Current date: 2026-09-21

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Datestamp limit: 2026-09-21 (0 days ago)

Created/updated limit: 2026-09-14 (7 days ago)

Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics

Setting default set: physics

OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-09-21&until=2026-09-21&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 685

Keyword score statistics

score 7 -- 3 abstracts

score 6 -- 3 abstracts

score 5 -- 3 abstracts

score 4 -- 5 abstracts

score 3 -- 8 abstracts

score 2 -- 11 abstracts

in total -- 33 abstracts

Articles that appeared on 2026-09-21

[abstract 1 / 33] Wow! (score: 7)
arXiv:2609.21118 [pdf, ps, other]

Title: Energy Partition in Relativistic Electron-Positron-Ion Reconnection

Authors: Nilay Mancini, Luca Comisso, Lorenzo Sironi,

Comments: 17 pages, 10 figures; includes End Matter and Supplemental Material

Subjects: astro-ph.HE physics.plasm-ph

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

Relativistic MAGNETic RECONNECTion, a prime mechanism for particle acceleration, has been extensively studied in electron--ion and pair plasmas, but how the dissipated energy is shared among species in electron--positron--ion plasmas, and in particular how ions are energized within a pair-dominated layer, remains poorly understood. We develop an analytic theory that couples single-particle orbit dynamics to the collective plasma response, and we validate it with particle-in-cell simulations spanning pair-dominated to electron--ion compositions. Particles are directly energized in electric-dominated regions until the RECONNECTed MAGNETic field deflects them into the outflow; the characteristic escape length is in turn set by the RELATIVISTIC skin depth of the RECONNECTion-heated mixture, including the ion contribution. Writing $\sigmastar$ for the MAGNETic energy available per particle in units of $m_ec^2$ and $μ=m_i/m_e$, the mean lepton energy scales as $\sigmastar$, whereas the mean ion energy scales as $μ^{1/3}(\sigmastar)^{2/3}$ when ions escape non-RELATIVISTICally from the electric-dominated regions and approaches the lepton energy when their escape is ultraRELATIVISTIC. The predicted energy fractions agree with simulations across composition, mass ratio, and MAGNETization. The ion share of the dissipated energy can fall far below the commonly assumed ion--lepton equipartition, reducing the energy available for hadronic and neutrino emission in RECONNECTion-powered astrophysical sources.

[abstract 2 / 33] Wow! (score: 7)
arXiv:2609.21278 [pdf, ps, other]

Title: Neutrino Emission from Proton Photon Jet Interactions in MicroQUASARs

Authors: Theodoros Smponias,

Comments: 19 pages, 7 Figures

Subjects: astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

MicroQUASARs are candidate sites for high energy particle production within our galaxy. Because their distances and compact emission regions limit direct observational constraints, numerical simulations are useful for connecting JET dynamics with possible multi messenger signatures. This work models neutrino production from RELATIVISTIC MAGNETohydrodynamic microQUASAR JETs, focusing on the proton photon channel associated with interactions between accelerated protons and ambient photon fields. Proton proton interactions are acknowledged as a possible process in dense environments, but they are not modeled in the present calculation. A ray tracing procedure is applied to the hydrodynamic simulation output to produce synthetic neutrino images from the perspective of a stationary observer. Synthetic spectra and intensity maps are presented and compared with representative sensitivities of current and future neutrino detectors.

[abstract 3 / 33] Wow! (score: 7)
arXiv:2609.21343 [pdf, ps, other]

Title: A Gamma-ray Emitting Head-Tail Radio Galaxy Swimming Through the Hot Medium of the Merging Cluster Abell 3627

Authors: Vaidehi S. Paliya, M. Böttcher, Swayamtrupta Panda, Kiran Wani, D. J. Saikia, Mahadev Pandge, C. S. Stalin,

Comments: ApJ, in press

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Head-tail radio sources are JETted ACTIVE GALACTIC NUCLEi (AGN) moving through the dense intracluster medium of galaxy clusters. They are extremely rare in the gamma-ray sky, likely because they are usually observed at large viewing angles. Therefore, every new gamma-ray detection of head-tail RADIO GALAXies allows us to probe the origin of the high-energy emission in this unique class of AGN. Here we report, for the first time, the association of ESO~0137-G007 (z=0.016), a head-tail RADIO GALAXy located at the outskirts of the merging cluster Abell 3627, with the gamma-ray source FL16Y~J1615.5$-$6034. The motion of the galaxy through the dense cluster environment and subsequent ram pressure and/or intracluster medium turbulence have led to the formation of a $>$500 kpc-long JET exhibiting a twisted, wiggly radio morphology. Its optical spectrum, obtained with the 4.1 m SOAR telescope, is devoid of emission lines, indicating that the underlying accretion activity is radiatively inefficient. From the measured line-of-sight stellar velocity dispersion, we estimate the mass of the central supermassive BLACK HOLE to be $(3.36\pm1.32)\times10^9$ \Msun. We briefly discuss several radiative models to explain the observed broadband spectral energy distribution of ESO~0137$-$G007. We conclude that deeper multi-wavelength observations of this unique gamma-ray emitting head-tail RADIO GALAXy will enable us to better understand the interaction of the JET with the hot cluster environment, thus setting the stage for the research of this class of AGN with the upcoming Square Kilometer Array.

[abstract 4 / 33] Yes (score: 6)
arXiv:2111.05752 [pdf, ps, other]

Title: Modeling general-RELATIVISTIC plasmas with collisionless moments and dissipative two-fluid MAGNETohydrodynamics

Authors: Elias R. Most, Jorge Noronha, Alexander A. Philippov,

Comments: 15 pages, minor corrections to equations

Subjects: astro-ph.HE gr-qc nucl-th

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Relativistic plasmas are central to the study of BLACK HOLE accretion, JET physics, neutron star mergers, and compact object MAGNETospheres. Despite the need to accurately capture the dynamics of these plasmas and the implications for RELATIVISTIC transients, their fluid modeling is typically done using a number of (overly) simplifying assumptions, which do not hold in general. This is especially true when the mean free path in the plasma is large compared to the system size, and kinetic effects start to become important. Going beyond common approaches used in the literature, we describe a fully RELATIVISTIC covariant 14-moment based two-fluid system appropriate for the study of electron-ion or electron-positron plasmas. This generalized Israel-Stewart-like system of equations of motion is obtained directly from the RELATIVISTIC Boltzmann-Vlasov equation. Crucially, this new formulation can account for non-ideal effects, such as anisotropic pressures and heat fluxes. We show that a RELATIVISTIC two-fluid plasma can be recast as a single fluid coupled to electroMAGNETic fields with (potentially large) out-of-equilibrium corrections. In particular, we keep all electron degrees of freedom, which provide self-consistent evolution equations for electron temperature and momentum. The equations outlined in this paper are able to capture the full two-fluid character of collisionless plasmas found in BLACK HOLE accretion and flaring processes around compact objects, as well Braginskii-like two-fluid MAGNETohydrodynamics applicable to weakly collisional plasmas inside accretion disks. This new formulation will be instrumental in the construction of a large class of next-generation simulations of RELATIVISTIC transient phenomena produced around BLACK HOLEs and neutron stars.

[abstract 5 / 33] Yes (score: 6)
arXiv:2609.21711 [pdf, ps, other]

Title: X-ray POLARIZATION of the Compton-thin Seyfert galaxy NGC 5506 with IXPE

Authors: Daniele Tagliacozzo, Alessandro Leonardo Lai, Andrea Gnarini, Giorgio Matt, Stefano Bianchi, Francesco Ursini, Andrea Marinucci, Alessia Tortosa, Sudip Chakraborty, Federico Ferretti, Vittoria Elvezia Gianolli, Elias Kammoun, Frédéric Marin, Herman Marshall, Riccardo Middei, Romana Mikusincova, Dawoon Kim,

Comments: 9 pages, 5 figures, 1 table

Subjects: astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

We report on the observation of the Compton-thin Seyfert galaxy NGC~5506 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation, with a net observing time of 975~ks, was partly simultaneous with \textit{NUSTAR} (52~ks) and \textit{XMM-Newton} (37~ks). Using a simple baseline model with IXPE data only, we find an upper limit on the 2--8~keV POLARIZATION fraction at the $99\%$ confidence level: $Π<3.1\%$. We then performed a spectropolarimetric analysis combining data from the three X-ray observatories. While pure spectral modeling confirms the presence of both RELATIVISTIC and cold distant reflection, in addition to the primary continuum power law, their contributions lead to somewhat different constraints on the coronal $Π$, depending on the specific assumptions. We also performed Monte Carlo simulations with the radiative transfer code \texttt{MONK}, exploring various coronal geometries. Comparing these results with the IXPE data, and assuming a radially extended corona, as suggested by previous observations of similar sources, the corresponding POLARIZATION upper limits require inclination angles below 40°.

[abstract 6 / 33] Yes (score: 6)
arXiv:2609.21923 [pdf, ps, other]

Title: Nonlinearly Causal General-Relativistic Two-Fluid Dissipative Magnetohydrodynamics

Authors: Elias R. Most, Samuel J. Dunham,

Comments: 82 pages,16 figures

Subjects: astro-ph.HE astro-ph.IM gr-qc nucl-th physics.plasm-ph

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

We present a formulation of general-RELATIVISTIC (GR) 19-moment dissipative MAGNETohydrodynamics (MHD), capable of handling all first-order dissipative terms (viscosity, heat conductivity, resistivity and Hall terms), as well as all ideal electron degrees of freedom (number density, momentum and energy) in a GR astrophysical two-fluid plasma. We derive necessary and sufficient nonlinear causality conditions for the constrained first-order 19-moment system, as well as both necessary and sufficient conditions for strong hyperbolicity. To assess the formulation numerically, we develop a high-resolution shock-capturing scheme that solves these equations in a performance-portable fashion. The scheme expresses all evolution equations, including the dissipative and electron sectors, in flux-divergence form, allowing us to model systems with scales separated by orders of magnitude without resolving kinetic scales everywhere on the grid. In addition, we use implicit integration methods to systematically overstep kinetic scales in MHD regions, such as cyclotron and plasma frequencies. To make the scheme as robust as GRMHD codes, we construct necessary and sufficient conditions for a conserved state to be physically admissible, and based on these construct a new physicality-enforcement scheme. As an exact validation comparison, we formulate and derive a full solution to dissipative two-fluid Bondi accretion in general relativity. We then validate the equations against a series of results from kinetic particle-in-cell models of BLACK HOLE accretion and MAGNETospheric dynamics, demonstrating that our formulation and scheme can correctly capture major features relevant for feedback on global scales of these solutions, including dimensionless RECONNECTion rates of order $0.1$ and Braginskii-like anisotropic pressures and heat fluxes.

[abstract 7 / 33] Yes (score: 5)
arXiv:2608.19796 [pdf, ps, other]

Title: Quasi-periodic Eruptions from Recurrent Satellite Black Hole Transits through Magnetized Galactic Nucleus Accretion Disks

Authors: Na Wang, Jing-Tong Xing, Tong Liu, Ya-Ping Li, Shuang-Liang Li,

Comments: 10 pages, 1 figure, accepted for publication in ApJL

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Quasi-periodic eruptions (QPEs) are recurrent soft X-ray flares from galactic nuclei, but their origin remains uncertain. The delayed ultraviolet (UV) counterpart detected in ZTF19acnskyy provides a new constraint on viable models. We present a two-channel model in which a satellite BLACK HOLE (sBH) repeatedly crosses a nuclear accretion disk threaded by a large-scale MAGNETic field. Gravitational focusing and dynamical drag generate hot, optically thick ejecta whose expansion and photon diffusion power the soft X-ray QPE. For fiducial Bondi-scale parameters, the model yields a characteristic X-ray duration of $\sim10^3\ \mathrm{s}$ and luminosity of $\sim10^{42}\ \mathrm{erg\,s^{-1}}$. For ZTF19acnskyy, the model reproduces the observed day-scale X-ray duration and energetics. Simultaneously, the sBH motion compresses and bends the background MAGNETic field, triggering in-disk RECONNECTion. The RECONNECTion channel provides the energy budget and photon-diffusion delay required for the variable UV component. Unfavorable MAGNETic fields or diffusion times longer than the QPE recurrence period can weaken or smear out the UV signal, potentially explaining the lack of clear UV counterparts in other QPE sources.

[abstract 8 / 33] Yes (score: 5)
arXiv:2609.21411 [pdf, ps, other]

Title: Gamma-ray Quasi-periodic Oscillations in the Changing Look Blazar B2 1420+326 (OQ 334)

Authors: Sunanda, Shubham Kishore, Alok C. Gupta,

Comments: Submitted to The Astrophysical Journal Letters (ApJL); 9 pages, 6 figures

Subjects: astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

In the FERMI-LAT gamma-ray light curve from January 1 to August 25, 2026, of the changing look BLAZAR B2 1420+326, we report here the detection of transient quasi-periodic oscillations (QPOs) of period ranging around 10-13 d. The source entered the flare state around May 7, 2026, and lasted till around mid-August, 2026 during which it depicted strong QPO signatures. We utilized standard techniques, including weighted wavelet Z-transform analysis, generalized Lomb-Scargle periodogram, and phase dispersion minimization, to search for and confirm these findings. Prior to the flare, the source displayed a mild damped oscillatory feature of similar periodicity with a damping timescale of around 20 d. Based on the period timescale and nature of the QPOs detected, we discuss possible physical mechanisms for the observed salient features.

[abstract 9 / 33] Yes (score: 5)
arXiv:2609.21930 [pdf, ps, other]

Title: Euclid: Quick Data Release (Q1) -- Optical hotspots in powerful RADIO GALAXies

Authors: M. J. Hardcastle, L. Bisigello, M. Bondi, M. Magliocchetti, L. K. Morabito, J. Petley, F. Ricci, H. J. A. Rottgering, K. Rubinur, D. J. B. Smith, D. Stern, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, M. Cropper, J. -G. Cuby, A. Da Silva, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, S. Ferriol, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, J. Hoar, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S. -M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, M. Schirmer, P. Schneider, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, J. Skottfelt, L. Stanco, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, O. R. Williams, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, J. García-Bellido, V. Scottez, F. Tarsitano, J. H. Knapen,

Comments: 11 pages, accepted by A&A

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

The hotspots of powerful RADIO GALAXies are the sites of high-energy particle acceleration, but radio observations give us limited information on the electron energy distributions that they generate, which affects our overall understanding of their physics and energetics. Optical SYNCHROTRON counterparts to RADIO GALAXy hotspots, which probe high electron energies, have been known for many years, but have only been studied in a small number of objects selected as being very bright in the radio. By combining Low-Frequency Array (LOFAR) observations with the Euclid Q1 data release in the Euclid Deep Field North, we identify 77 powerful RADIO GALAXies with hotspots and show that a small but significant fraction of them, 7--15\%, may have detected infrared and optical counterparts to their hotspots. The hotspot spectral energy distributions in our clearest cases are consistent with particle acceleration up to (but not beyond) 1\,TeV in energy on the assumption of field strengths close to equipartition, whereas non-detected hotspots either do not reach such high electron energies or would have to have very different electron energy spectra or significantly sub-equipartition MAGNETic field strengths. Two new candidate optical hotspots are clearly detected matching high-resolution LOFAR data; one is remarkable as both the highest-redshift optical hotspot known to date ($z \approx 1.6$) and also the first optical detection of the hotspot of the inner lobe of a restarting source. We discuss approaches to performing a large-scale study of hotspots with the full wide-area Euclid surveys, particularly when combined with the international baselines of LOFAR, enabling for the first time a statistical analysis of high-energy particle acceleration in hotspots.

[abstract 10 / 33] Yes (score: 4)
arXiv:2504.15959 [pdf, ps, other]

Title: A Novel Relationship Between Gamma Ray Burst Duration And Photospheric Radius

Authors: Ranadeep Ghosh Dastidar, Paul Duffell,

Comments: 10 pages, 8 plots

Subjects: astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Long Gamma Ray Bursts (lGRBs) are associated with JETs in Type Ic broadline SUPERNOVAe. The Collapsar model provides a theoretical framework for the JET formation from the core collapse of a massive star in such SUPERNOVAe. The GRB can only be produced after a successful JET break out from the star. Under this formalism the GRB duration ($t_{\rm{90}}$) has been hypothesized to be the difference between the central engine activity duration ($t_{\rm{eng}}$) and the JET breakout time ($t_{\rm{bo}}$), that is $t_{\rm{90}} = t_{\rm{eng}} - t_{\rm{bo}}$. This disallows $t_{\rm{90}} > t_{\rm{eng}}$ and puts a lower bound on successful lGRB JET central engine duration ($t_{\rm{eng}} > t_{\rm{bo}}$), various numerical simulations have shown otherwise. This study considers a photospheric GRB emission from a RELATIVISTIC JET punching out of a Wolf-Rayet-like star. We use the bolometric lightcurve generated to calculate the lGRB duration ($t_{\rm{90}}$) for varying engine duration. We find for longer engine duration the lGRB lightcurve reflects the JET profile and $t_{\rm{90}} \approx t_{\rm{eng}}$. While for shorter engine duration, the $t_{\rm{90}}$ has photospheric radius ($R_{\rm{ph}}$) dependence. This can be modeled by a relation, $t_{\rm{90}} = t^{\rm{90}}_{\rm{eng}} + 0.03\left(\frac{R_{\rm{ph}}}{c}\right)$, where c is the speed of light, with a lower bound on $t_{\rm{90}}$ for a successful lGRB. This relation should be most relevant for possible low-luminous lGRBs originating from a collapsar with central engine duration comparable to the JET breakout time.

[abstract 11 / 33] Yes (score: 4)
arXiv:2601.04955 [pdf, ps, other]

Title: Overmassive BLACK HOLEs and little red dots naturally form in simulations

Authors: Sunmyon Chon, Shingo Hirano, Tomoaki Ishiyama, Seok-Jun Chang, Volker Springel,

Comments: Published in Nature 657, 621--625 (2026); 14 figures

Subjects: astro-ph.GA astro-ph.CO astro-ph.SR

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

The origin of supermassive BLACK HOLEs (SMBHs) remains a long-standing problem in astrophysics. Recent JWST observations reveal an unexpectedly abundant population of overmassive BLACK HOLEs at $z>4$--$6$, where the BH masses lie far above local scaling relations and are not reproduced by current cosmological models. How such overmassive BLACK HOLEs form and rapidly grow within young galaxies has remained unclear. Here we present fully cosmological radiation-hydrodynamic simulations that self-consistently follow the birth, early growth, and emergent observable signatures of SMBHs in proto-cluster environments. We find that heavy seeds of order $10^{6}\,M_\odot$ naturally form, exceeding typical theoretical expectations by an order of magnitude. These seeds rapidly develop dense, optically thick disks whose strong electron scattering produces broad H$α$ emission comparable to that seen in little red dots (LRDs). Sustained super-Eddington accretion then drives fast growth to $\sim3\times10^{7}\,M_\odot$ by $z\simeq 8$. This is the first demonstration that unifies LRDs to a short-lived, enshrouded phase of heavy-seed formation, which naturally evolve into the overmassive QUASARs detected by JWST and ultimately the progenitors of today's SMBHs.

[abstract 12 / 33] Yes (score: 4)
arXiv:2604.06305 [pdf, ps, other]

Title: Wild is the wind from low-luminosity AGN: A JET-driven gas bubble blowing out a massive CO-dark outflow in ESO 420-G13

Authors: J. A. Fernández-Ontiveros, L. Spinoglio, M. Pereira-Santaella, A. Hernán-Caballero, E. Hatziminaoglou, E. Pérez-Montero, J. M. Vílchez, B. Pérez-Díaz, R. Amorín, M. A. Malkan, K. M. Dasyra,

Comments: 12+8 pages, 7+5 figures. Accepted for publication in A&A

Subjects: astro-ph.GA

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

We present JWST/MIRI mid-infrared integral field spectroscopy combined with ALMA CO(2-1) observations of the post-starburst galaxy ESO 420-G13, hosting a low-luminosity AGN. The unprecedented spatial and spectral resolution of MIRI enables a detailed study of the molecular and ionised gas kinematics, excitation, and energetics in the nuclear kiloparsec, revealing the impact of AGN feedback in a system with modest radiative output. Despite its faint radio and X-ray emission ($L_{2-10keV} \sim 10^{40}$ erg/s), ESO 420-G13 exhibits powerful kinetic feedback in the form of massive molecular and ionised gas outflows, with a total kinetic power of $\sim 1.4 \times 10^{41}$ erg/s. This corresponds to a JET-ISM coupling efficiency of ~3.8%, within the range observed in more powerful AGN. The feedback is driven by a previously undetected compact JET, traced by collimated coronal-line and extended X-ray emission to >870 pc from the nucleus. The interaction is strongest ~370 pc north of the nucleus, where a fast ionised gas stream emerges perpendicular to the JET axis, coinciding with a bend in the JET direction. Enhanced velocity dispersion in warm H$_2$ surrounds this gas stream, consistent with an expanding molecular bubble. Massive molecular outflows are detected at its edges; the blueshifted outflow is devoid of CO emission, likely due to CO destruction in shocks or by COSMIC RAYs from the JET-ISM interaction. About 5% of the central molecular reservoir has already been expelled, and the remaining gas is turbulent and warm, suggesting an ongoing phase of AGN-driven feedback in this post-starburst galaxy. Our results highlight the enormous potential of mid-IR imaging spectroscopy to uncover JET-driven feedback in low-luminosity AGN. Without the spatially resolved MIRI diagnostics, the kinetic power of the AGN in ESO 420-G13 and its role in shaping the host galaxy ISM would have remained hidden.

[abstract 13 / 33] Yes (score: 4)
arXiv:2609.16135 [pdf, ps, other]

Title: Analog Gravity in Magneto-Viscous Fluids: Enhanced Analog Hawking Temperature in Accretion Disks

Authors: Aliv Sahoo, Mayank Pathak, Banibrata Mukhopadhyay,

Comments: 28 pages including 7 figures (20 png files). Comments are welcome!

Subjects: gr-qc astro-ph.HE physics.flu-dyn

Created: 2026-09-14; Updated: 2026-09-21; Datestamp: 2026-09-21

We present a three-dimensional visco-MAGNEToacoustic framework for analog gravity in MAGNETohydrodynamic (MHD) flows. While standard fluid dissipation typically breaks the Lorentzian signature of acoustic metrics, we demonstrate that evaluating wave perturbations in the eikonal limit alongside the Shakura-Sunyaev $α$-viscosity prescription preserves a well-defined effective spacetime geometry for the fast MAGNEToacoustic mode. The slow-MAGNEToacoustic mode and Alfvén mode do not admit a non-degenerate metric. To investigate analog horizon thermodynamics, we utilize astrophysical accretion disks as background media, specifically modeling numerical MAGNETized advective accretion flows around rotating BLACK HOLEs and analytical advection-dominated inflow-outflow solutions (ADIOS). Standard self-similar ADIOS models strictly enforce a constant Mach number, precluding horizon formation. We therefore introduce a MAGNETic field perturbation that breaks self-similarity, generates a dynamic Mach number, and enables the formation of a visco-MAGNEToacoustic horizon. By evaluating the spontaneous phonon emission at these horizons, we reveal that the analog Hawking temperature is highly sensitive to the MAGNETic field topology; the spatial orientation of the background MAGNETic gradients dictates whether the Hawking radiation is amplified or suppressed. Furthermore, we find that increasing the viscosity parameter leads to a monotonic increase in the analog Hawking temperature.

[abstract 14 / 33] Yes (score: 4)
arXiv:2609.21732 [pdf, ps, other]

Title: Beyond Disk Truncation: X-ray Reverberation Signatures of an Outflowing Corona

Authors: Ke Qin, Bei You, Adam Ingram, Barbara De Marco,

Comments: 16 pages, 10 figures

Subjects: astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

The corona in BLACK HOLE X-ray binaries (BHXRBs) is likely dynamic during outbursts. A mildly RELATIVISTIC outflowing corona has been proposed to explain hard spectra, weak disk reflection, and the higher than expected POLARIZATION degree observed in the hard state of X-ray binaries. In this work, we investigate the spectral and timing effects of coronal outflow using Monte Carlo radiative-transfer simulations. The model consists of a geometrically thin, optically thick truncated disk and an ellipsoidal corona with a prescribed bulk outflow velocity. We calculate the Comptonized continuum, the disk reflection component, and the lag-frequency spectra for different outflow velocities and disk truncation radii. We find that increasing the outflow velocity reduces the reflection fraction through RELATIVISTIC beaming, because fewer Comptonized photons irradiate the disk. For $β\lesssim 0.5$, the high-frequency soft lag is only weakly affected by the outflow velocity, whereas increasing the disk truncation radius shifts the zero-crossing frequency($ν_0$) to substantially lower frequencies. Thus, timing properties can help distinguish the coronal-outflow scenario from the disk-truncation scenario. We further apply the model to MAXI J1820+070 and find that its unusual $R-Γ$ anti-correlation during the plateau phase is qualitatively consistent with a contracting corona accompanied by increasing bulk velocity. Disk recession alone would predict the opposite evolution of $ν_0$ under the assumptions of our model. Future POLARIZATION calculations will provide an additional test of extended outflowing-corona models.

[abstract 15 / 33] (score: 3)
arXiv:2607.20233 [pdf, ps, other]

Title: Identifying Kilonovae in the Presence of Optical Afterglow for the Wide Field Survey Telescope

Authors: Huan Yang, Zhengyan Liu, Liang-Duan Liu, Wen Zhao, Zigao Dai,

Comments: 26 pages, 13 figures,

Subjects: astro-ph.HE astro-ph.IM

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Identifying kilonovae associated with binary neutron star mergers is often complicated by the presence of a dominant SYNCHROTRON afterglow. In this work, we evaluate the performance of the Wide Field Survey Telescope (WFST) in identifying kilonova signals in composite afterglow-kilonova transients. Using a numerical framework based on the Fisher information matrix, we simulate $10,000$ realizations for each of two scenarios: an AT2017gfo-based template model and a physically sampled population that accounts for kilonova diversity. Our results indicate that kilonova identification is primarily limited by source distance. In both scenarios, the identification efficiency is largely insensitive to variations in afterglow microphysical parameters and exceeds $80\%$ at distances within approximately $600~\rm Mpc$ for AT2017gfo-like events. Under our adopted assumptions and a short GAMMA-RAY BURST (sGRB)-triggered target-of-opportunity (ToO) observational strategy, we estimate that the WFST could identify $0.1-1.2$ kilonovae per year in the optimistic scenario. Furthermore, we find that the discriminating power of color-based filters rapidly saturates, reaching a stable plateau by the second night after the merger. We therefore propose a staged observing strategy that prioritizes high-cadence $g$ and $r$-band monitoring during the first night and incorporates the $z$ band from the second night onward. This strategy improves the identification precision by exploiting the increasingly prominent red excess produced by the kilonova. Our results provide a physical basis for optimizing WFST observing resources to efficiently detect and characterize kilonovae in the multimessenger era.

[abstract 16 / 33] (score: 3)
arXiv:2609.20920 [pdf, ps, other]

Title: Little Red Dots As Super-Eddington Fountain Flows

Authors: Nicholas Kaaz, Eliot Quataert, Taya Govreen-Segal, Hanpu Liu,

Comments: 25 pages, 14 figures. Comments welcome!

Subjects: astro-ph.HE

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

Little red dots (LRDs) may be powered by supermassive BLACK HOLEs (SMBHs) accreting above the Eddington limit. Spectroscopy of LRDs often shows absorption troughs blueshifted by $\sim100-300\,{\rm km\,s^{-1}}$, implying a slow wind. This is puzzling: super-Eddington disks drive much faster winds, $\gtrsim10^3-10^4\,{\rm km\,s^{-1}}$. We argue that LRDs are super-Eddington SMBHs viewed off-axis and engulfed in a slow wind that covers most sight-lines; the fast wind escapes near the poles. Trapped light puffs the inner disk into a quasi-spherical envelope that launches the slow wind. The wind may be ``photon-tired'', meaning the light only barely unbinds it. Such marginally unbound winds lead to fountain flows, where some gas escapes and the rest falls back. We model the envelope with idealized, spherically symmetric ``marginally unbound'' ($v\sim v_{\rm esc}$) and ``photon-tired'' winds. We feed these profiles into the radiative transfer code Sirocco to study how the wind reprocesses the light from an accreting $10^6\,M_\odot$ SMBH. We describe most of the wind as a ``Balmer cocoon'' -- a Compton-thick region in which depletion of Balmer continuum photons ($hν>3.4\,{\rm eV}$) rather than Lyman continuum photons ($hν> 13.6\,{\rm eV}$) keeps the gas ionized. The spectra span the range of LRD-like sources: ``little blue dots'' at lower outflow rates ($\sim2.5\,M_\odot\,{\rm yr}^{-1}$); V-shaped LRDs with a Balmer break ($\sim5-10\,M_\odot\,{\rm yr}^{-1}$); and red LRDs with full breaks ($\sim15\,M_\odot\,{\rm yr}^{-1}$). Our Balmer line profiles show P~Cygni features atop broad, exponential wings, as is observed. The break is possible at lower wind densities than in LTE models because Lyman~$α$ trapping sustains our $n=2$ hydrogen population and electron scattering enhances the optical depth. Our arguments are also applicable to winds from supermassive stars or quasi-stars.

[abstract 17 / 33] (score: 3)
arXiv:2609.20929 [pdf, ps, other]

Title: From IFS Maps to 3D Structure I: Constraining Geometry in the Circumgalactic Medium

Authors: Mandy C. Chen, Michael Rauch, Zhijie Qu, Gwen C. Rudie, Hsiao-Wen Chen, James R. Beattie,

Comments: 20 pages, 5 figures, submitted to AAS Journals

Subjects: astro-ph.GA

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

The three-dimensional geometric structure of the cool (T~$10^4$ K) circumgalactic medium (CGM) -- the line-of-sight depth and the number of discrete clumps -- is poorly constrained. Existing inferences come predominantly from QUASAR absorption-line statistics, but these pencil-beam probes provide limited spatial and kinematic information. Here we show that spatially resolved emission-line maps from integral field spectrograph (IFS) observations provide complementary, novel constraints on cool CGM geometry when projection effects are accounted for. Observations of a sample of CGM nebulae yield measurements of the line-of-sight and the plane-of-sky velocity dispersions, with ratios $σ_{\rm los}/σ_{\rm pos}$ ranging from ~1 to ~2.5. Using direct numerical simulations of isotropic turbulence projected through emitting slabs of varying depth $L_{\rm los}$, we show that the ratio $σ_{\rm los}/σ_{\rm pos}$ allows us to probe $L_{\rm los}/L_{\rm neb}$, where $L_{\rm neb}$ is the nebular extent on the plane of the sky. We find that the inferred line-of-sight depth is typically ~0.1-$5\,L_{\rm neb}$, indicating that these nebulae are broadly comparable in depth and projected extent. Although the cool CGM is intrinsically clumpy, at the current IFS data resolution, each beam aggregates enough clumps that the projected dispersion ratio approaches its volume-filling value. Consequently, the emission kinematics provide little additional information on the detailed clump configuration beyond consistency with the clump incidence rates inferred from absorption-line surveys. These findings serve as a theoretical framework for the turbulence diagnostics developed in the companion paper (Paper II). Together, these papers demonstrate how IFS emission-line kinematics can provide a quantitative probe of the 3D CGM, complementary to absorption-line and emerging FRB approaches.

[abstract 18 / 33] (score: 3)
arXiv:2609.20947 [pdf, ps, other]

Title: Euclid Quick Data Release (Q1) Euclid spectroscopy of QUASARs. 2. Physical properties from spectral fitting

Authors: Euclid Collaboration, J. Calhau, G. Calderone, A. Feltre, M. Scialpi, V. Allevato, H. Landt, F. Ricci, Y. Fu, L. Spinoglio, F. Shankar, L. Nicastro, A. Viitanen, G. Zamorani, M. Mezcua, F. La Franca, D. Stern, E. Lusso, J. Wolf, A. Paulino-Afonso, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Dusini, A. Ealet, S. Escoffier, M. Farina, S. Ferriol, F. Finelli, S. Fotopoulou, N. Fourmanoit, M. Frailis, M. Fumana, L. Gabarra, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, W. G. Hartley, S. V. H. Haugan, S. Hemmati, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, M. Huertas-Company, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, V. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, P. Monaco, A. Mora, M. Moresco, C. Moretti, L. Moscardini, C. Neissner, S. -M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, I. Risso, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, C. Surace, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, D. Vibert, Y. Wang, J. Weller, A. Zacchei, E. Zucca, M. Ballardini, P. Bergamini, S. Borgani, E. Bozzo, C. Burigana, R. Cabanac, A. Cappi, T. Castro, J. A. Escartin Vigo, J. García-Bellido, T. Gasparetto, A. Loureiro, J. Macias-Perez, R. Maoli, R. B. Metcalf, M. Pöntinen, E. Sarpa, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, J. A. Acevedo Barroso, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, G. Arico, F. Atrio-Barandela, E. Aubourg, M. Baes, L. Baumont, L. Bazzanini, D. Bertacca, M. Bethermin, F. Beutler, L. Bisigello, A. Blanchard, L. Blot, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, T. E. Collett, S. Conseil, A. R. Cooray, P. Corcho-Caballero, B. Csizi, O. Cucciati, H. Dannerbauer, S. Davini, T. de Boer, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, V. Duret, A. Enia, Y. Fang, A. Farina, A. G. Ferrari, A. Finoguenov, F. Fontanot, A. Franco, K. Ganga, R. Gavazzi, E. Gaztanaga, Z. Ghaffari, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, N. A. Hatch, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, J. Kim, C. C. Kirkpatrick, A. Kovács, I. Kovačić, K. Koyama, S. Kruk, M. C. Lam, G. Leroy, J. Lesgourgues, L. Linke, S. J. Liu, X. Lopez Lopez, G. Maggio, F. Mannucci, F. R. Marleau, C. J. A. P. Martins, M. Migliaccio, M. Miluzio, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, A. Nersesian, S. Nesseris, F. Oppizzi, F. Pace, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, G. Rodighiero, K. Rojas, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, A. Schneider, D. Sciotti, E. Sellentin, S. Serjeant, J. G. Sorce, M. Talia, K. Tanidis, C. Tao, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, C. Uhlemann, C. Valieri, A. Venhola, G. Verza, S. Vinciguerra, M. von Wietersheim-Kramsta, L. Wang, A. H. Wright,

Comments: 24 pages, 17 figures, 4 tables, online data available at https://github.com/astrocalhau/LinesInTheSky . Submitted to A&A

Subjects: astro-ph.GA

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

A substantial volume of spectroscopic data has become available with the Euclid Data Release (Q1), which represents a unique opportunity to study QUASARs (QSOs) in the Euclid Deep Fields, provide spectroscopic measurements, and estimates of their physical properties. We present results from a spectroscopic analysis of QSOs with HE < = 22.5 using Q1. We use external catalogues from surveys such as the Dark Energy Spectroscopic Instrument (DESI), Gaia, Wide-field Infrared Survey Explorer (WISE), and the QUasars as BRIght beacons for Cosmology in the Southern hemisphere (QUBRICS) for the QSO selection and redshift determination, totaling 5489 QSOs. We provide measurements of the line fluxes, full widths at half-maximum, and respective uncertainties for the emission lines of Euclid spectra based on fitting statistica and signal-to-noise ratio (S/N). Of the total 5489 QSOs, 5387 are successfully fitted. We find that 45% of the total number of successfully fitted spectra are free of problematic artefacts allowing for trustworthy measurements. Our final Euclid QSO sample spans a redshift range of 0.01 < = z < = 4.8 and shows a median spectral index of αλ = - 1.17. Finally, we estimate BLACK HOLE masses with single epoch methods for 1213 sources, using the He I λ10830, Pa β, H α, H β, and Mg II emission lines, obtainning a mean logarithmc mass of log10 (MBH / Msolar) = 8.7 and mean Edigton ratio of λEdd = 0.34. The catalogue with the physical properties of this sample together with the software developed for the analysis is available online for scientific exploitation.

[abstract 19 / 33] (score: 3)
arXiv:2609.21076 [pdf, ps, other]

Title: A mechanism for fast radio bursts and their narrow spectra

Authors: Andrei M. Beloborodov, Ivan Demidov,

Comments: 26 pages, 13 figures, submitted to ApJ

Subjects: astro-ph.HE

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

We find an emission mechanism for fast radio bursts (FRBs) capable of producing broad and narrow spectra. It operates in MAGNETar explosions, which launch an electroMAGNETic pulse from the inner MAGNETosphere at radii $r_0\sim 10^{7}$ cm. Plasma inside the pulse accelerates outward with Lorentz factor $Γ(r)\approx r/r_0$. Before exiting the MAGNETosphere at radius $r\sim 10^{10}$ cm, the pulse passes through ambient kHz waves that populate the MAGNETospheres of active MAGNETars. We show that the waves experience stimulated scattering inside the pulse, with the boost factor $Γ^2$ converting them into radial GHz radiation. This process exponentially amplifies tiny GHz seeds to extreme luminosities consistent with observed FRBs. The produced GHz burst rides inside the explosion pulse, which helps it escape to distant observers. The FRB duration and energy are controlled by the pulse duration and energy. In a saturated emission regime, the predicted burst contains an ultrastrong microsecond component.

[abstract 20 / 33] (score: 3)
arXiv:2609.21136 [pdf, ps, other]

Title: Effects of Physical Cooling on the Structure of Circumbinary Disks

Authors: Minjae V. Kim, Julian H. Krolik, Scott C. Noble,

Comments: 23 pages, 14 figures

Subjects: astro-ph.HE astro-ph.SR

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

Radiation pressure and radiative cooling often play an important role in deciding the structure and dynamics of astrophysical objects. In this paper, we present a radiative MHD simulation of a circumbinary disk (CBD) around an equal-mass SMBBH. It employs an approximate thermodynamic model based on local thermodynamic equilibrium and diffusion cooling which captures how the internal energy evolves in an optically thick region. The disk reaches a quasi-steady state within $r=5a$ whose mass distribution differs substantially from the one obtained from simulations without physical thermodynamics: the local maximum in the azimuthally-averaged surface density and the lump are completely erased; the time-averaged inner edge becomes more eccentric; and the vertical density distribution depends strongly on the radius. These changes are attributable to the enhancement of the MAGNETic fields caused by the cooling-driven vertical compression of the disk. Our result emphasizes that the basic properties of the inner CBD are sensitive to both radiation and MAGNETic physics.

[abstract 21 / 33] (score: 3)
arXiv:2609.21606 [pdf, ps, other]

Title: Combining astrometry with pulsar timing: the first joint analysis of very low frequency gravitational waves

Authors: Lorenzo Filipello, William Beordo, Volodymyr Akhmetov, Mariateresa Crosta, Mario Gilberto Lattanzi,

Comments:

Subjects: astro-ph.IM astro-ph.CO astro-ph.HE gr-qc

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

The pHz to sub-nHz GW regime remains largely unexplored but is crucial for mapping the early inspiral stage of SMBHBs and probing early-Universe physics. Astrometry and pulsar timing offer orthogonal and deeply complementary secular observables to investigate this frequency band. We aim to present the first joint data analysis combining real astrometric proper motions with binary pulsar timing, to search for and constrain continuous gravitational waves (CWs) sourced by SMBHBs in the ultra-low-frequency regime ($10^{-12} \le f_{GW} \le10^{-9} Hz$). We employ a Bayesian model selection and upper limit estimation framework to combine apparent proper motion displacements of $\sim 1.5 \times 10^6$ QUASARs from the Gaia CRF3 catalog with the line-of-sight orbital period derivatives ($\dot{P}_b$) of 11 high-precision binary pulsars. To prevent spurious detections, we heavily model instrumental and astrophysical systematics: we propagate the Galactic potential uncertainty for pulsars via Monte Carlo simulations and perform a Vector Spherical Harmonics (VSH) decomposition up to the octupole order (l=3) for QUASARs. We find no statistically significant evidence for a CWs signal in the joint analysis ($\ln B_{joint} = -0.42 \pm 0.03$). In the absence of detection, we set the tightest constraints to date on CW strain in the pHz band, yielding a 95% upper limit of $h_0\le6.4x10^{-11}$ at a reference frequency of $f_{ref} = 4 \times 10^{-10}$ Hz. The combined dataset achieves full sky coverage and improves single-dataset upper limits by 20%-30%. Combining orthogonal observables successfully breaks spatial degeneracies intrinsic to isolated searches. Furthermore, forecasts from inj.-rec. indicate that with the extended temporal baseline and reduced uncertainties of the upcoming Gaia DR4, this joint framework is poised to break the $h_0 < 10^{-11}$ upper limit barrier for sub-nHz CWs.

[abstract 22 / 33] (score: 3)
arXiv:2609.22074 [pdf, ps, other]

Title: The AGN Channel in 3D: Scattering Belts and the Importance of Eccentricity in the Black Hole Population

Authors: Connar Rowan, Martin E. Pessah,

Comments: 11 pages, 4 figures

Subjects: astro-ph.GA astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Active galactic nuclei (AGN) are a promising origin for observed gravitational wave mergers. Current population synthesis models are limited to 1D N-body or Monte Carlo methods which rely on statistical approaches to resolving dynamical scatterings. We present three-dimensional hybrid $N$-body simulations of a population of BLACK HOLEs (BHs) surrounding an AGN using a new code in development, AGNBI, where close interactions are directly simulated for both single and binary objects. Our results show binary formations occur throughout the AGN disk, particularly where the migration time is long. While BHs efficiently migrate and pair up in migration traps, they are frequently disrupted by ionisation or exchanges from binary-single and binary-binary interactions. We report a broadened radial distribution of formations and mergers about the trap radius when accounting for binary-single and binary-binary interactions, which we describe as a "scattering belt''. We assess the influence of the pre-existing BH population. When we model a non-zero eccentricity distribution in the BH population, the binary formations and mergers are suppressed by an order of magnitude compared to a non-eccentric population as fewer BHs embed in the AGN disk. We report an approximate merger rate of $\mathcal{R}_\mathrm{GW}\approx2\text{--}12\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$ with maximum BH masses of $10^2\text{--}10^3\,M_\odot$ through hierarchical mergers, where lower initial velocity dispersions produce larger BHs. The mass and mass ratio distributions are comparatively flat, suggesting AGN may be more relevant for high-mass or unequal-mass gravitational wave sources.

[abstract 23 / 33] (score: 2)
arXiv:2602.04376 [pdf, ps, other]

Title: Light deflection in the graviMAGNETic dipole spacetime

Authors: Clémentine Dassy, Jan Govaerts,

Comments: 3 pages, 1 figure. Published under licence in Journal of Physics: Conference Series by IOP Publishing Ltd. CC BY 4.0. Content from this work may be used under the terms of the Creative Commons Attribution 4.0 International licence. Any further distribution of this work must maintain attribution to the authors and the title of the work, journal citation, and DOI

Subjects: gr-qc

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

The graviMAGNETic dipole is an asymptotically flat, stationary, axisymmetric vacuum solution to Einstein's General Relativity describing two non-extreme BLACK HOLEs with equal masses and opposite NUT charges connected by a Misner string. The string tension's can be set to zero by choosing the BLACK HOLE separation accordingly, yielding a stable system of oppositely rotating BLACK HOLEs at a fixed distance. Numerical simulations of massless particle geodesics reveal gravitational lensing effects for extended sources at infinity on the equatorial plane or on the vertical axis.

[abstract 24 / 33] (score: 2)
arXiv:2604.18910 [pdf, ps, other]

Title: Cross Subtype Transferability of Machine Learning Photometric Redshift Relations in Low Redshift Seyfert AGN

Authors: Uzay Aydin,

Comments: Revised manuscript

Subjects: astro-ph.GA

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Photometric redshift estimation for ACTIVE GALACTIC NUCLEi (AGN) is complicated by the combined effects of host-galaxy light, nuclear emission, dust attenuation, and broadband spectral diversity. We investigate whether machine learning photo-z relations trained on one low-redshift Seyfert subtype remain valid when transferred to another, and whether probabilistic subtype classification can be used to identify sources for which a specialised regressor is reliable. Using spectroscopically selected Seyfert I and Seyfert II samples from SDSS, matched to AllWISE photometry over 0 < z_spec <= 0.6, we constructed a common 45-feature representation from SDSS ugriz and WISE W1-W4 data. Random Forest and XGBoost regressors were evaluated within each subtype, followed by controlled cross-subtype transfer tests, redshift and sample size-matched experiments, feature ablations, and an independent classifier-gated regression test. The subtype specific models achieved strong within-sample performance, with the Seyfert II model reaching R2 = 0.965 and sigma_NMAD = 0.0169. However, transfer between Seyfert I and Seyfert II produced a clear and asymmetric degradation in accuracy that persisted after matching the samples and restricting the photometric inputs. A probabilistic Seyfert classifier further identified subsets for which the Seyfert II regressor was more reliable, while extrapolation beyond the redshift range represented in training produced systematic underestimation. These results demonstrate that AGN photo-z performance depends strongly on the population and redshift domain represented in the training data, supporting subtype-aware calibration and applicability-based source selection.

[abstract 25 / 33] (score: 2)
arXiv:2605.20112 [pdf, ps, other]

Title: Gravitational-wave constraints on $H_0$ are robust to putative redshift evolution in the binary BLACK HOLE mass spectrum at current sensitivity

Authors: Alessandro Agapito, Viola De Renzis, Michele Mancarella,

Comments: 12 + 5 pages, 6 + 7 figures

Subjects: astro-ph.CO astro-ph.HE gr-qc

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Spectral-siren cosmology constrains the Hubble constant $H_0$ using gravitational-wave observations of compact-binary coalescences. The method combines luminosity distances inferred from the waveform with redshift information statistically encoded in population features of the source-frame mass spectrum. Because the detector measures redshifted masses, structure in the intrinsic mass distribution acts as an internal ``ruler,'' making the inference sensitive to assumptions about the population model. In particular, redshift evolution of the mass spectrum is widely discussed as a potential systematic for $H_0$ measurements. We revisit spectral-siren constraints with the GWTC-4.0 binary BLACK HOLE catalog, explicitly allowing the main mass scales of a standard parametric mass model to evolve with redshift. We find no compelling evidence for evolution at current sensitivity. Allowing evolution produces a modest, nonstatistically significant shift of the $H_0$ posterior toward lower values, which we interpret with targeted posterior and event-level diagnostics. Importantly, the associated systematic uncertainty is subdominant to that induced by alternative redshift-independent descriptions of the mass spectrum, such as the number of spectral features and the functional form used to model them. Our results indicate that, at current sensitivity, spectral-siren constraints on $H_0$ are robust to redshift evolution of the mass spectrum within the flexibility explored here. Using injection studies, we show that this mild $H_0$ shift is reproduced when a nonevolving underlying population is analyzed with an evolving model, consistent with an overflexible population description at the present signal-to-noise. The sign and magnitude of the shift can, however, depend on detector sensitivity and redshift reach as the population features become increasingly constrained directly by the data.

[abstract 26 / 33] (score: 2)
arXiv:2609.09725 [pdf, ps, other]

Title: Aarmed with Data: Bumps, Outflows, and Disk-like Emission in TDE 2025aarm

Authors: Aysha Aamer, Kate D. Alexander, Charlotte R. Angus, Panos Charalampopoulos, Megan Newsome, Iair Arcavi, Giorgos Leloudas, Matt Nicholl, Jennifer Andrews, Katie Auchettl, Thomas de Boer, K. Azalee Bostroem, Y. -Z. Cai, Kenneth C. Chambers, Collin T. Christy, Sara Faris, Noah Franz, Sebastian Gomez, Maider González-Bañuelos, Mariusz Gromadzki, Paul J. Groot, Claudia Gutiérrez, Brian Hsu, Mark Huber, Thomas L. Killestein, Chien-Cheng Lin, Thomas B. Lowe, Peter Lundqvist, Dylan Magill, Seppo Mattila, Francesca Onori, Gregory S. H. Paek, Jeniveve Pearson, Miika Pursiainen, Niko Pyykkinen, Conor Ransome, Sara Romagnoli, Jennifer Shi, Manisha Shrestha, Nathan Smith, Maximilian Stritzinger, Bhagya Subrayan, Richard Wainscoat, Ziyang Y. Wang, Simon de Wet, Hannah Wichern,

Comments: Submitted to ApJ, metadata updated

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

The origin of the optical emission in tidal disruption events (TDEs) remains one of the major outstanding questions in the field, in part due to the limited number of nearby events with high-cadence monitoring to track their evolving photometric and spectroscopic properties. We present multi-wavelength observations of the nearby ($z=0.01368$) TDE\,2025aarm, including near-daily spectroscopic coverage prior to the optical peak. Its proximity makes it one of the brightest TDEs discovered, reaching a peak magnitude of $m_r\sim15.5$ ($M_r\sim-18$). The light curve deviates from a smooth evolution, exhibiting multiple rebrightening episodes visible in both the individual filter light curves and the bolometric luminosity. Blackbody modelling reveals that these rebrightenings are associated with an increase in temperature of $> 5,000-10,000$\,K, while the inferred photospheric radius remains approximately constant. Simultaneously, the H$α$ line not only increases in blueshift but also broadens, suggesting a link between the continuum rebrightenings to changes in the kinematics of the line-forming gas. We identify a persistent absorption component at $\sim-3900$\,km\,s$^{-1}$ in multiple Balmer lines, providing further evidence for outflowing material. The H$α$ profile also exhibits excess flux compared to a Gaussian on both sides of the line, inconsistent with simple scattering-dominated outflow models. Disk-profile modelling provides evidence for the emergence of a disk-like component least $\sim20$ days after peak, with substantial changes in the disk properties between $\sim50$ and 60 days. These observations highlight the complexity of TDE emission processes and demonstrate how dense multi-wavelength monitoring can disentangle the roles of accretion, reprocessing, and outflows in shaping TDE emission.

[abstract 27 / 33] (score: 2)
arXiv:2609.12279 [pdf, ps, other]

Title: Dynamics for Spin-$1/2$ Particles in Einstein-Gauss-Bonnet Gravity II: Non-Relativistic Case

Authors: E. Maciel,

Comments: 48 page, 9 figures, 1 table

Subjects: gr-qc

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

In this work, I investigate the non-RELATIVISTIC quantum dynamics of spin-1/2 particles in Einstein-Gauss-Bonnet (EGB) gravity and establish a direct connection between higher-curvature corrections, fermionic dynamics, and the phenomenology of compact objects. Starting from the Dirac Hamiltonian in a static, spherically symmetric EGB spacetime, we perform a Fold-Wouthuysen transformation and derive the effective Hamiltonian, including RELATIVISTIC kinetic, gravitational, spin-orbit, and higher-curvature contributions. Heisenberg equations are then used to obtain the dynamics of velocity, force, and spin, revealing explicit EGB corrections for both translational motion and spin transport. In particular, the spin-orbit sector induces a modified precession frequency whose fractional deviation from general relativity scales as $δ_Ω=-4(ξ/M^{2})(M/ρ)^{3}$, providing a clear dimensionless signature of the Gauss-Bonnet coupling. Through Ehrenfest's theorem, we also establish the correspondence between the dynamics of quantum operators and their semiclassical gravitational limit. As an astrophysical application, we consider the stellar-mass BLACK HOLE A0620-00 and show that prospective relative sensitivities in spin precession on the order of $10^{-3}$ to $10^{-4}$ can probe Gauss-Bonnet couplings in the range of approximately $10^{6}$ to $10^{8}\,{\rm m}^{2}$, depending on the orbital radius. This result identifies fermionic spin precession as a complementary channel for testing gravity with higher-curvature corrections and provides a quantum-mechanical framework connecting modified gravitational dynamics to precision phenomenology in strong-gravity regimes.

[abstract 28 / 33] (score: 2)
arXiv:2609.15547 [pdf, ps, other]

Title: The Multiphase CGM in the Epoch of Reionization: CII and CIV absorbers around [OIII] Emitters

Authors: C. Piscitelli, V. D'Odorico, M. Galbiati, M. Bischetti, G. Cupani, R. Dutta, S. Cantalupo, S. Di Stefano, S. T. Guida, K. Knudsen, C. Mazzucchelli, L. Paquereau, L. Pentericci, R. Rana, F. Ricci, F. Salvestrini, A. Tortosa, A. Travascio, C. Vignali, L. Zappacosta,

Comments: Accepted for publication in A&A

Subjects: astro-ph.GA

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

We investigate the multiphase circumgalactic medium (CGM) during the Epoch of Reionization (EoR, $z>6$) by cross-correlating cool- CII and warm-ionized CIV absorption systems with star-forming [OIII] emitters. JWST/NIRCam wide-field slitless spectroscopy from the EIGER survey is combined with medium- and high-resolution optical/NIR spectra of six background QUASARs, including new VLT/X-Shooter observations of PSO J159-02. We analyze the relation between 16 CII and 14 CIV absorbers ($\log(N) > 13.0$) and 136 galaxies, within an impact parameter of R$_{\perp} \leq$ 1000 pkpc and a line-of-sight separation of $Δv \leq 500$ km/s. We detect a statistically significant excess of both ions around galaxies compared to a randomized background. We observe that the CIV covering fraction remains enhanced up to $\sim 1$ pMpc, whereas CII drops to the background level beyond $\sim 0.5$ pMpc, demonstrating that the warm-ionized phase is more spatially extended than cooler gas. Jointly, the 3D galaxy-absorber spatial clustering is significantly weaker than the galaxy-galaxy auto-correlation. This provides direct physical evidence that early carbon enrichment is not confined to the virial radius of massive star-forming systems; rather, a substantial fraction of these metals permeates the diffuse intergalactic medium (IGM) or is injected by a widespread population of faint, undetected dwarf galaxies. Finally, we note a rapid radial decline of the CIV covering fraction compared with lower redshift samples at $z<2$ and $z\sim3-4$ pointing out an evolving CGM ionization structure where early metals reside predominantly in lower ionization states. In conclusion, we determine a conservative lower limit for the observed carbon mass of $\rm M_{CII + CIV} \geq 2.8 \times 10^6 \, M_{\odot}$ within 300 pkpc.

[abstract 29 / 33] (score: 2)
arXiv:2609.20898 [pdf, ps, other]

Title: Thermodynamic topology of MAGNETic GMGHS BLACK HOLEs: the $\overline {W}^{1-}$ subclass

Authors: Dejiang Yin, Qi-Qi Liang, Yu-Die Wan, Li-Yun Zhang,

Comments: submitted,commands are welcome!

Subjects: gr-qc

Created: 2026-09-17; Updated: 2026-09-21; Datestamp: 2026-09-21

Thermodynamic topology provides a topological classification of BLACK HOLE states and their branch structures in thermodynamic parameter space. We investigate the thermodynamic topology of the charged nonextremal MAGNETic Gibbons--Maeda family in four-dimensional asymptotically flat Einstein--Maxwell--dilaton gravity, with particular emphasis on its string-theory member at the dilaton coupling $a=1$, the Gibbons--Maeda--Garfinkle--Horowitz--Strominger (GMGHS) BLACK HOLE. An analytic classification over the complete domain of regular outer horizons shows that the dilaton coupling separates the family into three limiting structures of the inverse Hawking temperature. At $a=1$, the GMGHS defect curve approaches a nonzero lower inverse temperature endpoint and contains a single unstable branch. In particular, the MAGNETic GMGHS BLACK HOLE provides an explicit realization of the previously proposed $\overline W^{1-}$ thermodynamic topological subclass within an asymptotically flat Einstein--Maxwell--dilaton solution. This result demonstrates that the global topological number $W$ alone does not completely characterize BLACK HOLE thermodynamic topology. The asymptotic behavior of the inverse Hawking temperature near the boundaries of the physical horizon domain provides an additional criterion for distinguishing thermodynamic topological subclasses with the same $W$.

[abstract 30 / 33] (score: 2)
arXiv:2609.21177 [pdf, ps, other]

Title: CRAFT HTR2: Polarimetry of 64 non-repeating fast radio bursts from the updated CRAFT catalogue

Authors: T. Dial, A. T. Deller, Marcin Glowacki, A. Bera, R. M. Shannon, Clancy W. James, Joscha N. Jahns-Schindler, Ziteng Wang, Akhil Jaini,

Comments: 17 pages, 7 figures. Submitted to MNRAS

Subjects: astro-ph.HE

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

We present high-time resolution spectro-polarimetric data for 34 new fast radio bursts (FRBs) discovered by the Commensal Real-time Fast Transients (CRAFT) survey on the Australian Square Kilometer Array Pathfinder (ASKAP) during the period May 2024 to June 2026. Most of these were detected by the higher-sensitivity CRAFT COherent (CRACO) detection system that was commissioned on the telescope during this period. This new sample doubles the size of the CRAFT HTR catalogue and probes a fainter population of FRBs thanks to the improved sensitivity of CRACO. We compare the distribution of extragalactic rotation measure (RM) and polarisation fraction to the CHIME and DSA catalogues. While no significant differences were seen between CRAFT and DSA, the extragalactic RM distribution seen in CHIME FRBs (which are detected at lower frequency) was substantially lower. Surprisingly, we find no significant differences in the linear polarisation fraction distribution between the three FRB catalogues, suggesting an indifference to the different telescope observing frequencies. We show tentative evidence for wider and fainter bursts possessing lower polarisation fractions; this is predominantly driven by the growing sample of unpolarised bursts that are, in almost all cases, wider ($\gg$10 ms) and fainter ($\ll$10$^{34}$ ergs s$^{-1}$ Hz$^{-1}$) than the median ASKAP detection.

[abstract 31 / 33] (score: 2)
arXiv:2609.21635 [pdf, ps, other]

Title: A method for enhanced gamma-proton discrimination with imaging atmospheric Cherenkov telescopes

Authors: Jianling Liu, Hu Liu,

Comments: 21 pages, 15 figures

Subjects: astro-ph.HE hep-ex

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Purpose: Very-high-energy gamma-ray astronomy is an important window to study the extreme astrophysical processes in the universe, and how to effectively distinguish between gamma photons and background signals (mainly protons) is a key technical challenge to realize very-high-energy gamma-ray detection. Spaceborne calorimeters record secondary particle spatial distributions, achieving a background rejection power of 10000-100000 near 1 TeV. Ground-based imaging Cherenkov telescopes measure Cherenkov photon angular distributions, yet they only reach a rejection factor of about 10 in this energy range, leaving substantial room for optimization. Methods: We use CORSIKA and sim_telarray to simulate H.E.S.S. detector responses. Photon emission positions are reconstructed from Cherenkov shower images. Inspired by analysis techniques for space-borne calorimeter, we propose new observables derived from the transverse distribution of Cherenkov photon emission positions to separate gamma-ray signals from proton backgrounds. We employ a likelihood-ratio method to combine single-telescope variables across multiple telescopes and compare its performance with conventional Hillas-based analysis. Results: The results show that observables built from the transverse distribution of Cherenkov photon emission positions are less sensitive to Cherenkov image size and outperform the Hillas width parameter for single-telescope gamma-proton discrimination. Furthermore, the likelihood ratio combining width yields substantially better performance than the conventional mean reduced scaled width: the improvement reaches roughly one order of magnitude near 1 TeV, and this enhancement remains above 50% for energies above 10 TeV.

[abstract 32 / 33] (score: 2)
arXiv:2609.21766 [pdf, ps, other]

Title: Dirac Cones in d-wave AlterMAGNETs Enable High-Conductivity and High-Efficiency Spin Sources

Authors: Tianye Yu, Junwen Lai, Peitao Liu, Xing-Qiu Chen, Yan Sun,

Comments:

Subjects: physics.comp-ph

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

Low critical charge-current density and low energy dissipation are highly desired in MAGNETic random-access memories, requiring spin sources to exhibit both high charge-to-spin conversion efficiency (CSE) and high charge conductivity. AlterMAGNETs with vanishing net MAGNETic moment and spin-splitting bands provide promising spin-source candidates for spin-splitting-torque MAGNETic random-access memories. However, achieving both high CSE and charge conductivity remains challenging in alterMAGNETs. In this work, we introduce Dirac cones into two-dimensional d-wave alterMAGNETs, where their intrinsically high carrier mobility enables tunable charge and spin conductivities with high CSE. Dirac-cone anisotropy provides an effective means of enhancing both CSE and charge conductivity, with cone tilting serving as an additional degree of tunability. Guided by this design principle, we identify a maximum CSE of 92% in Cr2SeTeS. When the FERMI level moves slightly away from the Dirac point, high CSE, high charge conductivity, and the resulting high spin conductivity can be simultaneously achieved. Our study advances the understanding of time-reversal-odd spin transport via Dirac-cone engineering and provides a practical route toward developing spin-source materials that combine high charge conductivity with highly efficient charge-to-spin conversion.

[abstract 33 / 33] (score: 2)
arXiv:2609.22080 [pdf, ps, other]

Title: Rotating Neutron Star Migrations as a Standardized Test for 3+1 Numerical Relativity

Authors: Óscar H. Petit, José A. Font, Nikolaos Stergioulas,

Comments: 15 pages, 14 figures

Subjects: gr-qc

Created: 2026-09-18; Updated: 2026-09-21; Datestamp: 2026-09-21

When simulating dynamically unstable neutron stars, truncation errors can introduce perturbations that drive the stellar configuration either toward gravitational collapse into a BLACK HOLE or toward migration to a dynamically stable, lower-density configuration. This mechanism has become a standard benchmark for validating general-RELATIVISTIC hydrodynamics codes in the case of spherically symmetric neutron-star models. In this work, we extend the analysis to the more general case of uniformly rotating neutron stars evolved in three spatial dimensions. We investigate these transitions using two equations of state: a cold polytrope and a hybrid prescription, which allow us to distinguish the barotropic response from the effects of shock-generated thermal pressure. We find that the migrated remnant remains close to uniform rotation after the transition, and we trace its quasi-radial pulsations through complementary diagnostics involving the central density, the rotation profile, and the axisymmetric gravitational-wave channel. We investigate the properties of these transitions and propose a standardized test for validating numerical-relativity codes by requiring the migration behavior to be consistent with the dynamics reported here.