Showing 1–50 of 1,432 results for author: Wang, X

Diagnosing the AGN population origin of TeV neutrinos with their spatial correlation

Authors: Xiao-Bin Chen, Ruo-Yu Liu, Xiang-Yu Wang

Abstract: The recent IceCube detection of TeV neutrinos from some nearby Seyfert galaxy (e.g., NGC~1068) suggests that active galactic nuclei (AGN) could make a significant contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV gamma-rays from NGC~1068 indicates neutrino production in compact gamma-ray-opaque region. The vicinity of the supermassive black hole, such as disk-corona,… ▽ More The recent IceCube detection of TeV neutrinos from some nearby Seyfert galaxy (e.g., NGC~1068) suggests that active galactic nuclei (AGN) could make a significant contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV gamma-rays from NGC~1068 indicates neutrino production in compact gamma-ray-opaque region. The vicinity of the supermassive black hole, such as disk-corona, is an ideal region, where the high radiation density leads to efficient neutrino production as well as the gamma-ray attenuation. Disk-corona models predict that the neutrino emission from AGNs correlates with X-ray emission, which traces the coronal activity. In this paper, we assess whether the X-ray AGN population origin for TeV neutrinos can be tested by using the spatial correlation between the neutrino population and X-ray AGN population with future neutrino telescopes. By performing simulations, we find that, the AGN origin of the neutrino background above 100\,TeV can be tested at a confidence level of $\sim2.4σ$ with five-year observations of IceCube-Gen2, which has an angular resolution of $\sim0.2$ degree. With better angular resolution and sensitivity in the energy range of above $300$\,TeV, a 30-${\rm km^3}$ underwater neutrino telescope, such as High-energy Underwater Neutrino Telescope (HUNT), is expected to reach a significance of $\sim8.6σ$ in testing the association after five years of exposure. △ Less

Submitted 22 December, 2025; originally announced December 2025.

The AGN nature of strong CIII emitters in the Early Universe with JWST

Authors: F. Arevalo-Gonzalez, R. Tripodi, M. Llerena, L. Pentericci, A. Plat, G. Barro, R. O. Amorín, B. Backhaus, A. Calabrò, N. J. Cleri, M. Dickinson, J. S. Dunlop, S. L. Finkelstein, M. Giavalisco, M. Hirschmann, J. Kartaltepe, A. M. Koekemoer, R. A. Lucas, L. Napolitano, E. Piconcelli, A. J. Taylor, F. Tombesi, J. R. Trump, X. Wang

Abstract: The semi-forbidden CIII] $λλ$1907,1909 doublet is a key tracer of high-ionization emission in the early universe. We present a study of CIII] emission in galaxies at z=5-7, using publicly available JWST/NIRSpec prism data from programs including CEERS, JADES, RUBIES and CAPERS. We built a sample of 61 CIII]-emitting galaxies, and we classified them as star-forming or active galactic nuclei (AGN) h… ▽ More The semi-forbidden CIII] $λλ$1907,1909 doublet is a key tracer of high-ionization emission in the early universe. We present a study of CIII] emission in galaxies at z=5-7, using publicly available JWST/NIRSpec prism data from programs including CEERS, JADES, RUBIES and CAPERS. We built a sample of 61 CIII]-emitting galaxies, and we classified them as star-forming or active galactic nuclei (AGN) host galaxies using (1) rest-frame UV and optical emission-line diagnostic diagrams, and (2) the presence/absence of broad Balmer emission lines. The UV diagnostics are based on the combination of the rest-frame equivalent width (EW) of CIII] versus CIII]/HeII $λ$1640, and the EW of CIV versus CIV/HeII $λ$1640. For optical diagnostics, we employ the OHNO diagram, which combines [OIII] $λ$5007, H$β$, [NeIII] $λ$3869, and [OII] $λλ$3727,3729- and we find it has a low efficiency on separating AGN from SFG. We find that half of the sources in our sample (29 out of 61 galaxies) exhibit at least one secure indication of AGN activity while 13 are potential AGNs based on the CIII] diagnostic. Physical properties, including stellar mass and star formation rate, are derived through spectral energy distribution modeling with Bagpipes. Our analysis reveals that JWST is uncovering a population of strong CIII] emitters at high redshift (5<z<7) with a median EW of 22.8 A. This EW is higher than that of a control sample of CIII] emitters at redshift 3<z<4 with a median EW of 4.7 A. We find that for the same range of Muv, the CIII] EW increases by $\sim$0.67 dex from 3<z<4 to 5<z<7, indicating strong redshift evolution in the line's strength. Finally, we identify five sources in our sample as Little Red Dots (LRDs); while four of these have already been identified as LRD in the literature, one is presented here for the first time. △ Less

Submitted 18 December, 2025; originally announced December 2025.

Comments: Submitted to A&A, 15 pages

Transitional Dynamics: Unveiling the Coexistence and Interplay of Type-B and Type-C QPOs in MAXI J1348-630

Authors: Xinlei Wang, Zhen Yan, Fu-Guo Xie, Jun-Feng Wang, Ya-Xing Li, Ren-Yi Ma

Abstract: Based on broadband timing analysis of Insight-HXMT and NICER data from the 2019 outburst of the black hole X-ray binary (BHXRB) MAXI J1348-630, we report the detection of the coexistence and competitive interplay between type-C and type-B quasi-periodic oscillations (QPOs). Specifically, the two QPO types were detected simultaneously but exhibited distinct energy dependencies: the type-C QPO was d… ▽ More Based on broadband timing analysis of Insight-HXMT and NICER data from the 2019 outburst of the black hole X-ray binary (BHXRB) MAXI J1348-630, we report the detection of the coexistence and competitive interplay between type-C and type-B quasi-periodic oscillations (QPOs). Specifically, the two QPO types were detected simultaneously but exhibited distinct energy dependencies: the type-C QPO was dominant in the hard X-ray band (10-30 keV), while the type-B QPO was more prominent in the soft X-ray band (1-10 keV). Further analysis reveals that the emergence of the type-C QPO suppresses the strength of the type-B QPO, particularly above 10 keV. Tracking the detailed evolution of these QPOs, we find that the weakening of the type-B QPO coincides with the strengthening of the type-C QPO, indicating a competitive interaction between them. These findings reveal a more complex relationship between type-B and type-C QPOs than previously recognized, suggesting they originate from distinct but interacting physical components within the accretion flow and/or jet, and providing new insights into the dynamics of accretion state transitions. △ Less

Submitted 15 December, 2025; originally announced December 2025.

Comments: 10 pages, 5 figures, Accepted for publication in The Astrophysical Journal

Constraining the dark matter origin of the halo-like 20 GeV $γ$-ray excess with the AMS-02 antiproton data

Authors: Xiao Wang, Kai-Kai Duan

Abstract: Very recently, a significant $\sim 20$ GeV gamma-ray excess in the Milky Way halo has been reported and a dark matter origin has been suggested. The inferred dark matter parameters are $ m_χ\sim 0.5-0.8 $ TeV and $ \langle σv \rangle \sim (5-8) \times 10^{-25}~{\rm cm^3~s^{-1}}$ for the $ b\bar{b} $ channel. If correct, prominent antiproton emission is produced and can be directly tested by the AM… ▽ More Very recently, a significant $\sim 20$ GeV gamma-ray excess in the Milky Way halo has been reported and a dark matter origin has been suggested. The inferred dark matter parameters are $ m_χ\sim 0.5-0.8 $ TeV and $ \langle σv \rangle \sim (5-8) \times 10^{-25}~{\rm cm^3~s^{-1}}$ for the $ b\bar{b} $ channel. If correct, prominent antiproton emission is produced and can be directly tested by the AMS-02 data. In this work we calculate the corresponding antiproton emission and show that the expected flux at $\sim 100$ GeV is already above the AMS-02 observation. A proper treatment on the antiproton background resulting from the high energy cosmic ray propagation would suggest an annihilation cross section of $< 2\times 10^{-26}~{\rm cm^3~s^{-1}}$, which is a few$\times 10$ times lower than that needed to interpret the potential signal. We therefore conclude that the $\sim 20$ GeV gamma-ray excess in the Milky Way halo is not a viable dark matter signal. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Comments: 9 pages, 2 figures

Measurement of the cosmic ray nickel energy spectrum from 10 GeV/n to 2 TeV/n with the DAMPE

Authors: F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. V. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong, G. Donvito, J. L. Duan , et al. (123 additional authors not shown)

Abstract: Nickel, one of the most stable elements alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of c… ▽ More Nickel, one of the most stable elements alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of cosmic-ray nickel spectrum from 10 GeV/n to 2 TeV/n with nine years of flight data. The nickel spectrum is consistent with a single power law with spectral index -2.60 +/- 0.03 from 40 GeV/n to 1 TeV/n. This work provides an accurate measurement of differential flux of nickel with kinetic energy extending to TeV/n for the first time. △ Less

Submitted 12 December, 2025; originally announced December 2025.

EP250827b/SN 2025wkm: An X-ray Flash-Supernova Powered by a Central Engine and Circumstellar Interaction

Authors: Gokul P. Srinivasaragavan, Dongyue Li, Xander J. Hall, Ore Gottlieb, Genevieve Schroeder, Heyang Liu, Brendan O'Connor, Chichuan Jin, Mansi Kasliwal, Tomás Ahumada, Qinyu Wu, Christopher L. Fryer, Annabelle E. Niblett, Dong Xu, Maria Edvige Ravasio, Grace Daja, Wenxiong Li, Shreya Anand, Anna Y. Q. Ho, Hui Sun, Daniel A. Perley, Lin Yan, Eric Burns, S. Bradley Cenko, Jesper Sollerman , et al. (69 additional authors not shown)

Abstract: We present the discovery of EP250827b/SN 2025wkm, an X-ray Flash (XRF) discovered by the Einstein Probe (EP), accompanied by a broad-line Type Ic supernova (SN Ic-BL) at $z = 0.1194$. EP250827b possesses a prompt X-ray luminosity of $\sim 10^{45} \, \rm{erg \, s^{-1}}$, lasts over 1000 seconds, and has a peak energy $E_{\rm{p}} < 1.5$ keV at 90% confidence. SN 2025wkm possesses a double-peaked lig… ▽ More We present the discovery of EP250827b/SN 2025wkm, an X-ray Flash (XRF) discovered by the Einstein Probe (EP), accompanied by a broad-line Type Ic supernova (SN Ic-BL) at $z = 0.1194$. EP250827b possesses a prompt X-ray luminosity of $\sim 10^{45} \, \rm{erg \, s^{-1}}$, lasts over 1000 seconds, and has a peak energy $E_{\rm{p}} < 1.5$ keV at 90% confidence. SN 2025wkm possesses a double-peaked light curve (LC), though its bolometric luminosity plateaus after its initial peak for $\sim 20$ days, giving evidence that a central engine is injecting additional energy into the explosion. Its spectrum transitions from a blue to red continuum with clear blueshifted Fe II and Si II broad absorption features, allowing for a SN Ic-BL classification. We do not detect any transient radio emission and rule out the existence of an on-axis, energetic jet $\gtrsim 10^{50}~$erg. In the model we invoke, the collapse gives rise to a long-lived magnetar, potentially surrounded by an accretion disk. Magnetically-driven winds from the magnetar and the disk mix together, and break out with a velocity $\sim 0.35c$ from an extended circumstellar medium with radius $\sim 10^{13}$ cm, generating X-ray breakout emission through free-free processes. The disk outflows and magnetar winds power blackbody emission as they cool, producing the first peak in the SN LC. The spin-down luminosity of the magnetar in combination with the radioactive decay of $^{56}$Ni produces the late-time SN LC. We end by discussing the landscape of XRF-SNe within the context of EP's recent discoveries. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: 43 pages, 20 Figures, Submitted to ApJ Letters

X-ray Polarization and Spectral Variations in an Extreme High-Synchrotron-Peaked Blazar 1ES 1101--232

Authors: Xin-Ke Hu, Jin Zhang, Fei Xie, Xiang-Gao Wang

Abstract: We present the first X-ray polarimetric observation of the extreme high-synchrotron-peaked blazar 1ES 1101--232, conducted by the Imaging X-ray Polarimetry Explorer (IXPE). The data analysis incorporates simultaneous and quasi-simultaneous observations from Swift-XRT and NuSTAR. Our results reveal a significant detection of X-ray polarization in the 2--6 keV band at a confidence level (CL) of 6.6… ▽ More We present the first X-ray polarimetric observation of the extreme high-synchrotron-peaked blazar 1ES 1101--232, conducted by the Imaging X-ray Polarimetry Explorer (IXPE). The data analysis incorporates simultaneous and quasi-simultaneous observations from Swift-XRT and NuSTAR. Our results reveal a significant detection of X-ray polarization in the 2--6 keV band at a confidence level (CL) of 6.6$σ$, with a polarization degree of $Π_{\rm X}=17.9\%\pm2.7\%$ and an electric vector position angle (EVPA) of $ψ_{\rm X}=10^\circ.0\pm4^\circ.4$. An even higher polarization degree of $Π_{\rm X}=38.9\%\pm9.1\%$ with an EVPA of $ψ_{\rm X}=13^\circ.9\pm6^\circ.7$ is observed within a narrower time interval, at a CL of 4.3$σ$. During the IXPE observational campaign, the X-ray spectrum of 1ES 1101--232 exhibits a clear soft-to-hard spectral evolution in the 0.3--10 keV band, although no significant flux variability is detected. Additionally, a clockwise hysteresis loop is identified in the flux--photon index plane. These findings collectively indicate that the X-ray emission from 1ES 1101--232 originates in a region characterized by a well-ordered magnetic field through synchrotron radiation. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: 16 pages, 10 figures, 3 tables, accepted for publication in ApJ

Curvaton-assisted hilltop inflation

Authors: Wen-Yuan Ai, Stephen F. King, Xin Wang, Ye-Ling Zhou

Abstract: Following the recent Atacama Cosmology Telescope (ACT) results, we consider hilltop inflation where the inflaton is coupled to a curvaton, simultaneously addressing two main challenges faced by conventional hilltop inflation models: the initial-value problem; and their viability for sub-Planckian field values. In standard single-field hilltop inflation, the inflaton must start extremely close to t… ▽ More Following the recent Atacama Cosmology Telescope (ACT) results, we consider hilltop inflation where the inflaton is coupled to a curvaton, simultaneously addressing two main challenges faced by conventional hilltop inflation models: the initial-value problem; and their viability for sub-Planckian field values. In standard single-field hilltop inflation, the inflaton must start extremely close to the maximum of the potential, raising concerns about the naturalness of the initial conditions. We demonstrate that the curvaton field not only solves the initial-value problem, but also opens up parameter space through modifying the curvature perturbation power spectrum, reviving the cubic and quartic hilltop inflation models in the sub-Planckian regime. We find viable parameter space consistent with the recent cosmological observations, and predict a sizable tensor-to-scalar ratio that can be tested in the next-generation Cosmic Microwave Background (CMB) experiments. △ Less

Submitted 9 December, 2025; originally announced December 2025.

Comments: 15 pages, 5 figures, 1 table

Investigating ionising sources and the complex interstellar medium of GHZ2 at $z=12.3$

Authors: M. Castellano, L. Napolitano, B. Moreschini, A. Calabrò, L. Christensen, M. Llerena, T. J. L. C. Bakx, F. Belfiore, D. Bevacqua, M. Dickinson, A. Fontana, G. Gandolfi, T. Gasparetto, A. Marconi, S. Mascia, E. Merlin, T. Morishita, T. Nanayakkara, D. Paris, L. Pentericci, B. Pérez-Díaz, G. Roberts-Borsani, S. Rojas Ruiz, P. Santini, T. Treu , et al. (5 additional authors not shown)

Abstract: An accurate characterisation of the physical properties of galaxies at cosmic dawn is key to understanding the origin of the high abundance of UV-bright galaxies at z$\gtrsim$10. We exploit deep NIRSpec PRISM observations of GHZ2 to constrain the sources of ionising radiation and the properties of the ISM in this bright, compact, and highly ionising galaxy at z=12.3. We measure with high significa… ▽ More An accurate characterisation of the physical properties of galaxies at cosmic dawn is key to understanding the origin of the high abundance of UV-bright galaxies at z$\gtrsim$10. We exploit deep NIRSpec PRISM observations of GHZ2 to constrain the sources of ionising radiation and the properties of the ISM in this bright, compact, and highly ionising galaxy at z=12.3. We measure with high significance the prominent N IV, C IV, He II, O III, C III, O II, and Ne III emission features previously detected in shallower observations, and confirm the detection of the N III] $λ1750$ multiplet, yielding tight constraints on the N/O ratio, which is found to be $\simeq$2 times the solar value. We also detect the Mg II $λ2800$, [Fe IV] $λ2833$ and Si II $λ1812$ doublets, the H8+HeI $λλ3889$ blend, and the Si IV+O IV] $λλ1400$ absorption complex. The O III $λ3133$ fluorescence line is only detected in the first observing epoch, implying variability on a rest-frame time span of 19 days, strongly suggesting the presence of an active nucleus. Combining the NIRSpec dataset with available optical and far-infrared constraints from MIRI and ALMA, we show that the emission spectrum of GHZ2 cannot be reproduced by single-density spectro-photometric models. Multi-zone photoionisation modelling performed with the HOMERUN code demonstrates that star formation must be occurring in a strongly stratified ISM, where both low-/intermediate-density gas and high-density regions (log($n_e$/cm$^{-3}) \gtrsim 4$) coexist. The GHZ2 emission landscape is consistent with either a composite star-formation plus AGN scenario, or with star formation occurring in a combination of radiation- and matter-bounded regions. Purely radiation-bounded stellar models fail to reproduce the observed He II emission, making an additional hard ionising component unavoidable. △ Less

Submitted 9 December, 2025; originally announced December 2025.

Comments: 16 pages, 11 figures, 2 tables. Submitted to The Open Journal of Astrophysics

The Milky Way Imaging Scroll Painting Survey: Data Release 1

Authors: Ji Yang, Qing-Zeng Yan, Yang Su, Shaobo Zhang, Xin Zhou, Yan Sun, Yiping Ao, Xuepeng Chen, Zhiwei Chen, Fujun Du, Min Fang, Yan Gong, Zhibo Jiang, Shengyu Jin, Binggang Ju, Chong Li, Yingjie Li, Yi Liu, Dengrong Lu, Chunsheng Luo, Yuehui Ma, Ruiqing Mao, Jixian Sun, Chen Wang, Hongchi Wang , et al. (10 additional authors not shown)

Abstract: We present the first data release (DR1) of the Milky Way Imaging Scroll Painting (MWISP) survey, a mapping in the J=(1-0) transition lines of 12CO, 13CO, and C18O toward the northern Galactic plane during 2011-2022. The MWISP survey was conducted using the PMO 13.7 m telescope at a spatial resolution of approximately 50" and a velocity resolution of 0.16 km/s at 115 GHz. DR1 fully covered 2310 squ… ▽ More We present the first data release (DR1) of the Milky Way Imaging Scroll Painting (MWISP) survey, a mapping in the J=(1-0) transition lines of 12CO, 13CO, and C18O toward the northern Galactic plane during 2011-2022. The MWISP survey was conducted using the PMO 13.7 m telescope at a spatial resolution of approximately 50" and a velocity resolution of 0.16 km/s at 115 GHz. DR1 fully covered 2310 square degrees within the Galactic longitude (l) and latitude (b) range of 9.75 deg =< l =< 229.75 deg and |b| =< 5.25 deg. The surveyed area was divided into cell units of 30'x30' for practical purposes and On-The-Fly (OTF) mapping was performed toward each target cell unit. The data were regridded into a regular 3D datacube in l-b-V_LSR with a pixel size of 30" in l-b axes and 0.16 km/s in theV_LSR axis. The median rms noise is 0.47 K, 0.25 K, and 0.25 K for 12CO, 13CO, and C18O, respectively. The equivalent 3 sigma sensitivity in 12CO luminosity is approximately 0.23 K km/s, making MWISP the most sensitive survey of its kind. In this paper, we describe the survey data, including the calibration, data cleaning, data mosaic processes, and the data products. The final mosaicked data cubes contain about 3.33x10^7 spectra (pixels) for each CO isotopologue line. Color composite images, made from the intensities of the isotopologue lines, and some concise descriptions are provided. We constructed a molecular cloud catalog based on the mosaicked 12CO data cube using the clustering algorithm DBSCAN, detecting 103,517 molecular clouds, 10,790 of which exhibit 13CO emission and 304 of which show C18O emission. Based on the histogram of voxel brightness temperature, we estimated a total 12CO flux of 7.69+/-0.38x10^7 K km/s arcmin^2, 82% of which is captured by the DBSCAN algorithm. The data, together with the cloud sample, provide unique information on molecular gas in the northern Milky Way. △ Less

Submitted 10 December, 2025; v1 submitted 9 December, 2025; originally announced December 2025.

Comments: Accepted for publication in ApJS. MWISP DR1 link: https://doi.org/10.57760/sciencedb.27351

The MALATANG survey: star formation, dense gas, and AGN feedback in NGC 1068

Authors: Shuting Lin, Siyi Feng, Zhi-Yu Zhang, Chunyi Zhang, Qing-Hua Tan, Junzhi Wang, Yu Gao, Xue-Jian Jiang, Yang Gao, Xiao-Long Wang, Junfeng Wang, Jian-Fa Wang, Satoki Matsushita, Aeree Chung, Kotaro Kohno, Tosaki Tomoka, Thomas R. Greve

Abstract: We aim to investigate the interplay between dense molecular gas, star formation, and active galactic nucleus (AGN) feedback in the luminous infrared galaxy (LIRG) NGC 1068 at sub-kiloparsec scales. We present the HCN (4-3) and HCO$^+$ (4-3) maps of NGC 1068, obtained with JCMT as part of the Mapping the dense molecular gas in the strongest star-forming galaxies (MALATANG) project, and perform spat… ▽ More We aim to investigate the interplay between dense molecular gas, star formation, and active galactic nucleus (AGN) feedback in the luminous infrared galaxy (LIRG) NGC 1068 at sub-kiloparsec scales. We present the HCN (4-3) and HCO$^+$ (4-3) maps of NGC 1068, obtained with JCMT as part of the Mapping the dense molecular gas in the strongest star-forming galaxies (MALATANG) project, and perform spatially resolved analyses of their correlations with infrared luminosity and soft X-ray emission. Spatially resolved relations between the luminosities of infrared dust emission and dense molecular gas tracers ($L_{\rm IR}-L'_{\rm dense}$) are found to be nearly linear, without clear evidence of excess contributions from AGN activity. The spatially resolved X-ray emission ($L^{\rm gas}_{0.5-2\,\mathrm{keV}}$) displays a radially-dependent twofold correlation with the star formation rate (SFR), suggesting distinct gas-heating mechanisms between the galaxy center and the outer regions. A super-linear scaling is obtained in galactic center regions with SFR surface density ($Σ_{\rm SFR}$) $>$ 8.2 $\times$ 10$^{-6}$ $M_\odot$ yr$^{-1}$ kpc$^{-2}$: log($L^{\rm gas}_{0.5-2\,\mathrm{keV}}$/erg s$^{-1}$) = 2.2 log(SFR/$M_\odot$ yr$^{-1}$) + 39.1. We further found a statistically significant super-linear correlation ($β= 1.34$ $\pm$ 0.86) between $L^{\rm gas}_{0.5-2\,\mathrm{keV}}$/SFR and HCN(4-3)/CO(1-0) intensity ratio, whereas no such trend is seen for HCO$^+$(4-3)/CO(1-0) or CO(3-2)/CO(1-0). These findings indicate that AGN feedback does not dominate star formation regulation on sub-kiloparsec scales, and that the excitation of dense gas traced by HCN (4-3) may be more directly influenced by high-energy feedback processes compared to HCO$^+$ (4-3) and CO (3-2). △ Less

Submitted 4 December, 2025; originally announced December 2025.

Comments: 12 pages, 7 figures. Accepted for publication in A&A

Beyond the Monsters: A More Complete Census of Black Hole Activity at Cosmic Dawn

Authors: Madisyn Brooks, Jonathan R. Trump, Raymond C. Simons, Justin Cole, Anthony J. Taylor, Micaela B. Bagley, Steven L. Finkelstein, Kelcey Davis, Ricardio O. Amorín, Bren E. Backhaus, Nikko J. Cleri, Mauro Giavalisco, Norman A. Grogin, Michaela Hirschmann, Benne W. Holwerda, Marc Huertas-Company, Jeyhan S. Kartaltepe, Dale D. Kocevksi, Anton M. Koekemoer, Ray A. Lucas, Fabio Pacucci, Xin Wang

Abstract: JWST has revealed an abundance of low-luminosity active galactic nuclei (AGN) at high redshifts ($z > 3$), pushing the limits of black hole (BH) science in the early Universe. Results have claimed that these BHs are significantly more massive than expected from the BH mass-host galaxy stellar mass relation derived from the local Universe. We present a comprehensive census of the BH populations in… ▽ More JWST has revealed an abundance of low-luminosity active galactic nuclei (AGN) at high redshifts ($z > 3$), pushing the limits of black hole (BH) science in the early Universe. Results have claimed that these BHs are significantly more massive than expected from the BH mass-host galaxy stellar mass relation derived from the local Universe. We present a comprehensive census of the BH populations in the early Universe through a detailed stacking analysis of galaxy populations, binned by luminosity and redshift, using JWST spectroscopy from the CEERS, JADES, RUBIES, and GLASS extragalactic deep field surveys. Broad H$α$ detections in $31\%$ of the stacked spectra (5/16 bins) imply median BH masses of $10^{5.21} - 10^{6.13}~ \rm{M_{\odot}}$ and the stacked SEDs of these bins indicate median stellar masses of $10^{7.84} - 10^{8.56} ~\rm{M_{\odot}}$. This suggests that the median galaxy hosts a BH that is at most a factor of 10 times over-massive compared to its host galaxy and lies closer to the locally derived $M_{BH}-M_*$ relation. We investigate the seeding properties of the inferred BHs and find that they can be well-explained by a light stellar remnant seed undergoing moderate Eddington accretion. Our results indicate that individual detections of AGN are more likely to sample the upper envelope of the $M_{BH}-M_*$ distribution, while stacking on ``normal" galaxies and searching for AGN signatures can overcome the selection bias of individual detections. △ Less

Submitted 24 November, 2025; originally announced November 2025.

Comments: 17 pages, 8 figures

Metal enrichment of galaxies in a massive node of the Cosmic Web at $z \sim 3$

Authors: Xiaohan Wang, S. Cantalupo, Weichen Wang, M. Galbiati, Charles C. Steidel, A. Pensabene, Shude Mao, A. Travascio, T. Lazeyras, N. Ledos, G. Quadri

Abstract: We present the mass-metallicity relation for star-forming galaxies in the MUSE Quasar Nebula 01 (MQN01) field, a massive cosmic web node at $z \sim 3.245$, hosting one of the largest overdensities of galaxies and AGNs found so far at $z > 3$. Through James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra and images from JWST and Hubble Space Telescope (HST), we identify a s… ▽ More We present the mass-metallicity relation for star-forming galaxies in the MUSE Quasar Nebula 01 (MQN01) field, a massive cosmic web node at $z \sim 3.245$, hosting one of the largest overdensities of galaxies and AGNs found so far at $z > 3$. Through James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra and images from JWST and Hubble Space Telescope (HST), we identify a sample of 9 star-forming galaxies in the MQN01 field with detection of nebular emission lines ($\rm Hβ$, [OIII], $\rm Hα$, [NII]), covering the mass range of $\rm 10^{7.5}M_\odot - 10^{10.5}M_\odot$. We present the relations of the emission-line flux ratios versus stellar mass for the sample and derive the gas-phase metallicity based on the strong line diagnostics of [OIII]$\lambda5008$/$\rm Hβ$ and [NII]$\lambda6585$/$\rm Hα$. Compared to the typical, field galaxies at similar redshifts, MQN01 galaxies show relatively higher [NII]$\lambda6585$/$\rm Hα$ and lower [OIII]$\lambda5008$/$\rm Hβ$ at the same stellar mass, which implies a higher metallicity by about $0.25\pm 0.07$ dex with respect to the field mass-metallicity relation. These differences are decreased considering the ``Fundamental Metallicity Relation'', i.e. if the galaxies' Star Formation Rates (SFR) are also taken into account. We argue that these results are consistent with a scenario in which galaxies in overdense regions assemble their stellar mass more efficiently (or, equivalently, start forming at earlier epochs) compared to field galaxies at similar redshifts. △ Less

Submitted 24 November, 2025; originally announced November 2025.

Comments: 17 pages, 12 figures (including Appendix); submitted to A&A

MAMMOTH-Grism: Revisiting the Mass-Metallicity Relation in Protocluster Environments at Cosmic Noon

Authors: Yiming Yang, Xin Wang, Xianlong He, Chao-Wei Tsai, Zheng Cai, Zihao Li, Matthew A. Malkan, Dong Dong Shi, Anahita Alavi, Fuyan Bian, James Colbert, Xiaohui Fan, Alaina L. Henry, Harry I. Teplitz, Xian Zhong Zheng

Abstract: We present one of the first measurements of the mass-metallicity relation (MZR) in multiple massive protoclusters at cosmic noon, using Hubble Space Telescope (HST) G141 slitless spectroscopy from the MAMMOTH-Grism survey. We identify 63 protocluster member galaxies across three overdense structures at $z = 2\text{-}3$ with robust detections of [OIII], H$β$, and [OII] emission. The sample spans ga… ▽ More We present one of the first measurements of the mass-metallicity relation (MZR) in multiple massive protoclusters at cosmic noon, using Hubble Space Telescope (HST) G141 slitless spectroscopy from the MAMMOTH-Grism survey. We identify 63 protocluster member galaxies across three overdense structures at $z = 2\text{-}3$ with robust detections of [OIII], H$β$, and [OII] emission. The sample spans gas-phase metallicities of $12 + \log(\text{O/H}) = 8.2\text{-}8.6$, dust-corrected H$β$-based star formation rates (SFRs) of $10$-$250\,M_\odot\,\text{yr}^{-1}$, and stellar masses of $M_\ast \sim 10^{9.4}$-$10^{10.5}\,M_\odot$, derived via spectral energy distribution fitting using deep HST and ground-based photometry. We stack spectra in five $M_\ast$ bins to obtain average metallicities and SFRs. Relative to field galaxies at similar redshifts, protocluster members show elevated SFRs at $M_\ast < 10^{10.25}\,M_\odot$ and a systematically shallower MZR: $12 + \log(\text{O/H}) = (6.96 \pm 0.13) + (0.143 \pm 0.017) \times \log(M_{\ast}/M_{\odot})$. We detect a mass-dependent environmental offset: massive protocluster galaxies are metal-poor compared to field counterparts of similar mass, whereas lower-mass systems exhibit comparable or mildly enhanced metallicities. This trend is consistent with a scenario where cold-mode accretion dilutes the interstellar medium (ISM) across the full mass range, while efficient recycling of feedback-driven outflows preferentially enriches the ISM in low-mass galaxies. Finally, we assess the dependence of metallicity offsets on local overdensity and find no significant trend, likely reflecting the survey's bias toward protocluster cores. △ Less

Submitted 20 November, 2025; originally announced November 2025.

Comments: 18 pages, 8 fqures, resubmitted after addressing the referee report

Unified Kraft Break at ~6500 K: A Newly Identified Single-Star Obliquity Transition Matches the Classical Rotation Break

Authors: Xian-Yu Wang, Songhu Wang, J. M. Joel Ong

Abstract: The stellar obliquity transition, defined by a $\textit{T}_{\rm eff}$ cut separating aligned from misaligned hot Jupiter systems, has long been assumed to coincide with the rotational Kraft break. Yet the commonly quoted obliquity transition (6100 or 6250 K) sits a few hundred kelvin cooler than the rotational break (~6500 K), posing a fundamental inconsistency. We show this offset arises primaril… ▽ More The stellar obliquity transition, defined by a $\textit{T}_{\rm eff}$ cut separating aligned from misaligned hot Jupiter systems, has long been assumed to coincide with the rotational Kraft break. Yet the commonly quoted obliquity transition (6100 or 6250 K) sits a few hundred kelvin cooler than the rotational break (~6500 K), posing a fundamental inconsistency. We show this offset arises primarily from binaries/multiple-star systems, which drive the cooler stellar obliquity transition ($6105^{+123}_{-133}$ K), although the underlying cause remains ambiguous. After removing binaries and higher-order multiples, the single-star stellar obliquity transition shifts upward to $6447^{+85}_{-119}$ K, in excellent agreement with the single-star rotation break ($6510^{+97}_{-127}$ K). This revision has two immediate consequences for understanding the origin and evolution of spin-orbit misalignment. First, the upward shift reclassifies some hosts previously labeled `hot' into the cooler regime; consequently, there are very few RM measurements of non-hot-Jupiter planets around genuinely hot stars ($T_{\rm eff}\gtrsim6500\,\mathrm{K}$), and previously reported alignment trends for these classes of systems (e.g., warm Jupiters and compact multi-planet systems) lose the power to discriminate the central question: are large misalignments unique to hot-Jupiter-like planets that can be delivered by high-$e$ migration, or are hot stars intrinsically more misaligned across architectures? Second, a single-star stellar obliquity transition near $6500\,\mathrm{K}$, coincident with the rotational break, favors tidal dissipation in outer convective envelopes; as these envelopes thin with increasing $T_{\rm eff}$, inertial-wave damping and magnetic braking weaken in tandem. △ Less

Submitted 21 December, 2025; v1 submitted 19 November, 2025; originally announced November 2025.

Comments: 16 pages, 4 figures, 1 table, accepted for publication in ApJL

Probing the influence of the protocluster environment on galaxy morphology at z = 2.23

Authors: Emmet Golden-Marx, Zheng Cai, Dongdong Shi, Xin Wang, Brian C. Lemaux, Benedetta Vulcani, Boris Haussler, Pablo Renard, Lu Shen, Finn Giddings

Abstract: As galaxies evolve in dense cluster and protocluster environments, they interact and quench their star formation, which gradually transforms the galaxy population from star-forming galaxies to quiescent galaxies. This transformation is identifiable by observing galaxy colors and can be seen in the morphological transformation of late-type galaxies into early-type galaxies, which creates the morpho… ▽ More As galaxies evolve in dense cluster and protocluster environments, they interact and quench their star formation, which gradually transforms the galaxy population from star-forming galaxies to quiescent galaxies. This transformation is identifiable by observing galaxy colors and can be seen in the morphological transformation of late-type galaxies into early-type galaxies, which creates the morphology-density relation seen when comparing populations in clusters to co-eval field galaxies. However, high-z (z > 2) galaxy morphology studies are hindered by the high angular resolution necessary to characterize morphology. We present a study of HST WFC3 F160W observations of protoclusters from the MAMMOTH survey (BOSS1244 and BOSS1542) at z ~ 2.23 with populations of previously identified HAEs. By measuring the Sersic index of 151 HAEs, we look for the early morphological transformation of star-forming galaxies in these well-studied, large, non-virialized protoclusters, which we believe are precursors of present-day clusters. We find the morphology of the populations of star-forming protocluster galaxies does not differ from the co-eval field. However, we identify a population of clumpy, potentially merging galaxies, which could lead to an increase in the population of early-type galaxies in these structures. Additionally, in BOSS1244, which has two previously identified massive quiescent galaxies including a BCG, we find an abundance of early-type galaxies near both the BCG and two co-eval high-z quasars. Although we find a strong similarity between the morphology of field and protocluster galaxies, the population of early-type star-forming galaxies surrounding the spectroscopically confirmed quiescent BCG in BOSS1244, something not seen in BOSS1542, may point to differences in the evolutionary state of these co-eval protoclusters and be a sign of an early forming cluster core in BOSS1244. △ Less

Submitted 18 November, 2025; originally announced November 2025.

Comments: Accepted to A&A on 11/11/2025. 20 pages. 14 figures, 2 tables

SN 2016iog: A fast declining Type II-L supernova with an ultra-faint tail, persistently interacting with circumstellar material

Authors: Z. -H. Peng, S. Benetti, Y. -Z. Cai, A. Pastorello, G. Valerin, A. Reguitti, A. Fiore, Q. -L. Fang, Z. -Y. Wang, M. Berton, L. Borsato, E. Cappellaro, E. Congiu, N. Elias-Rosa, V. Granata, J. Isern, G. La Mura, P. Ochner, R. Raddi, G. Terreran, L. Tomasella, M. Turatto, S. -Y. Yan, S. -P. Pei, C. -Y. Wu , et al. (4 additional authors not shown)

Abstract: We present optical photometric and spectroscopic observations of the rapidly declining Type IIL supernova (SN) 2016iog. SN 2016iog reached its peak $\sim$ 14 days after explosion, with an absolute magnitude in the $V$ band of $-18.64 \pm 0.15$ mag, followed by a steep decline of $8.85 \pm 0.15$~mag~(100\,d)$^{-1}$ post-peak. Such a high decline rate makes SN~2016iog one of the fastest declining Ty… ▽ More We present optical photometric and spectroscopic observations of the rapidly declining Type IIL supernova (SN) 2016iog. SN 2016iog reached its peak $\sim$ 14 days after explosion, with an absolute magnitude in the $V$ band of $-18.64 \pm 0.15$ mag, followed by a steep decline of $8.85 \pm 0.15$~mag~(100\,d)$^{-1}$ post-peak. Such a high decline rate makes SN~2016iog one of the fastest declining Type~IIL SNe observed to date. The rapid rise in the light curve, combined with the nearly featureless continuum observed in the spectrum at +9.3 days, suggests the presence of interaction. In the recombination phase, we observed broad H$α$ lines that persist at all epochs. In addition, the prominent double-peaked H$α$ feature observed in the late-time spectrum (+190.8 days) is likely attributable either to significant dust formation within a cool dense shell or to asymmetric circumstellar material. These features suggest the presence of sustained interaction around SN~2016iog. We propose that the observed characteristics of SN~2016iog can be qualitatively explained by assuming a low-mass H-rich envelope surrounding a red supergiant progenitor star with low-density circumstellar material. △ Less

Submitted 18 November, 2025; v1 submitted 16 November, 2025; originally announced November 2025.

Comments: 26 pages, 19 figures. Accepted by Astronomy and Astrophysics

Imaging and polarization patterns of various thick disks around Kerr-MOG black holes

Authors: Xinyu Wang, Huan Ye, Xiao-Xiong Zeng

Abstract: We investigate the imaging and polarization properties of Kerr-MOG black holes surrounded by geometrically thick accretion flows. The MOG parameter $α$ introduces deviations from the Kerr metric, providing a means to test modified gravity in the strong field regime. Two representative accretion models are considered: the phenomenological radiatively inefficient accretion flow (RIAF) and the analyt… ▽ More We investigate the imaging and polarization properties of Kerr-MOG black holes surrounded by geometrically thick accretion flows. The MOG parameter $α$ introduces deviations from the Kerr metric, providing a means to test modified gravity in the strong field regime. Two representative accretion models are considered: the phenomenological radiatively inefficient accretion flow (RIAF) and the analytical ballistic approximation accretion flow (BAAF). Using general relativistic radiative transfer, we compute synchrotron emission and polarization maps under different spins, MOG parameters, inclinations, and observing frequencies. In both models, the photon ring and central dark region expand with increasing $α$, whereas frame dragging produces pronounced brightness asymmetry. The BAAF model predicts a narrower bright ring and distinct polarization morphology near the event horizon. By introducing the net polarization angle $χ_{\text{net}}$ and the second Fourier mode $\angleβ_2$, we quantify inclination- and frame-dragging-induced polarization features. Our results reveal that both $α$ and spin significantly influence the near-horizon polarization patterns, suggesting that high-resolution polarimetric imaging could serve as a promising probe of modified gravity in the strong field regime. △ Less

Submitted 17 November, 2025; v1 submitted 12 November, 2025; originally announced November 2025.

Comments: 36 pages, 15 figures

An axisymmetric shock breakout indicated by prompt polarized emission from the type II supernova 2024ggi

Authors: Yi Yang, Xudong Wen, Lifan Wang, Dietrich Baade, J. Craig Wheeler, Alexei V. Filippenko, Avishay Gal-Yam, Justyn Maund, Steve Schulze, Xiaofeng Wang, Chris Ashall, Mattia Bulla, Aleksandar Cikota, He Gao, Peter Hoeflich, Gaici Li, Divya Mishra, Ferdinando Patat, Kishore C. Patra, Sergiy S. Vasylyev, Shengyu Yan

Abstract: The death of massive stars is triggered by an infall-induced bounce shock that disrupts the star. How such a shock is launched and propagates through the star is a decade-long puzzle. Some models assume that the shock can be reenergized by absorbing neutrinos, leading to highly aspherical explosions. Other models involve jet-powered shocks that lead to bipolar explosions reflected in the geometry… ▽ More The death of massive stars is triggered by an infall-induced bounce shock that disrupts the star. How such a shock is launched and propagates through the star is a decade-long puzzle. Some models assume that the shock can be reenergized by absorbing neutrinos, leading to highly aspherical explosions. Other models involve jet-powered shocks that lead to bipolar explosions reflected in the geometry of the shock-breakout emission. We report measurement of the geometry of the shock breakout through unprecedentedly early spectropolarimetry of the nearby type II supernova 2024ggi starting ~1.2 days after the explosion. The measurement indicates a well-defined symmetry axis of the shock breakout, which is also shared by the hydrogen-rich envelope that emerged after the circumstellar matter was engulfed by the ejecta, revealing a persisting and prominent symmetry axis throughout the explosion. These findings suggest that the physical mechanism driving the explosion of massive stars manifests a well-defined axial symmetry and acts on large scales. △ Less

Submitted 11 November, 2025; originally announced November 2025.

Comments: Science Advances: https://www.science.org/doi/10.1126/sciadv.adx2925 ESO PR: https://www.eso.org/public/news/eso2520/

Mock Observations for the CSST Mission: Main Surveys-the Slitless Spectroscopy Simulation

Authors: Xin Zhang, Yue-dong Fang, Cheng-liang Wei, Guo-liang Li, Feng-shan Liu, Hang-xin Ji, Hao Tian, Nan Li, Xian-min Meng, Jian-jun Chen, Xia Wang, Rui Wang, Chao Liu, Zhong-wen Hu, Ran Li, Peng Wei, Jing Tang

Abstract: The China Space Station Telescope (CSST), slated to become China's largest space-based optical telescope in the coming decade, is designed to conduct wide-field sky surveys with high spatial resolution. Among its key observational modes, slitless spectral observation allows simultaneous imaging and spectral data acquisition over a wide field of view, offering significant advantages for astrophysic… ▽ More The China Space Station Telescope (CSST), slated to become China's largest space-based optical telescope in the coming decade, is designed to conduct wide-field sky surveys with high spatial resolution. Among its key observational modes, slitless spectral observation allows simultaneous imaging and spectral data acquisition over a wide field of view, offering significant advantages for astrophysical studies. Currently, the CSST is in the development phase and lacks real observational data. As a result, the development of its data processing pipeline and scientific pre-research must rely on the mock data generated through simulations. This work focuses on developing a simulation framework for the CSST slitless spectral imaging system, analyzing its spectral dispersing properties and structural design. Additionally, the detection performance of the slitless spectral system is assessed for various astrophysical targets. Simulation results demonstrate that nearly all 1st order spectra are accompanied by corresponding 0th order images, facilitating accurate source identification. Furthermore, the GI spectral band exhibits superior detection efficiency compared to the GV and GU bands, establishing it as the primary observational band for stellar and galactic studies. This work successfully develops a simulation framework for the CSST slitless spectroscopic equipment. △ Less

Submitted 16 November, 2025; v1 submitted 10 November, 2025; originally announced November 2025.

Charge-dependent spectral softenings of primary cosmic-rays from proton to iron below the knee

Authors: DAMPE Collaboration, Francesca Alemanno, Qi An, Philipp Azzarello, Felicia-Carla-Tiziana Barbato, Paolo Bernardini, Xiao-Jun Bi, Hugo Valentin Boutin, Irene Cagnoli, Ming-Sheng Cai, Elisabetta Casilli, Jin Chang, Deng-Yi Chen, Jun-Ling Chen, Zhan-Fang Chen, Zi-Xuan Chen, Paul Coppin, Ming-Yang Cui, Tian-Shu Cui, Ivan De Mitri, Francesco de Palma, Adriano Di Giovanni, Tie-Kuang Dong, Zhen-Xing Dong, Giacinto Donvito , et al. (124 additional authors not shown)

Abstract: In most particle acceleration mechanisms, the maximum energy of the cosmic rays can achieve is charge dependent. However, the observational verification of such a fundamental relation is still lack due to the difficulty of measuring the spectra of individual particles from one (kind of) source(s) up to very high energies. This work reports direct measurements of the carbon, oxygen, and iron spectr… ▽ More In most particle acceleration mechanisms, the maximum energy of the cosmic rays can achieve is charge dependent. However, the observational verification of such a fundamental relation is still lack due to the difficulty of measuring the spectra of individual particles from one (kind of) source(s) up to very high energies. This work reports direct measurements of the carbon, oxygen, and iron spectra from ~ 20 gigavolts to ~ 100 teravolts (~ 60 teravolts for iron) with 9 years of on-orbit data collected by the Dark Matter Particle Explorer (DAMPE). Distinct spectral softenings have been directly detected in these spectra for the first time. Combined with the updated proton and helium spectra, the spectral softening appears universally at a rigidity of ~ 15 teravolts. A nuclei mass dependent softening is rejected at a confidence level of > 99.999%. Taking into account the correlated structures at similar energies in the large-scale anisotropies of cosmic rays, one of the most natural interpretations of the spectral structures is the presence of a nearby cosmic ray source. In this case, the softening energies correspond to the acceleration upper limits of such a source, forming the so-called Peters cycle of the spectra. The results thus offer observational verification of the long-standing prediction of the charge-dependent energy limit of cosmic ray acceleration. △ Less

Submitted 10 November, 2025; v1 submitted 7 November, 2025; originally announced November 2025.

Comments: This update corrects typos in the tables

Massive stars exploding in a He-rich circumstellar medium XII. SN 2024acyl: A fast, linearly declining Type Ibn supernova with early flash-ionisation features

Authors: Y. -Z. Cai, A. Pastorello, K. Maeda, J. -W. Zhao, Z. -Y. Wang, Z. -H. Peng, A. Reguitti, L. Tartaglia, A. V. Filippenko, Y. Pan, G. Valerin, B. Kumar, Z. Wang, M. Fraser, J. P. Anderson, S. Benetti, S. Bose, T. G. Brink, E. Cappellaro, T. -W. Chen, X. -L. Chen, N. Elias-Rosa, A. Esamdin, A. Gal-Yam, M. González-Bañuelos , et al. (41 additional authors not shown)

Abstract: We present a photometric and spectroscopic analysis of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of about -17.58 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands, similar to most SNe Ibn. The optical pseudobolometric light curve peaks at ($3.5\pm0.8) \times 10^{42}$ erg s$^{-1}$, with a total radiated energy of… ▽ More We present a photometric and spectroscopic analysis of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of about -17.58 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands, similar to most SNe Ibn. The optical pseudobolometric light curve peaks at ($3.5\pm0.8) \times 10^{42}$ erg s$^{-1}$, with a total radiated energy of $(5.0\pm0.4) \times 10^{48}$ erg. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni \Hei~lines and flash-ionisation emission lines of C {\sc iii}, N {\sc iii}, and He {\sc ii}. The P-Cygni \Hei~features gradually evolve and become emission-dominated in late-time spectra. The \Ha~line is detected throughout the entire spectral evolution, which indicates that the CSM is helium-rich with some residual amount of H. Our multiband light-curve modelling yields estimates of the ejecta mass of $M_{ej}$ = $0.98^{+0.30}_{-0.20} \, \msun$, with a kinetic energy of $E_{k} = 0.13^{+0.03}_{-0.02} \times 10^{51}$ erg, and a $^{56}Ni$ mass of $M_{\mathrm{Ni}} = 0.017 \, \msun$. The inferred CSM properties are characterised by a mass of $M_{\rm{CSM}} = 0.39^{+0.04}_{-0.04}$ \msun, an inner radius of $R_0$=$15.6^{+1.9}_{-2.0}$ AU, and a density $ρ_{CSM} = (1.32\pm0.22)\times10^{-11} \, \mathrm{g\,cm^{-3}}$. The multi-epoch spectra are well reproduced by the CMFGEN/ \texttt{he4p0} model, corresponding to a He-ZAMS mass of 4~M$_\odot$. These findings are consistent with a scenario of an SN powered by ejecta-CSM interaction, originating from a low-mass helium star that evolved within an interacting binary system where the CSM with some residual hydrogen may originate from the mass-transfer process. In addition, a channel of core-collapse explosion of a late-type Wolf-Rayet star with H, or an Ofpe/WN9 star with fallback accretion, cannot be entirely ruled out. △ Less

Submitted 6 November, 2025; originally announced November 2025.

Comments: 19 pages, 12 figures

First Associated Neutrino Search for a Failed Supernova Candidate with Super-Kamiokande

Authors: F. Nakanishi, K. Abe, S. Abe, Y. Asaoka, M. Harada, Y. Hayato, K. Hiraide, K. Hosokawa, T. H. Hung, K. Ieki, M. Ikeda, J. Kameda, Y. Kanemura, Y. Kataoka, S. Miki, S. Mine, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Noguchi, G. Pronost, K. Sato, H. Sekiya, M. Shiozawa , et al. (221 additional authors not shown)

Abstract: In 2024, a failed supernova candidate, M31-2014-DS1, was reported in the Andromeda galaxy (M31), located at a distance of approximately 770 kpc. In this paper, we search for neutrinos from this failed supernova using data from Super-Kamiokande (SK). Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for neutrino events in… ▽ More In 2024, a failed supernova candidate, M31-2014-DS1, was reported in the Andromeda galaxy (M31), located at a distance of approximately 770 kpc. In this paper, we search for neutrinos from this failed supernova using data from Super-Kamiokande (SK). Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for neutrino events in the SK data. Using this window, we develop a dedicated analysis method for failed supernovae and apply it to M31-2014-DS1, by conducting a cluster search using the timing and energy information of candidate events. No significant neutrino excess is observed within the search region. Consequently, we place an upper limit on the electron antineutrino luminosity from M31-2014-DS1 and discuss its implications for various failed SN models and their neutrino emission characteristics. Despite the 18 MeV threshold adopted to suppress backgrounds, the search remains sufficiently sensitive to constrain the Shen-TM1 EOS, yielding a 90% confidence level upper limit of 1.76 \times 10^{53} erg on the electron antineutrino luminosity, slightly above the expected value of 1.35 \times 10^{53} erg. △ Less

Submitted 5 November, 2025; v1 submitted 5 November, 2025; originally announced November 2025.

Comments: 11 pages, 4 figures, and 1 table

A semi-analytical mock galaxy catalog for the CSST extragalactic surveys from the Jiutian simulations

Authors: Zhenlin Tan, Lizhi Xie, Jiaxin Han, Yisheng Qiu, Fabio Fontanot, Gabriella De Lucia, Qi Guo, Qingyang Li, Jiale Zhou, Wenkang Jiang, Xin Wang, Feihong He, Chichuan Jin, Yipeng Jing, Ming Li, Xiaodong Li, Wenxiang Pei, Wenting Wang, Xiaohu Yang, Yu Yu

Abstract: We introduce a mock galaxy catalog built for the CSST extragalactic surveys using the primary runs of the Jiutian $N$-body simulation suites. The catalogs are built by coupling the GAlaxy Evolution and Assembly (GAEA) semi-analytical model of galaxy formation with merger trees extracted from the simulations using the Hierarchical Bound-Tracing (HBT+) algorithm. The spectral energy distributions (S… ▽ More We introduce a mock galaxy catalog built for the CSST extragalactic surveys using the primary runs of the Jiutian $N$-body simulation suites. The catalogs are built by coupling the GAlaxy Evolution and Assembly (GAEA) semi-analytical model of galaxy formation with merger trees extracted from the simulations using the Hierarchical Bound-Tracing (HBT+) algorithm. The spectral energy distributions (SEDs) and broadband magnitudes are computed using the neural-network-based stellar population synthesizer StarDuster, which is trained on radiative transfer simulations to account for detailed galaxy geometry in modeling dust obscuration. Galaxy light-cones up to $z=5$ are subsequently generated with the BLiC light-cone builder which interpolates the properties of galaxies over time using an optimized interpolation scheme. The resulting catalogs exhibit good convergence in many statistical properties of the galaxy population produced from two different resolution simulations. The catalogs reproduce a number of observed galaxy properties across a range of galaxy mass and redshift, including the stellar mass functions, the luminosity function, gas mass fraction, galaxy size-mass relation and galaxy clustering. We also present the photometric and redshift distributions of galaxies expected to be observed in the CSST surveys. △ Less

Submitted 9 November, 2025; v1 submitted 5 November, 2025; originally announced November 2025.

Comments: accepted by SCPMA, data products will be released at https://jiutian.sjtu.edu.cn

Searching Within Galaxies for the Earliest Signs of Quenching With Spatially Resolved Star Formation Histories in UVCANDELS

Authors: Charlotte Olsen, Eric Gawiser, Charlotte Welker, Harry Teplitz, Kartheik Iyer, Xin Wang, Marc Rafelski, Rogier A. Windhorst, Anton Koekemoer, Anahita Alavi, Ben Sunnquist, Norman Grogin, Yicheng Guo, Christopher J. Conselice, L. Y. Aaron Yung, Kalina Nedkova, Bahram Mobasher, Ray A. Lucas, Vihang Mehta, Y. Sophia Dai, Jonathan P. Gardner

Abstract: Understanding the complicated processes that regulate star formation and cause a galaxy to become quiescent is key to our comprehension of galaxy evolution. We used nine well resolved star-forming z<1 galaxies from the UVCANDELS survey, where a total of 10 HST bands including UV follow up in UVIS/F275W allow us to reconstruct the star formation histories (SFHs) of regions across each galaxy. This… ▽ More Understanding the complicated processes that regulate star formation and cause a galaxy to become quiescent is key to our comprehension of galaxy evolution. We used nine well resolved star-forming z<1 galaxies from the UVCANDELS survey, where a total of 10 HST bands including UV follow up in UVIS/F275W allow us to reconstruct the star formation histories (SFHs) of regions across each galaxy. This approach provides a powerful tool to explore the spatio-temporal connection between star formation and galaxy evolution. The spatial and temporal profiles of stellar mass and star formation rate surface density were obtained from the SFHs of these regions. We measure scaling relations and projected radial profiles of regions within each galaxy at the time of observation and at 1 Gyr lookback time, noting possible trends in the evolution. By comparing the change in star formation over time we can infer the timing and location of star formation and see early signs of star formation shut off before quenching occurs. We compared the star formation rate density -- stellar mass density scaling relations for individual galaxies as they evolve from 1 Gyr lookback time. The correlation lines pivot around a log-stellar mass surface density of 7.25 [$M_\odot$ $kpc^{-2}$] may be evidence of a self-regulating process on these scales. Radial profiles of galaxy Log sSFR show an overall decrease over 1 Gyr, but five galaxies show a greater change in Log sSFR at the outskirts than the center indicating a possible early onset of quenching in these galaxies. △ Less

Submitted 4 November, 2025; originally announced November 2025.

Comments: 31 pages, 28 figures. Submitted to ApJ

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

Authors: Guanhong Lin, Dejia Zhou, Jianli Zhang, Jialang Ding, Fei Liu, Xiaoyun Ma, Yuan Liang, Ruan Duan, Liaoyuan Liu, Xuanyu Wang, Xiaohui Yan, Yingrou Zhan, Yuting Chu, Jing Qiao, Wei Wang, Jie Zhang, Zerui Wang, Meng Liu, Chenchen Miao, Menquan Liu, Meng Guo, Di Li, Pei Wang

Abstract: Fast radio bursts (FRBs) are extremely bright, millisecond duration cosmic transients of unknown origin. The growing number of wide-field and high-time-resolution radio surveys, particularly with next-generation facilities such as the SKA and MeerKAT, will dramatically increase FRB discovery rates, but also produce data volumes that overwhelm conventional search pipelines. Real-time detection thus… ▽ More Fast radio bursts (FRBs) are extremely bright, millisecond duration cosmic transients of unknown origin. The growing number of wide-field and high-time-resolution radio surveys, particularly with next-generation facilities such as the SKA and MeerKAT, will dramatically increase FRB discovery rates, but also produce data volumes that overwhelm conventional search pipelines. Real-time detection thus demands software that is both algorithmically robust and computationally efficient. We present Astroflow, an end-to-end, GPU-accelerated pipeline for single-pulse detection in radio time-frequency data. Built on a unified C++/CUDA core with a Python interface, Astroflow integrates RFI excision, incoherent dedispersion, dynamic-spectrum tiling, and a YOLO-based deep detector. Through vectorized memory access, shared-memory tiling, and OpenMP parallelism, it achieves 10x faster-than-real-time processing on consumer GPUs for a typical 150 s, 2048-channel observation, while preserving high sensitivity across a wide range of pulse widths and dispersion measures. These results establish the feasibility of a fully integrated, GPU-accelerated single-pulse search stack, capable of scaling to the data volumes expected from upcoming large-scale surveys. Astroflow offers a reusable and deployable solution for real-time transient discovery, and provides a framework that can be continuously refined with new data and models. △ Less

Submitted 4 November, 2025; originally announced November 2025.

Comments: 17 pages, 14 figures

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

Authors: K. Abe, S. Abe, Y. Asaoka, M. Harada, Y. Hayato, K. Hiraide, K. Hosokawa, T. H. Hung, K. Ieki, M. Ikeda, J. Kameda, Y. Kanemura, Y. Kataoka, S. Miki, S. Mine, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Noguchi, G. Pronost, K. Sato, H. Sekiya, R. Shinoda, M. Shiozawa , et al. (223 additional authors not shown)

Abstract: We report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3~MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with $22,500\times956.2$$~\rm m^3\cdot day$ exposure. %$22.5{\rm k}\times956.2$$~\rm m^3\cdot day$ exposure. Starting in the summer of 2020, SK introduced 0.01\% gadolinium (Gd) by mass into its ultra-pure water to enhance the… ▽ More We report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3~MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with $22,500\times956.2$$~\rm m^3\cdot day$ exposure. %$22.5{\rm k}\times956.2$$~\rm m^3\cdot day$ exposure. Starting in the summer of 2020, SK introduced 0.01\% gadolinium (Gd) by mass into its ultra-pure water to enhance the neutron capture signal, termed the SK-VI phase. This was followed by a 0.03\% Gd-loading in 2022, a phase referred to as SK-VII. We then conducted a DSNB search using 552.2~days of SK-VI data and 404.0~days of SK-VII data through September 2023. This analysis includes several new features, such as two new machine-learning neutron detection algorithms with Gd, an improved atmospheric background reduction technique, and two parallel statistical approaches. No significant excess over background predictions was found in a DSNB spectrum-independent analysis, and 90\% C.L. upper limits on the astrophysical electron anti-neutrino flux were set. Additionally, a spectral fitting result exhibited a $\sim1.2σ$ disagreement with a null DSNB hypothesis, comparable to a previous result from 5823~days of all SK pure water phases. △ Less

Submitted 3 November, 2025; originally announced November 2025.

Neutrino and Cascade Gamma-Ray Emission from Magnetized Turbulent Coronae in Seyfert Galaxies

Authors: Xing-Jian Wang, Jing-Fu Hu, Hao-Ning He, Cheng-Qun Pang

Abstract: Recent neutrino observations from the IceCube Collaboration suggest that Seyfert galaxies are promising candidate sources of neutrinos. Within the standard disk-corona model, we assume that protons are accelerated by a non-resonant acceleration mechanism driven by magnetized turbulence in the corona. These accelerated protons interact with ambient radiation or matter, producing high-energy neutrin… ▽ More Recent neutrino observations from the IceCube Collaboration suggest that Seyfert galaxies are promising candidate sources of neutrinos. Within the standard disk-corona model, we assume that protons are accelerated by a non-resonant acceleration mechanism driven by magnetized turbulence in the corona. These accelerated protons interact with ambient radiation or matter, producing high-energy neutrinos and gamma rays. In this scenario, gamma rays are largely absorbed within the corona. The neutrino luminosity depends primarily on the properties of the corona (such as the X-ray luminosity and radius) and the spectral energy distribution of the target photons. This study demonstrates the relation between the neutrino luminosity and the X-ray luminosity, and further discusses the contribution of cascade gamma rays to coronal radiation. Notably, MeV gamma rays can effectively escape the source, together with neutrinos, and serve as key observational probes for testing this model. Future MeV gamma-ray telescopes, such as AMEGO-X and e-ASTROGAM, are expected to detect such gamma-ray signatures, providing a critical multi-messenger test of the hadronic corona model. △ Less

Submitted 31 October, 2025; originally announced November 2025.

Probing the Penrose Process: Images of Split Hotspots and Their Observational Signatures

Authors: Zhixing Zhao, Zhong-Ying Fan, Xiaobao Wang, Minyong Guo, Bin Chen

Abstract: While theoretically established for decades, the Penrose process - energy extraction from rotating black holes - still lacks clear observational evidence. A promising theoretical framework posits magnetic reconnection in the ergosphere as a trigger, causing a plasmoid to separate into an escaping positive-energy fragment and an infalling negative-energy one. In this work, we investigate the observ… ▽ More While theoretically established for decades, the Penrose process - energy extraction from rotating black holes - still lacks clear observational evidence. A promising theoretical framework posits magnetic reconnection in the ergosphere as a trigger, causing a plasmoid to separate into an escaping positive-energy fragment and an infalling negative-energy one. In this work, we investigate the observational imprints of this scenario. We treat the energized plasmoid as a hotspot and calculate its light curves for a realistic plasma magnetization. In particular, we further compare with the scenario in which the plasmoid, after fragmentation, falls into the black hole with positive energy, while all other conditions remain unchanged. Our results reveal that the process of fragmentation generates distinct flares, whose characteristics depend heavily on whether the infalling fragment carries negative or positive energy. We propose that these differences serve as identifiable signatures of the Penrose process. △ Less

Submitted 31 October, 2025; originally announced October 2025.

Quantifying Spectroscopic Flux Variations Between JWST NIRISS and NIRSpec: Slit Losses in Emission Line Measurements of z$\sim$1-3 Galaxies

Authors: Nicolò Dalmasso, Peter J. Watson, Tommaso Treu, Michele Trenti, Benedetta Vulcani, Themiya Nanayakkara, Maruša Bradač, Tucker Jones, Kristan Boyett, Xin Wang, Sara Mascia, Laura Pentericci

Abstract: We analyze JWST NIRISS and NIRSpec spectroscopic observations in the Abell 2744 galaxy cluster field. From approximately 120 candidates, we identify 12 objects with at least a prominent emission lines among \Oii, \Hb, \Oiiia, \Oiiib, and \Ha that are spectroscopically confirmed by both instruments. Our key findings reveal systematic differences between the two spectrographs based on source morphol… ▽ More We analyze JWST NIRISS and NIRSpec spectroscopic observations in the Abell 2744 galaxy cluster field. From approximately 120 candidates, we identify 12 objects with at least a prominent emission lines among \Oii, \Hb, \Oiiia, \Oiiib, and \Ha that are spectroscopically confirmed by both instruments. Our key findings reveal systematic differences between the two spectrographs based on source morphology and shutter aperture placement. Compact objects show comparable or higher integrated flux in NIRSpec relative to NIRISS (within 1$σ$ uncertainties), while extended sources consistently display higher flux in NIRISS measurements. This pattern reflects NIRSpec's optimal coverage for compact objects while potentially undersampling extended sources. Quantitative analysis demonstrates that NIRSpec recovers at least $63\%$ of NIRISS-measured flux when the slit covers $>15\%$ of the source or when $R_e<1$kpc. For lower coverage or larger effective radii, the recovered flux varies from $24\%$ to $63\%$. When studying the \Ha/\Oiiib emission line ratio, we observe that measurements from these different spectrographs can vary by up to $\sim$0.3 dex, with significant implications for metallicity and star formation rate characterizations for individual galaxies. These results highlight the importance of considering instrumental effects when combining multi-instrument spectroscopic data and demonstrate that source morphology critically influences flux recovery between slit-based and slitless spectroscopic modes in JWST observations. △ Less

Submitted 30 October, 2025; originally announced October 2025.

Comments: Published on MNRAS-Monthly Notices of the Royal Astronomical Society; 11 pages, 8 figures, 2 tables

Evidence of cosmic-ray acceleration up to sub-PeV energies in the supernova remnant IC 443

Authors: Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, G. H. Chen, H. X. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen , et al. (291 additional authors not shown)

Abstract: Supernova remnants (SNRs) have been considered as the primary contributors to cosmic rays (CRs) in our Galaxy. However, the maximum energy of particles that can be accelerated by shocks of SNRs is uncertain observationally and theoretically, and the role of contribution to CRs around PeV energies by SNRs is unclear. In this study, we present observations of high-energy $γ$-ray emission from the SN… ▽ More Supernova remnants (SNRs) have been considered as the primary contributors to cosmic rays (CRs) in our Galaxy. However, the maximum energy of particles that can be accelerated by shocks of SNRs is uncertain observationally and theoretically, and the role of contribution to CRs around PeV energies by SNRs is unclear. In this study, we present observations of high-energy $γ$-ray emission from the SNR IC 443 using the Large High Altitude Air Shower Observatory (LHAASO). The morphological analysis reveals a pointlike source whose location and spectrum are consistent with those of the Fermi-LAT-detected compact source with $π^0$-decay signature, and a more extended source which is consistent with a newly discovered source, previously unrecognized by Fermi-LAT. The spectrum of the point source can be described by a power-law function with an index of $\sim3.0$, extending beyond $\sim 30$ TeV without apparent cutoff. Assuming a hadronic origin of the $γ$-ray emission, the $95\%$ lower limit of accelerated protons reaches about 300 TeV. The extended source might be coincident with IC 443, SNR G189.6+3.3 or the putative pulsar wind nebula CXOU J061705.3+222127, and can be explained by either a hadronic or leptonic model. The LHAASO results provide compelling evidence that CR protons up to sub-PeV energies can be accelerated by the SNR. △ Less

Submitted 29 October, 2025; originally announced October 2025.

Extreme equivalent width-selected low-mass starbursts at $z=4-9$: insights into their role in cosmic reionization

Authors: M. Llerena, L. Pentericci, R. Amorín, A. Ferrara, M. Dickinson, F. Arevalo, A. Calabrò, L. Napolitano, S. Mascia, P. Arrabal Haro, R. Begley, N. J. Cleri, K. Davis, W. Hu, J. S. Kartaltepe, A. M. Koekemoer, R. A. Lucas, E. McGrath, D. J. McLeod, C. Papovich, T. M. Stanton, A. J. Taylor, R. Tripodi, X. Wang, L. Y. A. Yung

Abstract: We investigate the properties of extreme emission line galaxies (EELGs) at $z=4-9$ and their role in reionization. Compact, low-mass galaxies with intense optical emission lines are linked to elevated specific star formation rates (sSFRs) and recent bursts of star formation. Feedback in these systems may enable the leakage of ionizing radiation into the intergalactic medium. Using JWST/NIRSpec spe… ▽ More We investigate the properties of extreme emission line galaxies (EELGs) at $z=4-9$ and their role in reionization. Compact, low-mass galaxies with intense optical emission lines are linked to elevated specific star formation rates (sSFRs) and recent bursts of star formation. Feedback in these systems may enable the leakage of ionizing radiation into the intergalactic medium. Using JWST/NIRSpec spectroscopy from the CAPERS, CEERS, and RUBIES surveys, we compile 160 NIRCam-selected EELGs in the EGS field. These galaxies show extreme rest-frame equivalent widths (EWs), with a median EW([O III]+H$β$)=1616Å and EW(H$α$)=763Å. They are low-mass (median log(M$_{\star}$/M$_{\odot}$)=8.26) with high sSFRs (median 43 Gyr$^{-1}$), above the $z\sim6$ main sequence. UV slopes are diverse, with a mean $β=-2.0$, and only 7% have extremely blue continua ($β<-2.6$). Emission-line diagnostics suggest stellar populations as the primary ionizing source, although an AGN fraction of 14% is found. These galaxies are efficient ionizing photon producers, with mean log($ξ_{\rm ion}$ [Hz erg$^{-1}$])=25.34, exceeding typical values at similar redshifts. Escape fractions, however, are heterogeneous: 9% of EELGs show escape fractions $>$10% for both Ly$α$ and LyC photons, while 82% lack detectable Ly$α$ emission. The median inferred LyC escape fraction is modest (4.4%) but enhanced in super-Eddington systems with sSFR >25 Gyr$^{-1}$. The galaxies are extremely compact, with a median effective radius of 0.49 kpc, and exhibit a recent star-formation burst. Our analysis indicates that sSFR and star-formation rate surface density are the primary drivers of their extreme emission line strengths. △ Less

Submitted 29 October, 2025; originally announced October 2025.

Comments: Submitted to A&A. Comments are welcome

A Viable New Model for Dark Matter

Authors: X. G. Wang, A. W. Thomas

Abstract: We present a new model of the dark sector involving Dirac fermion dark matter, with axial coupling to a dark photon which provides a portal to Standard Model particles. In the non-relativistic limit, this implies that the dominant effective operator relevant to direct detection is ${\cal O}_8$. The resulting event rate for direct detection is suppressed by either the dark matter velocity or the mo… ▽ More We present a new model of the dark sector involving Dirac fermion dark matter, with axial coupling to a dark photon which provides a portal to Standard Model particles. In the non-relativistic limit, this implies that the dominant effective operator relevant to direct detection is ${\cal O}_8$. The resulting event rate for direct detection is suppressed by either the dark matter velocity or the momentum transfer. In this scenario there are much wider regions of the dark parameter space that are consistent with all of the existing constraints associated with thermal relic density, direct detection and collider searches. △ Less

Submitted 28 October, 2025; originally announced October 2025.

Comments: 8 pages, 3 figures

Report number: ADP-25-34/T1296

SN 2024iss: A Double-peaked Type IIb Supernova with Evidence of Circumstellar Interaction

Authors: Liyang Chen, Xiaofeng Wang, Qinyu Wu, Moira Andrews, Joseph Farah, Paolo Ochner, Andrea Reguitti, Thomas G. Brink, Jujia Zhang, Cuiying Song, Jialian Liu, Alexei V. Filippenko, David J. Sand, Irene Albanese, Kate D. Alexander, Jennifer Andrews, K. Azalee Bostroem, Yongzhi Cai, Collin Christy, Ali Esamdin, Andrea Farina, Noah Franz, D. Andrew Howell, Brian Hsu, Maokai Hu , et al. (32 additional authors not shown)

Abstract: We present optical, ultraviolet, and X-ray observations of supernova (SN) 2024iss, a Type IIb SN that shows a prominent double-peaked light curve. We modeled the first peak with a semianalytical shock-cooling model and the X-ray emission with a free-free model. We compare the envelope radius and mass-loss rate with other Type IIb SNe to explore the relationships between the progenitor envelope and… ▽ More We present optical, ultraviolet, and X-ray observations of supernova (SN) 2024iss, a Type IIb SN that shows a prominent double-peaked light curve. We modeled the first peak with a semianalytical shock-cooling model and the X-ray emission with a free-free model. We compare the envelope radius and mass-loss rate with other Type IIb SNe to explore the relationships between the progenitor envelope and the circumstellar material (CSM). The shock-cooling peak in the $V$-band light curve reached $M_V = -17.33\pm 0.26$mag, while the $^{56}$Ni-powered second peak attained $M_V = -17.43\pm 0.26$mag. Early spectra show an photospheric velocity of $\sim19,400\,km\,s^{-1}$ at 3.82days from the H$α$ P~Cygni profile. The Balmer lines persist at least +87 days after the explosion, characterizing hydrogen-rich ejecta. Modeling the first light-curve peak suggests an extended envelope with a mass of $0.11\pm0.04\,M_{\odot}$ and a radius of $244\pm43~R_{\odot}$. Fitting the second light-curve peak with an Arnett-like model indicates a typical $^{56}$Ni mass of $ 0.117\pm0.013~M_{\odot}$ and a relatively low ejecta mass of $1.272\pm0.343\,M_{\odot}$. X-ray observations reveal bright thermal bremsstrahlung emission and indicate a mass-loss rate of $1.6\times10^{-5}\ M_{\odot} \ \rm{yr}^{-1}$. SN 2024iss occupies a transitional position between the two subclasses of extended (eIIb) and compact (cIIb) Type IIb SNe. Its envelope radius and pre-explosion mass-loss rate appear to be correlated as theoretically predicted. The observational properties of SN 2024iss are compatible with a binary interaction scenario being the dominant mechanism for envelope stripping. Furthermore, the low column density of neutral hydrogen suggests a compact CSM with an outer radius of $\lesssim1.3\times10^{14}$ cm, indicating that the progenitor star experienced eruptive mass loss within $\sim4\,yr$ of its terminal explosion. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Comments: 24 pages, 14 figures, submitted to A&A

Early Evidence for Polar Orbits of Sub-Saturns Around Hot Stars

Authors: Emma Dugan, Xian-Yu Wang, Agustin Heron, Hareesh Gautham Bhaskar, Malena Rice, Cristobal Petrovich, Songhu Wang

Abstract: Sub-Saturns have been reported to preferentially occupy near-polar orbits, but this conclusion has so far been based primarily on systems with cool host stars; obliquity measurements for sub-Saturns orbiting hot stars remain scarce. Expanding the census into the hot-star regime is essential to test whether the polar preference persists across the Kraft break and to diagnose the underlying excitati… ▽ More Sub-Saturns have been reported to preferentially occupy near-polar orbits, but this conclusion has so far been based primarily on systems with cool host stars; obliquity measurements for sub-Saturns orbiting hot stars remain scarce. Expanding the census into the hot-star regime is essential to test whether the polar preference persists across the Kraft break and to diagnose the underlying excitation mechanisms. In this work, we present Rossiter-McLaughlin observations of TOI-1135 b, a sub-Saturn orbiting a hot star with $T_{\rm eff}=6320\pm120$ K, using WIYN/NEID. We confirm its near-polar architecture, measuring a sky-projected obliquity of $λ=-68.1^{+7.5}_{-5.3}$ degrees and a true obliquity of $ψ=72.2^{+6.4}_{-6.6}$ degrees. Coupling our new measurement with stellar-obliquity data from the literature, we find that sub-Saturns and hot Jupiters around cool stars are unlikely to be drawn from the same parent distribution at the $5.2σ$ level, consistent with weaker tidal realignment induced by lower-mass planets. Of the two known misaligned sub-Saturns around hot stars, both are near-polar, suggesting that the polar preference may extend above the Kraft break. Moreover, their obliquities lie near $\sim 65$ degrees, supporting predictions from secular resonance crossing for sub-Saturns around rapidly rotating hot stars. △ Less

Submitted 23 October, 2025; originally announced October 2025.

Comments: 16 pages, 3 figures, accepted for publication in ApJL

On the origin of ~ 100 TeV neutrinos from the Seyfert galaxy NGC 7469

Authors: Qi-Rui Yang, Xiao-Bin Chen, Ruo-Yu Liu, Xiang-Yu Wang, Martin Lemoine

Abstract: The origin of TeV-PeV neutrinos detected by IceCube remains largely unknown. The most significant individual neutrino source is the close-by Seyfert galaxy NGC 1068 at 4.2$σ$ level with a soft spectral index. Another notable candidate is the Seyfert galaxy NGC 7469, which has been recently proposed as a potential neutrino emitter. The likelihood fit of the IceCube data for this source returned a v… ▽ More The origin of TeV-PeV neutrinos detected by IceCube remains largely unknown. The most significant individual neutrino source is the close-by Seyfert galaxy NGC 1068 at 4.2$σ$ level with a soft spectral index. Another notable candidate is the Seyfert galaxy NGC 7469, which has been recently proposed as a potential neutrino emitter. The likelihood fit of the IceCube data for this source returned a very hard spectral index of ~ 1.9 and the excess is dominated by two high-energy events, issued as two neutrino alerts IC220424A and IC230416A. The energies of the two neutrinos are estimated to be 100-200 TeV, implying a maximum proton energy > 2 PeV, significantly higher than that in NGC 1068. The lack of lower-energy neutrinos from NGC 7469 also suggests a neutrino spectrum harder than that of NGC 1068. In this paper, we analyze the Fermi-LAT observations of NGC 7469, which yield non-detection. By requiring the cascade flux accompanying neutrino production not to exceed the upper limit of the GeV flux, the size of the neutrino-emitting region can be constrained when the neutrino flux takes a high value of the allowed range. We suggest that protons are accelerated to PeV energies via turbulence or magnetic reconnection in the corona of NGC 7469 and interact with OUV photons from the accretion disk and X-rays from the corona through the $pγ$ process, producing neutrinos with energy of 100-200 TeV. In the turbulence acceleration scenario, the required maximum proton energy can be achieved with a magnetization parameter close to unity ($σ\sim 1$), while in the reconnection scenario, a magnetization parameter with $σ\sim 10$ is needed. In both scenarios, a pair dominated composition for the corona is preferred. The difference in the neutrino spectrum between NGC 7469 and NGC 1068 could be due to a different magnetization despite that they belong to the same type of AGN. △ Less

Submitted 22 October, 2025; originally announced October 2025.

Comments: 11 pages, 7 figures

Imaging and Polarimetric Signatures of Konoplya-Zhidenko Black Holes with Various Thick Disk

Authors: Xinyu Wang, Yukang Wang, Xiao-Xiong Zeng

Abstract: We investigate the imaging properties of spherically symmetric Konoplya-Zhidenko (KZ) black holes surrounded by geometrically thick accretion flows, adopting a phenomenological radiatively inefficient accretion flow (RIAF) model and an analytical ballistic approximation accretion flow (BAAF) model. General relativistic radiative transfer is employed to compute synchrotron emission from thermal ele… ▽ More We investigate the imaging properties of spherically symmetric Konoplya-Zhidenko (KZ) black holes surrounded by geometrically thick accretion flows, adopting a phenomenological radiatively inefficient accretion flow (RIAF) model and an analytical ballistic approximation accretion flow (BAAF) model. General relativistic radiative transfer is employed to compute synchrotron emission from thermal electrons and generate horizon-scale images. For the RIAF model, we analyze the dependence of image morphology on the deformation parameter, observing frequency, and flow dynamics. The photon ring and central dark region expand with increasing deformation parameter, with brightness asymmetries arising at high inclinations and depending on flow dynamics and emission anisotropy. The BAAF disk produces narrower rings and darker centers, while polarization patterns trace the brightness distribution and vary with viewing angle and deformation, revealing spacetime structure. These results demonstrate that intensity and polarization in thick-disk models provide probes of KZ black holes and near-horizon accretion physics. △ Less

Submitted 19 October, 2025; originally announced October 2025.

Comments: 35pages,14figures

When Tiny Halos Stir Spacetime: Gravitational Waves from Fifth-Force Mergers

Authors: Xinpeng Wang, Yifan Lu, Zachary S. C. Picker, Alexander Kusenko, Misao Sasaki

Abstract: Dark matter fermions interacting via attractive fifth forces mediated by a light mediator can form dark matter halos in the very early universe. We show that bound systems composed of these halos are capable of generating gravitational wave (GW) signals detectable today, even when the individual halos are very light. The Yukawa force dominates the dynamics of these halo binaries, rather than gravi… ▽ More Dark matter fermions interacting via attractive fifth forces mediated by a light mediator can form dark matter halos in the very early universe. We show that bound systems composed of these halos are capable of generating gravitational wave (GW) signals detectable today, even when the individual halos are very light. The Yukawa force dominates the dynamics of these halo binaries, rather than gravity. As a result, large GW signals can be produced at initially extremely high frequencies, which are then redshifted to frequency bands accessible to current or future GW observatories. In addition, the resulting GW signals carry distinctive features that enable future observations to distinguish them from conventional ones. Notably, even if only a tiny fraction of dark matter experiences strong fifth-force interactions, such effects provide a new avenue to discover self-interacting dark matter through GW observations. △ Less

Submitted 14 October, 2025; originally announced October 2025.

Comments: 17 pages, 6 figures

Rotation of Polarization Angle in Gamma-Ray Burst Prompt Phase. III. The Influence of the Magnetic Field Orientation

Authors: Xing-Yao Wang, Jia-Sheng Li, Mi-Xiang Lan

Abstract: Polarization is very sensitive to the configuration of the magnetic field in the radiation region. In addition to polarization curve and polarization spectrum, studies of polarization angle (PA) rotation spectrum is also crucial. In this paper, we use a simple parametric magnetic reconnection model with a large-scale aligned magnetic field in the radiation region to study the effects of field orie… ▽ More Polarization is very sensitive to the configuration of the magnetic field in the radiation region. In addition to polarization curve and polarization spectrum, studies of polarization angle (PA) rotation spectrum is also crucial. In this paper, we use a simple parametric magnetic reconnection model with a large-scale aligned magnetic field in the radiation region to study the effects of field orientation on the PA rotations. Under different field orientations, variations of the PA rotation with parameters and the PA rotation spectra are studied. We find that the conclusions obtained in our previous works are almost independent of the field orientations. The area of the parameter space with $Δ$PA $>10^\circ$ will shrink as the value of field orientation ($δ$) increases for $0^\circ<δ<90^\circ$. The $Δ$PA values would be the same for two complementary field orientations. For two particular magnetic field orientations ($δ=0^\circ$ and $90^\circ$), the $Δ$PA would also only be $0^\circ$ or $90^\circ$ within the burst duration. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: 9 pages, 2 figures, 1 table, ApJ accepted

Proton-rich production of lanthanides: the νi process

Authors: Xilu Wang, Amol V. Patwardhan, Yangming Lin, Junbo Zheng, Michael J. Cervia, Yanwen Deng, A. Baha Balantekin, Haining Li, Ian U. Roederer, Rebecca Surman

Abstract: The astrophysical origin of the lanthanides is an open question in nuclear astrophysics. Besides the widely studied $s$, $i$, and $r$ processes in moderately-to-strongly neutron-rich environments, an intriguing alternative site for lanthanide production could in fact be robustly $\textit{proton-rich}$ matter outflows from core-collapse supernovae under specific conditions -- in particular, high-en… ▽ More The astrophysical origin of the lanthanides is an open question in nuclear astrophysics. Besides the widely studied $s$, $i$, and $r$ processes in moderately-to-strongly neutron-rich environments, an intriguing alternative site for lanthanide production could in fact be robustly $\textit{proton-rich}$ matter outflows from core-collapse supernovae under specific conditions -- in particular, high-entropy winds with enhanced neutrino luminosity and fast dynamical timescales. In this environment, excess protons present after charged particle reactions have ceased can continue to be converted to neutrons by (anti-)neutrino interactions, producing a neutron capture reaction flow up to A~200. This scenario, christened the $νi$ process in a recent paper, has previously been discussed as a possibility. Here, we examine the prospects for $νi$ process through the lens of stellar abundance patterns, bolometric lightcurves, and galactic chemical evolution models, with a particular focus on hypernovae as candidate sites. We identify specific lanthanide signatures for which the $νi$ process can provide a credible alternative to $r$/$i$ processes. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: 14 pages, 5 figures

Report number: NT@UW-25-11, N3AS-25-013

Feeding the dead: neutral gas inflow with suppressed star formation in a long-quenched ancient massive galaxy at z~2.7 observed with JWST/NIRSpec

Authors: Davide Bevacqua, Danilo Marchesini, Paolo Saracco, Francesco La Barbera, Richard Pan, Sirio Belli, Gabriel Brammer, Guido De Marchi, Fabio R. Ditrani, Giovanna Giardino, Karl Glazebrook, Valentina La Torre, Jamie Lin, Adam Muzzin, Namrata Roy, Paola Santini, Benedetta Vulcani, Peter J. Watson, Xin Wang

Abstract: We report the spectroscopic detection of neutral gas inflow into a massive ($M_* \simeq 4\times 10^{10} M_\odot$) quiescent galaxy observed at $z_{\rm{spec}} = 2.6576$ with JWST. From the redshifted absorption of the NaI doublet at $λλ5890, 5896 $ Ang, we estimate an inflow velocity $v=278^{+79}_{-79}$ km s$^{-1}$ and a column density $\log(N_{NaI}/\rm{cm^2}) = 13.02^{+0.03}_{-0.03}$. We derive th… ▽ More We report the spectroscopic detection of neutral gas inflow into a massive ($M_* \simeq 4\times 10^{10} M_\odot$) quiescent galaxy observed at $z_{\rm{spec}} = 2.6576$ with JWST. From the redshifted absorption of the NaI doublet at $λλ5890, 5896 $ Ang, we estimate an inflow velocity $v=278^{+79}_{-79}$ km s$^{-1}$ and a column density $\log(N_{NaI}/\rm{cm^2}) = 13.02^{+0.03}_{-0.03}$. We derive the inflowing mass of the gas $M_{in} = 1.6^{+0.1}_{-0.1} \times 10^8 M_\odot$ and rate $\dot{M}_{in} = 19^{+6}_{-7} \, M_\odot \, \rm{yr}^{-1}$. The presence of several surrounding galaxies suggests that the galaxy may be accreting gas from nearby companions. However, we cannot confirm it with current data and the intergalactic medium or cosmic filaments are also viable sources of the inflowing gas. Despite the ongoing inflow, the galaxy remains quiescent, with an upper limit to the star formation rate of $0.2 \, M_\odot \, \rm{yr}^{-1}$. Moreover, its star formation history suggests that the galaxy has remained quiescent during the past $\sim1$ Gyr, with half of its stars formed by redshift $z_{50}=11^{+18}_{-3}$. We discuss that the inflow is not massive, dense, or long-lived enough to ignite significant star formation, or it is fueling low-level AGN activity instead. This is direct evidence that quiescent galaxies can accrete cold gas after their quenching while keeping their star formation subdued. Follow-up observations with JWST and ALMA will be needed to constraint the nature of the inflowing gas. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: Submitted to ApJ

MSA-3D: Uncovering Weak AGNs and Resolved Outflows in Disguise in $z\sim1$ Star-Forming Galaxies

Authors: Namrata Roy, Alaina Henry, Tucker Jones, Ivana Barisic, Ryan L. Sanders, Kevin Bundy, Matthew A. Malkan, Themiya Nanayakkara, Karl Glazebrook, Timothy Heckman, Juan M. Espejo Salcedo, Xin Wang, Danail Obreschkow, Tommaso Treu

Abstract: We present spatially resolved rest-optical spectroscopy of 38 star-forming galaxies at 0.5 < z < 1.7 from the JWST/NIRSpec MSA-3D survey, which uses slit-stepping to build IFU-like datacubes at 0.1'' resolution. We map emission-line morphology, excitation, and kinematics of the warm ionized gas using [N II]/H$α$, [S II]/H$α$, and [O III]/H$β$. Relative to z$\sim$0 galaxies at fixed stellar mass, o… ▽ More We present spatially resolved rest-optical spectroscopy of 38 star-forming galaxies at 0.5 < z < 1.7 from the JWST/NIRSpec MSA-3D survey, which uses slit-stepping to build IFU-like datacubes at 0.1'' resolution. We map emission-line morphology, excitation, and kinematics of the warm ionized gas using [N II]/H$α$, [S II]/H$α$, and [O III]/H$β$. Relative to z$\sim$0 galaxies at fixed stellar mass, our sources show systematically lower [N II]/H$α$ and [S II]/H$α$ and elevated [O III]/H$β$, consistent with harder radiation fields and lower metallicities. Radially, [O III]/H$β$ profiles are typically flat or mildly positive, whereas [N II]/H$α$ also remains flat or declines outward, mirroring metallicity trends. On kpc scales, we find a strong positive correlation between [N II]/H$α$ and velocity dispersion ($σ$), linking local excitation to turbulent or shock-driven kinematics. Six galaxies ($\sim$ 16% of the sample) host spatially localized regions with elevated [N II]/H$α$, high EW(H$α$), and V_RMS = $\sqrt{V^2 + σ^2} > 200$ km/s, indicative of weak AGN activity, shocks, or outflows. For these candidates we infer modest warm-ionized outflow rates of 1-4 Msun/yr and kinetic powers $\sim$ 0.1-1% of the AGN bolometric luminosity (from central [O III] or H$α$). These values place our sample at the low-energy tail of known AGN-driven outflows yet in continuity with $\dot{M_{out}}-L_{AGN}$ scaling relations across 0 < z < 6. A completeness assessment shows MSA-3D is sensitive to AGN with $L_{AGN} \geq 10^{43}$ erg/s, underscoring both the promise and current limitations of detecting weak AGN activity in distant galaxies with resolved spectroscopy. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: 26 pages, 16 figures. Submitted to ApJ

JWST Spectroscopy of SN Ia 2022aaiq and 2024gy: Evidence for Enhanced Central Stable Ni Abundance and a Deflagration-to-Detonation Transition

Authors: Lindsey A. Kwok, Chang Liu, Saurabh W. Jha, Stéphane Blondin, Conor Larison, Adam A. Miller, Mi Dai, Ryan J. Foley, Alexei V. Filippenko, Jennifer E. Andrews, Moira Andrews, Katie Auchettl, Carles Badenes, Thomas G. Brink, Kyle W. Davis, Andreas Flörs, Lluís Galbany, Or Graur, D. Andrew Howell, Sahana Kumar, Réka Könyves-Tóth, Natalie LeBaron, Colin W. Macrie, Keiichi Maeda, Kate Maguire , et al. (24 additional authors not shown)

Abstract: We present optical + near-infrared (NIR) + mid-infrared (MIR) observations of the normal Type Ia supernovae (SN Ia) 2022aaiq and 2024gy in the nebular phase, continuously spanning 0.35-28 microns. Medium-resolution JWST spectroscopy reveals novel narrow ($v_{\mathrm{FWHM}}<1500$ km s$^{-1}$) [Ni II] 1.94 and 6.64 micron cores in both events. The MIR [Ni II] 6.64 micron line exhibits a distinct nar… ▽ More We present optical + near-infrared (NIR) + mid-infrared (MIR) observations of the normal Type Ia supernovae (SN Ia) 2022aaiq and 2024gy in the nebular phase, continuously spanning 0.35-28 microns. Medium-resolution JWST spectroscopy reveals novel narrow ($v_{\mathrm{FWHM}}<1500$ km s$^{-1}$) [Ni II] 1.94 and 6.64 micron cores in both events. The MIR [Ni II] 6.64 micron line exhibits a distinct narrow core atop a broader base, indicating a central enhancement of stable Ni. This structure points to high central densities consistent with a near-Chandrasekhar-mass ($M_{Ch}$) progenitor or a high-metallicity sub-$M_{Ch}$ progenitor. From detailed line-profile inversions of SN 2024gy, we derive emissivity profiles for stable iron-group elements (IGEs), radioactive material, and intermediate-mass elements (IMEs), revealing spatially distinct ejecta zones. The [Ni III] 7.35 micron line shows a shallow-to-steep slope transition -- a "broken-slope" morphology -- that matches predictions for delayed detonation explosions with separated deflagration and detonation ashes. We also reanalyze and compare to archival JWST spectra of SN 2021aefx and the subluminous SN 2022xkq. We estimate a stable $^{58}$Ni mass of $\sim0.1$ M$_\odot$ for SN 2024gy, consistent with delayed detonation models, and $\sim0.01$ M$_\odot$ for SN 2022xkq, favoring sub-$M_{Ch}$ scenarios. These results demonstrate that resolved line profiles, now accessible with JWST, provide powerful diagnostics of explosion geometry, central density, and progenitor mass in SN Ia. △ Less

Submitted 14 October, 2025; v1 submitted 10 October, 2025; originally announced October 2025.

Comments: 30 pages, 17 figures, 2 tables, submitted to AAS Journals

Galaxy Metallicity Gradients in the Reionization Epoch from the FIRE-2 Simulations

Authors: Xunda Sun, Xin Wang, Fangzhou Jiang, Houjun Mo, Luis C. Ho, Qianqiao Zhou, Xiangcheng Ma, Hu Zhan, Andrew Wetzel, Russell L. Graf, Philip F. Hopkins, Dusan Keres, Jonathan Stern

Abstract: We employ the high-redshift suite of FIRE-2 cosmological hydrodynamic zoom-in simulations to investigate the evolution of gas-phase metallicity radial gradients in galaxies in the epoch of reionization (EoR). Our sample consists of 22 galaxies spanning the redshift range $z \sim 10-5$. We find that galaxies at $z\sim10$ exhibit a median metallicity gradient of $-0.15\,\mathrm{dex\cdot kpc^{-1}}$ w… ▽ More We employ the high-redshift suite of FIRE-2 cosmological hydrodynamic zoom-in simulations to investigate the evolution of gas-phase metallicity radial gradients in galaxies in the epoch of reionization (EoR). Our sample consists of 22 galaxies spanning the redshift range $z \sim 10-5$. We find that galaxies at $z\sim10$ exhibit a median metallicity gradient of $-0.15\,\mathrm{dex\cdot kpc^{-1}}$ with substantial scatter, which gradually flatten to $-0.1\,\mathrm{dex\cdot kpc^{-1}}$ at $z\sim6$, accompanied by a reduction in scatter. In the EoR, metallicity gradients correlate positively with stellar mass: more massive galaxies display flatter gradients with smaller scatter, broadly consistent with recent JWST observations. At fixed stellar mass, galaxies with higher star formation rates (SFRs) exhibit steeper negative gradients, while sSFR shows a strong anti-correlation with gradient slope. Because EoR galaxies in FIRE-2 generally lack significant rotational support, we adopt the ratio of peak-to-peak velocity shear to twice the velocity dispersion ($Δv/2σ$) as a proxy for the strength of gas flows. We find a strong positive correlation between metallicity gradients and $Δv/2σ$: galaxies with lower $Δv/2σ$ (i.e., weaker gas flows) tend to exhibit steeper negative gradients. Furthermore, galaxies with steeper gradients display higher central SFR surface densities, suggesting localized star formation with inefficient interstellar medium mixing that drives inside-out chemical enrichment in galaxy evolution in the early Universe. △ Less

Submitted 10 October, 2025; originally announced October 2025.

Comments: 16 pages, 19 figures, 1 table

A Giant Peanut-shaped Ultra-High-Energy Gamma-Ray Emitter Off the Galactic Plane

Authors: Zhen Cao, Felix Aharonian, Yunxiang Bai, Yiwei Bao, Denis Bastieri, Xiaojun Bi, YuJiang Bi, Mr Bian WenYi, A. Butkevich, Chengmiao Cai, Wenyu Cao, Zhe Cao, Jin Chang, Jinfan Chang, Mr Aming Chen, Ensheng Chen, Mr Guo-Hai Chen, Mr Huaxi Chen, Liang Chen, Long Chen, Mingjun Chen, Mali Chen, Qihui Chen, Shi Chen, Suhong Chen , et al. (291 additional authors not shown)

Abstract: Ultra-high-energy (UHE), exceeding 100 TeV (10^12 electronvolts), γ-rays manifests extreme particle acceleration in astrophysical sources. Recent observations by γ-ray telescopes, particularly by the Large High Altitude Air Shower Observatory (LHAASO), have revealed a few tens of UHE sources, indicating numerous Galactic sources capable of accelerating particles to PeV (10^15 electronvolts) energi… ▽ More Ultra-high-energy (UHE), exceeding 100 TeV (10^12 electronvolts), γ-rays manifests extreme particle acceleration in astrophysical sources. Recent observations by γ-ray telescopes, particularly by the Large High Altitude Air Shower Observatory (LHAASO), have revealed a few tens of UHE sources, indicating numerous Galactic sources capable of accelerating particles to PeV (10^15 electronvolts) energies. However, discerning the dominant acceleration mechanisms (leptonic versus hadronic), the relative contributions of specific source classes, and the role of particle transport in shaping their observed emission are central goals of modern UHE astrophysics. Here we report the discovery of a giant UHE γ-ray emitter at -17.5° off the Galactic plane - a region where UHE γ-ray sources are rarely found. The emitter exhibits a distinctive asymmetric shape, resembling a giant "Peanut" spanning 0.45° \times 4.6°, indicative of anisotropic particle distribution over a large area. A highly aged millisecond pulsar (MSP) J0218+4232 is the sole candidate accelerator positionally coincident with the Peanut region. Its association with UHE γ-rays extending to 0.7 PeV, if confirmed, would provide the first evidence of a millisecond pulsar powering PeV particles. Such a finding challenges prevailing models, which posit that millisecond pulsars cannot sustain acceleration to PeV energies. The detection reveals fundamental gaps in understanding particle acceleration, cosmic-ray transport, and interstellar magnetic field effects, potentially revealing new PeV accelerator (PeVatron) classes. △ Less

Submitted 25 October, 2025; v1 submitted 8 October, 2025; originally announced October 2025.

Towards the Giant Radio Array for Neutrino Detection (GRAND): the GRANDProto300 and GRAND@Auger prototypes

Authors: GRAND Collaboration, Jaime Álvarez-Muniz, Rafael Alves Batista, Aurélien Benoit-Lévy, Teresa Bister, Martina Bohacova, Mauricio Bustamante, Washington Carvalho, Yiren Chen, LingMei Cheng, Simon Chiche, Jean-Marc Colley, Pablo Correa, Nicoleta Cucu Laurenciu, Zigao Dai, Rogerio M. de Almeida, Beatriz de Errico, João R. T. de Mello Neto, Krijn D. de Vries, Valentin Decoene, Peter B. Denton, Bohao Duan, Kaikai Duan, Ralph Engel, William Erba , et al. (96 additional authors not shown)

Abstract: The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of ultra-high-energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interaction -- gamma rays, and, especially, neutrinos. GRAND will do so using large arrays of radio ant… ▽ More The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of ultra-high-energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interaction -- gamma rays, and, especially, neutrinos. GRAND will do so using large arrays of radio antennas that look for the radio signals emitted by the air showers initiated by the interactions of the UHE particles in the atmosphere. Since 2023, three small-scale prototype GRAND arrays have been in operation: GRAND@Nançay in France, GRAND@Auger in Argentina, and GRANDProto300 in China. Together, their goal is to validate the detection principle of GRAND under prolonged field conditions, achieving efficient, autonomous radio-detection of air showers. We describe the hardware, software, layout, and operation of the GRAND prototypes and show the first radio spectra measured by them. Despite challenges, the successful operation of the prototypes confirms that the GRAND instrumentation is apt to address the goals of the experiment and lays the groundwork for its ensuing stages. △ Less

Submitted 25 September, 2025; originally announced September 2025.

Comments: 28 pages, 16 figures, 2 tables

A Two-Stage Kick Scenario for the Peculiar LMXB GX 1+4

Authors: Xiangyu Ivy Wang, Shi-Jie Gao, Xiang-Dong Li

Abstract: The low-mass X-ray binary (LMXB) GX 1+4 stands out with its unique properties. Despite being an old system, it hosts a strongly magnetized neutron star (NS), a trait usually linked to younger systems. Its exceptionally long orbital period (1160 days) and low eccentricity (0.101) imply that the NS formed with minimal mass loss and a weak natal kick. These features collectively point towards the NS… ▽ More The low-mass X-ray binary (LMXB) GX 1+4 stands out with its unique properties. Despite being an old system, it hosts a strongly magnetized neutron star (NS), a trait usually linked to younger systems. Its exceptionally long orbital period (1160 days) and low eccentricity (0.101) imply that the NS formed with minimal mass loss and a weak natal kick. These features collectively point towards the NS having formed through the accretion induced collapse (AIC) of a white dwarf (WD). However, GX 1+4's unusually high peculiar velocity (~ 189.36 km/s) defies standard AIC explanations. To address this discrepancy, we propose a two-stage kick scenario within the AIC framework: an initial natal kick followed by a delayed electromagnetic "rocket effect" kick. Our Monte Carlo simulations indicate that while the natal kick (< 100 km/s) can generate a wide range of orbital eccentricities, the subsequent rocket kick (~ 240-480 km/s) explains both the high systemic velocity and low eccentricity. This two-stage kick mechanism naturally reproduces the observed characteristics of GX 1+4, provided that the NS's initially buried magnetic field re-emerges after the acceleration process ends. Our study represents the first attempt to quantitatively constrain the kick velocities in GX 1+4 and underscores the importance of possible rocket kicks in forming such peculiar LMXB systems. △ Less

Submitted 25 September, 2025; originally announced September 2025.

Comments: 9 pages, 5 figures; Published in the Astrophysical Journal Letters

Multiwavelength study of Galactic PeVatron LHAASO J0341+5258

Authors: P. Bangale, X. Wang

Abstract: Galactic PeVatrons are astrophysical sources accelerating particles up to a few PeV (~10$^{15}$ eV). The primary method to identify both electron and proton PeVatrons is the observation of $γ$-ray radiation at ultra-high energies (UHE; E$>$100 TeV). In 2021, LHAASO detected 14 steady $γ$-ray sources with photon energies above 100 TeV and up to 1.4 PeV. Most of these sources can be plausibly associ… ▽ More Galactic PeVatrons are astrophysical sources accelerating particles up to a few PeV (~10$^{15}$ eV). The primary method to identify both electron and proton PeVatrons is the observation of $γ$-ray radiation at ultra-high energies (UHE; E$>$100 TeV). In 2021, LHAASO detected 14 steady $γ$-ray sources with photon energies above 100 TeV and up to 1.4 PeV. Most of these sources can be plausibly associated with objects such as supernova remnants, pulsar wind nebulae, and stellar clusters. However, LHAASO J0341$+$5258 is detected as an unidentified PeVatron, emitting $γ$ rays at energies above hundreds of TeV. It is extended in nature and notably bright, with a flux $>$ 20% of the Crab Nebula's flux above 25 TeV. Multiwavelength observations are required to identify the PeVatron responsible for the UHE $γ$ rays, understand the source morphology and association, and shed light on the emission processes. Here, we will present the results from the VERITAS and HAWC observations of this PeVatron, along with a discussion on potential emission scenarios through multiwavelength modeling. △ Less

Submitted 24 September, 2025; originally announced September 2025.

Comments: Proceedings paper presented at the 39th International Cosmic Ray Conference (ICRC2025), held 15-24 July, 2025, in Geneva, Switzerland

Investigation of hadronic cross sections of cosmic ray carbon and oxygen on BGO from 200 GeV to 10 TeV energy at the DAMPE experiment

Authors: F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, E. Catanzani, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, Y. X. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong , et al. (122 additional authors not shown)

Abstract: The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, f… ▽ More The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, for a calorimetric experiment like DAMPE, uncertainties in hadronic models persist as a major barrier in achieving more accurate measurements of fluxes of cosmic ray nuclei. This study centers on the measurement of the inelastic hadronic cross sections of carbon and oxygen nuclei interacting with BGO crystals target over an extensive energy range, spanning from 200 GeV to 10 TeV. For carbon nuclei interacting with the BGO target, the measurements of the cross sections have achieved a total relative uncertainty of less than 10% below 8 TeV for carbon, and below 3 TeV for oxygen. For oxygen nuclei, the same level of precision was attained below 3 TeV. Additionally, we compare the experimental results with Geant4 and FLUKA simulations to validate the accuracy and consistency of these simulation tools. Through comprehensive analysis of the inelastic hadronic interaction cross sections, this research provides validation for the hadronic interaction models used in DAMPE's cosmic-ray flux measurements. △ Less

Submitted 21 September, 2025; originally announced September 2025.

VVV-WIT-13: an eruptive young star with cool molecular features

Authors: Zhen Guo, Philip Lucas, Sergey N. Yurchenko, Tomasz Kaminski, Matias Montesinos, Sergei Nayakshin, Vardan Elbakyan, Javier Osses, Alessio Caratti o Garatti, He Zhao, Radostin Kurtev, Jura Borissova, Calum Morris, Dante Minniti, Javier Alonso-García, Vitor Fermiano, Roberto K. Saito, Niall Miller, Gabriella Zsidi, H. D. S. Muthu, Cesar Briceño, Carlos Contreras Peña, A. E. Lynas-Gray, Jonathan Tennyson, Lingzhi Wang , et al. (5 additional authors not shown)

Abstract: Here we investigate an infrared eruptive source, identified from the decade-long VISTA Variables in the Via Lactea survey (VVV). We named this target after a group of variable sources discovered by VVV, as VVV-WIT-13, with WIT standing for "What Is This?", due to its unique photometric variation behaviour and the mysterious origin of the outburst. This target exhibited an outburst with a 5.7 mag a… ▽ More Here we investigate an infrared eruptive source, identified from the decade-long VISTA Variables in the Via Lactea survey (VVV). We named this target after a group of variable sources discovered by VVV, as VVV-WIT-13, with WIT standing for "What Is This?", due to its unique photometric variation behaviour and the mysterious origin of the outburst. This target exhibited an outburst with a 5.7 mag amplitude in the Ks-band, remained on its brightness plateau for 3.5 years, and then rapidly faded to its pre-eruptive brightness afterwards. We aim to reveal the variable nature and outburst origin of VVV-WIT-13 by presenting our follow-up photometric and spectroscopic observations along with theoretical models. We gathered photometric time series in both near- and mid-infrared wavelengths. We obtained near-infrared spectra during the outburst and decaying stages on XSHOOTER/VLT and FIRE/Magellan, and then fitted the detected molecular absorption features using models from ExoMol. We applied 2D numerical simulations to re-create the observables of the eruptive phenomenon. We observe deep AlO absorption bands in the infrared spectra of VVV-WIT-13, during the outburst stage, along with other more common absorption bands (e.g. CO). Our best-fit model suggests a 600 K temperature of the AlO absorption band. In the decaying stage, the AlO bands disappeared, whilst broad blue-shifted H2 lines arose, a common indicator of stellar wind and outflow. The observational evidence suggests that the CO and TiO features originate from an outflow or a wind environment. We find that VVV-WIT-13 is an eruptive young star with instability occurring in the accretion disk. One favoured theoretical explanation of this event is a disrupted gas clump at a distance of 3 au from the source. If confirmed, this would be the first such event observed in real time. △ Less

Submitted 23 September, 2025; v1 submitted 18 September, 2025; originally announced September 2025.

Comments: 13 pages, 14 figures

Journal ref: A&A 703, A141 (2025)