Earth and Planetary Astrophysics
Systematic determination of dust properties for a sample of 133 spatially resolved debris discs
J. P. Marshall, S. Hengst, R. Young et al. (+6 more)
Determination of the composition and size distribution of
dust grains in debris discs is strongly dependent on constraining the underlying spatial distribution of that
dust through multi-wavelength, spatially resolved imaging spanning near-infrared to millimetre wavelengths. To date, spatially resolved imaging exists for well over a hundred debris disc systems. Simple analytical radiative transfer models of debris
dust emission can reveal trends in disc properties as a function of their host
stars' luminosities. Here we present such an analysis for 133 debris discs, calculating the
dust grain minimum sizes ($s_{\rm min}$),
dust masses ($M_{\rm dust}$), and exponents of the size distribution ($q$) in conjunction with their architectures determined at far-infrared or millimetre wavelengths. The distribution of $q$ at far-infrared to millimetre wavelengths is characterised for the first time, finding a value of $3.49^{+0.38}_{-0.33}$. We further newly identify a trend between $q$ and $R_{\rm disc}$, which may be indicative of velocity dependent fragmentation, or grain growth at large radii. We find the disc masses inferred from this analysis are consistent with those of protoplanetary discs. Finally, we identify samples of debris discs suitable for further characterisation at millimetre and centimetre wavelengths, expanding the number of spatially resolved systems upon which future studies of these statistics can be based.
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All authors J. P. Marshall, S. Hengst, R. Young, F. Kemper, L. Matrà, N. Pawellek, H. Kobayashi, P. Scicluna, S. T. Zeegers
Solar and Stellar Astrophysics
Two-stage primary acceleration in filament initial eruption under a fan-spine magnetic configuration
Haitang Li, Ke Yu, Chang Zhou et al. (+6 more)
Understaning the filament rising process is crucial for unveiling the triggering mechanisms of the coronal mass ejections and
forecasting the space weather. In this paper, we present a detailed study on the filament initial eruption under a fan-spine structure. It was found that the filament underwent two distinct acceleration stages corresponding to a calss M1.0 and M4.6
flare event, respectively. The first acceleration stage commenced with the filament splitting, after which the upper portion was subsequently heated being a hot channel and slow rose at an average speed of 22 km/s. A set of hot reverse C-shaped loops appeared repeatedly during the filament splitting and a hook structure was recognized at this phase, suggesting ongoing growth of the
magnetic flux rope (MFR). When it reached a certain altitude, the hot channel appeared to get into a quasi-static phase with its upper edge seriously decelerated and lower edge expanding downward. Approximately 30 minutes later, as a distinct annular ribbon appeared outside the hook structure, the hot channel rose again at a velocity over 50 km/s accompanied with rapid footpoints drifting, and experienced the second acceleration stage with its axial flux increased to 1.1 X 10^{21} Mx. It is deduced that the filament initial eruption under a
magnetic dome possess multi kinetic process. We suggest that the
magnetic reconnection taken place within and beneath the filament continues to trigger the growth of pre-eruptive MFR and the first acceleration, when the
magnetic reconnection above the filament plays a key role in the second acceleration.
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All authors Haitang Li, Ke Yu, Chang Zhou, Qiang Liu, Xin Cheng, Jinhan Guo, Feiyang Sha, Ye Qiu, Yu Liu
Astrophysics of Galaxies
Interstellar Medium in Extremely High Star-Formation Regions: A Prospect of Observations on the Millimetron Space Observatory
E.O. Vasiliev, S.A. Drozdov, P.V. Baklanov et al. (+5 more)
High
star-formation rate and active
galactic nucleus' emission can significantly transform the interstellar medium. In ultra-luminous infrared
galaxies, in which the
star-formation rate reaches thousands of
solar masses per year, the gas and
dust are considerably affected by the ionizing radiation,
cosmic rays and shock waves, that can be about a factor of 100–1000 larger than typical values in quiet
star-forming
galaxies. In these conditions, the emissivity of the gas and
dust changes: in dense gas, high ionic and molecular transitions become excited, while
dust grains are heated to high temperatures. In this paper, we analyze the possibilities for studying the interstellar medium in extreme conditions of ultra-luminous infrared
galaxies at
redshifts of $\sim 0-3$, utilizing the atomic and molecular lines, and
dust continuum in far infrared range of $100-500\mu$m. We discuss the prospect of observations using the instruments of the Millimetron Space Observatory.
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All authors E.O. Vasiliev, S.A. Drozdov, P.V. Baklanov, O.P. Vorobyov, S.Yu. Dedikov, M.S. Kirsanova, T.I. Larchenkova, N.N. Shakhvorostova
Astrophysics of Galaxies
Chemical complexity in star formation induced by stellar feedback: cores shock-formed by the supernova remnant W44
G. Cosentino, I. Jiménez-Serra, F. Fontani et al. (+8 more)
Low-velocity shocks from
Supernova Remnants (SNRs) may set the physical and chemical conditions of
star formation in molecular clouds. Recent evidence suggests that the Sun might have formed through this process. However, the chemical conditions of shock-induced
star forming region remain poorly constrained. We study the chemical complexity of a shock-impacted clump, with potential to yield
star formation, named the Clump, and located at the interface between the SNR W44 and the infrared dark cloud G034.77-00.55. We test whether the Clump has chemical properties consistent with those observed in
star forming regions unaffected by SNRs. We use high-sensitivity, broad spectral surveys at 3 and 7 mm obtained with the 30m
antenna at IIRAM and the 40 m YEBES
antenna, to identify D-bearing species and complex organic molecules (COMs) toward the Clump. For all species, we estimate molecular abundances and compare them with those observed across
star forming regions at different evolutionary stages and masses, as well as comets. We detect multiple deuterated molecules (DCO+, DNC, DCN, CH2DOH) and COMs (CH3OH, CH3CHO, CH3CCH, CH3CN, CH3SH) with excitation temperatures of 5-13 K. To the best of our knowledge, this is the first detection of COMs toward a site of SNR-cloud interaction. The derived D/H ratios (0.01-0.04) and COM abundances are consistent with those reported toward typical low-mass starless cores and comparable to cometary values. The overall level of chemical complexity is relatively low, in line with an early evolutionary stage. We suggest that the Clump is a early stage shock-induced low-mass
star forming region, not yet protostellar. We speculate that SNR shocks may set the physical and chemical conditions to form
stars. The resulting chemical budget may be preserved along the formation process of a planetary system, being finally incorporated into planetesimals and cometesimals.
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All authors G. Cosentino, I. Jiménez-Serra, F. Fontani, P. Gorai, C.-Y. Law, J. C. Tan, R. Fedriani, A. T. Barnes, P. Caselli, S. Viti, J. D. Henshaw
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Long-wavelength UV-LEDs and charge management in the detection of gravitational waves in space
Yuandong Jia, Yinbowen Zhang, Suwen Wang et al. (+8 more)
For the charge management system in gravitational wave detection missions, a continuous discharge strategy is considered by continuously illuminating a test mass (TM) with weak light in such a way to strike a balance between the charging and discharging rates and at the same time avoids the requirement for frequent activation of charge measurements. Built on experiments by one of us based on a simple parallel plate model for inertial sensor, in the present work a more sophisticated inertial sensor model that mimics the surface properties and work function of a cubical TM of an inertial sensor in space (like that of the LISA Pathfinder) is employed to study bipolar charge management system that utilizes UV-LEDs with peak wavelengths of 269 nm, 275 nm, 280 nm, and 295 nm that are longer than the standard 255 nm commonly employed for direct TM illumination. Experimental results indicate that the 275 nm UV-LED achieves optimal performance, maintaining the TM potential closer to zero and at the same time accommodates both rapid discharge and continuous discharge strategies. The present work provides useful input in the future study of system design and optimization for the charge management system.
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All authors Yuandong Jia, Yinbowen Zhang, Suwen Wang, Guozhi Chai, Zemin Zhang, Yi Zhang, Hongxin Li, Shuanglin Huang, Hongqing Huo, Zongfeng Li, Yun Kau Lau
Astrophysics of Galaxies
Relationship between Poincaré Sections and Spectral Characteristics of Orbits of Globular Clusters in the Central Region of the Galaxy
Anisa Bajkova, Anton Smirnov and Vadim Bobylev
In the paper, orbital dynamics, regular or chaotic, of globular clusters (GCs) in the central region of the
Galaxy, which is subject to the greatest influence of the rotating bar, has been studied. Such methods for determining chaos as Poincaré sections and spectral methods have been compared. The relationship between the Poincaré sections and the spectral characteristics of the orbits has been estimated. The sample includes 45 globular clusters in the central region of the
Galaxy with a radius of 3.5 kpc. To form the 6D-phase space required for integrating the orbits, the most accurate astrometric data to date from the
Gaia satellite, as well as new refined average distances, have been used. The following, most realistic, bar parameters have been adopted: mass $10^{10} M_\odot$, length of the major semi-axis of the bar model in the form of a triaxial ellipsoid is 5 kpc, angle of rotation of the bar axis is $25^o$, rotation velocity is 40 km s$^{-1}$ kpc $^{-1}$. The result of the study is that a 100% correlation between the classification by Poincaré sections and the spectral characteristics of the orbits has been established. Consequently, the classification by Poincaré sections can be replaced by a more visual analysis of the amplitude spectra of the orbits. Thus, two lists of GCs: with regular and chaotic dynamics have been compiled. The GCs with varying degrees of orbital chaos have separately been distinguish.
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High Energy Astrophysical Phenomena
Surface temperature of an accretion disk around a wormhole Kerr-mimicker
A. Karakonstantakis and W. Kluźniak
It has been suggested that spinning wormholes may mimic Kerr black holes in astronomical sources such as X-ray binaries and supermassive compact objects in centers of
galaxies. With recent advances in instrumentation this could be tested if clear differences between wormhole and black hole
accretion were identified. We aim to quantitatively determine the extent to which the orbital properties of test particles in the
gravity of a spinning wormhole may differ from those of a Kerr black hole. We seek to find an observable related to disk
accretion that would be clearly different for Kerr black holes and Kerr-like wormholes. We use the standard Lagrangian approach to derive the orbital properties of test particles from an effective potential. We use standard thin disk theory to infer the disk surface temperature. We find that at a given circumferential radius the physical quantities relating to circular orbits in the equatorial plane are exactly the same for the spinning wormhole and a black hole of the same mass and angular momentum, if only the two space-time metrics differ in the g_rr component alone. However, for a wormhole there are no orbits of radius less than that of its throat. Non-circular orbits, bound or unbound, are affected by the radial distance function; in particular, the angle of apsidal precession in Kerr-like wormholes will differ from that in Kerr black holes. A Kerr-like wormhole is a perfect black hole mimicker in relation to the orbital properties in the equatorial plane. The angular velocity, specific energy, specific angular momentum, and Lense-Thirring precession rate are the same for a Kerr black hole and a Kerr-like wormhole in circular orbits of the same circumference. We find that the area of the (geometrically thin)
accretion disk is different, and this yields a visibly suppressed disk temperature for traversable wormholes with a sufficiently wide throat.
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Solar and Stellar Astrophysics
The influence of Parker spiral on the reflection-driven turbulence
Khurram Abbas and Jonathan Squire
The
solar wind is observed to undergo substantial heating as it expands through the heliosphere, with measured temperature profiles exceeding those expected from adiabatic cooling. A plausible source of this heating is reflection-driven
turbulence (RDT), in which gradients in the background Alfvén speed partially reflect outward-propagating Alfvén waves, seeding counter-propagating fluctuations that interact and dissipate via
turbulence. Previous RDT models assume a radial background
magnetic field, but at larger radii the interplanetary field is known to be twisted into the Parker Spiral (PS). Here, we generalize RDT phenomenology to include a PS, using three-dimensional expanding-box magnetohydrodynamic (MHD) simulations to test the ideas and compare the resulting
turbulence to the radial-background-field case. We argue that the underlying RDT dynamics remain broadly similar with a PS, but the controlling scales change: as the azimuthal field grows it "cuts across" perpendicularly stretched, pancake-like eddies, producing outer scales perpendicular to the
magnetic field that are much smaller than in the radial-background case. Consequently, the outer-scale nonlinear turnover time increases more slowly with heliocentric distance in PS geometry, weakening the tendency (seen in radial-background models) for the cascade to 'freeze' into quasi-static, magnetically dominated structures. This allows the system to dissipate a larger fraction of the fluctuation energy as heat, also implying that the
turbulence remains strongly imbalanced (with high normalized cross-helicity) out to larger heliocentric distances. We complement our heating results with a detailed characterization of the
turbulence (e.g., spectra, switchbacks, and compressive fractions) providing a set of concrete predictions for comparison with spacecraft observations.
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Cosmology and Nongalactic Astrophysics
Prospects for an independent measurement of $\boldsymbol{\ell}$=1,2,3 CMB anisotropy multipoles using the anisotropic Sunyaev-Zel'dovich effect
D.I. Novikov, T.I. Larchenkova, A.O. Mihalchenko et al. (+3 more)
We investigate the prospects for observing a specific spectral distortion of the
cosmic microwave background, which occurs due to the anisotropy of the radiation when it is scattered by hot
plasma of
galaxy clusters. Detection of this anisotropic Sunyaev-Zel'dovich effect would enable an independent measurement of the CMB anisotropy multipoles with $\ell = 1, 2, 3$, allow the Sachs-Wolfe and integrated Sachs-Wolfe (Rees-Sciama) effects to be separated, and partially solve the
cosmic variance problem for low multipoles. We applied the Least Response Method for component separation in the data processing and estimated the required sensitivity of the experiment for such observations. We test our approach on a simulated signal that is contaminated by various foregrounds with poorly defined spectral shapes, along with distortions of the relic blackbody spectrum caused by the Sunyaev-Zel'dovich effect and its relativistic corrections.
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All authors D.I. Novikov, T.I. Larchenkova, A.O. Mihalchenko, A.M. Osipova, K.O. Parfenov, S.V. Pilipenko
Solar and Stellar Astrophysics
Revisiting the Evolutionary Status of Massive Stars at the central parsec of the Milky Way
A.C. Gormaz-Matamala, J. Cuadra, B. Kubátová et al. (+2 more)
Massive
stars and their winds have a large influence in their environment, e.g, determining the
accretion rate on to the
Galactic Centre (GC) super-massive black hole Sgr A*. The winds of those
stars collide and are accreted, at a rate that depends on their chemical composition. Here we aim to revisit the evolutionary status of the evolved massive
stars at the GC, by means of new tracks based on updated mass-loss rate recipes for the earlier stages of massive
stars. We use the Geneva-
evolution-code for initial
stellar masses ranging from 20 to 60 $M_\odot$, for
metallicity $Z=0.020$. We adopt a new mass-loss rate recipe for the line-driven winds of O-type
stars and B-supergiants, plus a new recipe for the
dust-driven winds of red supergiants (RSG). Additionally, we set up initial rotation $\Omega/\Omega_\text{crit}=0.4$, and we adopt the Ledoux criterion for the treatment of convection in inner layers. We found that
evolution models adopting new mass-loss rate prescriptions predict that
stars will lose less of their outer layers during their initial phases, while a big reduction of mass happens at the RSG phase. As a consequence, the resulting Wolf-Rayet (WR)
stars are less radially homogeneous in their inner structure from the core to the surface. Also, these new
evolution models predict the absence of hydrogen-free WN
stars. These evolutionary predictions agree better with the observed chemical abundances of the WR
stars at the GC. We provide a table with the chemical H, He, and CNO abundances calculated for the different subtypes of WR
stars. We propose a different re-arrangement of the WR subtypes to be used for the modelling of the collision of their winds. We discuss the potential implications of these changes for the colliding winds generated from the massive
stars at the GC, which are accreting onto the supermassive black hole Sgr A*.
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All authors A.C. Gormaz-Matamala, J. Cuadra, B. Kubátová, J. Kubát, S. Ekström
Cosmology and Nongalactic Astrophysics
Phase-space perturbation theory for cosmic large-scale structure
Hannes Heisler, Marvin Sipp and Matthias Bartelmann
We consider a perturbative approach to the Vlasov-Poisson system for
cosmic structure formation that does not rely on any truncation of the momentum-cumulant hierarchy. The generally non-trivial linear solution is computed by solving a Volterra-type integral equation and higher orders are obtained recursively. As expected, the results of Eulerian standard perturbation theory are recovered for perfectly cold initial conditions. Deviating slightly from the latter by introducing a homogeneous and isotropic initial velocity dispersion, we show that all higher momentum cumulants are generated dynamically at any perturbative order. We support our numerical solutions by an analytical large-scale approximation. Our approach serves as a basis for exploring different background-perturbation splits of the phase-space density and non-perturbative techniques.
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Solar and Stellar Astrophysics
BSN: Light Curve Modeling and Orbital Evolution of the Total-Eclipse Contact Binary EZ Oct
Asma Ababafi, Atila Poro, Mehmet Tanriver et al. (+1 more)
We present the first detailed multiband (BVR_cI_c and TESS) photometric analysis of the short-period binary EZ Oct. This study combines ground-based observations conducted at a Southern Hemisphere observatory in Argentina with data from the TESS mission. Investigating the orbital period variations of EZ Oct reveals a steadily increasing period consistent with a quadratic trend. We present a new ephemeris and estimate the mass transfer rate as \dot{M}=1.353*10^{-8} M_{\odot}/year, indicating ongoing conservative mass transfer from the less massive to the more massive
star. Light curve modeling was performed using the PHOEBE Python code in conjunction with the MCMC approach, and the inclusion of a cold starspot was required to achieve an adequate fit. Absolute parameters were estimated using
Gaia DR3 parallax and astrophysical equations. Our analysis shows that EZ Oct is a total-eclipse contact binary with a mass ratio of 1.969, a fillout factor of 0.106, and an inclination of 82.13deg. Based on the
stellar masses and temperatures of the components, the target system belongs to the W-subtype of contact binaries. The positions of the component
stars were displayed on the mass-luminosity and mass-radius diagrams to illustrate their evolutionary status. Moreover, we investigated the relationship between orbital period and
stellar luminosity in contact binary
stars using a sample of 461 systems with P<0.5 days. We highlight the position of EZ Oct in the mass ratio-inclination parameter space, showing that it lies within the densely populated region of contact binaries.
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All authors Asma Ababafi, Atila Poro, Mehmet Tanriver, Eduardo Fernández Lajús
Instrumentation and Methods for Astrophysics
Limits on Unintended Radio Emission from Geostationary and Geosynchronous Satellites in the SKA-Low Frequency Range
S. J. Tingay, N. Hurley-Walker, K. Ross et al. (+3 more)
We search data from the GLEAM-X survey, obtained with the Murchison Widefield Array (MWA) in 2020, for the presence of
radio frequency interference from distant Earth-orbiting satellites, in the form of unintended emissions similar to those recently seen from objects in Low Earth Orbits (LEO). Using the GLEAM-X Dec = 1.6 degree pointing, which is stationary in azimuth (on the local Meridian) and elevation (near the celestial Equator), the very wide field of view of the MWA maintains custody of a large number of satellites in geostationary and geosynchronous (GEO) orbits in this direction for long periods of time. We use one night of GLEAM-X data in the 72 - 231 MHz frequency range to form stacked images at the predicted coordinates of up to 162 such satellites, in order to search for unintended
radio emission. In the majority of cases, we reach 4 sigma upper limits of better than 1 mW Equivalent Isotropic Radiated Power (EIRP) in a 30.72 MHz bandwidth (dual polarisation), with the best limits below 10 uW. No convincing evidence for unintended emissions at these detection thresholds was found. This study builds on recent work showing an increasing prevalence of unintended emissions from satellites in LEO. Any such emission from objects in GEO could be a significant contributor to
radio frequency interference experienced by the low frequency Square Kilometre Array and warrants monitoring. The current study forms a baseline for comparisons to future monitoring.
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All authors S. J. Tingay, N. Hurley-Walker, K. Ross, T. J. Galvin, J. Morgan, B. Venville
Astrophysics of Galaxies
Generating LSB-optimised synthetic images for simulated galaxies
Maarten Baes, Peter Camps, Andrea Gebek et al. (+3 more)
We introduce an emission-biasing scheme in the SKIRT radiative transfer code that enables efficient generation of synthetic
galaxy images optimized for low-surface-brightness (LSB) science. Standard Monte Carlo radiative transfer simulations achieve high signal-to-noise in bright regions but require prohibitively many
photon packets to reach reliable depth in
galaxy outskirts. By assigning
stellar particles bias factors that scale with their smoothing lengths, our method boosts
photon emission from low-density regions while conserving energy through weight corrections. Tests on a Milky-Way-like
galaxy from the TNG50 cosmological simulation show that bias factors proportional to the smoothing length substantially extend the reliable LSB regime, providing an inexpensive improvement for deep synthetic imaging of simulated
galaxies.
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All authors Maarten Baes, Peter Camps, Andrea Gebek, Arno Lauwers, Joop Schaye, Paul Vauterin
Earth and Planetary Astrophysics
SPHEREx Pre-Perihelion Mapping of $\mathrm{H_2O}$, $\mathrm{CO_2}$, and $\mathrm{CO}$ in Interstellar Object 3I/ATLAS
Carey M. Lisse, Yoonsoo P. Bach, Brendan P. Crill et al. (+35 more)
From 01- to 15-Aug-2025UT, the SPHEREx spacecraft observed interstellar object 3I/ATLAS. Using $R=40-130$ spectrophotometry at $\lambda=0.7-5$ $\mu$m, light curves, spectra, and imaging of ATLAS were obtained. From these, robust detections of water gas emission at $2.7-2.8$ $\mu$m and $CO_2$ gas at $4.23-4.27$ $\mu$m plus tentative detections of $^{13}CO_2$ and $CO$ gas were found. A slightly extended $H_2O$ coma was detected, and a huge $CO_2$ atmosphere of extending out to at least $4.2 \times 10^{5}$ km was discovered. Gas production rates and 1$\sigma$ errors for $H_2O$, $^{12}CO_2$, $^{13}CO_2$, and $CO$ were $Q_{gas} = 3.2 \times 10^{26} \pm 20\%$, $1.6 \times 10^{27} \pm 10\%$, $1.3 \times 10^{25} \pm 25\%$, and $1.0 \times 10^{26} \pm 25\%$, respectively. Co-addition of all $\lambda = 1.0-1.5$ $\mu$m scattered light continuum images from produced a high SNR image consistent with an unresolved source. The scattered light lightcurve showed $\lesssim 15\%$ variability over the observation period. The absolute brightness of ATLAS at $1.0-1.5$ $\mu$m is consistent with a $< 2.5$ km radius
nucleus surrounded by a 100 times brighter coma. The $1.5-4.0$ $\mu$m continuum structure shows a strong feature commensurate with water ice absorption seen in KBOs and distant comets. The observed cometary behavior of ATLAS, including its preponderance of $CO_2$ emission, lack of $CO$ output, small size, and predominance of large icy chunks of material in a flux-dominant coma is similar to the behavior of short period comet 103P/Hartley 2, the ”hyperactive comet” flyby target of the NASA Deep Impact extended mission in 2010. This correspondence suggests that ISOs can be significantly thermally processed before ejection into the ISM, and by comparison to 1I and 2I, can be widely variable in their physical outcome.
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All authors Carey M. Lisse, Yoonsoo P. Bach, Brendan P. Crill, Phil M. Korngut, Ari J. Cukierman, Sean A. Bryan, Asantha Cooray, C. Darren Dowell, Michael W. Werner, Joseph L. Hora, Zafar Rustamkulov, Jeong-Eun Lee, Bumhoo Lim, Y. R. Fernandez, Volker Tolls, W. T. Reach, O. Doré, Michael Zemcov, James J. Bock, Yun-Ting Cheng, C. Champagne, Seungwon Choi, M. Connelley, J. P. Emery, Spencer Everett, Andreas L. Faisst, Jooyeon Geem, Howard Hui, Masateru Ishiguro, Sunho Jin, Hangbin Jo, Max Mahlke, Daniel C. Masters, Gary J. Melnick, Chi H. Nguyen, Roberta Paladini, M. L. Sitko, Yujin Yang
Instrumentation and Methods for Astrophysics
Back-End System of BURSTT
Kai-Yang Lin, Chih-Yi Wen, Homin Jiang et al. (+7 more)
The Bustling Universe
Radio Survey
Telescope in Taiwan (BURSTT) is a new-generation wide-angle
radio telescope specifically designed to survey Fast
Radio Bursts (FRBs), energetic millisecond-duration pulses of unknown extragalactic origin. To realize its scientific potential, which includes detecting approximately 50 FRBs per year and sub-arcsecond localization capability, the system is designed to perform real-time beamforming and pulse search over the \SI{60}{\degree} $\times$ \SI{120}{\degree} field of view. This paper provides a detailed account of the design, implementation, and performance validation of the BURSTT back-end System. The system employs an efficient multi-stage processing architecture: initial beamforming is executed on the Xilinx ZCU216 RF System-on-Chip (RFSoC) platform; data is then transferred to Intel Xeon servers, where AVX-512 and AMX instruction sets are utilized for the second stage of beamforming and channelization, achieving high computational efficiency to ensure real-time capability. A highly optimized bonsai de-dispersion
algorithm performs a real-time pulse search and triggering across 256 beams, which, upon detection, issues commands to the distributed outrigger system to save voltage data for very-long baseline interferometry (VLBI) precise localization. System performance has been validated through beamforming tests using bright
radio sources and real-time detection of known
pulsars, confirming the high fidelity of the signal processing pipeline.
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All authors Kai-Yang Lin, Chih-Yi Wen, Homin Jiang, Jen-Hung Wang, Sujin Eie, Shih-Hao Wang, Yao-Huan Tseng, Hsien-Chun Tseng, Daniel Baker, Ue-Li Pen
Cosmology and Nongalactic Astrophysics
Squeezed Limit non-Gaussianity Estimation with Cosmic Shear
Shi-Hui Zang and Moritz Münchmeyer
We present a new method to constrain local
primordial non-Gaussianity using the large-scale modulation of the local
lensing power spectrum. Our work extends our recently proposed $\pi$-field method for
primordial non-Gaussianity estimation to spherical coordinates and applies it to
galaxy lensing. Our approach is computationally efficient and only requires binned multipole power spectra $C_\ell(z_1,z_2)$ on large scales, as well as their covariance. Our method is simpler to implement than a full bispectrum
estimator, but still contains the full squeezed-limit information. We validate our model using a suite of N-body simulations and demonstrate its accuracy in recovering the $f_{\mathrm{NL}}$ values. We then perform a Fisher forecast for an LSST-like weak
lensing survey, finding $\sigma_{f_{\mathrm{NL}}} \simeq 44$. Our approach readily combines with other $f_{\mathrm{NL}}$-sensitive fields such as kSZ velocity reconstruction and clustering-based $\pi$-fields, for a future combined $f_{\mathrm{NL}}$
estimator using various large-scale
galaxy and CMB observables.
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High Energy Astrophysical Phenomena
Revisiting PBH accretion, evaporation and their cosmological consequences
Jitumani Kalita and Debaprasad Maity
Primordial black holes (PBHs) provide a unique probe of the early Universe. Their cosmological
evolution is governed by the competition between mass
accretion and Hawking evaporation. In this paper we look into the details impact of
accretion. Most of the earlier analysis relied on non-relativistic
accretion models. In this work, we reinvestigate this in a fully relativistic framework for Kerr PBHs in the radiation-dominated era. We derive relativistic
accretion rate and compute
spin-dependent efficiency $\lambda_{\text{Kerr}}(a_*)$. Using this result, we construct coupled
evolution equations for the PBH mass and
spin that include both relativistic
accretion and
spin-dependent evaporation. Our analysis shows that relativistic
accretion significantly increases PBH masses and consequently suppresses their
spins, causing all PBHs to become effectively Schwarzschild well before evaporation. These effects strengthen the Big Bang Nucleosynthesis (BBN) bound on the initial PBH mass by a factor of $\sim 4$–$5$, reduce the mass required for survival to the present epoch to $\sim 2.7\times 10^{14}\,\mathrm{g}$, and shift the viable particle like DM parameter space. Notably the early
accretion induced
spin-down effect further washes out the well known high-frequency,
spin-induced feature in the high frequency
stochastic gravitational-wave background, modifying predictions for future detectors.
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High Energy Astrophysical Phenomena
Chao-Ming Li, Ruo-Yu Liu and Huirong Yan
Interstellar
magnetic field is essential in various astrophysical phenomena and processes.
Pulsar halos are a recently discovered class of TeV gamma-ray sources formed by escaping electrons/positrons from
pulsars. The morphology of the
halo is regulated by the
diffusion of those escaping particles, and hence carries information of the interstellar
magnetic field. We suggest that the morphology of TeV
pulsar halos can be used as a novel probe of the properties of interstellar
magnetic field around the
pulsar, such as the Alfvénic Mach number and the mean direction. We establish a theoretical relation between these quantities and the observational features of the
halo's morphology based on the anisotropic
diffusion model, and show how X-ray observations of the
pulsar halos can further improve the diagnosis of the
magnetic field.
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Solar and Stellar Astrophysics
Small EUV Brightenings in the Quiet Solar Atmosphere: New Insights from the Solar Orbiter Mission
Susanna Parenti
One of the many outcomes of the
Solar Orbiter mission is the evidence for the
solar atmosphere being filled by highly impulsive bursts, down to about 200 km scale: the limit of the EUV instruments' spatial resolution. Small-scale events of this kind were already known, but their observation was occasional or with limited, lower resolution.
Solar Orbiter has revealed that small scale, highly impulsive events are everywhere on the quiet Sun, all the time, at even smaller scales. Their similarity with known larger features, are the witnesses that the physical processes causing them are independent of the spatial scales involved. Their highly dynamic property is the signature of energy transfer and/or local dissipation. Their investigation can thus elucidate on the dominant physical processes acting on the
solar atmosphere and on the possible role in the origin of the hot
solar corona. In this review, we will present a summary of the observational and simulation results on this topic, led by the results from data taken by the Extreme Ultraviolet Imager (EUI)/High Resolution Imagers (HRIEUV) instrument. Here, we will cover both statistical properties and analyses of individual events.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Evaporation of Primordial Black Holes in a Thermal Universe: A Thermofield Dynamics Approach
Ayan Chatterjee, Jitumani Kalita and Debaprasad Maity
We investigate the impact of a finite temperature environment on the Hawking radiation from black holes (BHs), with particular focus on Kerr BHs immersed in a cosmological thermal bath. The emitted particles from BHs interact with the thermal background and thermalize, leading to a modification in the Hawking radiation spectrum. By employing the methods of Thermofield Dynamics (TFD), a real time formalism of thermal
quantum field theory, we derive the modified occupation numbers of the Hawking spectrum for asymptotically flat spacetimes like the Schwarzschild and the Kerr geometries. These corrections depend on the interplay between the BH temperature and the ambient bath temperature. We apply this formalism in the early universe reheating background scenario arising after inflation and demonstrate that the thermal correction to Hawking spectrum enhances the evaporation rate of
primordial black holes (PBHs). As a result, the lifetime of PBH shortens compared to the zero temperature
vacuum and leads to interesting cosmological consequences.
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Cosmology and Nongalactic Astrophysics
Dynamical Dark Energy and the Unresolved Hubble Tension: Multi-model Constraints from DESI 2025 and Other Probes
Zhuoming Zhang, Tengpeng Xu and Yun Chen
We present a
Bayesian comparative analysis of five cosmological models: $\Lambda$CDM, $w$CDM, $w_0w_a$CDM, $\phi$CDM (with scalar-field dark energy), and an interacting dark energy scenario (the $\xi$-index model), to investigate dark energy
evolution and the Hubble tension. Utilizing the latest data from the Dark Energy Spectroscopic Instrument (DESI) DR2 (
Baryon Acoustic Oscillations, BAO), Pantheon+ (Type Ia
Supernovae, SNIa), and
Cosmic Microwave Background (CMB) data (including
lensing) from Planck and the Atacama Cosmology
Telescope (ACT), we report three key findings. First, the Hubble constant ($H_0$) inferred from the combined data consistently aligns with early-universe measurements across all models, indicating a persistent Hubble tension. Second, we find compelling evidence for dynamical dark energy: early-universe (CMB) constraints favor a phantom phase (with an equation-of-state parameter $w < -1$), while late-universe (BAO/SNIa) data prefer quintessence ($w > -1$). Third, the full
dataset suggests a late-time interaction between dark energy and matter. Our results demonstrate that dark energy evolves with
cosmic time, challenging the cosmological constant paradigm.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Black Holes as Catalysts for Cosmic String Detection and Axion Dark Matter Genesis
Ishan Swamy and Deobrat Singh
The global $U_{PQ}(1)$ Peccei-Quinn (PQ)
symmetry, proposed to resolve the strong CP problem, predicts the existence of the
axion, a pseudo Nambu-Goldstone
boson and a leading dark matter candidate. The spontaneous breaking of this
symmetry generates global strings that decay predominantly via the emission of massive
axions and gravitational waves. In this work, we investigate the decay of
cosmic axion strings in the vicinity of a Schwarzschild black hole and estimate the corresponding energy losses and decay timescales of the resulting string loops. For
primordial black holes (PBHs) with masses as small as $10^{-16} M_\odot$, the total radiated energy by the string is found to be on the order of $10^{27}$ GeV, encompassing both
axion emission and gravitational waves. A key finding is that the presence of a central black hole significantly accelerates the decay of
cosmic string loops, substantially reducing their lifetimes. We present these results as an initial estimate of
axion radiation from PBH-
cosmic string systems along with the decay time as an important observational signature for
axions strings.
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High Energy Astrophysical Phenomena
Interplay between Escaping Cosmic Rays and Interstellar Medium: Driving of Galactic Winds and Shaping the Local Proton Spectrum
Jiro Shimoda, Katsuaki Asano and Shu-ichiro Inutsuka
We study the effects of escaping
cosmic rays (CRs) on the interstellar medium (ISM) around their source with spherically symmetric CR-hydrodynamical simulations taking into account the
evolution of the CR energy spectrum, radiative cooling, and thermal conduction. We show how the escaping CRs accelerate and heat the ISM depending on the CR
diffusion coefficient. The CR heating effects are potentially responsible for the recent observations of the unexpected H$\alpha$ and [OIII]$\lambda5007$ lines in old
supernova remnants. The implied gas
outflow rate by CRs can be comparable to the
Galactic star formation rate, compatible with the
Galactic wind required for polluting the
halo gas with metals. Assuming a locally suppressed CR
diffusion and a few nearby CR sources in the Local Bubble, we also propose alternative interpretations for the
Galactic CR
proton spectrum around the Earth measured with CALET, AMS02, and Voyager 1.
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Cosmology and Nongalactic Astrophysics
Counting voids and filaments: Betti Curves as a Topological Probe for Cosmology
Jiayi Li and Cheng Zhao
Topological analysis of
galaxy distributions has gathered increasing
attention in cosmology, as they are able to capture non-Gaussian features of large-scale structures (LSS) that are overlooked by conventional two-point clustering statistics. We utilize Betti curves, a summary statistic derived from persistent homology, to characterize the multiscale topological features of the LSS, including connected components, loops, and voids, as a complementary cosmological probe. Using
halo catalogs from the Quijote suite, we construct Betti curves, assess their sensitivity to cosmological parameters, and train automated machine learning based emulators to model their dependence on cosmological parameters. Our
Bayesian inference recovers unbiased estimation of cosmological parameters, notably $n_{\mathrm{s}}$, $\sigma_8$, and $\Omega_{\mathrm{m}}$, while validation on sub-box simulations confirms robustness against
cosmic variance. We further investigate the impact of
redshift-space distortions (RSD) on Betti curves and demonstrate that including RSD enhances sensitivity to growth-related parameters. By jointly analyzing Betti curves and the power spectrum, we achieve significantly tightened constraints than using power spectrum alone on parameters such as $n_{\mathrm{s}}$, $\sigma_8$, and $w$. These findings highlight Betti curves – especially when combined with traditional two-point statistics – as a promising, interpretable tool for future
galaxy survey analyses.
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Cosmology and Nongalactic Astrophysics
Inference of $B$-mode polarization in the presence of non-Gaussian foregrounds
Sen Li, Chang Feng and Filipe B. Abdalla
The inflationary $B$-mode signals encode invaluable information about the origin of our Universe and searching for potential signatures of
primordial gravitational waves (PGWs) is one of the major science goals for future precision observations of
cosmic microwave background (CMB) polarization. However, dominant $B$-mode signals of both
Galactic foreground contamination and gravitational
lensing effects prevent direct measurements of the PGW $B$-mode signals. There are existing proposals which can effectively eliminate these two contaminants but issues remain for future high-sensitivity and multifrequency CMB polarization observations, such as spatially-varying spectral energy distribution (SED) of polarized foreground and cosmological $B$-mode signals due to
primordial magnetic fields (PMFs). In this work, we investigate inference of PGW $B$-mode signals in the presence of both complexities. We employ a constrained moment internal linear combination (cMILC) method to remove polarization signals arising from spatially varying SEDs. Also, we employ a power-spectrum-based approach to extracting both the
Galactic and cosmological $B$-mode components. Two methods have been validated by mock data and different consistency tests have been performed. We apply these two methods to end-to-end simulations for future high-sensitivity and multifrequency polarization observations and investigate the detectability of different $B$-mode signals in the presence of non-Gaussian polarized foregrounds under different scenarios. This study will be important for new physics studies with $B$-mode signatures.
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High Energy Astrophysical Phenomena
EP241217a: a likely Type II GRB with an achromatic bump at z = 4.59
Hao Zhou, Jia Ren, Chen-Wei Wang et al. (+22 more)
EP241217a is an X-ray transient detected by the Einstein Probe (EP) lasting for about 100 seconds and without accompanying $\gamma$-ray detection. The optical spectroscopy reveals the
redshift of EP241217a is 4.59. By combining the $\gamma$-ray upper limit provided by GECAM-C, there is a considerable possibility that EP241217a is a typical Type II gamma-ray burst (GRB), but it is fainter than the detection threshold of any available $\gamma$-ray monitors (i.e., $E_{\gamma,{\rm iso}}\lesssim10^{53}$ erg). The X-ray light curve exhibits a plateau lasting for $\sim5\times10^4$ seconds. However, the joint analysis with optical data suggests the presence of an achromatic bump peaking at $\sim3\times10^4$ s after the trigger, indicating the actual duration of the X-ray plateau may be significantly shorter than it appears. To interpret the achromatic bump, we adopt the scenario of a mildly relativistic jet coasting in a wind-like medium and encountering a rapid density enhancement of the circumburst medium, which is likely induced by the the interaction of the progenitor's
stellar wind and the interstellar medium. However, this model cannot fully explain observed data, and some issues do exist, e.g., the observed spectrum is harder than the model prediction. Consequently, we conclude that the scenario of a mildly relativistic jet coasting in the wind-like medium cannot explain all observed features of EP241217a. In addition, some alternative models commonly invoked to explain X-ray plateaus are discussed, but there are more or less issues when they are applied to EP241217a. Therefore, further theoretical modeling is encouraged to explore the origin of EP241217a.
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All authors Hao Zhou, Jia Ren, Chen-Wei Wang, Xing Liu, Bin-Yang Liu, Andrew J. Levan, Jillian Rastinejad, Jin-Jun Geng, Hao Wang, Peter K. Blanchard, Wen-fai Fong, Benjamin Gompertz, Daniele B. Malesani, Charles D. Kilpatrick, Gavin P. Lamb, Brian D. Metzger, Matt Nicholl, Nial R. Tanvir, Yun Wang, Yu Rong, Run-Duo Liang, Zhi-Xing Ling, Dong Xu, Zhi-Ping Jin, Da-Ming Wei
Astrophysics of Galaxies
FEASTS Compared with Simulations: Abnormally Irregular and Extended HI Morphologies at a Column Density of $10^{18}\,\text{cm}^{-2}$ in TNG50 and Auriga
Xuchen Lin, Jing Wang, Guinevere Kauffmann et al. (+2 more)
With new atomic-hydrogen (HI) observations of FAST Extended Atlas of Selected Targets Survey (FEASTS), we present the first statistical comparison of HI morphology between observations and cosmological simulations, focusing on low-column density ($10^{18}\,\text{cm}^{-2}$) regions of Milky Way-like central
galaxies. We select a 330-
galaxy sample from IllustrisTNG50 (TNG50) matched to 33 FEASTS
galaxies by
stellar and HI masses, and mock observe them to the FAST resolution and depth at corresponding inclinations and distances for a fair comparison. In contrast to FEASTS, abnormally irregular and extended morphology is found in more than one-third of TNG50
galaxies, especially those massive and HI poor.
Stellar feedback is the property that most significantly correlates with the HI morphological deviation from observations, although these deviations mostly occur at a high
stellar or black-hole mass. These results indicate that in TNG50,
stellar feedback significantly influences the HI morphology at $10^{18}\,\text{cm}^{-2}$, while active
galactic nucleus (AGN) feedback has not so direct a role as expected. With an additional sample from Auriga, we find that the
magnetic field may help HI to be more regular in its morphology, while improving the mass resolution does not alleviate the discrepancy from observation. This study reveals the potential of constraining future simulations of
galaxies by observing low-column density HI.
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All authors Xuchen Lin, Jing Wang, Guinevere Kauffmann, Volker Springel, Rüdiger Pakmor
High Energy Astrophysical Phenomena
Simulation Study of Binary Mergers of Galaxy Clusters I: Properties of Merger Shocks and Radio Emission
Hyesung Kang, Dongsu Ryu and Jeongbhin Seo
We investigate binary mergers of
galaxy clusters, the formation of shocks, and the resulting
radio relics using three-dimensional simulations. The initial setup consists of two idealized spherical subclusters with a mass ratio below three, each permeated by turbulent
magnetic fields, and we follow their merger with a high-order accurate magnetohydrodynamic (MHD) code. In parallel, we track the acceleration of
cosmic-ray electrons (CRe) via diffusive shock acceleration (DSA) at merger-driven shocks, together with radiative cooling and
Fermi-II (turbulent) acceleration in the postshock region, employing a newly developed Eulerian Fokker-Planck solver. Synchrotron emission is computed from the simulated CRe distribution and
magnetic fields. In this paper, we detail these numerical approaches and present the first results obtained with them. Two prominent axial shocks emerge along the merger axis; the shock ahead of the heavier subcluster systematically attains a higher Mach number, although it is more compact, than that ahead of the lighter subcluster. Turbulent
magnetic fields, which are both inherited from the initial conditions and amplified during the merger, produce patchy, fine-scale structures in the
radio surface brightness. Because of the combined effects of turbulent acceleration, spatially nonuniform
magnetic fields, and the curved geometry of merger shocks, the volume-integrated
radio spectra show deviations from the canonical power-law steepening expected for a planar shock with a uniform field. Reacceleration of preexisting fossil CRe enhances the surface brightness. Our results highlight the coupled roles of merger dynamics, MHD
turbulence, and CRe physics in shaping the observed properties of
radio relics in cluster outskirts.
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Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn
Shock trapping and inertial escape: Dust-particle clustering in compressible turbulence
Anikat Kankaria and Samriddhi Sankar Ray
We study the dynamics and clustering of
dust particles with inertia in shock-dominated compressible
turbulence using the two-dimensional, stochastically forced Burgers equation. At small Stokes numbers, shock trapping leads to extreme density inhomogeneities and nearly singular aggregation, with correlation dimensions approaching zero. With increasing inertia, particles undergo inertial escape and intermittently cross shock fronts, producing a sharp crossover from shock-dominated trapping to quasi-ballistic dynamics. This crossover is accompanied by a pronounced reduction in density fluctuations, a continuous increase of the correlation dimension from zero to the
embedding dimension, and a power-law dependence of density fluctuations on the Stokes number over an extended intermediate regime. In this regime, particle distributions show scale-free coarse-grained density statistics arising from repeated trap–escape dynamics. This behaviour is qualitatively distinct from inertial-particle clustering in incompressible
turbulence and is directly relevant to
dust concentration in shock-rich regions of protoplanetary discs and other compressible astrophysical environments.
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