+2 more)
The identification of $\gamma$-rays from the predominant hadronic-background is a key aspect in their ground-based detection using Imaging Atmospheric Cherenkov
Telescopes (IACTs). While current methods are limited in their ability to exploit correlations in complex data, deep learning-based models offer a promising alternative by directly leveraging image-level information. However, several challenges involving the robustness and applicability of such models remain. Designing model architectures with inductive biases relevant for the task can help mitigate the problem. Three such deep learning-based models are proposed, trained, and evaluated on simulated data: (1) a hybrid convolutional and graph neural network model (CNN-GNN) using both image and graph data; (2) an enhanced CNN-GNN variant that incorporates additional reconstructed information within the graph construction; and (3) a graph neural network (GNN) model using image moments serving as a baseline. The new combined convolution and graph-based approach demonstrates improved performance over traditional methods, and the inclusion of reconstructed information offers further potential in generalization capabilities on real observational data.
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All authors Abhay Mehta, Dan Parsons, Tim Lukas Holch, David Berge, Matthias Weidlich
High Energy Astrophysical Phenomena
Exploring the Most Extreme Blazars: New Insights from MAGIC
L. Foffano, C. Arcaro, A. Arbet-Engels et al. (+8 more)
Extremely high-peaked BL Lac objects (or extreme blazars) are unique extragalactic laboratories where particle acceleration processes are pushed at their physical limits. In these blazars, synchrotron emission peaking above keV energies is reprocessed to very-high-energy (VHE, energies > 100 GeV) gamma rays, often resulting in very hard TeV spectra. Over the past two decades, they have attracted a growing interest from the scientific community, both experimentally and theoretically, as crucial targets for understanding the diversity within the blazar class. On the experimental side, new sources have been detected and characterized, populating the extreme blazars class. Notably, VHE campaigns have revealed evidence of emerging spectral differences in this energy band, suggesting inhomogeneity within this class of sources. Recent studies have also unveiled intriguing differences in the temporal
evolution of their spectral emission. On the theoretical side, these spectral differences are challenging the current standard emission and acceleration models for blazars, suggesting the need for more complex theoretical frameworks. In this contribution, we present the latest results from recent MAGIC Collaboration observing campaigns aimed to enlarge the extreme blazars population at VHE and understand the origin of their extreme properties. Furthermore, we will present the results of the most recent observations, discussing analogies and differences with well-known sources such as the archetypal 1ES 0229+200, as well as interpretations of their non-conventional spectral emission.
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All authors L. Foffano, C. Arcaro, A. Arbet-Engels, F. D'Ammando, P. Da Vela, J. Jormanainen, D. Linder, S. Menon, E. Prandini, S. Ventura, E. Visentin
Solar and Stellar Astrophysics · Cross-listed from nucl-th
Microscopic study of nuclei synthesis in pycnonuclear reaction $^{12}$C + $^{12}$C in neutron stars
S.P. Maydanyuk, Ju-Jun Xie, V.S. Vasilevsky et al. (+1 more)
Purpose To investigate synthesis of
nuclei in pycnonuclear reactions in dense medium of
neutron stars on the basis of understanding, how the compound
nucleus is formed during collision of two
nuclei. To implement microscopic formulation of
nuclear interactions and fusion in pycnonuclear reactions in dense medium. Methods (1)
Nuclei synthesis in pycnonuclear reaction in dense medium of
neutron star is investigated in the folding approximation of the cluster model. (2) Formation of compound
nucleus in dense medium is studied with the method of Multiple Internal Reflections. Results (1) Wave functions of resonance states of $^{24}$Mg are determined by interaction of two $^{12}$C
nuclei. (2) Clear maxima of probability of formation of compound
nucleus in dense
stellar medium are established at first time. (3) Difference between quasibound energies for potential of Woods-Saxon type and folding potentials with the shell-model approximation for wave functions is essential. (4) Formation of the compound
nucleus is much more probable in the quasibound states than in states of zero-point vibrations. (5) Only the first quasibound energies for $^{12}$C + $^{12}$Care smaller than the barrier maximums. At these energies compound
nuclear system has barrier which prevents its decay going through tunneling phenomenon. This is the new excited
nucleus $^{24}$Mg synthesised in the
neutron star. \item[Conclusions] Cluster approach with folding potential provides significant modification of picture of formation of compound
nucleus, previously obtained concerning the potential of Woods-Saxon type. The highest precision is provided by the folding potential, created by semi-realistic nucleon-nucleon potential and shell-model description of the internal structure of interacting $p$-shell
nuclei.
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All authors S.P. Maydanyuk, Ju-Jun Xie, V.S. Vasilevsky, K.A. Shaulskyi
Solar and Stellar Astrophysics
Abundance Pattern Fitting with Bayesian Inference: Constraining First Stars' Properties and Their Explosion Mechanism with Extremely Metal-poor Stars
Ruizheng Jiang, Haining Li, Gang Zhao et al. (+2 more)
The abundance patterns of extremely metal-poor
stars preserve a fossil record of the Universe's earliest chemical enrichment by the
supernova explosions from the
evolution of first generation of
stars, also referred to as Population III (or Pop III). By applying
Bayesian inference to the analysis of abundance patterns of these ancient
stars, this study presents a systematic investigation into the properties and explosion mechanism of Pop III
stars. We apply NLTE corrections to enhance the reliability of abundance measurements, which significantly reduces the discrepancies in abundances between observations and theoretical yields for odd-Z elements, such as Na and Al. Our
Bayesian framework also enables the incorporation of explodability and effectively mitigates biases introduced by varying resolutions across different
supernova model grids. In addition to confirming a top-heavy ($\alpha=0.54$) initial mass function for massive Pop III
stars, we derive a robust mass–energy relation ($E\propto M^2$) of the first
supernovae. These findings demonstrate that
stellar abundance analysis provides a powerful and independent approach for probing early
supernova physics and the fundamental nature of the first
stars.
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All authors Ruizheng Jiang, Haining Li, Gang Zhao, Qianfan Xing, Wenyu Xin
Astrophysics of Galaxies
A Comparison of Star Formation Rates by Different Tracers in Nearby Galaxies
Huynh Anh N. Le, Jong-Hak Woo, Yongquan Xue et al. (+3 more)
We utilize a large sample of $\sim$113,000
galaxies ($z < 0.3$) from the Sloan Digital Sky Survey with high-quality data to compare
star formation rates (SFRs) across multiple diagnostic methods and examine their connection to Active
Galactic Nuclei (AGNs) strength, indicated by Eddington ratio. Our sample encompassed
star-forming (SF), composite, Seyfert, and LINER
galaxies. Our analysis utilizes various SFRs indicators, including observed infrared flux ($\rm SFR_{FIR}$) from AKARI/Herschel ($\sim$4,100 sources), the MPA-JHU catalog ($\rm SFR_{Dn4000}$), the ANN catalog ($\rm SFR_{ANN}$), the GSWLC catalog ($\rm SFR_{SED}$ and $\rm SFR_{MIR}$), as well as \OII\ and \Ha\ emission lines ($\rm SFR_{[OII]}$ and $\rm SFR_{H\alpha}$). Within SF
galaxies, SFRs measurements from different tracers exhibited differences, with offsets and scatter below 0.26 dex and 0.29 dex, respectively. Moreover, non-SF
galaxies (composite, Seyfert, and LINER) displayed discrepancies among SFR tracers, particularly for LINER
galaxies, with offsets below 0.86 dex and a scatter of 0.57 dex. Additionally, our findings revealed robust correlations between SFRs and specific SFRs (sSFRs) with Eddington ratios. Eddington ratio exhibited gradual transitions in the (s)SFRs-
stellar mass diagrams.
Galaxies with high Eddington ratios displayed high
star formation activity, similar to blue SF
galaxies. Furthermore, we observed decreasing sSFR trends from SF
galaxies to composite, Seyfert, and LINER
galaxies. Our results may provide insight into our understanding of (s)SFRs traced by different approaches and their connection to AGN activities.
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All authors Huynh Anh N. Le, Jong-Hak Woo, Yongquan Xue, Ashraf Ayubinia, Changseok Kim, Xiaozhi Lin
Astrophysics of Galaxies
Constraints on dark matter models from the stellar cores observed in ultra-faint dwarf galaxies: Self-interacting dark matter
Jorge Sanchez Almeida
It has been proposed that the
stellar cores observed in ultra-faint
dwarf (UFD)
galaxies reflect underlying dark matter (DM) cores that cannot be formed by
stellar feedback acting on collisionless cold dark matter (CDM)
halos. Assuming this claim is correct, we investigate the constraints that arise if such cores are produced by self-interacting dark matter (SIDM). We derive the range of SIDM cross-sections (sigma/m) required to reproduce the observed core sizes. These can result from
halos in either the core-formation phase (low sigma/m) or the core-collapse phase (high sigma/m), yielding a wide allowed range (sim 0.3 – 200 cm2/g) consistent with values reported in the literature for more massive
galaxies. We also construct a simple model relating
stellar mass to core radius - two observables likely connected in SIDM. This model reproduces the
stellar core sizes and masses in UFDs with sigma/m consistent with those derived above. It also predicts a trend of increasing core radius with
stellar mass, in agreement with observations of more massive
dwarf galaxies. The model central DM densities match observations when assuming the SIDM profile to originate from an initial CDM
halo that follows the mass-concentration relation. Since
stellar feedback is insufficient to form cores in these
galaxies, UFDs unbiasedly anchor sigma/m at low velocities. If the core-collapse scenario holds (i.e., high sigma/m), UFD
halos are thermalized on kpc scales, approximately two orders of magnitude larger than the
stellar cores. These large thermalization scales could potentially influence substructure formation in more massive systems.
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Cosmology and Nongalactic Astrophysics
Resurging from the ashes: A spectral study of seven candidate revived radio fossils in nearby low-mass galaxy clusters
L. Bruno, A. Botteon, D. Dallacasa et al. (+17 more)
Complex energy transfer processes in the intracluster medium (ICM) can revive fossil (with spectral ages $\gg100$ Myr)
plasma initially generated by
radio galaxies. This leads to the re-ignition of faint
radio sources with irregular and filamentary morphologies, and ultra-steep ($\alpha \gtrsim 1.5$) synchrotron spectra, which can be more easily detected at low frequencies ($\sim 100$ MHz). These sources offer the opportunity to investigate the microphysics of the ICM and its interplay with
radio galaxies, the origin of seed relativistic electrons, the merging history of the host cluster, and the phenomenology of
radio filaments. The study of revived sources has so far been hampered by the requirement of sensitive and high-resolution multi-frequency
radio data at low frequencies to characterise their spatial properties and provide a proper classification. We aim to perform the analysis of a sample of candidate revived sources identified among nearby ($z\leq0.35$) and low-mass ($M_{500}\leq5\times 10^{14} M_\odot$) Planck clusters in the footprint of LoTSS-DR2. By inspecting LoTSS-DR2 images at 144 MHz, we identified 7 targets with patchy and filamentary morphologies, which have been followed-up with the uGMRT at 400 MHz. By combining LOFAR and uGMRT data, we obtained high-resolution images and spectral index maps, which we used to interpret the nature of the sources. All targets show regions with very steep spectra, confirming the effectiveness of our morphology-based selection in identifying fossil
plasma. Based on their morphology, spectral properties, and optical associations, we investigated the origin of the targets. We found a variety of promising revived fossil sources, while also showing that apparently intricate structures can be easily misclassified in the absence of high-resolution and multi-band data.
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All authors L. Bruno, A. Botteon, D. Dallacasa, T. Venturi, M. Balboni, N. Biava, M. Brienza, M. Brüggen, G. Brunetti, F. de Gasperin, E. De Rubeis, G. Di Gennaro, F. Gastaldello, A. Ignesti, T. Pasini, K. Rajpurohit, A. Shulevski, K. S. L. Srikanth, R. J. van Weeren, X. Zhang
Astrophysics of Galaxies
MEGATRON: the impact of non-equilibrium effects and local radiation fields on the circumgalactic medium at cosmic noon
Corentin Cadiou, Harley Katz, Martin P. Rey et al. (+22 more)
We present three cosmological radiation-hydrodynamic zoom simulations of the progenitor of a Milky Way-mass
galaxy from the MEGATRON suite. The simulations combine on-the-fly radiative transfer with a detailed non-
equilibrium thermochemical network (81 ions and molecules), resolving the cold and warm gas in the circumgalactic medium (CGM) on spatial scales down to 20 pc and on average 200 pc at
cosmic noon. Comparing our full non-
equilibrium calculation with local radiation to traditional post-processed photoionization
equilibrium (PIE) models assuming a uniform UV background (UVB), we find that non-
equilibrium physics and local radiation fields fundamentally impact the thermochemistry of the CGM. Recombination lags and local radiation anisotropy shift ions away from their PIE+UVB values and modify covering fractions (for example, HI damped Ly$\alpha$ absorbers differ by up to 40%). In addition, a resolution study with cooling-length refinement allows us to double the resolution in the cold and warm CGM gas, reaching 120 pc on average. When refining on cooling length, the mass of the lightest cold clumps decreases tenfold to $\approx 10^4\,M_\odot$, their boundary layers develop sharper ion stratification, and the warm gas is better resolved, boosting the abundance of warm gas tracers such as CIV and OIII. Together, these results demonstrate that non-
equilibrium thermochemistry coupled to radiative transfer, combined with physically motivated resolution criteria, is essential to predict circumgalactic absorption and emission signatures and to guide the design of targeted observations with existing and upcoming facilities.
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All authors Corentin Cadiou, Harley Katz, Martin P. Rey, Oscar Agertz, Jeremy Blaizot, Alex J. Cameron, Nicholas Choustikov, Julien Devriendt, Uliana Hauk, Gareth C. Jones, Taysun Kimm, Isaac Laseter, Sergio Martin-Alvarez, Kosei Matsumoto, Camilla T. Nyhagen, Autumn Pearce, Francisco Rodríguez Montero, Joki Rosdahl, Víctor Rufo Pastor, Mahsa Sanati, Aayush Saxena, Adrianne Slyz, Richard Stiskalek, Anatole Storck, Wonjae Yee
High Energy Astrophysical Phenomena
Estimation of intrinsic fast radio burst width and scattering distributions from CRAFT data
C. W. James, J. Hoffmann, J. X. Prochaska et al. (+1 more)
The intrinsic width and scattering distributions of fast
radio bursts (FRBs) inform on their emission mechanism and local environment, and act as a source of detection bias and, hence, an obfuscating factor when performing FRB population and cosmological studies. Here, we utilise a sample of 29 FRBs with measured high-time-resolution properties and known
redshift, which were detected using the Australian Square Kilometre Array Pathfinder (ASKAP) by the Commensal Real-time ASKAP Fast Transients Survey (CRAFT), to model these distributions. Using this sample, we estimate the completeness bias of intrinsic width and scattering measurements, and fit the underlying, de-biased distributions in the host rest-frame. In no case do our model fits prefer a down-turn at high values of the intrinsic distributions of either parameter in the 0.01-40 ms range probed by the data. Rather, when assuming a spectral scattering index of $\alpha = -4$, we find that the intrinsic scattering distribution at 1\,GHz is consistent with a log-uniform distribution above 0.04 ms, and that this functional form is strongly favoured over the lognormal descriptions used by previous works. We also find that the intrinsic width distribution rises as a Gaussian in log-space in the 0.03-0.3 ms range, with a log-uniform distribution above that slightly preferred to a lognormal distribution. This confirms previous works suggesting that FRB observations are currently strongly width- and scattering-limited, and we encourage FRB searches to be extended to higher values of time-width. It also implies a bias in FRB host
galaxy studies, although the form of that bias is uncertain. Finally, we find that our updated width and scattering models - when implemented in the zDM code - produce $\sim$10% more FRBs at
redshift z=1 than at z=0 when compared to alternative width/scattering models.
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All authors C. W. James, J. Hoffmann, J. X. Prochaska, M. Glowacki
Astrophysics of Galaxies
On the Formation of GW231123 in Population III Star Clusters
Shuai Liu, Long Wang, Ataru Tanikawa et al. (+2 more)
GW231123 is a binary black hole merger whose primary component lies within or above the pair-instability mass gap, while the secondary component falls within this gap. The standard theory of
stellar evolution is significantly challenged by this event. We investigate the formation of candidate progenitors of GW231123 in Population III (Pop III)
star clusters. We find that they could form through
stellar mergers, binary black hole mergers, and mixed mergers. The mass distribution of these candidate progenitors covers the component masses of GW231123. Under our model assumptions, their predicted merger rate density spans the range of $0.001-0.26{\rm Gpc^{-3}yr^{-1}}$, encompassing that of GW231123. These findings suggest that GW231123 may originate from Pop III
star clusters. Furthermore, such candidate progenitors are expected to be detectable by future gravitational wave detectors LISA/Taiji/TianQin/DECIGO/
Cosmic Explorer/Einstein
Telescope, which would provide valuable insights into the formation scenarios of events like GW231123.
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All authors Shuai Liu, Long Wang, Ataru Tanikawa, Weiwei Wu, Michiko S. Fujii
Earth and Planetary Astrophysics
Infall Explains the Disk Kinematics of AB Aur Without Gravitational Instability
Josh Calcino, Daniel J. Price and Chris W. Ormel
Late-stage infall onto protoplanetary disks can produce large scale spiral arms. In this paper we used 3D smoothed particle hydrodynamics and radiative transfer simulations to study the kinematic perturbations induced in disks by infalling material. We found that deviations from Keplerian rotation are predominantly in the radial and vertical velocity components, spatially correlated with spiral arms in the gas surface density. The infall produces observable wiggles in the channel maps, analogous to those produce by the gravitational instability (GI), along with large-scale arcs and filaments. GI induced spiral arms produce radial velocity perturbations that point towards the center of the spiral arm owing to their higher self-
gravity. We found a similar signature from infall-induced spiral arms, despite not including self-
gravity in our simulation. Our study suggests that recent evidence of GI in the kinematics of the disk around AB Aur may instead be due to the observed infall, without the need for invoking GI. We further show that a unified model invoking infall onto a central binary can explain the CO morphology and kinematics, scattered light spirals, and mm-continuum emission in AB Aur.
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High Energy Astrophysical Phenomena
Discovery of Changing-Look behavior in AGN NGC 3822: A long-term multiwavelength study
Narendranath Layek, Prantik Nandi, Sachindra Naik et al. (+7 more)
We present a comprehensive long-term multi-wavelength study of the active
galactic nucleus (AGN) NGC 3822, based on 17 years (2008 to 2025) of X-ray, ultraviolet (UV), and optical observations.The
dataset includes observations from Swift, XMM-Newton, and NuSTAR, the Very Large
Telescope, and the Himalayan Chandra
Telescope. Our multiwavelength light curve analysis reveals flux variations across X-ray to optical/UV bands, with an increased variability amplitude at shorter wavelengths. X-ray spectral analysis indicates the presence of intrinsic absorption during the 2016 and 2022 observations; however, this absorption disappeared before and after these epochs. The presence and absence of the absorber are attributed to clouds moving in and out of the line of sight. During the long-term monitoring period, the bolometric luminosity of the source varies between ($1.32-17)\times10^{43}$ erg s$^{-1}$. Optical spectroscopic monitoring reveals changing-look (CL) behaviour in NGC~3822, characterized by the appearance and disappearance of broad emission lines (BELs). These CL transitions are associated with changes in the Eddington ratio rather than changes in the obscuration. The BELs appear only when the Eddington ratio is relatively high ($\sim 3.8\times10^{-3}$) and disappear when it drops to a lower value ($\sim 0.9\times10^{-3}$).
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All authors Narendranath Layek, Prantik Nandi, Sachindra Naik, Birendra Chhotaray, Arghajit Jana, Priyadarshee P. Dash, Neeraj Kumari, C. S. Stalin, Srikanth Bandari, S. Muneer
High Energy Astrophysical Phenomena
Gaussian process analysis of type-B quasiperiodic oscillations in the black hole X-ray binary MAXI J1348-630
Yiran Wang, Ruican Ma, Haiyun Zhang et al. (+1 more)
We analyzed Insight-HXMT data of the black hole X-ray binary MAXI J1348-630 during the type-B QPO phase of its 2019 outburst. Using the Gaussian process method, we applied an additive composite kernel model consisting of an SHO, a DRW, and an additional white noise (AWN) to data from three energy bands: LE (1-10 keV), ME (10-30 keV), and HE (30-150 keV). We find that for the DRW component, correlations on the timescale of $\tau_{\rm DRW}\sim10$ s are absent in the LE band, while they persist in the ME and HE bands over the full duration of the light curves. This energy-dependent behavior may reflect thermal instabilities, with the shorter correlation timescale in the disk compared to the corona. Alternatively, it may reflect variable Comptonizations of seed
photons from different disk regions. Inner-disk
photons are scattered by a small inner corona, producing soft X-rays. Outer-disk
photons interact with an extended, jet-like corona, resulting in harder emission. The QPO is captured by an SHO component with a stable period of $\sim 0.2$ s and a high quality factor of $\sim 10$. The absence of significant
evolution with energy or time of the SHO component suggests a connection between the
accretion disk and the corona, which may be built by coherent oscillations of disk-corona driven by magnetorotational instability. The AWN components are present in all the three-band data and dominate over the DRW and SHO components. We interpret the AWN as another fast DRW with its $\tau_{\rm DRW} < 0.01$ s. It may trace high-frequency fluctuations that occur in both the inner region of the
accretion disk and the corona. Overall, our work reveals a timescale hierarchy in the coupled disk-corona scenario: fast DRW < SHO < disk DRW < corona DRW.
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All authors Yiran Wang, Ruican Ma, Haiyun Zhang, Dahai Yan
Cosmology and Nongalactic Astrophysics
Luminosity distance dispersion in Swiss-cheese cosmology as a function of the hole size distribution
Thippayawis Cheunchitra, Andrew Melatos and Rachel Webster
The luminosity distance-
redshift ($D_{\rm L}$–$z$) relation derived from Type Ia
supernovae (SNe Ia) yields evidence for a nonzero cosmological constant. SNe Ia analyses typically fit to the functional form $D_{\rm L}(z)$ derived theoretically from the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) metric. Yet, the metric in the epoch relevant to SNe Ia measurements deviates slightly from FLRW due to gravitational clumping of mass into large-scale structures like filaments and voids, whose sizes span many orders of magnitude. The small deviation is modeled typically by scalar perturbations to the FLRW metric. Each line of sight to a SNe Ia passes through a random sequence of structures, so $D_{\rm L}$ differs stochastically from one line of sight to the next. Here, we calculate the $D_{\rm L}$ dispersion in an exact Lemaitre-Tolman-Bondi Swiss-cheese universe with a power-law hole size distribution, as a function of the lower cut-off $R_{\rm min}$ and logarithmic slope $\gamma$. We find that the standard deviation of $D_{\rm L}$ scales as $\sigma_{D_{\rm L}} \propto z^{2.25\pm0.01} (R_{\rm min}/24\pm1\,{\rm Mpc})^{(0.157\pm0.003)\left[\gamma - (1.16\pm0.02)\right]}$ for
redshifts in the range $0.5 \lesssim z \lesssim 2.1$. The scaling shows that the $D_{\rm L}$ dispersion is dominated by a few large voids rather than the many small voids.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Demagnifying gravitational lenses as probes of dark matter structures and nonminimal couplings to gravity
Hong-Yi Zhang
Magnification of total image fluxes is typically considered a defining feature of gravitational microlensing. In contrast, I will show that nonminimal couplings to
gravity can generate regions of negative gravitational potential
curvature, giving rise to the distinctive possibility of demagnification. Such events, appearing as flux troughs in microlensing light curves, provide a direct probe of dark matter structures and, crucially, offer a means to disentangle nonminimal couplings to
gravity from other astrophysical and cosmological models.
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Astrophysics of Galaxies
Monitoring of 3C 286 with ALMA, IRAM, and SMA from 2006 to 2025: Stability, Synchrotron Ages, and Frequency-Dependent Polarization Attributed to Core-Shift
Minchul Kam, Hiroshi Nagai, Motoki Kino et al. (+23 more)
We present the results of multi-frequency monitoring of the
radio quasar 3C 286, conducted using three instruments: ALMA at 91.5, 103.5, 233.0, and 343.4 GHz, the IRAM 30-m
Telescope at 86 and 229 GHz, and SMA at 225 GHz. The IRAM measurements from 2006 to 2024 show that the total flux of 3C 286 is stable within measurement uncertainties, indicating long-term stability up to 229 GHz, when applying a fixed Kelvin-to-Jansky conversion factor throughout its
dataset. ALMA data from 2018 to 2024 exhibit a decrease in flux, which up to 4% could be attributed to an apparent increase in the absolute brightness of Uranus, the primary flux calibrator for ALMA with the ESA4 model. Taken together, these results suggest that the intrinsic total flux of 3C 286 has remained stable up to 229 GHz over the monitoring period. The polarization properties of 3C 286 are stable across all observing frequencies. The electric vector position angle (EVPA) gradually rotates as a function of wavelength squared, which is well described by a single power-law over the full frequency range. We therefore propose using the theoretical EVPA values from this model curve for absolute EVPA calibration between 5 and 343.4 GHz. The Faraday rotation measure increases as a function of frequency up to (3.2+/-1.5)x10^4 rad m^-2, following RM proportional to nu^alpha with alpha = 2.05+/-0.06. This trend is consistent with the core-shift effect expected in a conical jet.
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All authors Minchul Kam, Hiroshi Nagai, Motoki Kino, Keiichi Asada, Rüdiger Kneissl, Iván Agudo, Sascha Trippe, Seiji Kameno, Ioannis Myserlis, Ramprasada Rao, Hojin Cho, Richard A. Perley, Bryan J. Butler, Mark Gurwell, Tomoki Matsuoka, Jongho Park, Carolina Casadio, Baltasar Vila Vilaro, Celia Verdugo, Matias Radiszcz, Kurt Plarre, Wanchaloem Khwammai, Diego Álvarez-Ortega, Juan Escudero, Clemens Thum, Garrett Keating
Cosmology and Nongalactic Astrophysics
Validation of the DESI-DR1 3x2-pt analysis: scale cut and shear ratio tests
N. Emas, A. Porredon, C. Blake et al. (+54 more)
Combined survey analyses of
galaxy clustering and weak gravitational
lensing (3x2-pt studies) will allow new and accurate tests of the standard cosmological model. However, careful validation is necessary to ensure that these cosmological constraints are not biased by uncertainties associated with the modelling of astrophysical or systematic effects. In this study we validate the combined 3x2-pt analysis of the Dark Energy Spectroscopic Instrument Data Release 1 (DESI-DR1) spectroscopic
galaxy clustering and overlapping weak
lensing datasets from the Kilo-Degree Survey (KiDS), the Dark Energy Survey (DES), and the Hyper-Suprime-Cam Survey (HSC). By propagating the modelling uncertainties associated with the non-linear matter power spectrum, non-linear
galaxy bias and
baryon feedback, we design scale cuts to ensure that measurements of the matter density and the amplitude of the matter power spectrum are biased by less than 30% of the statistical error. We also test the internal consistency of the data and weak
lensing systematics by performing new measurements of the
lensing shear ratio. We demonstrate that the DESI-DR1 shear ratios can be successfully fit by the same model used to describe
cosmic shear correlations, and analyse the additional information that can be extracted about the source
redshift distributions and intrinsic
alignment parameters. This study serves as crucial preparation for the upcoming cosmological parameter analysis of these
datasets.
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All authors N. Emas, A. Porredon, C. Blake, J. DeRose, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. Cuceu, A. de la Macorra, A. Dey, B. Dey, P. Doel, S. Ferraro, J. E. Forero-Romero, C. Garcia-Quintero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, S. Heydenreich, K. Honscheid, D. Huterer, M. Ishak, S. Joudaki, R. Joyce, E. Jullo, S. Juneau, R. Kehoe, D. Kirkby, T. Kisner, A. Kremin, A. Krolewski, O. Lahav, M. Landriau, J. U. Lange, L. Le Guillou, A. Leauthaud, M. Manera, R. Miquel, S. Nadathur, W. J. Percival, F. Prada, G. Rossi, R. Ruggeri, E. Sanchez, C. Saulder, A. Semenaite, H. Seo, J. Silber, D. Sprayberry, Z. Sun, G. Tarlé, B. A. Weaver, R. H. Wechsler, R. Zhou
High Energy Astrophysical Phenomena
The Gamma-ray Luminosity Function of Flat-Spectrum Radio Quasars
Garima Rajguru, Lea Marcotulli, Marco Ajello et al. (+2 more)
We have utilized the largest sample of $\gamma$-ray selected
Fermi flat-spectrum
radio quasars (FSRQs) ever used (519 sources) to construct the luminosity function and its
evolution through the
cosmic history. In addition to spanning large
redshift ($0<z\lesssim 4$) and luminosity ranges ($2.9\times10^{43}$ erg s$^{-1}$ - $7.3\times10^{48}$ erg s$^{-1}$), this sample also has a robust calculation of the detection efficiency associated with its observation, making its selection effects and biases well understood. We confirm that the local luminosity function is best explained by a double power law. The
evolution of the luminosity function of FSRQs follows a luminosity-dependent density
evolution. FSRQs experience positive
evolution with their space density growing with increasing
redshift up to a maximum
redshift, after which the numbers decrease. This peak in
redshift occurs at larger
redshifts for higher luminosity sources and at lower
redshifts for lower luminosity sources. We find an unexpected similarity between the luminosity function of FSRQs and that of BL Lacertae objects at intermediate luminosity. This could be a sign of a strong genetic link between the two blazar sub-classes or that BL Lac samples are contaminated by large amounts of FSRQs with their jets nearly perfectly aligned with our line of sight.
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All authors Garima Rajguru, Lea Marcotulli, Marco Ajello, Mattia Di Mauro, Meg Urry
Solar and Stellar Astrophysics
Empirical Optimization of the Source-Surface Height in the PFSS extrapolation
Munehito Shoda, Kyogo Tokoro, Daikou Shiota et al. (+1 more)
The potential field source surface (PFSS) method is a widely used
magnetic field extrapolation technique in the space weather community. The only free parameter in the PFSS method is the source-surface height ($R_{\rm SS}$), beyond which all field lines are open. Although $R_{\rm SS}$ is known to vary with
solar activity, there is no consensus on how to determine it for a given surface
magnetic field distribution. In this study, we investigate the nature of $R_{\rm SS}$ using a long-period (2006-2023) data, covering two
solar minima and one maximum. We adopt ADAPT-GONG magnetograms and determine $R_{\rm SS}$ by matching the open flux estimated from observations at 1 au with that calculated using the PFSS method. Our analysis reveals that $R_{\rm SS}$ increases slightly after the
solar minima and around the
solar maximum, and that it can be characterized by both the mean unsigned photospheric
magnetic field strength and the dipolarity parameter $f_{\rm dip}$, defined as $f_{\rm dip} = B_{\rm dip}^2/(B_{\rm dip}^2 + B_{\rm quad}^2 + B_{\rm oct}^2)$, with $B_{\rm dip}$, $B_{\rm quad}$, and $B_{\rm oct}$ denoting the magnitudes of dipolar, quadrupolar, and octupolar components of photospheric radial
magnetic field, respectively. Our results suggest that $R_{\rm SS}$ does not exhibit a simple monotonic dependence on the
solar activity and must be determined by properly considering both surface
magnetic field strength and global field structure.
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All authors Munehito Shoda, Kyogo Tokoro, Daikou Shiota, Shinsuke Imada
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Beyond $\rho^{2/3}$ Scaling: Microscopic Origins and Multimessengers of High-Density Nuclear Symmetry Energy
Bao-An Li
Nuclear symmetry energy $E_{\mathrm{sym}}(\rho)$ encoding the cost to make
nuclear matter more
neutron rich has been the most uncertain component of the EOS of dense
neutron-rich nucleonic matter. It affects significantly the radii,
tidal deformations, cooling rates and frequencies of various oscillation modes of isolated
neutron stars as well as the strain amplitude and frequencies of gravitational waves from their mergers, besides its many effects on structures of
nuclei as well as the dynamics and observables of their collisions. Siemens (1970s) observed that $E_{\mathrm{sym}}(\rho)$ scales as $(\rho/\rho_0)^{2/3}$ near the saturation density $\rho_0$ of
nuclear matter, since both the kinetic part and the potential contribution (quadratic in momentum) exhibit this dependence. The scaling holds if: (1) the nucleon isoscalar potential is quadratic in momentum, and (2) the isovector interaction is weakly density dependent. After examining many empirical evidences and understanding theoretical findings in the literature we conclude that: (1) Siemens' $\rho^{2/3}$ scaling is robust and serves as a valuable
benchmark for both
nuclear theories and experiments up to $2\rho_0$ but breaks down at higher densities, (2) Experimental and theoretical findings about $E_{\mathrm{sym}}(\rho)$ up to $2\rho_0$ are broadly consistent, but uncertainties remain large for its
curvature $K_{\mathrm{sym}}$ and higher-order parameters, (3) Above $2\rho_0$, uncertainties grow due to poorly constrained
spin-isospin dependent tensor and three-body forces as well as the resulting nucleon short-range correlations. Looking forward, combining multimessengers from both observations of
neutron stars and terrestrial heavy-ion reaction experiments is the most promising path to finally constraining precisely the high-density $E_{\mathrm{sym}}(\rho)$ and the EOS of supradense
neutron-rich matter.
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Cosmology and Nongalactic Astrophysics
Everyone wants something better than $\Lambda$CDM
Michael S. Turner
The current cosmological paradigm, $\Lambda$CDM, is characterized its expansive description of the history of the Universe, its deep connections to particle physics and the large amounts of data that support it. Nonetheless, $\Lambda$CDM's critics argue that it has been falsified or must be discarded for various reasons. Critics and boosters alike do agree on one thing: it is the not the final cosmological theory and they are anxious to see it replaced by something better! I review the status of $\Lambda$CDM, provide my views of the path forward, and discuss the role that the “Hubble tension” might play.
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