Current date: 2025-07-01
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Created/updated limit: 2025-06-24 (7 days ago)
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Scoring abstracts
Number of records retrieved: 964
Keyword score statistics
score 8 -- 1 abstracts
score 7 -- 1 abstracts
score 6 -- 6 abstracts
score 5 -- 4 abstracts
score 4 -- 6 abstracts
score 3 -- 7 abstracts
score 2 -- 24 abstracts
in total -- 49 abstracts
Articles that appeared on 2025-07-01
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[abstract 1 / 49] Wow! (score: 8)
- Title: Two-Component gamma-ray Emission Spectrum and X-Ray Polarization of the Radio Galaxy Pictor AAuthors: Jia-Xuan Li, Xin-Ke Hu, Ji-Shun Lian, Yu-Wei Yu, Wei Deng, Kuan Liu, Hai-Ming Zhang, Liang Chen, Jin Zhang,Comments: 22 Pages, 10 Figures, 4 Tables, accepted by ApJSubjects: astro-ph.HECreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Pictor A is a $γ$-ray emitting RADIO GALAXy and has a bright hotspot called WHS, located $\sim$4 arcmin away from the nucleus. In this work, we present an analysis of its 16-year FERMI-LAT data and report the Imaging X-ray Polarimetry Explorer (IXPE) observations for this source. Our analysis of the FERMI-LAT observations reveals evidence of two components in the average $γ$-ray spectrum of Pictor A, exhibiting a statistically significant hardening from $Γ_{\rm γ,1}=3.25\pm0.15$ to $Γ_{\rm γ,2}=1.81\pm0.07$ at a break energy of $2.46\pm0.09$ GeV. Notably, variability of $γ$-rays is evident in Pictor A, predominantly driven by the component below the break energy, while the component above the break energy remains stable. Furthermore, our analysis reveals that a power-law function provides an adequate fit for the high-flux-state spectrum, while a broken power-law function remains necessary to accurately model the low-flux-state spectrum. We suggest that the low-energy component originates from the nucleus, while the high-energy component primarily stems from WHS. The broadband spectral energy distributions of both nucleus and WHS can be well represented by a simple leptonic model, with both $γ$-ray components attributed to the SYNCHROTRON-self-Compton (SSC) process. Analysis of IXPE data provides upper limits on the POLARIZATION degree of $Π_{\rm X}<$6.6% for the nucleus and $Π_{\rm X}<$56.4% for the WHS within the 2--8 keV band. For the nucleus, this result aligns with X-ray emission originating from the SSC process. However, the upper limit of $Π_{\rm X}<$56.4% for WHS is insufficient to conclusively determine the X-ray emission mechanism in this region.
[abstract 2 / 49] Wow! (score: 7) - Title: Modeling BLAZAR broadband emission with convolutional neural networks -- III. proton SYNCHROTRON and hybrid modelsAuthors: N. Sahakyan, D. Bégué, A. Casotto, H. Dereli-Bégué, V. Vardanyan, M. Khachatryan, P. Giommi, A. Pe'er,Comments: submitted to ApJSubjects: astro-ph.HE astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Modeling the broadband emission of BLAZARs has become increasingly challenging with the advent of multimessenger observations. Building upon previous successes in applying convolutional neural networks (CNNs) to leptonic emission scenarios, we present an efficient CNN-based approach for modeling BLAZAR emission under proton SYNCHROTRON and hybrid lepto-hadronic frameworks. Our CNN is trained on extensive numerical simulations generated by SOPRANO, which span a comprehensive parameter space accounting for the injection and all significant cooling processes of electrons and protons. The trained CNN captures complex interactions involving both primary and secondary particles, effectively reproducing electroMAGNETic and neutrino emissions. This allows for rapid and thorough exploration of the parameter space characteristic of hadronic and hybrid emission scenarios. The effectiveness of the trained CNN is demonstrated through fitting the spectral energy distributions of two prominent BLAZARs, TXS 0506+059 and PKS 0735+178, both associated with IceCube neutrino detections. The modeling is conducted under assumptions of constant neutrino flux across distinct energy ranges, as well as by adopting a fitting that incorporates the expected neutrino event count through a Poisson likelihood method. The trained CNN is integrated into the Markarian Multiwavelength Data Center (MMDC; https://www.mmdc.am), offering a robust tool for the astrophysical community to explore BLAZAR JET physics within a hadronic framework.
[abstract 3 / 49] Yes (score: 6) - Title: Neutrino emission and corona heating induced by high-energy proton interactions in Seyfert galaxiesAuthors: A. Neronov, O. Kalashev, D. V. Semikoz, D. Savchenko, M. Poleshchuk,Comments: 7 pages, 3 figuresSubjects: astro-ph.HECreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Recent detection of very-high-energy neutrino emission from Seyfert type ACTIVE GALACTIC NUCLEi (AGN) provides a new insight into the physics of the AGN central engines. We notice that if high-energy protons responsible for neutrino emission are accelerated close to the surface of the accretion disk, the neutrino flux may have no unambiguously identifiable electroMAGNETic counterpart. This is because the electroMAGNETic power released in interactions of high-energy protons would only contribute to the heating of the disk surface and corona above the disk, rather than escape from the source. Given that the heat deposited in the corona is released in the hard X-ray range we notice that there still might be an "indirect" electroMAGNETic counterpart of the neutrino signal: the hard X-ray flux variability may be strongly or weakly correlated with the neutrino flux variations, depending on the importance of the high-energy proton heating in the disk/corona heat balance. If heating by high-energy protons provides a sizable contribution to the overall corona heating rate, the overall flux of diffuse GeV neutrino background from Seyfert galaxies may be comparable to the X-ray background flux and the high-energy tail of this background can provide a sizable contribution to the astrophysical neutrino flux in the TeV band.
[abstract 4 / 49] Yes (score: 6) - Title: X-ray investigation of the remarkable galaxy group Nest200047Authors: Anwesh Majumder, A. Simionescu, T. Plšek, M. Brienza, E. Churazov, I. Khabibullin, F. Gastaldello, A. Botteon, H. Röttgering, M. Brüggen, N. Lyskova, K. Rajpurohit, R. A. Sunyaev, M. W. Wise,Comments: 21 pages, 15 figures. Accepted for publication in A&ASubjects: astro-ph.CO astro-ph.HECreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
Galaxy groups are more susceptible to feedback from the central ACTIVE GALACTIC NUCLEi (AGN) due to their lower gravitational binding energy compared to clusters. This makes them ideal laboratories to study feedback effects on the overall energy and baryonic mass budget. We study the LOFAR-detected galaxy group Nest200047, where there is clear evidence of multiple generations of radio lobes from the AGN. Using 140 ks Chandra and 25 ks XMM-Newton data, we investigate thermodynamic properties of the the intragroup medium including any excess energy due to the central AGN. We also investigate X-ray properties of the central BLACK HOLE and constrain the $2-10$ keV X-ray flux. We used spectral analysis techniques to measure various thermodynamic profiles across the whole field of view. We also used both imaging and spectral analysis to detect and estimate the energy deposited by potential shocks and cavities. Due to the faint emission from the object beyond the core, various background effects were considered. Nest200047 has significant excess entropy, and the AGN likely contributes to a part of it. There is an excess energy of $(5-6.5) \times 10^{60}$ erg within 400 kpc, exceeding the binding energy. The pressure profile indicates that gas is likely being ejected from the system, resulting in a baryon fraction of $\sim4\%$ inside $r_{500}$. From scaling relations, we estimate a BLACK HOLE mass of $(1-4)\times 10^9 M_{\odot}$. An upper limit of $2.1 \times 10^{40}$ erg s$^{-1}$ was derived on the BLACK HOLE bolometric luminosity, which is $\sim$2.5% of the Bondi accretion power. Nest200047 is likely part of a class of over-heated galaxy groups like ESO 3060170, AWM 4 and AWM 5. Such excessive heating may lead to high quenching of STAR FORMATION. Moreover, the faint X-ray nuclear emission in Nest is likely due to the accretion energy being converted into JETs rather than radiation.
[abstract 5 / 49] Yes (score: 6) - Title: Multimessenger Emission from Very-High-Energy Black Hole-Jet Systems in the Milky WayAuthors: Jose Carpio, Ali Kheirandish, Bing Zhang,Comments:Subjects: astro-ph.HE hep-phCreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
MicroQUASARs, compact binary systems with an accreting stellar-mass BLACK HOLE or neutron star, are promising candidates for high-energy particle acceleration. Recently, the LHAASO collaboration reported on the detection of $>100$ TeV $γ$-ray emission from five microQUASARs, suggesting that these sources are efficient particle accelerators. In microQUASARs, high-energy $γ$-rays can be produced in large-scale JETs or winds. In this work, we explore the X-ray, $γ$-ray and neutrino emission from SS 433, V4641 Sgr and GRS 1905+105. We consider leptonic and hadronic scenarios to explain the spectra observed by LHAASO and other high-energy $γ$-ray detectors. We estimate the neutrino flux associated with the hadronic component and investigate the detectability of neutrinos from these sources in current and future neutrino telescopes. We find that among the three sources, V4641 Sgr has the best prospects of observation with a combined next-generation neutrino telescopes.
[abstract 6 / 49] Yes (score: 6) - Title: Probing Binary Neutron Star Merger Ejecta and Remnants with Gravitational Wave and Radio ObservationsAuthors: Kara Merfeld, Alessandra Corsi,Comments: 29 pages, 22 figures. Submitted to journal. Comments welcomeSubjects: astro-ph.HE astro-ph.CO gr-qcCreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
We present a study aimed at quantifying the detectability of radio counterparts of binary neutron star (BNS) mergers with total masses $\lesssim 3$\,M$_{\odot}$, which may form neutron star (NS) remnants. We focus on mergers localized by gravitational-wave (GW) observations to sky areas $\lesssim 10$\,deg$^2$, a precision that greatly facilitates optical counterpart identification and enables radio discovery even without detections at other wavelengths. Widely separated GW detectors are essential for building samples of well-localized BNS mergers accessible to US-based radio telescopes, with minimum yearly detection rates (assuming the smallest values of the BNS local merger rate) ranging from a few with current GW detectors to hundreds with next-generation GW instruments. Current GW networks limit well-localized detections to $z\lesssim 0.2$, while next-generation GW detectors extend the reach to $z\lesssim 0.8$, encompassing the median redshift of short GAMMA-RAY BURSTs (GRBs). With next-generation radio arrays operating at a several tens of GHz and providing an order of magnitude improvement in sensitivity compared to the most sensitive ones available today, short GRB-like JET afterglows can be detected for a large fraction of the considered BNS mergers. At lower radio frequencies, detections with current radio interferometric arrays are feasible, though subject to SYNCHROTRON self-absorption effects. The enhanced sensitivity and survey speed of future radio interferometers operating at a few GHz, combined with the higher detection rate of well-localized BNSs enabled by next-generation GW observatories, are key to probing disk-wind and dynamical ejecta afterglows, as well as remnant diversity.
[abstract 7 / 49] Yes (score: 6) - Title: Constraining the Origin of FRB 20121102A's Persistent Radio Source with Long-Term Radio ObservationsAuthors: Mohit Bhardwaj, Arvind Balasubramanian, Yasha Kaushal, Shriharsh P. Tendulkar,Comments: 20 pages, 3 figures, 3 tablesSubjects: astro-ph.HECreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The persistent radio source (PRS) associated with FRB 20121102A, the first precisely localized repeating fast radio burst (FRB), provides key constraints on both its local environment and the nature of the underlying FRB engine. We present a seven-year (2016-2023) temporal analysis of the PRS, combining new uGMRT observations with archival data across L-band frequencies. We find no statistically significant long-term trend in its L-band flux density. The observed variability is consistent with refractive interstellar scintillation, and the data do not require the PRS to be a source exhibiting strong intrinsic variability. This stability challenges models predicting rapid fading from evolving MAGNETized outflows, such as those powered by young MAGNETars or RELATIVISTIC shocks. Our low-frequency observations show no evidence for spectral evolution between 1.4 GHz and 745 MHz, with a measured spectral index of $α= -0.15 \pm 0.08$, in agreement with values reported from earlier observations in 2016-2017. The PRS remains compact, exhibits a flat radio spectrum, and-if powered by an intermediate-mass BLACK HOLE accreting at a low Eddington ratio-its radio and X-ray properties are broadly consistent with the fundamental plane of radio-loud AGNs. While not conclusive, this scenario represents a viable alternative to MAGNETar wind nebula models and warrants further investigation. Furthermore, we find no statistically significant correlation between FRB burst activity and the luminosity of associated PRSs among repeating sources. This apparent decoupling challenges simple progenitor models that directly link bursts and persistent emission. Together, these results suggest that the FRB engine and PRS may in some systems originate from physically distinct sources, underscoring the need for flexible models to explain the diverse environments of repeating FRBs.
[abstract 8 / 49] Yes (score: 6) - Title: A possible two-fold scenario for the disc-corona of the luminous AGN 1H 0419--577: a high-density disc or a warm coronaAuthors: Delphine Porquet, James N. Reeves, Valentina Braito,Comments: Accepted for publication in A&A, 12 pages (+appendix)Subjects: astro-ph.HECreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
[abridged] 1H 0419-577 is a highly-accreting, luminous BLS1 AGN. This study aims to characterise its disc-corona system using, for the first time, simultaneous XMM-Newton and NUSTAR observations, performed in May and November 2018. We conducted high-resolution grating spectroscopy to identify potential soft X-ray absorption and emission features. To measure the hot corona temperatures from the spectral analysis above 3 keV, we also included data from a previous NUSTAR observation from June 2015. We characterised the disc-corona system properties by analysing the broadband spectra and the SED from UV to hard X-rays. 1H 0419-577 was observed in a bare-like high-flux state at both epochs, with negligible neutral and ionised absorption along its line of sight at both Galactic and AGN rest-frames. However, several soft X-ray emission lines were detected, notably a broad and intense OVII line indicating an accretion disc origin at only a few tens of gravitational radii. The broadband X-ray spectra revealed a prominent, absorption-free smooth soft X-ray excess, a weak Fe Kalpha complex, and a lack of a Compton hump. Fitting data above 3 keV yielded apparent moderate hot corona temperatures of ~20-30 keV for the 2018 and 2015 observations, depending on the model applied. The 2018 X-ray broadband spectra were well reproduced by either a RELATIVISTIC reflection model with a high-density accretion disc (~10^18 cm^-2), or a hybrid model combining warm and hot coronae with RELATIVISTIC reflection. We performed the SED analysis for the latter scenario, which indicated that both the hot and warm coronae would have a small spatial extent. Both scenarios can successfully reproduce the two 2018 observations of 1H 0419-577, but they imply very different physical conditions, for example, in terms of disc density, temperature and accretion power released in the hot corona and the origin of the UV emission.
[abstract 9 / 49] Yes (score: 5) - Title: Velocity evolution of broad-lined type-Ic SUPERNOVAe with and without GAMMA-RAY BURSTsAuthors: Gabriel Finneran, Laura Cotter, Antonio Martin-Carrillo,Comments: 63 pages. Updated following peer review. Accepted for publication in A&ASubjects: astro-ph.HECreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
More than 60 broad-lined type Ic (Ic-BL) SUPERNOVAe (SNe) are associated with a long GAMMA-RAY BURST (GRB). However, many type Ic-BL SNe exhibit no sign of an associated GRB. On average, the expansion velocities of GRB-associated type Ic-BL SNe (GRB-SNe) are greater than those of type Ic-BL SNe without an associated GRB. This work presents the largest spectroscopic sample of type Ic-BL SNe with and without GRBs to date, consisting of 61 ordinary type Ic-BL SNe and 13 GRB-SNe. The goal of this work is to compare the evolution of SN expansion velocities in cases where an ultra-RELATIVISTIC JET has been launched (GRB-SNe) and cases where no GRB JET is inferred from observations (ordinary type Ic-BL SNe), to search for possible JET influences. To do this we measured the expansion velocities of the Fe II and Si II features observed in the spectra of type Ic-BL SNe using a spline fitting method and fitted the velocity evolution with single and broken power-laws. In each analysis we compared two populations: ordinary type Ic-BL SNe and GRB-SNe. We find that the expansion velocities of the Fe II and Si II features are similar between these populations, in contrast with previous studies. The Fe II and Si II power-law indices indicate that GRB-SNe decline at similar rates to ordinary type Ic-BL SUPERNOVAe. Broken power-law evolution appears to be more common for the Si II feature. This observation may hint at a two-component ejecta model, such as a GRB JET or a cocoon. Neither the velocities nor their evolution can be used to distinguish between ordinary type Ic-BL SNe and GRB-SNe. Velocities consistent with broken power-law evolution may indicate the presence of a GRB JET in some of these ordinary type Ic-BL SNe, but this is likely not as robust as late-time radio surveys. These results suggest that GRB-SNe and ordinary type Ic-BL SNe are drawn from the same underlying population of events.
[abstract 10 / 49] Yes (score: 5) - Title: Spectroastrometry and Reverberation Mapping of Active Galactic Nuclei. II. Measuring Geometric Distances and Black Hole Masses of Four Nearby QuasarsAuthors: Yan-Rong Li, Jinyi Shangguan, Jian-Min Wang, Ric Davies, Daryl J. Santos, Frank Eisenhauer, Yu-Yang Songsheng, Hartmut Winkler, Jesús Aceituno, Hua-Rui Bai, Jin-Ming Bai, Michael S. Brotherton, Yixian Cao, Yong-Jie Chen, Pu Du, Feng-Na Fang, Jia-Qi Feng, Helmut Feuchtgruber, Natascha M. Förster Schreiber, Yi-Xin Fu, Reinhard Genzel, Stefan Gillessen, Luis C. Ho, Chen Hu, Jun-Rong Liu, Dieter Lutz, Thomas Ott, Romain G. Petrov, Sebastian Rabien, Taro Shimizu, Eckhard Sturm, Linda J. Tacconi, Yi-Lin Wang, Zhu-Heng Yao, Shuo Zhai, Hao Zhang, Yi-Peng Zhao, Yu Zhao,Comments: 21 pages, 15 figures, 4 tables; ApJ in pressSubjects: astro-ph.GA astro-ph.COCreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
The geometric distances of ACTIVE GALACTIC NUCLEi (AGNs) are challenging to measure because of their exceptionally compact structure yet vast cosmic distances. A combination of spectroastrometry and reverberation mapping (SARM) of broad-line regions (BLRs) constitutes a novel means to probe the geometric distance of AGNs, which has recently become practically feasible owing to successful interferometric observations with VLTI/GRAVITY. Here, we perform SARM analysis of four nearby QUASARs: Mrk 509, PDS 456, 3C 273, and NGC 3783. Results for the former two are reported for the first time and the latter two are revisited using our improved BLR dynamical modeling that includes the radial-dependent responsivity of BLRs. This allows us to self-consistently account for the emissivity weighting of the BLR in spectroastrometry and responsivity weighting in reverberation mapping. We obtain angular-diameter distances of the four QUASARs, from which we derive a Hubble constant of $H_0=69_{-10}^{+12}\,\rm km\,s^{-1}\,Mpc^{-1}$. Although this constitutes a large uncertainty for a measurement of $H_0$, it is anticipated that the precision will improve to a competitive level once a greater number of AGNs are accessible following the upgrade of GRAVITY in the near future. From SARM analysis, the BLACK HOLE masses of the four QUASARs are also measured with the statistical uncertainty ranging from 0.06 to 0.23 dex, consistent with the correlations between BLACK HOLE masses and properties of the host bulges.
[abstract 11 / 49] Yes (score: 5) - Title: Evidence for Large-Scale Cold Gas Outflows Associated with Nuclear Winds in Reionization-Era QuasarsAuthors: Yongda Zhu, Marcia J. Rieke, Luis C. Ho, Yang Sun, George H. Rieke, Feng Yuan, Tom J. L. C. Bakx, George D. Becker, Jinyi Yang, Eduardo Bañados, Manuela Bischetti, Christopher Cain, Xiaohui Fan, Yoshinobu Fudamoto, Seyedazim Hashemi, Ryota Ikeda, Zhiyuan Ji, Xiangyu Jin, Weizhe Liu, Yichen Liu, Jianwei Lyu, Hai-Xia Ma, Tsutomu T. Takeuchi, Hideki Umehata, Feige Wang, Wei Leong Tee,Comments: 17 pages; resubmittedSubjects: astro-ph.GA astro-ph.COCreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
Accreting supermassive BLACK HOLEs (SMBHs) are thought to influence the evolution of their host galaxies through multi-phase feedback driven by powerful nuclear outflows. Although this mechanism is central to theoretical models of SMBH--galaxy co-evolution across cosmic time, direct observational evidence connecting nuclear winds to large-scale cold gas outflows remains limited, especially in the early universe. Here we report statistical evidence for such a connection in a sample of luminous QUASARs at $z \sim 5.5$. We compare stacked [C\,{\sc ii}] 158 $μ$m emission profiles from ALMA observations, which trace galactic-scale neutral gas, for QUASARs with and without broad absorption lines (BALs) that indicate powerful nuclear winds on sub-kiloparsec scales. The BAL QUASAR stack exhibits a significant (S/N = 4.45) blueshifted broad component in the [C\,{\sc ii}] line profile, with a velocity offset of $Δv_{\rm b} = -2.1 \times 10^2\,\mathrm{km\,s^{-1}}$ and a full width at half maximum of $1.18 \times 10^3\,\mathrm{km\,s^{-1}}$, whereas the non-BAL stack shows no such feature. We estimate that a few percent to one-quarter of the nuclear wind energy may be transferred to cold neutral gas on kiloparsec scales. These results suggest that BAL winds can couple to the host galaxy's interstellar medium, providing empirical support for models of multi-phase AGN feedback. This mechanism may also contribute to the observed diversity in $M_{\rm BH}/M_*$ among luminous QUASARs recently identified by JWST.
[abstract 12 / 49] Yes (score: 5) - Title: NUSTAR Detection of an Absorption Feature in ESP 39607: Evidence for an Ultra-Fast Inflow?Authors: Alessandro Peca, Michael J. Koss, Roberto Serafinelli, Claudio Ricci, C. Megan Urry, Giulia Cerini, Peter G. Boorman,Comments: Accepted for publication in ApJSubjects: astro-ph.HE astro-ph.GACreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
We report the serendipitous discovery of an absorption feature at 4.8 keV in the NUSTAR spectra of ESP 39607, a Seyfert 2 galaxy at $z = 0.201$, observed in May 2023 and August 2024. The feature is detected in both observations with individual significance levels between 2 and 3$σ$, computed with multiple statistical methods. The combined probability of detecting it in both observations is $\gtrsim$4$σ$. The absorption feature is consistent with an ultra-fast inflow (UFI) potentially associated with Fe XXV or Fe XXVI K$α$ transitions. The inferred inflow velocity is $\sim$0.15-0.20$c$, with an estimated launching radius of 22-89 $R_g$, depending on the assumed iron transition and whether radiation pressure is accounted for. Photoionization modeling associates the UFI primarily with Fe XXV K$α$ absorption, blended with a minor contribution from Fe XXVI K$α$. Alternative explanations, including associations with the warm-hot intergalactic medium or outflows of lighter elements, were investigated but found unlikely. If confirmed, this detection represents a rare example of a UFI, providing valuable evidence into extreme and/or non-standard accretion processes near supermassive BLACK HOLEs. Follow-up observations with higher-resolution X-ray spectroscopy, such as with XMM-Newton or XRISM, will be essential to confirm the nature of this feature and better constrain the physical mechanisms driving it.
[abstract 13 / 49] Yes (score: 4) - Title: Machine Learning Approach for Estimating Magnetic Field Strength in Galaxy Clusters from Synchrotron EmissionAuthors: Jiyao Zhang, Yue Hu, A. Lazarian,Comments: 14 pages, 8 figures, accepted for publication in ApJSubjects: astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Magnetic fields play a crucial role in various astrophysical processes within the intracluster medium, including heat conduction, COSMIC RAY acceleration, and the generation of SYNCHROTRON radiation. However, measuring MAGNETic field strength is typically challenging due to the limited availability of Faraday Rotation Measure sources. To address the challenge, we propose a novel method that employs Convolutional Neural Networks (CNNs) alongside SYNCHROTRON emission observations to estimate MAGNETic field strengths in galaxy clusters. Our CNN model is trained on either Magnetohydrodynamic (MHD) turbulence simulations or MHD galaxy cluster simulations, which incorporate complex dynamics such as cluster mergers and sloshing motions. The results demonstrate that CNNs can effectively estimate MAGNETic field strengths with median uncertainties of approximately $0.22μ$G, $0.01μ$G, and $0.1μ$G for $β= 100$, 200, and 500 conditions, respectively. Additionally, we have confirmed that our CNN model remains robust against noise and variations in viewing angles with sufficient training, ensuring reliable performance under a wide range of observational conditions. We compare the CNN approach with the traditional MAGNETic field strength estimates method that assumes equipartition between COSMIC RAY electron energy and MAGNETic field energy. Unlike the equipartition method, this CNN approach does not rely on the equipartition assumption, offering a new perspective for comparing traditional estimates and enhancing our understanding of COSMIC RAY acceleration mechanisms.
[abstract 14 / 49] Yes (score: 4) - Title: Revealing the $χ_{\rm eff}$-$q$ correlation among Coalescing Binary Black Holes and { Tentative} Evidence for AGN-driven Hierarchical MergersAuthors: Yin-Jie Li, Yuan-Zhu Wang, Shao-Peng Tang, Tong Chen, Yi-Zhong Fan,Comments: 14 pages, 9 figures, comments welcome!Subjects: astro-ph.HE astro-ph.GACreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
The origin of the correlation between the effective spins ($χ_{\rm eff}$) and mass ratios ($q$) of LIGO-Virgo-KAGRA's binary BLACK HOLEs (BBHs) is still an open question. Motivated by the recent identification of two subpopulations of the BBHs, in this work we investigate the potential $χ_{\rm eff}-q$ correlation for each subpopulation. Surprisingly, the $χ_{\rm eff}$-$q$ correlation {either significantly weakens or disappears} for the low-mass subpopulation if we introduce a second $χ_{\rm eff}$ distribution for the high-mass subpopulation, which likely originates from hierarchical mergers. {This suggests that the $χ_{\rm eff}$-$q$ correlation in the overall population can be explained by the superposition of two distinct subpopulations.} {We find Bayesian evidence strongly favoring two separate $χ_{\rm eff}$ distributions over a single mass-ratio-dependent distribution, with Bayes factors $\ln\mathcal{B}>4.2$.} The first subpopulation has a narrow $χ_{\rm eff}$ distribution peaking at $\sim0.05$, whose primary-mass function {showing a rapid decline beyond} $\sim 40M_{\odot}$, in agreement with first-generation BBHs. The second $χ_{\rm eff}$ distribution is broad and peaks at $μ_{χ,2} \sim 0.4$, aligning with predictions for hierarchical mergers in ACTIVE GALACTIC NUCLEus (AGN) disks. {However, we cannot exclude negative $χ_{\rm eff}$values in the second subpopulation, suggesting hierarchical mergers might occur both in AGN disks and stellar clusters. Furthermore, the inferred second $χ_{\rm eff}$ distribution might alternatively arise from other formation channels, such as stable mass transfer or chemically homogeneous evolution, if not interpreted as hierarchical mergers.}
[abstract 15 / 49] Yes (score: 4) - Title: Ultrahigh Energy Cosmic Ray Production in Binary Neutron Star MergersAuthors: Glennys R. Farrar,Comments:Subjects: astro-ph.HE hep-phCreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
We predict the spectrum and composition of ultrahigh energy COSMIC RAYs (UCRs for short) generated in a binary neutron star merger, exploiting the highly constrained initial conditions to make quantitative predictions for the cutoff energy for various nuclei. The key mechanism producing UCRs heavier than helium is acceleration in the MAGNETized turbulent outflow outside the JETs. We find the rigidity cutoff of this component is $\mathcal{R}_{\rm cut} \equiv E_{\rm cut}/eZ \approx 6-9$ EV, consistent with the measured value $\mathcal{R}_{\rm cut} = 6.8^{+5.8}_{-2.8}\,$EV from fitting data. This agreement strengthens the case that BNS mergers are the main site of UCR production. The JETs may also be capable of accelerating particles to ultrahigh energy: these UCRs would be protons and/or helium, in a ratio that depends on the neutron star equation of state. We estimate the cutoff energies of such a component to be $E_{\rm cut}\approx\! 10\,$EeV for p and $\approx\! 30\,$EeV for He. Such a JET component may explain the hint of a secondary light population at higher energy found in the analysis of Muzio et al. (2019). With more precise data, the locus of production of helium and intermediate mass nuclei can be inferred from their rigidity structure, and the predicted small deviations from a pure Peters Cycle can be checked. Predicting the relative abundances of different elements and the total energy in UCRs per merger event is feasible, but beyond the scope of this paper. This scenario predicts that each neutrino above 1 PEV is co-directional with a gravitational wave arriving ~1 day earlier, and that the highest energy UCRs have masses heavier than iron.
[abstract 16 / 49] Yes (score: 4) - Title: The effectively optically thin accretion flow and its implication in supermassive BLACK HOLEsAuthors: Mingjun Liu, B. F. Liu, Yilong Wang, Huaqing Cheng, Weimin Yuan,Comments: 11 pages, 9 figures, accepted for publication in MNRASSubjects: astro-ph.HECreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
Based on a unified description of various accretion flows, we find a long-ignored solution - the effectively optically thin accretion flow, occurring at accretion rates around Eddington value. As a consequence of radiation-pressure dominance, the density in a standard thin disc (SSD) decreases with the increase of accretion rates, making the innermost region effectively optically thin. Further increase in accretion rate leads to a rise of the temperature so that the Compton cooling is able to balance the accretion released energy. We demonstrate that the effectively optically thin flow is characterized by moderate temperature and large scattering optical depth, producing a multi-color Wien spectrum. For an appropriate accretion rate, the accretion flow transforms from an outer SSD to an inner effectively optically thin flow. Thus, the spectra of the whole accretion flow exhibit two components, i.e., a multi-color Wien spectrum at higher frequency and a multi-color blackbody, the former could provide an alternative origin of soft X-ray excess or formation of warm corona in ACTIVE GALACTIC NUCLEi (AGNs). Our stability analysis proves it is thermally stable and viscously unstable, indicating its existence in accreting systems. We show that effectively optically thin accretion flow exists in supermassive BLACK HOLEs for accretion rates around 0.1 to 10 times Eddington value, bridging the SSD at low accretion rates and slim disc at high rates. By comparing the predictions and average spectra of AGN, we constrain the viscosity parameter to be $α\sim 0.03$, in good agreement with that derived from observed variability.
[abstract 17 / 49] Yes (score: 4) - Title: Probing the detectability of electroMAGNETic signatures from Galactic isolated BLACK HOLEsAuthors: Javier Rodrigo Martinez, Valenti Bosch Ramon, Florencia Laura Vieyro, Santiago del Palacio,Comments: 15 pages, 7 figures. Accepted for publication in the section "2. Astrophysical processes" of Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
Context: A large number of isolated BLACK HOLEs (IBHs) are expected to populate the Galaxy. However, only one has been confirmed by the analysis of a microlensing event, and no confirmed emission detection from an IBH has been reported so far. Aims: We analysed the detectability of electroMAGNETic signatures from IBHs moving in the Galaxy. Methods: We considered accretion from the interstellar medium onto an IBH and assumed the formation of an outflow. We modelled the accretion process and the interaction of the outflow with the surrounding medium on large scales, including mechanical feedback on the accretion process. Furthermore, we also calculated the emission from three different regions: the accretion region, the radiation from the outflow medium interaction structure, and the emission of RELATIVISTIC particles that diffuse in the surrounding medium. Results: Multiwavelength emission associated with Galactic IBHs can be detected in systems moving through a very dense medium. Thermal emission from accretion could be observed in the mid infrared and in hard X rays with current and forthcoming observatories. Thermal and non thermal emission from the outflow medium shock could also be detected in the radio and millimetre ranges. Moreover, detection of the emission from particles diffusing in a dense medium could be feasible in gamma rays. Applying our model to the IBH associated with the gravitational microlensing event MOA2011BLG191 OGLE2011BLG0462, we inferred that radio and infrared detection of the IBH is plausible. Also, we derived that IBHs could be modest Galactic COSMIC RAY contributors, potentially reaching a 1% contribution at 1 PeV. Finally, by extending our model to primordial BLACK HOLEs, we conclude that efficient leptonic acceleration in their outflow medium interactions would rule them out as a major DARK MATTER component.
[abstract 18 / 49] Yes (score: 4) - Title: Continuum optical-UV and X-ray variability of AGN: current results and future challengesAuthors: Maurizio Paolillo, Iossif Papadakis,Comments: Review paper in press on "La Rivista del Nuovo Cimento" of the Italian Physics Society (SIF); 63 pages + 40 pages of references. This preliminary version is affected by some compiling issues in the bibliography which is not always in alphabetical order. Will be fixed in the final versionSubjects: astro-ph.HE astro-ph.CO astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Active Galactic Nuclei (AGN) are believed to be powered by accretion of matter onto a supermassive BLACK HOLE. A fundamental ingredient in shaping our understanding of AGN is their variability across the entire electroMAGNETic spectrum. Variability studies have the potential to help us understand the geometry of the emitting regions (in various energy bands), their causal relations, and the physics of the accretion processes. This review focuses on the observational properties of AGN variability in the optical/UV/X-ray bands (where most of the AGN luminosity is emitted) and their dependence on the AGN physical parameters (i.e. mass, luminosity, accretion rate). We also discuss possible interpretations in the context of accreting compact systems, and we review the use of variability as a tool to discover AGN and trace their properties across cosmic time, using both ground and space facilities. Finally, we discuss the opportunities and challenges provided by current and next-generation optical/X-ray surveys, to use variability as an effective tool to probe the growth of super massive BLACK HOLEs in the Universe.
[abstract 19 / 49] (score: 3) - Title: MaNGA AGN dwarf galaxies (MAD). III. The role of mergers and environment in ACTIVE GALACTIC NUCLEus activity in dwarf galaxiesAuthors: A. Eróstegui, M. Mezcua, M. Siudek, H. Domínguez Sánchez, V. Rodríguez Morales,Comments: Accepted in Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
Investigating whether and how galaxy mergers affect BLACK HOLE growth can be determinant for BLACK HOLE-galaxy evolution models and, in particular, for understanding how early Universe seed BLACK HOLEs grew to become supermassive. However, while mergers have been observed to enhance the ACTIVE GALACTIC NUCLEus (AGN) activity, and thus BLACK HOLE growth in massive galaxies, it is yet not known how this relation and the role of the environment translates to dwarf galaxies (the most likely hosts of the early seed BLACK HOLEs), since there are scarce and mixed results in the literature. We want to assess the impact of galaxy mergers and the environment on AGN triggering in dwarf galaxies. We use a sample of 3280 dwarf galaxies with integral-field spectroscopic data from the MaNGA survey to study the AGN fraction throughout the merger process and how it is affected by the environment (characterized by galaxy isolation, being in a void, and group richness). We also compare the fraction of interacting galaxies in AGN and non-AGN dwarf galaxies. We find that dwarf galaxy mergers can ignite AGNs at separations below 20 kpc. The AGN fraction increases notoriously after the first pass and remains enhanced until the final stage. Despite this, mergers are not the dominant AGN triggering mechanism. We also find that the environment has a non-negligible impact on AGN activity in dwarf galaxies, as the AGN fraction increases when moving to lower density environments. These findings provide the most statistically robust constraints to date on the effects of dwarf galaxy mergers and environment on AGN activity and BLACK HOLE growth.
[abstract 20 / 49] (score: 3) - Title: Exploring the parameter space of hierarchical triple BLACK HOLE systemsAuthors: M. Attia, Y. Sibony,Comments: Accepted for publication in A&A. Abstract abridged for arXivSubjects: astro-ph.HE astro-ph.GA astro-ph.SR gr-qcCreated: 2025-06-26; Updated: 2025-07-01; Datestamp: 2025-07-01
We present a comprehensive exploration of hierarchical triple BLACK HOLE (BH) systems to address the "initial separation" problem in gravitational wave astrophysics. This problem arises because isolated BH binaries must have extremely small initial separations to merge within a Hubble time via gravitational wave (GW) emission alone, separations at which their stellar progenitors would have merged prematurely. Using a modified JADE secular code incorporating GW energy loss, we systematically investigate a seven-dimensional parameter space: masses of three BHs (5-100 $M_\odot$ inner binary, 1-200 $M_\odot$ tertiary), inner/outer semimajor axes (1-200 AU and 100-10,000 AU), outer orbit eccentricity (0-0.9), and mutual inclination (40°-80°). We employed an adaptive MCMC approach sampling the merger/nonmerger transition boundary across nearly 15 million simulations. Results reveal merger-conducive regions correspond to asymmetric inner binary masses, large inner separations where von Zeipel-Lidov-Kozai (ZLK) mechanism operates effectively without RELATIVISTIC precession suppression, small outer separations providing stronger perturbations, and large outer eccentricities bringing the tertiary closer at pericenter. Merger probability correlates positively with mutual inclination. We developed a classification scheme for nonmerging systems based on GW emission and ZLK oscillations. A trained neural network predicts merger outcomes with 99% ROC score and 95% accuracy (99.7% for high-confidence predictions), enabling rapid population synthesis. Validation against N-body integrations showed 87% qualitative agreement, confirming our methodology captures essential triple BH dynamics while enabling unprecedented-scale exploration of configurations resolving the initial separation problem.
[abstract 21 / 49] (score: 3) - Title: Constraining Cubic Curvature Corrections to General Relativity with Quasi-Periodic OscillationsAuthors: Alireza Allahyari, Liang Ma, Shinji Mukohyama, Yi Pang,Comments: 15 pages, 2 figures, 1 tableSubjects: gr-qc astro-ph.CO astro-ph.HECreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
We investigate observational constraints on cubic curvature corrections to general relativity by analyzing quasi-periodic oscillations (QPOs) in accreting BLACK HOLE systems. In particular, we study Kerr BLACK HOLE solution corrected by cubic curvature terms parameterized by $β_5$ and $β_6$. While $β_6$ corresponds to a field-redefinition invariant structure, the $β_5$ term can in principle be removed via a field redefinition. Nonetheless, since we work in the frame where the accreting matter minimally couples to the metric, $β_5$ is in general present. Utilizing the corrected metric, we compute the QPO frequencies within the RELATIVISTIC precession framework. Using observational data from GRO J1655$-$40 and a Bayesian analysis, we constrain the coupling parameters to $|β_5| < (27.73\,\mathrm{km})^4$ and $|β_6| < (15.34\,\mathrm{km})^4$. These bounds improve upon existing constraints from big-bang nucleosynthesis and the speed of gravitational waves.
[abstract 22 / 49] (score: 3) - Title: Influence of external MAGNETic fields on charged particle motion around a Schwarzschild-like BLACK HOLEAuthors: Sojida Mannobova, Gulnisa Abdukayumova, Farruh Atamurotov, Ahmadjon Abdujabbarov, X. Gao, G. Mustafa,Comments: 16 pages, 17 figures, 1 tableSubjects: gr-qcCreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
We investigate the dynamics of charged and neutral particles in the vicinity of a Schwarzschild-like BLACK HOLE immersed in an external MAGNETic field. We find that the innermost stable circular orbits (ISCOs) for charged particles are systematically smaller than those of neutral particles, demonstrating a fundamental distinction in their orbital dynamics. In the presence of a strong MAGNETic field, charged particle ISCOs can approach arbitrarily close to the event horizon. We show that collisions between charged particles in ISCOs and neutral particles falling from infinity can produce unbounded center-of-mass energies in the strong-field regime, suggesting the BLACK HOLE MAGNETosphere as a natural particle accelerator. Additionally, we apply the RELATIVISTIC precession model to study quasi-periodic oscillations around the Schwarzschild-like BLACK HOLE, treating orbital perturbations as coupled harmonic oscillators. Our results provide new insights into high-energy astrophysical processes near MAGNETized BLACK HOLEs and offer observational signatures through quasi-periodic oscillating frequencies that could be detected by current and future X-ray missions.
[abstract 23 / 49] (score: 3) - Title: On the origin of short-lived cocoon in 3C84: powered by tidal disruption events ?Authors: Nozomu Kawakatu, Motoki Kino, Keiichi Wada,Comments: 25pages, 13 figures, accepted by the ApJSubjects: astro-ph.HE astro-ph.GACreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
We evaluated the JET power and the density of ambient matter in 3C 84 by using the momentum balance along the JET axis and the transonic condition for the cocoons observed at two different scales (approximately 1 and 6 parsec scales). For the inner cocoon, we precisely determined the ratio of JET power to ambient density $L_{\rm j}/n_{\rm a}$ to be $(0.3-0.7)\times 10^{43}\,{\rm erg}\,{\rm s}^{-1}\,{\rm cm}^3$. Similarly, for the outer cocoon, we found that this value is more than an order of magnitude larger at $(0.9-3.7)\times 10^{44}\,{\rm erg}\,{\rm s}^{-1}\,{\rm cm}^3$. This indicates that the outer cocoon is formed by a powerful JET that propagates through an ambient density of $20-300\,{\rm cm}^{-3}$ with a JET power of $10^{45-46.5}\,{\rm erg}\,{\rm s}^{-1}$. On the other hand, the inner cocoon is formed by a weaker JET with a power of $10^{43-44}\,{\rm erg}\,{\rm s}^{-1}$, propagating through a relatively low-density environment of $6-20\, {\rm cm}^{-3}$. These results suggest that: 1) with respect to the difference in $n_{\rm a}$, it appears to support the hypothesis that the inner cocoon, recently formed about 10 years ago, is expanding in the low-density cocoon created by the JET emitted about 25-50 years ago. 2) to achieve the short-lived and high $L_{\rm j}$ that generated the outer cocoon, a large mass accretion rate must be required over a short period to activate the JET. These may imply the extreme accretion event driven by the tidal disruption events (TDEs) of massive stars and/or the disk instability.
[abstract 24 / 49] (score: 3) - Title: Acceleration and Transport of the Unstable Cosmic-ray Isotope $^{60}$Fe in Supernova-Enriched EnvironmentsAuthors: Xin-Yue Shi, Martin Pohl, Michael M. Schulreich,Comments: 16 pages, 6 figures, accepted for publication in ApJ, comments are welcomeSubjects: astro-ph.HECreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The unstable isotope $^{60}$Fe, with a half-life of 2.6 million years, is produced primarily in SUPERNOVA explosions. The observed presence of $^{60}$Fe in COSMIC RAYs and its detection in deep-sea crusts and sediments suggest two possible scenarios: either the direct acceleration of $^{60}$Fe from SUPERNOVA ejecta or its enrichment in the circumstellar material surrounding SUPERNOVA progenitors, which indicates COSMIC RAY production in clusters of SUPERNOVAe. Focusing on the latter scenario, we consider an environment shaped by successive SUPERNOVA explosions, reminiscent of the Local Bubble around the time of the most recent SUPERNOVA explosion. We independently tracked the evolution of the $^{60}$Fe mass ratio within the Local Bubble using passive scalars. To investigate the spectra of protons and $^{60}$Fe, we explicitly modelled cosmic-ray acceleration and transport at the remnant of the last SUPERNOVA by simultaneously solving the hydrodynamical equations for the SUPERNOVA outflow and the transport equations for COSMIC RAYs, scattering turbulence, and large-scale MAGNETic field, using the time-dependent acceleration code RATPaC. The main uncertainty in our prediction of the local $^{60}$Fe flux at about $pc=1$ GeV/nuc is the MAGNETic-field structure in the Local Bubble and the cosmic-ray diffusion beyond the approximately $100$ kyr of evolution covered by our study. We found that if the standard galactic propagation applies, the local $^{60}$Fe flux would be around 3% of that measured. If there is a sustained reduction in the diffusion coefficient at and near the Local Bubble, then the expected $^{60}$Fe flux could be up to 30% of that measured.
[abstract 25 / 49] (score: 3) - Title: Spectropolarimetric synthesis of forbidden lines in MHD models of coronal bright pointsAuthors: Ernest Alsina Ballester, Daniel Nóbrega-Siverio, Fernando Moreno-Insertis, Supriya Hebbur Dayananda,Comments: Accepted for publication in Astronomy & Astrophysics. 15 pages, 10 figures. Paper additionally contains a one-page appendix with one figure. Additional animation pertaining to the online material is available as an ancillary fileSubjects: astro-ph.SRCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The inference of the MAGNETic field vector from spectropolarimetric observations is crucial for understanding the physical processes governing the solar corona. We investigate which information on the MAGNETic fields of coronal bright points (CBP) can be gained from the intensity and POLARIZATION of the Fe XIII 10747 A, Fe XIV 5303 A, Si X 14301 A, and Si IX 39343 A forbidden lines. We apply the P-CORONA synthesis code to a CBP model in the very low corona, obtained with the Bifrost code, and to a larger global model to study the impact of the outer coronal material along the line of sight (LoS). The enhanced density within the CBP produces an intensity brightening, but suppresses the linear POLARIZATION. The circular POLARIZATION from such regions often approaches 0.1% of the intensity. The contribution from the coronal material along the LoS depends strongly on its temperature, and is weaker for lines with a peak response at higher temperatures (Fe10747 at 1.7 MK; Fe5303 at 2 MK). The weak field approximation (WFA) provides information on the longitudinal MAGNETic fields in the strongest-emitting spatial intervals along the LoS, and is more reliable in the regions of the CBP where the field does not change sign. This tends to coincide with the regions where there is a strong correlation between the circular POLARIZATION and the wavelength derivative of the intensity. Considering roughly 30 minutes of time evolution, the CBP signals are somewhat attenuated but are still identifiable, while the area where the WFA can be suitably applied remains substantial. The circular POLARIZATION of the Fe5303 and especially Fe10747 lines are valuable diagnostics for the MAGNETic fields in the higher-temperature regions of the CBP, which could be exploited with future coronagraphs with similar capabilities to Cryo-NIRSP/DKIST, but designed to observe below 1.05 solar radii.
[abstract 26 / 49] (score: 2) - Title: Calculation of Photocarrier Generation from Optical Absorption for Time-domain Simulation of Optoelectronic DevicesAuthors: Liang Chen, Ming Dong, Ran Zhao, Hakan Bagci,Comments:Subjects: physics.optics cs.CE physics.comp-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Photocarrier generation rate in optoelectronic materials is often calculated using the Poynting vector in the frequency domain. However, this approach is not accurate in time-domain simulations of photoconductive devices because the instantaneous Poynting vector does not distinguish between power flux densities of optical and low-frequency electroMAGNETic fields. The latter is generated by photocurrents and is not supposed to contribute to the photocarrier generation since the corresponding photon energy is smaller than the bandgap energy of the optoelectronic material. This work proposes an optical absorption-based model to accurately calculate the generation rate in time-domain simulations. The proposed approach considers the material dispersion near the optical frequency corresponding to the bandgap energy of the optoelectronic material and calculates the instantaneous optical absorption from the POLARIZATION current density associated with this dispersion model. Numerical examples show that the proposed method is more accurate than the Poynting vector-based approach in calculating the instantaneous optical absorption. The method is further validated against experimental results via simulations of a photoconductive device, where the Poynting vector-based approach results in divergent carrier densities when the low-frequency fields are strong.
[abstract 27 / 49] (score: 2) - Title: (SHERRY) JCMT-SCUBA2 High Redshift Bright Quasar Survey -- II: the environment of z~6 QUASARs in sub-millimeter bandAuthors: Qiong Li, Ran Wang, Xiaohui Fan, Xue-Bing Wu, Linhua Jiang, Eduardo Bañados, Bram Venemans, Yali Shao, Jianan Li, Jeff Wagg, Roberto Decarli, Chiara Mazzucchelli, Alain Omont, Frank Bertoldi, Sean Johnson, Christopher J. Conselice, Chengpeng Zhang,Comments: 12 pages, 8 figures and 2 tables, published in ApJ. The author list has been revised to align with the published version. We apologize for any confusion caused and thank our collaborators for their understandingSubjects: astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The formation of the first supermassive BLACK HOLEs is expected to have occurred in some most pronounced matter and galaxy overdensities in the early universe. We have conducted a sub-mm wavelength continuum survey of 54 $z\sim6$ QUASARs using the Submillimeter Common-User Bolometre Array-2 (SCUBA2) on the James Clerk Maxwell Telescope (JCMT) to study the environments around $z \sim 6$ QUASARs. We identified 170 submillimeter galaxies (SMGs) with above 3.5$σ$ detections at 450 or 850 \um\, maps. Their FIR luminosities are 2.2 - 6.4 $\times$ 10$^{12} L_{\odot}$, and STAR FORMATION rates are $\sim$ 400 - 1200 M$_{\odot}$ yr$^{-1}$. We also calculated the SMGs differential and cumulative number counts in a combined area of $\sim$ 620 arcmin$^2$. To a $4σ$ detection (at $\sim$ 5.5 mJy), SMGs overdensity is $0.68^{+0.21}_{-0.19}$($\pm0.19$), exceeding the blank field source counts by a factor of 1.68. We find that 13/54 QUASARs show overdensities (at $\sim$ 5.5 mJy) of $δ_{SMG}\sim$ 1.5 - 5.4. The combined area of these 13 QUASARs exceeds the blank field counts with the overdensity to 5.5 mJy of \dsmg $\sim$ $2.46^{+0.64}_{-0.55}$($\pm0.25$) in the regions of $\sim$ 150 arcmin$^2$. However, the excess is insignificant on the bright end (e.g., 7.5 mJy). We also compare results with previous environmental studies of Lyman alpha emitters (LAEs) and Lyman-Break Galaxies (LBGs) on a similar scale. Our survey presents the first systematic study of the environment of QUASARs at $z\sim6$. The newly discovered SMGs provide essential candidates for follow-up spectroscopic observations to test whether they reside in the same large-scale structures as the QUASARs and search for protoclusters at an early epoch.
[abstract 28 / 49] (score: 2) - Title: On the Physical Nature of Ly$α$ Transmission Spikes in High Redshift Quasar SpectraAuthors: Hanjue Zhu, Nickolay Gnedin, Camille Avestruz,Comments: 10 pages, 8 figures, comments are welcomeSubjects: astro-ph.CO astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
We investigate Lyman-alpha (Ly$α$) transmission spikes at $5.2 < z < 6.8$ using synthetic QUASAR spectra from the ``Cosmic Reionization On Computers" simulations. We focus on understanding the relationship between these spikes and the properties of the intergalactic medium (IGM). Disentangling the complex interplay between IGM physics and the influence of galaxies on the generation of these spikes presents a significant challenge. To address this, we employ Explainable Boosting Machines, an interpretable machine learning algorithm, to quantify the relative impact of various IGM properties on the Ly$α$ flux. Our findings reveal that gas density is the primary factor influencing absorption strength, followed by the intensity of background radiation and the temperature of the IGM. Ionizing radiation from local sources (i.e. galaxies) appears to have a minimal effect on Ly$α$ flux. The simulations show that transmission spikes predominantly occur in regions of low gas density. Our results challenge recent observational studies suggesting the origin of these spikes in regions with enhanced radiation. We demonstrate that Ly$α$ transmission spikes are largely a product of the large-scale structure, of which galaxies are biased tracers.
[abstract 29 / 49] (score: 2) - Title: Chronicling the reionization history at $6\lesssim z \lesssim 7$ with emergent QUASAR damping wingsAuthors: Dominika Ďurovčíková, Anna-Christina Eilers, Huanqing Chen, Sindhu Satyavolu, Girish Kulkarni, Robert A. Simcoe, Laura C. Keating, Martin G. Haehnelt, Eduardo Bañados,Comments: 29 pages, 14 figuresSubjects: astro-ph.CO astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The spectra of high-redshift ($z\gtrsim 6$) QUASARs contain valuable information on the progression of the Epoch of Reionization (EoR). At redshifts $z<6$, the observed Lyman-series forest shows that the intergalactic medium (IGM) is nearly ionized, while at $z>7$ the observed QUASAR damping wings indicate high neutral gas fractions. However, there remains a gap in neutral gas fraction constraints at $6\lesssim z \lesssim 7$ where the Lyman series forest becomes saturated but damping wings have yet to fully emerge. In this work, we use a sample of 18 QUASAR spectra at redshifts $6.0
[abstract 30 / 49] (score: 2) - Title: Non-local, diaMAGNETic electroMAGNETic effects in MAGNETically insulated transmission linesAuthors: E. G. Evstatiev, M. H. Hess, N. D. Hamlin, B. T. Hutsel,Comments:Subjects: physics.plasm-phCreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
We identify the time-dependent physics responsible for the critical reduction of current losses in MAGNETically insulated transmission lines (MITLs) due to uninsulated space charge limited (SCL) currents of electrons emitted by field stress. A drive current of sufficiently short pulse length introduces a strong enough time dependence that steady state results alone become inadequate for the complete understanding of current losses. The time-dependent physics can be described as a non-local, diaMAGNETic electroMAGNETic response of space charge limited currents. As the pulse length is increased or equivalently, the MITL length reduced, these time-dependent effects diminish and current losses converge to those predicted by the well-known Child-Langmuir law in the external (vacuum) fields. We present a simple one-dimensional (1D) model that encapsulates the essence of this physics. We find excellent agreement with 2D particle-in-cell (PIC) simulations for two MITL geometries, Cartesian parallel plate and azimuthally symmetric straight coaxial. Based on the 1D model, we explore various scaling dependencies of MITL losses with relevant parameters, e.g., peak current, pulse length, geometrical dimensions, etc. We propose an improved physics model of MAGNETic insulation in the form of a Hull curve, which could also help improve predictions of current losses by common circuit element codes, such as BERTHA. Lastly, we describe how to calculate temperature rise due to electron impact within the 1D model.
[abstract 31 / 49] (score: 2) - Title: Exploring the anisotropic gravitational wave background from all-sky mock gravitational wave event cataloguesAuthors: Zhencheng Li, Zhen Jiang, Yun Liu, Xi-Long Fan, Liang Gao, Yun Chen, Tengpeng Xu,Comments: 13 pages 5 figuresSubjects: astro-ph.HE gr-qcCreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
Anisotropic stochastic gravitational wave background (SGWB) serves as a potential probe of the large-scale structure (LSS) of the universe. In this work, we explore the anisotropic SGWB from local ($z < \sim 0.085$) merging stellar mass compact binaries, specifically focusing on merging stellar binary BLACK HOLEs, merging neutron-star-black-hole binaries, and merging binary neutron stars. The analysis employs seven all-sky mock lightcone gravitational wave event catalogues, which are derived from the Millennium simulation combined with a semi-analytic model of galaxy formation and a binary population synthesis model. We calculate the angular power spectra $\mathrm{C}_\ell$ at multipole moments $\ell$, expressed as $\text{log}_{10} [\ell(\ell+1)\mathrm{C}_\ell/(2π)]$, based on the skymaps of the overdensity $δ_\mathrm{GW}$ in the anisotropic SGWB. The spectra for all three source types exhibit an approximately linear increase with $\text{log}_{10} \ell$ at higher $\ell$ (e.g., $\ell > \sim 30 - 300$) in seven catalogues, with a characteristic slope of $\sim 2$. The spectra of seven catalogues exhibit considerable variations, arising from fluctuations in spatial distribution, primarily in the radial distribution, of nearby sources (e.g., $< 50$ Mpc/h). After subtracting these nearby sources, the variations become much smaller and the spectra for the three source types become closely aligned (within discrepancies of a factor of $\sim 2$ across $\ell = 1 - 1000$ for all catalogues). We also find that including further sources results in a rapid decrease in the anisotropy.
[abstract 32 / 49] (score: 2) - Title: Three-dimensional Helical-rotating Plasma Structures in Beam-generated Partially Magnetized PlasmasAuthors: Jian Chen, Andrew T. Powis, Igor D. Kaganovich, Zhibin Wang,Comments:Subjects: physics.plasm-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Azimuthal structures emerging in beam-generated partially MAGNETized plasmas are investigated using three-dimensional particle-in-cell/Monte Carlo collision simulations. Two distinct instability regimes are identified at low pressures. When the gas pressure is sufficiently high, quasi-neutrality is attained and 2D spiral-arm structures form as a result of the development of a lower-hybrid instability, resulting in enhanced cross-field transport. At lower pressures, quasi-neutrality is not achieved and a 3D helical-rotating plasma structure forms due to development of the diocotron instability. Analytical formulas are proposed for the critical threshold pressure between these regimes and for the rotation frequency of the helical structures. Preliminary experimental verification is provided.
[abstract 33 / 49] (score: 2) - Title: DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha ForestAuthors: DESI Collaboration, M. Abdul-Karim, J. Aguilar, S. Ahlen, C. Allende Prieto, O. Alves, A. Anand, U. Andrade, E. Armengaud, A. Aviles, S. Bailey, A. Bault, J. Behera, S. BenZvi, D. Bianchi, C. Blake, A. Brodzeller, D. Brooks, E. Buckley-Geer, E. Burtin, R. Calderon, R. Canning, A. Carnero Rosell, P. Carrilho, L. Casas, F. J. Castander, R. Cereskaite, M. Charles, E. Chaussidon, J. Chaves-Montero, D. Chebat, T. Claybaugh, S. Cole, A. P. Cooper, A. Cuceu, K. S. Dawson, R. de Belsunce, A. de la Macorra, A. de Mattia, N. Deiosso, J. Della Costa, A. Dey, B. Dey, Z. Ding, P. Doel, J. Edelstein, D. J. Eisenstein, W. Elbers, P. Fagrelius, K. Fanning, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, C. Garcia-Quintero, L. H. Garrison, E. Gaztañaga, H. Gil-Marín, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, C. Gordon, D. Green, G. Gutierrez, J. Guy, C. Hahn, M. Herbold, H. K. Herrera-Alcantar, M. -F. Ho, K. Honscheid, C. Howlett, D. Huterer, M. Ishak, S. Juneau, N. G. Karaçaylı, R. Kehoe, S. Kent, D. Kirkby, T. Kisner, F. -S. Kitaura, S. E. Koposov, A. Kremin, O. Lahav, C. Lamman, M. Landriau, D. Lang, J. Lasker, J. M. Le Goff, L. Le Guillou, A. Leauthaud, M. E. Levi, Q. Li, T. S. Li, K. Lodha, M. Lokken, C. Magneville, M. Manera, P. Martini, W. L. Matthewson, P. McDonald, A. Meisner, J. Mena-Fernández, R. Miquel, J. Moustakas, D. Muñoz Santos, A. Muñoz-Gutiérrez, A. D. Myers, J. A. Newman, G. Niz, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, J. Pan, W. J. Percival, I. Pérez-Ràfols, M. M. Pieri, C. Poppett, F. Prada, D. Rabinowitz, A. Raichoor, C. Ramírez-Pérez, M. Rashkovetskyi, C. Ravoux, J. Rich, C. Rockosi, A. J. Ross, G. Rossi, V. Ruhlmann-Kleider, E. Sanchez, N. Sanders, S. Satyavolu, D. Schlegel, M. Schubnell, H. Seo, A. Shafieloo, R. Sharples, J. Silber, F. Sinigaglia, D. Sprayberry, T. Tan, G. Tarlé, P. Taylor, W. Turner, F. Valdes, M. Vargas-Magaña, M. Walther, B. A. Weaver, M. Wolfson, C. Yèche, P. Zarrouk, R. Zhou, H. Zou,Comments: Accepted for publication in PRD. Updated authors and references. 29 pages and 13 figures. This DESI Collaboration Publication is part of the Data Release 2 publication series (see https://data.desi.lbl.gov/doc/papers )Subjects: astro-ph.COCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
We present the Baryon Acoustic Oscillation (BAO) measurements with the Lyman-alpha (LyA) forest from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI) survey. Our BAO measurements include both the auto-correlation of the LyA forest absorption observed in the spectra of high-redshift QUASARs and the cross-correlation of the absorption with the QUASAR positions. The total sample size is approximately a factor of two larger than the DR1 dataset, with forest measurements in over 820,000 QUASAR spectra and the positions of over 1.2 million QUASARs. We describe several significant improvements to our analysis in this paper, and two supporting papers describe improvements to the synthetic datasets that we use for validation and how we identify damped LyA absorbers. Our main result is that we have measured the BAO scale with a statistical precision of 1.1% along and 1.3% transverse to the line of sight, for a combined precision of 0.65% on the isotropic BAO scale at $z_{eff} = 2.33$. This excellent precision, combined with recent theoretical studies of the BAO shift due to nonlinear growth, motivated us to include a systematic error term in LyA BAO analysis for the first time. We measure the ratios $D_H(z_{eff})/r_d = 8.632 \pm 0.098 \pm 0.026$ and $D_M(z_{eff})/r_d = 38.99 \pm 0.52 \pm 0.12$, where $D_H = c/H(z)$ is the Hubble distance, $D_M$ is the transverse comoving distance, $r_d$ is the sound horizon at the drag epoch, and we quote both the statistical and the theoretical systematic uncertainty. The companion paper presents the BAO measurements at lower redshifts from the same dataset and the cosmological interpretation.
[abstract 34 / 49] (score: 2) - Title: Probing the transition from classical to quantum radiation reaction in RELATIVISTIC plasmaAuthors: Haidar Al-Naseri, Gert Brodin,Comments:Subjects: physics.plasm-ph hep-ph hep-thCreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
We study the transition from classical radiation reaction, described by the Landau-Lifshitz model, to the quantum mechanical regime. The plasma is subject to a circularly polarized field where the self-consistent plasma current is the source of the electroMAGNETic field through Ampere's law. The radiation reaction implies wave energy loss, frequency up-conversion, and a modified distribution function. Increasing the value of the quantum $χ$-parameter, the quantum results gradually differ from the classical ones. Moreover, the deviation between models also depends on the plasma parameters, including density and temperature. We discuss the implications of our findings.
[abstract 35 / 49] (score: 2) - Title: Kilonova constraints for the LIGO/Virgo/KAGRA neutron star merger candidate S250206dm: GW-MMADS observationsAuthors: Lei Hu, Tomás Cabrera, Antonella Palmese, James Freeburn, Mattia Bulla, Igor Andreoni, Xander J. Hall, Brendan O'Connor, Ariel Amsellem, Clécio R. Bom, Malte Busmann, Jennifer Fabà, Julius Gassert, Sena Kalabalik, Keerthi Kunnumkai, Daniel Gruen, Luidhy Santana-Silva, André Santos, Tomás Ahumada, Jonathan Carney, Michael W. Coughlin, Xingzhuo Chen, K. E. Saavik Ford, Daniel E. Holz, Mansi M. Kasliwal, Ignacio Magaña Hernandez, Cassidy Mihalenko, Rosalba Perna, Arno Riffeser, Christoph Ries, Lena Schnappinger, Michael Schmidt, Julian Sommer, Sarah Teague, Pablo Vega, Olga Volchansky, Lifan Wang, Yajie Zhang,Comments: 20 pages, 5 figures, submitted to ApJL, comments welcomeSubjects: astro-ph.HECreated: 2025-06-27; Updated: 2025-07-01; Datestamp: 2025-07-01
Gravitational wave (GW) neutron star mergers with an associated electroMAGNETic counterpart constitute powerful probes of binary evolution, the production sites of heavy elements, general relativity, and the expansion of the universe. Only a handful of candidate GW binary mergers during the fourth LIGO/Virgo/KAGRA observing run (O4) so far are believed to include a neutron star. We present optical-near infrared follow-up observations of the candidate neutron-star BLACK HOLE GW merger S250206dm. This is the first high-significance mass gap neutron star-BLACK HOLE candidate observed by multiple GW detectors (thus having a significantly smaller sky localization than one-detector events), offering the first opportunity to effectively follow up a GW event of this kind. Our GW MultiMessenger Astronomy DECam Survey (GW-MMADS) campaign consisted of a wide-field search using the Dark Energy Camera (DECam) and T80-South (T80S), as well as galaxy-targeted observations using the Southern Astrophysical Research (SOAR) imager and the Wendelstein 2.1m 3-channel camera. No viable kilonova counterpart was found in our observations. We use our observation depths to place competitive constraints on kilonova models similar to or brighter than the GW170817 kilonova AT 2017gfo within our observed fields, ruling out 100\% of such models with SOAR galaxy-targeted observations and $\sim43$\% (48\%) with DECam (DECam and T80S).
[abstract 36 / 49] (score: 2) - Title: Optical appearance of Schwarzschild BLACK HOLEs with optically thin and thick accretion disks at various inclination anglesAuthors: Jiawei Chen, Jinsong Yang,Comments: 14 pages,16 figuresSubjects: gr-qc astro-ph.HECreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
In this paper, we systematically investigate the optical appearance of a Schwarzschild BLACK HOLE illuminated by three geometrically thin accretion disk models under varying observational inclination angles. Based on the geometric relationship between the BLACK HOLE and observer, we first divide the accretion disk into co-side and counter-side semi-disks. Subsequently, we analyze their differences in photon orbit distributions, transfer functions, and received intensities. Our results reveal distinct inclination-dependent behaviors between the two semi-disks: when the inclination approaches $π/2$, the co-side semi-disk develops richer ring structures with the lensed emission dominating the total brightness. Furthermore, through explicit specification of the emission profiles of the three models, we present optical images for both optically thin and thick disk scenarios at different inclinations. The results demonstrate that: (i) the bright rings in all three models become progressively compressed and deviate from circularity as inclination increases; (ii) for thick disks, partial rings are obscured and the overall intensity is lower than thin disks. These results may advance our understanding of general BLACK HOLE imaging processes and provide a new approach to test gravitational theories through optical morphology studies.
[abstract 37 / 49] (score: 2) - Title: XRISM View of the Newly Detected Galactic Source MAXI J1744-294Authors: Kaushik Chatterjee, Santanu Mondal, Biswaraj Palit, Chandra B. Singh, Sujoy Kumar Nath, Mayukh Pahari, Brajesh Kumar, Wei Wang, Hsiang-Kuang Chang,Comments: 10 Pages, 6 Figures, 2 Tables (Suggestions are welcome!)Subjects: astro-ph.HECreated: 2025-06-28; Updated: 2025-07-01; Datestamp: 2025-07-01
The transient Galactic source MAXI J1744-294 went into an outburst in 2025 for the very first time. We study the spectral properties of this source during this outburst using archival data from the XRISM satellite for both of its Resolve and Xtend instruments. We have analyzed the source during one epoch, on March 03, 2025, or MJD 60737, on which XRISM data were available. Using both phenomenological and physical model fitting approaches for continuum emissions, along with line emission and interstellar absorption models, we analyzed the spectral data in the broad 2-10 keV energy band. From our spectral analysis, we have found the existence of multiple iron lines, which are different components of the Fe XXV emission. These line complexes arise from two highly ionized plasmas with ionization rate ~ 10000 erg cm/s with distinct turbulent velocities: one broad (vturb ~ 2513 km/s) from hot gas at the inner accretion disk, and one narrow (vturb ~ 153 km/s ) scattered by nearby photoionized gas. The source is a moderately spinning BLACK HOLE with a spin of 0.63-0.70, a mass of 5.7-10.1 Solar masses, and a disk inclination angle of 19-24 degrees. The spectral model fitted parameters suggest that the source is in the soft spectral state. The source is situated in a crowded field near the Galactic center, resulting in a very high hydrogen column density.
[abstract 38 / 49] (score: 2) - Title: Relativistic excitation of compact starsAuthors: Zhiqiang Miao, Xuefeng Feng, Zhen Pan, Huan Yang,Comments: 23 pages, 9 figuresSubjects: gr-qcCreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
In this work, we study the excitation of a compact star under the influence of external gravitational driving in the RELATIVISTIC regime. Using a model setup in which a wave with constant frequency is injected from past null infinity and scattered by the star to future null infinity, we show that the scattering coefficient encodes rich information of the star. For example, the analytical structure of the scattering coefficient implies that the decay rate of a mode generally plays the role of ``star excitation factor'', similar to the ``BLACK HOLE excitation factor'' previously defined for describing BLACK HOLE mode excitations. With this star excitation factor we derive the transient mode excitation as a binary system crosses a generic mode resonance of a companion star during the inspiral stage. This application is useful because previous description of resonant mode excitation of stars still relies on the mode and driving force decomposition based on the Newtonian formalism. In addition, we show that the scattering phase is intimately related to the total energy of spacetime and matter under the driving of a steady input wave from infinity. We also derive the relevant tidal energy of a star under steady driving and compare that with the dynamic tide formula. We estimate that the difference may lead to $\mathcal{O}(0.5)$ radian phase modulation in the late stage of the binary neutron star inspiral waveform.
[abstract 39 / 49] (score: 2) - Title: Ultra High Energy Neutrino Event KM3-230213A as a Signal of Electroweak Vacuum Turbulence in Merging Black Hole BinariesAuthors: Alexander S. Sakharov, Rostislav Konoplich, Merab Gogberashvili,Comments: 21 pages, 1 figure, 4 tablesSubjects: astro-ph.HE hep-phCreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
The recent detection of the ultra-high-energy neutrino event KM3-230213A ($\sim$220 PeV) by KM3NeT telescope poses a challenge to conventional astrophysical models, particularly in light of the absence of similar $\gtrsim$100 PeV events in IceCube data, despite its larger exposure. We propose a novel mechanism in which binary BLACK HOLE mergers act as transient neutrino sources via gravitationally induced electroweak vacuum instability. In this scenario, the extreme spacetime curvature near the horizons during the final inspiral phase destabilizes the Higgs vacuum, triggering nucleation of true-vacuum bubbles. Collisions between these bubbles produce microscopic BLACK HOLEs that rapidly evaporate via Hawking radiation, emitting intense, short-lived bursts of neutrinos with energies exceeding 100 PeV. The resulting neutrino fluence follows a heavy-tailed distribution, allowing rare but highly luminous sources to account for events like KM3-230213A while remaining consistent with IceCube's non-detections. This framework links gravitational wave sources to ultra-high-energy neutrino production and suggests that future multi-messenger observations may detect electroMAGNETic signatures from microscopic BLACK HOLE evaporation.
[abstract 40 / 49] (score: 2) - Title: An investigation into correlations between FRB and host galaxy propertiesAuthors: M. Glowacki, A. Bera, C. W. James, J. Paterson, A. T. Deller, A C. Gordon, L. Marnoch, A. R. Muller, J. X. Prochaska, S. D. Ryder, R. M. Shannon, N. Tejos, A. G. Mannings,Comments: Submitted to PASA. 21 pages, 6 figures, 6 tablesSubjects: astro-ph.HECreated: 2025-06-29; Updated: 2025-07-01; Datestamp: 2025-07-01
Impulsive radio signals such as fast radio bursts (FRBs) are imprinted with the signatures of multi-path propagation through ionised media in the form of frequency-dependent temporal broadening of the pulse profile (scattering). The dominant source of scattering for most FRBs is expected to be within their host galaxies, an assumption which can be tested by examining potential correlations between properties of the FRBs and global properties of their hosts. Using results from the CRAFT survey, we investigate correlations across a range of host galaxy properties against attributes of the FRB that encode propagation effects: scattering timescale tau, polarisation fractions, and absolute Faraday rotation measure. From 21 host galaxy properties considered, we find three correlated with tau, including the stellar surface density (or compactness; Pearson p-value p = 0.002 and Spearman p = 0.010), mass-weighted age (Spearman p-value p = 0.009), and a weaker correlation with gas-phase metallicity (Spearman p = 0.017). Weakly significant correlations are also found with Halpha equivalent widths and gravitational potential. From 10,000 trials of reshuffled datasets, we expect 2 strong Spearman correlations only 2% of the time, and three weaker correlations in 6.6% of cases. Compact host galaxies may have more ionised content which scatters the FRB further. No correlation is seen with host galaxy inclination, which weakens the case for an inclination bias, as previously suggested for samples of localised FRBs. A strong (p = 0.002) correlation is found for absolute rotation measure with optical disc axis ratio b/a; greater rotation measures are seen for edge-on host galaxies. Further high-time resolution FRB detections, coupled with localisation and detailed follow-up on their host galaxies, are necessary to corroborate these initial findings and shed further light into the FRB mechanism.
[abstract 41 / 49] (score: 2) - Title: On Bell's dynamical route to special relativityAuthors: Frederick W. Strauch,Comments: 4 figures; supplemental included in sourceSubjects: physics.hist-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
This paper develops the approach to special relativity put forward by John S. Bell. The classical dynamics of an electron orbiting a nucleus in uniform motion is solved analytically and compared to numerical simulations for an accelerated nucleus. The RELATIVISTIC phenomena of length contraction and time dilation are shown to result from the electric and MAGNETic forces on the electron when its motion is analyzed in a single frame of reference. The relevance of these results for understanding the theory of special relativity is discussed.
[abstract 42 / 49] (score: 2) - Title: Investigation of resonant layer response in electron viscosity regimeAuthors: Yeongsun Lee, Jace Waybright, Jong-Kyu Park,Comments:Subjects: physics.plasm-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
We present a supplementary study of previous work in Waybright and Park [Phys. Plasmas 31, 022502 (2024)] which demonstrates a substantial effect of electron viscosity on the resonant layer response to non-axisymmetric MAGNETic perturbations. A main refinement is to include a curl element of electron viscosity in the generalized Ohm's law. The refinement reveals a resonant layer response in the Electron Viscosity (EV) regime corresponding to slowly rotating and highly viscous plasmas.
[abstract 43 / 49] (score: 2) - Title: The interaction of turbulence, MAGNETic islands and zonal fields in fluid plasma models with cubic non-linearitiesAuthors: Daniele Villa, Nicolas Dubuit, Olivier Agullo, Xavier Garbet,Comments:Subjects: physics.plasm-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
It is shown that MAGNETic islands generated by pressure-gradient-driven turbulence are common across a wide range of conditions. The interaction among turbulence, MAGNETic island and other large scale structures (the zonal flow and the zonal current), largely determines the dynamics of the system. Turbulence takes a background role, providing energy to the large-scale structures, without influencing their evolution directly. The growth of the zonal current is linearly related to that of the MAGNETic island, while the zonal flow has a strongly sheared region where the island has its maximum radial extension. The zonal current is found to slow down the formation of large-scale MAGNETic islands, while the zonal flow is needed to have the system move its energy to larger and larger scales. The driving instability in the system is the fluid Kinetic Ballooning Mode (KBM) instability at high beta, while the tearing mode is kept stable. The formation of MAGNETic-island-like structures at the spatial scale of the fluid KBM instability is observed quite early in the non-linear phase for most cases studied, and a slow coalescence process evolves the MAGNETic structures towards larger and larger scales. Cases that did not show this coalescence process, nor the formation of the small scale island-like structures, were seen to have narrower mode structures for comparable instability growth rates, which was achieved by varying the MAGNETic shear. The islands often end up exceeding the radial box size late in the non-linear phase, showing unbounded growth. The impact on the pressure profile of turbulence driven MAGNETic islands is not trivial, showing flattening of the pressure profile only far from the resonance, where the zonal flow is weaker, and the appearance of said flattening is slow, after the island has reached a sufficiently large size, when compared with collisional time scales.
[abstract 44 / 49] (score: 2) - Title: Studying the multi-phase interstellar medium in the Large Magellanic Cloud with SRG/eROSITA -- I. Analysis of diffuse X-ray emissionAuthors: Martin G. F. Mayer, Manami Sasaki, Frank Haberl, Kisetsu Tsuge, Yasuo Fukui, Chandreyee Maitra, Miroslav D. Filipovic, Zachary J. Smeaton, Lister Staveley-Smith, Baerbel Koribalski, Sean Points, Patrick Kavanagh,Comments: Accepted for publication by A&A; 22 pages, 14 figures, 1 table; Abstract abridgedSubjects: astro-ph.HE astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The Large Magellanic Cloud (LMC), being a nearby and actively star-forming satellite galaxy of the Milky Way, is an ideal site to observe the multi-phase interstellar medium (ISM) of a galaxy across the electroMAGNETic spectrum. We aim to exploit the available SRG/eROSITA all-sky survey data to study the distribution, composition and properties of the diffuse X-ray emitting hot gas in the LMC. We construct multi-band X-ray images of the LMC, reflecting the morphology and temperatures of the diffuse hot gas. By performing spatially resolved X-ray spectroscopy of 175 regions, we constrain the distribution, physical state, and composition of the hot ISM phase throughout the LMC. We combine our constraints with multiwavelength data to obtain a comprehensive view of the different ISM phases. We measure a total X-ray luminosity of the hot ISM phase of $1.9\times10^{38}\,\mathrm{erg\,s^{-1}}$ ($0.2-5.0\,\mathrm{keV}$ band), and constrain its thermal energy to around $5\times10^{54}\,\mathrm{erg}$. The typical density and temperature of the X-ray emitting plasma are around $5\times10^{-3}\,\mathrm{cm^{-3}}$ and $0.25\,\mathrm{keV}$, respectively, with both exhibiting broad peaks in the southeast of the LMC. The observed degree of X-ray absorption correlates strongly with the distribution of foreground HI gas, whereas a spatial anticorrelation between the hot and cold ISM phases is visible on sub-kpc scales within the disk. The abundances of light metals show a strong gradient throughout the LMC, with the north and east exhibiting a strong $α$-enhancement, as expected from observed massive stellar populations there. In contrast, the enigmatic ``X-ray spur'' exhibits a local deficit in $α$-elements, and a peak in hot-gas pressure at $P/k\sim10^5\,\mathrm{K\,cm^{-3}}$, consistent with a dominant energy input through tidally driven gas collisions.
[abstract 45 / 49] (score: 2) - Title: A hybrid numerical algorithm based on the stochastic particle Shakhov and DSMC methodAuthors: Hao Jin, Sha Liu, Sirui Yang, Junzhe Cao, Congshan Zhuo, Chengwen Zhong,Comments:Subjects: physics.comp-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The Direct Simulation Monte Carlo (DSMC) method is widely employed for simulating rarefied nonequilibrium gas flows. With advances in aerospace engineering and micro/nano-scale technologies, gas flows exhibit the coexistence of rarefied and continuum/near-continuum regimes, which calls for larger time steps and coarser spatial grids for efficient numerical simulation. However, the mesh sizes and time steps in DSMC are constrained by the single-scale nature of the Boltzmann equation and the explicit treatment of collision term following operator splitting. To overcome the resulting computational inefficiency, the Time-Relaxed Monte Carlo (TRMC) method introduces a suitable time discretization of the Boltzmann equation, allowing for significantly larger time steps. Besides, domain decomposition methods leverage the complementary strengths of continuum and particle-based approaches, facilitating the efficient simulation of multi-scale gas flows. However, in TRMC method, the physically accurate high-order terms are truncated and approximated through convergence to a local Maxwellian distribution. Meanwhile, the continuum breakdown criteria employed in hybrid methods are either empirical or semi-empirical. Recently, a timescale-based decomposition of the Boltzmann equation has been proposed to enable a more rational coupling between DSMC and Navier-Stokes. Inspired by this strategy, a novel hybrid particle method is proposed to couple the stochastic particle Shakhov with DSMC, in which the collision operator is decomposed into two sub-steps based on local observation timescale and the relaxation time. The validity and accuracy of the proposed method are demonstrated through a series of benchmark cases, including 1-D sod shock tube, 2-D hypersonic flow around cylinder and JET expansion into the vacuum, 3-D hypersonic flows around sphere and X-38 like vehicle in near-continuum flow regimes.
[abstract 46 / 49] (score: 2) - Title: Sagittarius A* near-infrared flares POLARIZATION as a probe of space-time I: Non-rotating exotic compact objectsAuthors: Nicolas Aimar, João Luís Rosa, Hanna Liis Tamm, Paulo Garcia,Comments: 14 pages, 9 figures, 7 tables; comments welcomeSubjects: astro-ph.HE gr-qcCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
The center of our galaxy hosts Sagittarius~A*, a supermassive compact object of $\sim 4.3\times 10^6$ solar masses, usually associated with a BLACK HOLE. Nevertheless, BLACK HOLEs possess a central singularity, considered unphysical, and an event horizon, which leads to loss of unitarity in a quantum description of the system. To address these theoretical inconsistencies, alternative models, collectively known as exotic compact objects, have been proposed. In this paper, we investigate the potential detectability of signatures associated with non-rotating exotic compact objects within the Sgr~A* polarized flares dataset, as observed through GRAVITY and future instruments. We examine a total of eight distinct metrics, originating from four different categories of static and spherically symmetric compact objects: Black Holes, Boson stars, Fluid spheres, and Gravastars. Our approach involves utilizing a toy model that orbits the compact object in the equatorial plane, at the Schwarzschild-Keplerian velocity. Using simulated astrometric and polarimetric data with present GRAVITY and future GRAVITY+ uncertainties, we fit the datasets across all metrics examined. We evaluated the detectability of the metric for each dataset based on the resulting $χ^2_\mathrm{red}$ and BIC-based Bayes factors. Plunge-through images of ECOs affect POLARIZATION and astrometry. With GRAVITY's present uncertainties, only a compact BOSON-star model is discernible. GRAVITY+'s improved sensitivity allows detection of most exotic compact object models. However, enhancing the astrophysical complexity of the hot spot model diminishes these outcomes. Presently, GRAVITY's uncertainties limit us to detecting just one exotic compact object metric. With GRAVITY+'s enhanced sensitivity, we can expect to uncover additional exotic compact object models and use Sgr~A* as a laboratory for fundamental physics.
[abstract 47 / 49] (score: 2) - Title: The impacts of tropospheric gravity wave-generated MSTIDs on skywaves at middle latitude North American sector observed and modeled using SuperDARN HF radarsAuthors: S. Chakraborty, P. A. Inchin, S. Debchoudhury, C. Heale, B. Bergsson, M. Zettergren, J. M. Ruohoniemi,Comments:Subjects: physics.space-ph physics.plasm-phCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Trans-ionospheric high frequency (HF: 3-30 MHz) response to gravity waves (GWs) is studied in the middle-latitude ionosphere in relation to thunderstorm activity. SuperDARN HF radar observations are compared against the model simulations to quantify the impact of GW-generated MSTID (medium-scale traveling ionospheric disturbances) activity on the skywaves traveling through ionospheric F-region heights. The tropospheric thunderstorm-driven convective source is modeled using MAGIC. The outputs are coupled with GEMINI to model ionospheric plasma response, which is then used to model SuperDARN HF radar observations using the PHaRLAP raytracing tool. Semi-concentric GWs were observed at different atmospheric heights, creating MSTIDs at F-region heights. PHaRLAP raytracing through the modeled ionosphere shows great qualitative agreement with SuperDARN daytime ground scatter observations. Modeled rays show possibilities of long ducting Pedersen rays, suggesting MSTID can create a plasma waveguide to duct rays at the F-region height.
[abstract 48 / 49] (score: 2) - Title: Listening Across the Cosmic Time: Standard Sirens from Ground- and Space-Based Missions in the Next DecadeAuthors: Alberto Salvarese, Hsin-Yu Chen, Alberto Mangiagli, Nicola Tamanini,Comments: Invited article for the Classical and Quantum Gravity special issue "Gravitational Wave Physics and Astrophysics Ten Years After GW150914"Subjects: astro-ph.COCreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
Precise measurement of the Hubble parameter will enable stringent tests of the standard model for cosmology. Standard sirens, using the luminosity distances measured by gravitational-wave observations of compact binary mergers, are expected to provide such measurements independently in the next decade. With the ground- and space-based gravitational wave observatories, the LIGO-Virgo-KAGRA (LVK) network and the Laser Interferometer Space Antenna (LISA), different types of standard sirens altogether will place constraints across a wide redshift range. In this paper, we forecast the precisions of standard siren Hubble parameter measurements and compare various scenarios, accounting for the dominant sources of systematic uncertainty. Specifically, we find a $2\%$ constraint on $H_0$, a $1.5-3\%$ constraint on $H(z)$ at $z=1$, and a $3-5\%$ constraint on $H(z)$ at $z=7$ when combining LVK and LISA standard sirens with precise redshift measurements from electroMAGNETic counterpart observations. We do not find a significant improvement when including standard sirens with no EM counterpart, but which rely on features in the BLACK HOLE mass distribution, and the potential systematics introduced by the possible redshift evolution of such features could further degrade the measurement accuracy if not properly accounted for.
[abstract 49 / 49] (score: 2) - Title: Beneath the Surface: >85% of z>5.9 QSOs in Massive Host Galaxies are UV-FaintAuthors: R. J. Bouwens, E. Banados, R. Decarli, J. Hennawi, D. Yang, H. Algera, M. Aravena, E. Farina, A. Gloudemans, J. Hodge, H. Inami, J. Matthee, R. Meyer, R. P. Naidu, P. Oesch, H. J. A. Rottgering, S. Schouws, R. Smit, M. Stefanon, P. van der Werf, B. Venemans, F. Walter, Y. Fudamoto,Comments: 13 pages, 6 figures, 4 tables, submitted to A&ASubjects: astro-ph.GACreated: 2025-06-30; Updated: 2025-07-01; Datestamp: 2025-07-01
We use [CII] observations of a large QSO sample to segregate sources by host galaxy mass, aiming to identify those in the most massive hosts. [CII] luminosity, a known tracer of molecular gas, is taken as a proxy for host mass and used to rank 190 QSOs at z>5.9, spanning a 6-mag UV luminosity range (-22
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