Current date: 2026-10-26
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Scoring abstracts
Number of records retrieved: 671
Keyword score statistics
score 9 -- 1 abstracts
score 7 -- 1 abstracts
score 6 -- 2 abstracts
score 5 -- 4 abstracts
score 4 -- 4 abstracts
score 3 -- 8 abstracts
score 2 -- 12 abstracts
in total -- 32 abstracts
Articles that appeared on 2026-10-26
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[abstract 1 / 32] Wow! (score: 9)
- Title: GRB 260924A: Extreme Energetics, Bright GeV Emission, and Exceptional X-ray and Optical LuminosityAuthors: Nissim Fraija, Peter Veres, Rosa L. Becerra, Antonio Galván-Gámez, Thomas Freeman, Simone Dichiara, Maria G Dainotti,Comments: 30 pages, 17 figures, 11 tablesSubjects: astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
We present a multiwavelength study of GRB~260924A at $z=3.51\pm0.10$ using \textit{FERMI}, \textit{SWIFT}, and ground-based optical and near-infrared observations. Its isotropic-equivalent gamma-ray energy, $E_{γ,\mathrm{iso}}\simeq9.79\times10^{54}$~erg, places it among the most energetic GRBs observed. The prompt emission comprised two bright episodes separated by weaker activity. The X-ray afterglow ranked among the most luminous in our comparison sample at selected post-flare epochs, with a luminosity comparable to that of GRB~221009A at a rest-frame time of 3.5~ks. At a common redshift of $z=1$, the optical afterglow outshone GRB~221009A by approximately 2~mag at 0.3~d and 1~mag near 1~d. LAT emission extended to approximately 1100~s and showed an early excess above the subsequent decay. The highest-energy photon, 43.3~GeV, arrived at 82~s during the first episode; a 14.2~GeV photon arrived at 304~s between episodes. We describe the afterglow light curves through forward-shock SYNCHROTRON and SYNCHROTRON self-Compton (SSC) emission, with reverse-shock SSC accounting for the early LAT excess. We connect the early and late afterglow phases by modelling the X-ray rebrightening at several kiloseconds through energy injection from trailing ejecta and evolving shock microphysics. The late afterglow suggests a stratified medium, modelled as $n(R)\propto R^{-1.2}$. Within this interpretation, the MAGNETic contrast $R_B\equiv(\varepsilon_{B,r}/\varepsilon_{B,f})^{1/2} \simeq2.6$ suggests MAGNETized ejecta, while the highest-energy LAT photons exceed the predicted SYNCHROTRON limit, supporting an SSC contribution.
[abstract 2 / 32] Wow! (score: 7) - Title: Testing the Correlations between X-ray Spectral Properties and Polarization for High Synchrotron Peaked BlazarsAuthors: M. Lynne Saade, Steven Ehlert, Ioannis Liodakis, Philip Kaaret, Fabrizio Tavecchio, Sara Capecchiacci, Riccardo Middei,Comments: Revised, submitted to MNRASSubjects: astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
IXPE has enabled the X-ray POLARIZATIONs of many BLAZARs to be measured. We present the first population study for high SYNCHROTRON peaked BLAZARs observed with IXPE using a uniform X-ray data analysis. We do not find any statistically significant correlations between the spectral properties of the BLAZARs and their X-ray polarimetric properties. The lack of significant correlations may imply that there is little connection between the energy distribution of the X-ray emitting electrons and the uniformity of the MAGNETic field in the X-ray emitting regions of these BLAZARs. These results will inform future theoretical work and potentially help narrow down the acceleration process of the SYNCHROTRON electrons.
[abstract 3 / 32] Yes (score: 6) - Title: An Extra-nuclear Water Maser in NGC 1106 Likely Driven By An AGN Shock: Implications for Maser-based Black Hole Mass MeasurementsAuthors: Macon Magno, Emmanuel Momjian, Krista L. Smith, O. Ivy Wong, Travis C. Fischer, Michael J. Koss, Chenoa D. Tremblay,Comments: Accepted to ApJ, 11 pages, 2 figures, 2 tablesSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
We present Very Large Array A-configuration ($0.13$'') 22 GHz spectral-line and continuum observations of the SWIFT-BAT detected Seyfert 2 galaxy, NGC 1106, aimed at localizing a water maser line offset from the host systemic velocity by 541 km s$^{-1}$. The 22 GHz continuum emission reveals a 352 pc extended structure within the nucleus of NGC 1106, and we spatially resolve the water maser emission to a compact region $\sim1$ kpc ($3.12$'') from the nucleus. Comparing our data with previous 22 GHz 1'' observations, we found that the water maser lies near the boundary of a radio extension aligned with the JET axis, likely arising from the interface between the ACTIVE GALACTIC NUCLEus (AGN) outflow and the host galaxy's ISM. To verify this, we compared the water maser in NGC 1106 to a known water maser in a star-forming region within the Milky Way, along with known extragalactic water masers associated with STAR FORMATION and AGN driven outflows. Overall, we found that the maser position, velocity offset, flux density, and alignment with the JET axis are consistent with an origin at the interface between the AGN outflow and the host ISM. Our results have important implications for maser-based BLACK HOLE mass measurements in which disk geometry is ambiguous. Since single-dish observations cannot spatially separate disk masers from outflow-driven masers, high-velocity maser features attributed to the accretion disk may also include contributions from kpc-scale shocks.
[abstract 4 / 32] Yes (score: 6) - Title: Collapsars Are Not Heavy $r$-Process FactoriesAuthors: Ore Gottlieb, Danat Issa, Jonatan Jacquemin-Ide,Comments:Subjects: astro-ph.HE astro-ph.GA astro-ph.SRCreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
Collapsar disks are proposed sources of $r$-process elements, but neutron-rich disk ejecta require gas to be both neutronized in the disk and ejected before accretion. The MAGNETic field that enables ejection also thickens the disk and accelerates the inflow, lowering both the density and the time available for weak processing. To compute the resulting neutronization, we evolve the electron fraction of the inflowing gas, adopting at each radius the temperature that maximizes the net neutronization rate for the local density and instantaneous composition. This yields a lower limit on $Y_{\rm e}$ that is independent of the disk's thermal history. We adopt an optimistic unbinding radius of $R_{\rm unb}=10\,r_g$ for all MAGNETic fluxes capable of launching outflows. Combining this ejection condition with favorable assumptions of low BLACK HOLE mass, ejection of midplane gas, and the upper end of the $γ$-ray burst (GRB) engine-power scale, which limits the accretion rate to $\dot M_{\rm BH}\lesssim0.4\,M_\odot\,{\rm s}^{-1}$, gives a fiducial lower bound $Y_{\rm e}\gtrsim0.33$, above the characteristic $Y_{\rm e}\approx 0.25$ threshold for heavy $r$-process production. Stronger MAGNETic flux, toward which JET-launching engines evolve, raises the lower bound to $Y_{\rm e}\gtrsim0.49$. We conclude that collapsar disk outflows cannot supply the heavy $r$-process yields invoked for a dominant enrichment channel. Only engines with unusually high accretion rates, potentially including exceptionally luminous GRBs, such as GRB 221009A, and direct-horizon collapsars, may produce heavy $r$-process ejecta.
[abstract 5 / 32] Yes (score: 5) - Title: SMMAN Studies of AGN Variability. I. Long-term Spectral Evolution and a Candidate $\sim1000$-day Quasi-periodic Modulation in 4C+72.28Authors: Xin Wang, Timur Mufakharov, Guiping Tan, Zhenhua Han, Ning Chang, Qi Yuan, Yunzhuo Wang, Xiang Liu, Lang Cui,Comments: 22 pages, 10 figures; submitted to ApJSubjects: astro-ph.GACreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The SMMAN project has carried out nine years of radio flux monitoring in the C and K bands of the BLAZAR 4C+72.28. The two bands show markedly different secular evolution, with a substantially stronger K-band decline producing a gradual decrease in the C-K spectral index. After accounting for this secular evolution, multiple timing diagnostics reveal a candidate quasi-periodic modulation with a characteristic timescale of $\sim1000$ d, most clearly in the C band. The C-band GLSP peak reaches a local significance of $3.29σ$, while its global significance remains modest at $\sim2σ$ and the monitoring baseline covers only about three cycles. Independent and joint MCMC fits support a phenomenological decomposition for both bands into a long-term linear trend and a recurrent component. Under the shared-period assumption, the joint fit returns a characteristic timescale of approximately 1027 d and a similar fractional recurrent amplitudes of $\simeq5.45\%$. Information-criterion comparisons favor the combined linear-plus-sinusoidal model in both bands. Cross-correlation analysis shows a nominal K-leading offset in the original light curves but a centroid consistent with zero lag after detrending, although the lag distributions overlap substantially. These results are consistent with a common recurrent modulation superposed on slower frequency-dependent JET evolution. Geometrical Doppler-factor modulation provides one plausible interpretation, although intrinsic and opacity-related processes cannot be excluded.
[abstract 6 / 32] Yes (score: 5) - Title: Radio Galaxies as UHECR Sources in Light of Recent MicroQUASAR ResultsAuthors: A. M. Taylor, J. H. Matthews,Comments: 9 pages, 7 figures, conference proceedings for Gamma2026Subjects: astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The recent discovery that microQUASARs operate as efficient particle accelerators brings back into focus the question as to whether their larger cousins, RADIO GALAXies, also operate as efficient accelerators. We here discuss what we presently know about particle acceleration in RADIO GALAXies, focusing particularly on the nearest such object, Centaurus A.
[abstract 7 / 32] Yes (score: 5) - Title: Magnetic Reconnection Modifies Cosmic-Ray Transport in the Interstellar MediumAuthors: Antoine Baldacchino-Jordan, Michal Hanasz, Vinod Pisharody, Dominik Wóltański, Artur Gawryszczak,Comments: 15 pages, 7 figures, submitted to The Astrophysical Journal Letters, comments welcomeSubjects: astro-ph.HE astro-ph.GACreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
We present numerical MAGNETohydrodynamic (MHD) simulations of the interstellar medium in gravity-stratified boxes with the Piernik MHD code. The system contains thermal gas, spectrally resolved cosmic-ray (CR) nuclei within the CRESP algorithm, and spectrally unresolved CR protons. CR protons drive gas outflows and undergo Coulomb and hadronic losses. CR nuclei undergo Coulomb losses. We also include the spallation of primary Carbon by thermal gas atoms, thereby decaying Car- bon into secondary stable Boron isotopes. We use the resistive-MHD approximation as a subgrid model for unresolved turbulent MAGNETic dissipation in current sheets. We perform a parameter study of the MAGNETic diffusivity η. The Boron-to-Carbon ratio B/C and hadronic γ-ray luminosity density are computed as diagnostics. We find that non-zero MAGNETic diffusivity modifies the MAGNETic topology, leading to a more horizontal field in the halo, thereby accumulating CRs in the disk region and signifi- cantly increasing the CR escape time. As a consequence, the local turbulent conditions and turbulent RECONNECTion in the interstellar medium should be considered when interpreting B/C and hadronic γ-ray luminosity observed at Earth. Our results suggest that the escape time and diffusion coefficient of CRs deduced from observational data in the vicinity of the Solar System cannot be extrapolated to the whole Galaxy.
[abstract 8 / 32] Yes (score: 5) - Title: The Galactic Center Gamma-Ray Excess and the Look-Elsewhere EffectAuthors: Isabel S. Sands, Philip F. Hopkins,Comments: 10 pages, 6 figures. Comments are welcomeSubjects: astro-ph.HE astro-ph.CO hep-phCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The origin of the excess of GeV gamma-rays in the Milky Way's galactic center observed by FERMI-LAT has been an open question for nearly two decades. The two leading interpretations of this signal are that it is produced either by annihilating DARK MATTER (DM), or arises from unresolved point sources, such as a novel population of millisecond pulsars. In both scenarios, uncertainties and limitations in the modeling of galactic diffuse gamma-ray emission, such as the steady-state approximation of COSMIC RAY (CR) propagation and assumption of an axisymmetric distribution of CRs, complicate the interpretation of the galactic center excess (GCE). Simulations with full MAGNETohydrodynamics (MHD) and CR transport can provide a new avenue for understanding the astrophysical phenomena that drive galactic diffuse gamma-ray emission. We utilize MHD simulations of Milky Way analogs with time-dependent, spectrally-resolved CR transport to reconstruct diffuse gamma-ray emission. Comparing instantaneous emission to a time-averaged baseline, we find residuals up to several times larger than the FERMI GCE, with a wide range of spectral shapes and spatial morphologies. At some simulation snapshots, the spectrum and morphology of the residuals resemble the FERMI GCE. Our results suggest that the FERMI GCE may be a manifestation of the look-elsewhere effect- a transient fluctuation in diffuse emission from stellar sources, observed at an inopportune moment- and motivate the development of new FERMI-LAT analysis templates that account for time-dependent CR transport.
[abstract 9 / 32] Yes (score: 4) - Title: The Loud Tail of the Supermassive Black Hole Binary Population: Multimessenger Candidates and Prospects for SKAOAuthors: Juhan Raidal, Ville Vaskonen, Juan Urrutia, Hardi Veermäe,Comments: 13 pages, 6 figuresSubjects: astro-ph.CO astro-ph.HE gr-qcCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
We assess whether electroMAGNETically identified supermassive BLACK HOLE (SMBH) binary candidates populate the rare, high-amplitude tail of the gravitational wave (GW) amplitude distribution. Using an SMBH binary population model fitted to the NANOGrav 15-year data, we find that 3C~66B and Mrk~501 are likely to stand out from the GW background, making them promising targets for individual-source searches. Furthermore, we show that individual detections can probe the binary hardening mechanism, as models with strong environmental hardening predict a higher abundance of individually resolvable binaries than purely GW-driven models. Applying the same population fits and accounting for the confusion noise from the unresolved population, we forecast that the Square Kilometre Array Observatory (SKAO) will resolve tens of individual binaries, with 3C~66B robustly detectable.
[abstract 10 / 32] Yes (score: 4) - Title: Image Morphology of Misaligned Magnetically Arrested DisksAuthors: Samuel Feyan, Cora Prather, Dominic O. Chang, Daniel C. M. Palumbo, Koushik Chatterjee, Michael D. Johnson,Comments: Submitted to ApJSubjects: astro-ph.HECreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
Horizon scale images probe the plasma dynamics and spacetime in the vicinity of accreting BLACK HOLEs. Interpreting these images requires models that connect image morphology to the structure of the underlying accretion flow. Disk misalignment is expected in many systems, yet most horizon scale image analyses assume that the emitting flow is aligned with the BLACK HOLE spin. We investigate whether tilted accretion flows produce image features distinguishable from axisymmetric flows and whether their effects can be absorbed by changes in aligned model parameters. Using general RELATIVISTIC MAGNETohydrodynamic simulations of tilted MAGNETically arrested disks spanning BLACK HOLE spins $a^*=-0.9375$ to $0.9375$ and initial disk tilts $0^\circ$ to $30^\circ$, we generate synthetic images and quantify their morphology through fits to an aligned, semi-analytic emission model. Using this approach, we show that high spin prograde models show little sensitivity to disk tilt, as the inner emitting flow aligns with the BLACK HOLE spin. In contrast, retrograde tilted disks develop warped, non-axisymmetric inner structure that distorts the inner shadow and strongly alters image morphology. While the aligned semi-analytic model reproduces most prograde images well, retrograde tilted disk images are fit less accurately and yield biased inferred parameters, especially for spin. The image morphologies indicate that tilt affects horizon scale images only when misalignment survives into the near horizon emitting region, motivating image models that include disk tilt as an explicit degree of freedom when alignment is uncertain.
[abstract 11 / 32] Yes (score: 4) - Title: Local Analogs of Little Red Dots: Clues to the X-ray WeaknessAuthors: Shi-Jiang Chen, Jun-Xian Wang, Zhen-Ya Zheng, Ruqiu Lin, Luis C. Ho, Zhen-Yi Cai, Chang-Hao Chen, Zsofi Igo, Jia-Lai Kang, Ruancun Li, Teng Liu, Wenke Ren, Zhen-Bo Su,Comments: Accepted. Our custom EP-FXT data analysis software available at https://github.com/AstroChensj/eFXTDAS. Comments are welcome!Subjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
A major question about JWST's little red dots (LRDs) at $z\sim4-8$ is the origin of their apparent X-ray weakness. Even deep Chandra stacks yield only tentative detections or broad-band limits and cannot distinguish among super-Eddington accretion, intrinsic X-ray weakness, and Compton-thick (CT) obscuration. Local analogs offer a powerful complementary route. At $z\sim0.3$, similarly luminous sources require $\sim10^{3-4}$ less exposure for comparable signal-to-noise, suffer less source confusion, and directly probe the diagnostic rest-frame soft X-rays. Here we present a pilot Einstein Probe/FXT study of six "local little red dots" (LLRDs), V-shaped broad-line green pea galaxies selected as low-redshift counterparts of LRDs. These sources show X-ray diversity: "X-normal" LLRDs resemble type 1 AGNs in X-ray luminosity and optical variability, whereas the "X-weak" stack lies $\sim0.5-0.7$ dex below standard unobscured-QUASAR scaling relations while remaining compatible with the representative LRD stack and 95% of published individual limits. The X-weak LLRDs also lack detected optical variability and have redder optical continua than X-normal LLRDs, making their V-shaped SEDs closer to those of high-redshift LRDs. The detection of the X-weak stack at $\sim3.3σ$ with the soft-X-ray-sensitive EP-FXT provides rest-frame $\sim2-3$ keV constraints difficult to reconcile with a typical unobscured super-Eddington model or a local-AGN-like CT geometry examined here, although modified variants remain possible. The simplest alternative is a mildly X-ray-weak corona ($Δα_{\mathrm{ox}}\sim-0.1$ to $-0.2$) with Compton-thin absorption ($N_{\mathrm{H}}\sim10^{22-23}$ cm$^{-2}$), consistent with the independent Balmer decrement/break diagnostics. Together with growing samples of local LRD analogs, our results offer a practical path for testing the physical nature of LRD X-ray weakness.
[abstract 12 / 32] Yes (score: 4) - Title: A Population Synthesis Model for Odd Radio Circles Produced by Shock-Bubble InteractionsAuthors: Yiting Wang, Sebastian Heinz, Alexander Tchekhovskoy,Comments: 10 figuresSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
Odd Radio Circles (ORCs) are edge-brightened rings of diffuse radio emission of roughly arcminute size whose physical origin remains debated. One proposed mechanism is vortex formation through Shock-Bubble interaction (SBI), in which a merger or accretion shock re-energizes a fossil radio lobe into an edge-brightened ring. We test whether this mechanism can reproduce the observed ORC abundance using a Monte Carlo population-synthesis model that combines the galaxy stellar mass function, the radio-AGN incidence relation, dark-matter halo merger histories, and the inflation and buoyant survival of AGN-inflated bubbles, with synthetic radio fluxes and ring geometries drawn from a grid of MAGNETohydrodynamic SBI simulations. Applying survey-specific selection to the ASKAP-EMU Pilot Survey (944 MHz) and the LOFAR Two-metre Sky Survey (LoTSS; 144 MHz), we predict $2.7^{+3.9}_{-1.6}$ detectable ORCs in the EMU Pilot, matching the three found there, and $268^{+331}_{-148}$ in LoTSS, of which $7.5^{+9.5}_{-4.2}$ have a counterpart at 1.4 GHz. The predicted hosts are mostly central galaxies in group-scale halos. The predicted rings are physically smaller and lie at lower redshifts than the galaxies identified as hosts of the known ORCs, suggesting that SBI produces mainly the nearby part of the ORC population, or that some ORCs are associated with the wrong host. The population synthesis model also predicts a large population of low surface brightness steep-spectrum ORCs in the LoTSS band, implying a large hidden population and predicting that deeper low-frequency surveys should uncover many more ORCs than are currently known. These results indicate that shock-bubble interactions can account for at least part of the observed incidence of ORCs.
[abstract 13 / 32] (score: 3) - Title: Effects of Alfvénicity on the Compressible Energy Cascade in Magnetohydrodynamic Solar Wind Turbulence: Evidence from Parker Solar Probe, Solar Orbiter, and WIND observationsAuthors: Nahuel Andrés, Carlos A. Gonzalez, Norberto Romanelli,Comments:Subjects: physics.plasm-ph astro-ph.SR physics.space-phCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The compressible MHD energy cascade in the solar wind is shaped by Alfvénicity, plasma fluctuations, and proton temperature, yet how these factors regulate the relative weight of compressible and incompressible energy transfer across heliocentric distances remains poorly understood. We apply compressible and incompressible exact relations to a large sample of 2-hour intervals from WIND (1~au), Parker Solar Probe ($<0.25$~au), and Solar Orbiter (0.3--1~au), classifying intervals as Alfvénic ($|σ_c|>0.75$) or non-Alfvénic ($|σ_c|<0.25$) and by wind speed, and examine the Yaglom-like and purely compressible components of the compressible cascade. Velocity fluctuation amplitude is the strongest predictor of the compressible cascade rate $\langle|\varepsilon_c|\rangle$, followed by density and MAGNETic field fluctuations. $\langle|\varepsilon_c|\rangle$ and $\langle|\varepsilon_i|\rangle$ are tightly correlated in all regimes, with their ratio organized by Alfvénicity and wind speed: non-Alfvénic and Alfvénic fast winds cluster along $\langle|\varepsilon_c|\rangle=\langle|\varepsilon_i|\rangle$, while Alfvénic slow wind shows a systematic excess consistent with internal energy contributions. The largest $\langle|\varepsilon_c|\rangle$ systematically occur in hotter intervals, with a two-decade increase from cool to hot events in Alfvénic slow and non-Alfvénic wind, a trend carried mainly by the purely compressible term, while the dominant Yaglom-like term controls the overall cascade magnitude. Alfvénicity and wind speed thus govern the efficiency of turbulent energy transfer across heliocentric distances, and the tight coupling between compressible and incompressible rates points to the need for compressible, multi-fluid descriptions of the solar wind dissipation budget.
[abstract 14 / 32] (score: 3) - Title: Separating the Optical to Near-Infrared Light of AGN and Their Host GalaxiesAuthors: Callum Dewsnap, Pauline Barmby, Sarah C. Gallagher,Comments: 24 pages including 14 figures; v2 adds mission acknowledgements and dataset DOIs, no other changesSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
The properties of galaxies that host ACTIVE GALACTIC NUCLEi (AGNs) offer clues to the conditions that enable accretion onto supermassive BLACK HOLEs. A galaxy's morphology can provide significant information on the evolutionary processes underway. By modeling the surface-brightness profiles of galaxies that host AGN, we can characterize physical properties of the host galaxy. With a sample of sources across a wide range of redshifts, we can investigate how both the supermassive BLACK HOLE and galaxy evolve over time. Applying the best practices from previous work, we perform Sersic + point source fits of 96 X-ray-selected AGN in the Extended Groth Strip across up to 13 bands of James Webb Space Telescope and Hubble Space Telescope imaging using AstroPhot. We examine both parametric (Sersic) and nonparametric methods in tandem to best determine the physical properties of the host galaxy. After separating the light of the host galaxy and the AGN, we perform independent CIGALE model fits to photometric spectral energy distributions to estimate physical properties including the host galaxy stellar mass and STAR FORMATION rate, and AGN disk luminosity. In the stellar-mass/star-formation-rate plane, the AGN host galaxies align with the population of massive non-AGN galaxies in the control sample across all redshifts. The AGN disk luminosities result in ratios of bolometric to X-ray flux within the expected range, 5-20:1. We provide an evaluation of the limitations of Sersic modeling to obtain galaxy properties and provide recommendations on best practices for multi-band AGN+host galaxy image decomposition with James Webb Space Telescope imaging.
[abstract 15 / 32] (score: 3) - Title: LHAASO Constraints on New-Source Cosmic Rays:Abundance Scenarios and Injection Spectral IndicesAuthors: Xu-Lin Dong, Pei-Pei Zhang, Qi-Ling Chen, Shu-Wang Cui, Yi-Qing Guo,Comments: 10 pages, 5 figuresSubjects: astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
Recent LHAASO observations indicate that microQUASARs and massive star clusters contribute to Galactic COSMIC RAYs, and likely also to the pre-knee spectral hardening. Their markedly different astrophysical environments, compared with SUPERNOVA remnants (SNRs), may imprint distinct cosmic-ray abundances. We investigate the spectra and composition of new-source COSMIC RAYs under two abundance scenarios: Case-1, the SNR-like composition with enhanced heavy nuclei, and Case-2, the surface abundances of microQUASAR companion stars. We constrain injection spectral indices using LHAASO proton, helium, and all-particle spectra, and use their
data for model discrimination. Under the assumption of a unified heavy-element injection spectrum, Case-2 fits the data significantly better than Case-1, but at the cost of large, physically unmotivated differences between heavy-element and He injection indices. This suggests the need to either relax the unified heavy-element injection-index assumption or explore alternative abundance patterns. We predict that if the new-source composition follows Case-1, the individual elemental spectral indices before the knee should remain nearly consistent; if it follows Case-2, the Mg, Si, and Fe spectra will be significantly softer than those of He, C, and O. Future element-resolved energy-spectrum measurements by HERD and LHAASO will provide a decisive test of this discriminating feature.
[abstract 16 / 32] (score: 3) - Title: ModeCast: One-Shot Prediction of Linear MHD Eigenmodes and Growth Rates in TokamaksAuthors: Alex Higginbottom, Zara Z. Ercan, Abetharan Antony, Guzman Sanchez Gonzalez, Rafael Grazzini Placucci, Armand Kassaï Koupaï, Artur P. Toshev,Comments: 40th Conference on Neural Information Processing Systems (NeurIPS 2026). Workshop: Sim2Science: ML with Imperfect Scientific ModelsSubjects: physics.plasm-phCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
Large-scale MAGNETohydrodynamic instabilities break plasma confinement, can trigger disruptions, and constrain fusion reactor design; modeling a single configuration against them takes hours with a reference solver such as JOREK, and a design study requires thousands of hours. ModeCast is the first learned surrogate to return the complete linear stability assessment for MHD modes. Trained on a comprehensive dataset of over 45,000 JOREK simulations across thousands of equilibria, it screens stability across toroidal mode numbers n=1-4 and predicts the full spatial structure and growth rate of unstable modes. With a second network of the same architecture replacing the equilibrium solve, the full pipeline from design parameters runs on one GPU up to 1,000,000x faster than JOREK's equilibrium and linear stability runs. The gain comes from building the linear-phase physics into the formulation, objective, and inputs, yielding up to six times more training data. ModeCast misses none of the unstable held-out cases, and its predicted fields reproduce the simulation's measured physics, from MAGNETic island topology to resistivity trends. On a fixed-geometry resistivity scan outside its training distribution, refitting only the 22k-parameter growth rate head of the 145M-parameter network on four simulation halves the held-out internal kink growth rate error, and fine-tuning the whole network adds little. Because it is differentiable and returns full fields, ModeCast could in the future assimilate experimental measurements, providing a bridge to real devices and accelerating progress toward commercial fusion. Project page: zenithon.ai/research/modecast.
[abstract 17 / 32] (score: 3) - Title: Tilt, warp, and dissipation flare in hydrodynamic disks around kicked compact objectsAuthors: Yoonsoo Kim,Comments: 19 pages, 15 figures, comments welcomeSubjects: astro-ph.HE astro-ph.GACreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
We study the dynamical response of a hydrodynamic disk to an impulsive kick imparted to a central massive object, focusing on the global properties of the material that remains gravitationally bound. We construct a simple analytic model and show that the bound material can acquire a significant tilt---or even a retrograde rotation---if the kick is directed close to the disk midplane. We perform 3D numerical simulations and show that (1) the bound material relaxes to a torus-like circularized flow of which total mass and angular momentum is in fair agreement with the analytic estimate, and (2) in spite of nonlinear hydrodynamic effects, a highly tilted or retrograde disk can be sufficiently formed. The simulations additionally reveal a transient warp in the kicked disk, suggesting a kick as a formation mechanism of tilted or warped disks around compact objects. About 10% of the kinetic energy the bound material acquired from the kick is converted to the internal energy, while the exact conversion efficiency depends on the kick angle and the initial surface mass density profile. The luminosity of this kick-driven dissipation flare can reach $\sim 10^{43}\,{\rm erg\,s^{-1}}$ for strong kicks ($V_{\rm kick} \sim 1000$km/s). We discuss the implications of our results for recoiling supermassive BLACK HOLEs, recoiled stellar-mass BLACK HOLEs in the disks of ACTIVE GALACTIC NUCLEi, and natal kicks on compact objects.
[abstract 18 / 32] (score: 3) - Title: Comparison of observed and theoretically calculated amplitudes of Forbush effects for events associated with the arrival of a shock waveAuthors: P. G. Kobelev, V. N. Zirakashvili, D. N. Dorosheva, V. A. Oleneva, E. G. Klepach, V. G. Yanke,Comments: 9 pages, 3 figuresSubjects: astro-ph.HE astro-ph.SRCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
This paper examines the role of plasma compression regions ahead of interplanetary coronal mass ejections in the formation of Forbush effects decreases in COSMIC RAY intensity during the first phase. The aim of this study is to identify and quantify the relationship between the structure of the CME (specifically, the parameters of the compression region behind the shock front) and the nature of the observed Forbush effect. To this end, events with intensity decrease amplitudes greater than 5 percent were selected, and a theoretical model of COSMIC RAY behavior at the shock front was tested using modern analytical methods and mathematical models. Analysis of the results for two dozen events revealed satisfactory agreement between the theory and observations. The key reason for some discrepancies is the need to integrate the MAGNETic field over the particle gyro radius. The obtained data provide insight into the mechanisms of COSMIC RAY modulation in such environments.
[abstract 19 / 32] (score: 3) - Title: Polarization Observations of NGC 315 with FASTAuthors: Wenjun Zhang, Xiaohui Sun, Jie Wang, Xuzhi Hu, Shengtao Wang,Comments:Subjects: astro-ph.GACreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
We present new continuum and POLARIZATION observations of RADIO GALAXy NGC 315 obtained with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) over 1.0-1.5 GHz. The FAST data detect diffuse large-scale polarized emission with a noise level of 0.065 mJy beam$^{-1}$ at resolution of $4'$. We derived a rotation measure (RM) map with an error of 1.1 rad m$^{-2}$ including systematic error. The intrinsic RM map was obtained after subtracting the Galactic foreground contribution. We estimated a total MAGNETic field strength of $\lesssim 1$ $μ$G across the source and a thermal electron density of $\sim 10^{-4}$ cm$^{-3}$ toward the northwest lobe. The fractional POLARIZATION analysis suggests a random MAGNETic-field component over a large area toward the northwest lobe.
[abstract 20 / 32] (score: 3) - Title: Probing the star-forming environment of GRB across cosmic ages with high-resolution X-ray spectroscopy: From \textit{XMM-Newton}/RGS and \textit{XRISM}/Resolve to \textit{NewAthena}/X-IFUAuthors: Luigi Piro, Aishwarya Linesh Thakur, Alfredo Luminari, Fabrizio Nicastro, Yair Krongold,Comments: 17 pages, 30 figures, 3 tables. Submitted to Astronomy and AstrophysicsSubjects: astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
Optical and infrared GRB absorption spectroscopy provides valuable insight into host-galaxy properties across cosmic time. However, the star-forming region embedding the progenitor, on scales $\lesssim 100~\mathrm{pc}$ is heavily ionized by the GRB emission, making X-ray spectroscopy the sole probe of its physical and chemical conditions. We characterize the GRB-embedding medium as a function of progenitor type and cosmic epoch via high-resolution X-ray spectroscopy. We extend our study to high-redshift GRBs to evaluate how effectively X-ray absorption signatures can distinguish between pristine, Pop~III-, and Pop~II-enriched environments. Using the time-dependent photoionization code \texttt{TEPID}, we self-consistently calculate the ionization structure of the absorber, the energies and the strengths of the resulting absorption lines. We analyze a flux-selected sample of GRBs showing strong evidence for time-dependent photoionization, and search for predicted narrow features in the RGS spectra. We also assess the performance of \textit{XRISM}/Resolve and \textit{NewAthena}/X-IFU in detecting these features. In the single archival case with sufficient RGS signal-to-noise ratio (GRB~090618 at $z=0.54$), we find $\approx 3σ$ combined evidence for narrow, highly ionized Fe~L absorption lines. For bright nearby GRBs, \textit{XRISM}/Resolve can detect Fe~K absorption lines even in its current gate-valve-closed configuration ($\sim 3$ expected events/yr). \textit{NewAthena}/X-IFU will enable systematic population studies of GRB environments, delivering redshifts with precision comparable to optical/IR spectroscopy, unaffected by dust obscuration and Ly-$α$ forest absorption. Crucially, it will precisely diagnose the density, size, metallicity, and abundance patterns, ultimately revealing whether high-$z$ GRBs originate in pristine, Pop~III-, or Pop~II-enriched media.
[abstract 21 / 32] (score: 2) - Title: Tracing the evolution of eccentric precessing binary BLACK HOLEs: a hybrid approachAuthors: Amitesh Singh, Nathan K. Johnson-McDaniel, Anuradha Gupta, Khun Sang Phukon,Comments: Revised after peer review and accepted for publication in Physical Review DSubjects: astro-ph.HE gr-qcCreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
To describe a general bound binary BLACK HOLE system, we need to consider orbital eccentricity and the misalignment of BLACK HOLEs' spin vectors with respect to the orbital angular momentum. Binary BLACK HOLEs often have a non-negligible eccentricity at formation, and dynamical interactions could produce binaries with non-negligible eccentricity in the bands of gravitational-wave (GW) detectors. The angle between each BLACK HOLE's spin vector and the binary's orbital angular momentum (referred to as the spin tilt) at formation also carries information about the formation channel. The spin tilts inferred in GW astronomy are usually those when the binary is in the band of a GW detector. Therefore, it is necessary to evolve the binary back in time to compute the tilts at formation. For certain binaries, the tilts in the formal limit of infinite orbital angular momentum, also known as tilts at infinity, could be a useful approximation to those at formation. Additionally, full orbit-averaged evolution to formation could be computationally infeasible in many situations, while the hybrid evolution we use to compute the tilts at infinity would be feasible. We thus generalize the publicly available tilts_at_infinity code to compute the tilts at infinity for eccentric, spin-precessing binaries. This code employs hybrid post-Newtonian evolution, starting with orbit-averaged evolution for higher frequencies and then transitioning to precession-averaged evolution to compute the tilts at infinity. We find that the transition frequency used in the quasicircular case still gives acceptably small errors in the eccentric case, and show that eccentricity and hybrid evolution both have a significant effect on the tilts at infinity for many binaries. We also give examples of cases where the tilts at infinity are and are not a good approximation to the tilts at formation in the eccentric case. (Abridged)
[abstract 22 / 32] (score: 2) - Title: Self-similar Worthington JETsAuthors: José M. Gordillo, Javier Rodríguez-Rodríguez, Vatsal Sanjay,Comments:Subjects: physics.flu-dynCreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
When a micron-sized bubble bursts, capillary waves deform the cavity into a cone that ejects a Worthington JET. The JET is born by inertial focusing, and the local collapse follows self-similar Euler solutions set by the semiangle $β$. Writing $r_j$ and $v_j$ for the dimensionless JET-base radius and velocity, the local Weber number $We_j=r_j v^2_j$ measures inertia relative to capillarity. The theory, supported by accurate numerical simulations gives $r_j\proptoτ^{α(β)}$ with $α\simeq0.63$ and, hence $We_j\gg1$, with $We_j\to\infty$ as $r_j\to0$, so inertia increasingly overwhelms capillarity. In simulations, the interface collapses onto a universal shape for more than two decades in dimensionless time when lengths are scaled using our prediction for $r_j$. For water, this gives incipient radii of $\mathcal{O}(1)$ nm, predicting nanometric sea-spray aerosols.
[abstract 23 / 32] (score: 2) - Title: Decoupling candidate dual AGN from chance superpositions in the GOTHIC survey via a deep-learning frameworkAuthors: Bhavesh Mukheja, Snehanshu Saha, Anwesh Bhattacharya, Mousumi Das, Françoise Combes, Sudhanshu Barway,Comments: Accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS; ref. MN-26-2211-P.R1) on 2026 October 22. Supplementary material has been incorporated into the main text. Code is available at https://github.com/BhaveshMukheja/yolo-dagnSubjects: astro-ph.GA cs.CV cs.LG math-ph math.MP physics.data-anCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
Dual ACTIVE GALACTIC NUCLEi (DAGN) mark a critical phase in the evolution of merging galaxies and the pairing of supermassive BLACK HOLEs, yet they remain difficult to identify in large imaging surveys because of projection effects and limited spatial resolution. Compact foreground stars and unresolved substructure can mimic dual nuclei through chance superposition, complicating automated detection. We revisit the 46,061 galaxies flagged but rejected as DAGN candidates by the GOTHIC pipeline, primarily because the two nuclei fell within the SDSS fibre aperture or exceeded its separation threshold. We train a supervised deep-learning framework based on the YOLOv11 oriented-bounding-box architecture on annotated SDSS imaging to separate genuine dual nuclei from foreground stellar contaminants and other spurious alignments. The final model attains a validation precision of 0.919, recall of 0.905, and $F_1$ of 0.912, and yields 29,605 dual-nucleus candidates after removing star-dominated and blended detections. Structured visual inspection indicates that $54.5$--$62\%$ are consistent with genuine dual nuclei, implying $\sim(1.4$--$1.8)\times10^{4}$ plausible systems. Cross-calibrating the YOLO separation against the deterministic GOTHIC centroid measurement and restricting to the compact regime ($d \le 6.87''$) gives a conservative subset of $\sim 13{,}672$ candidates, reaching calibrated separations of $\sim 0.56''$. Spectroscopy of the most compact ($\le 1$ kpc) systems shows spectra dominated by stellar absorption, with no resolved double-peaked emission, so confirmation requires higher-resolution follow-up. The catalogue is a statistically refined list of candidates, not confirmed DAGN. Nonetheless, deep-learning detection substantially reduces contamination and expands the plausible DAGN census.
[abstract 24 / 32] (score: 2) - Title: Exceptional points and hysteresis in Kerr-Newman quasi-normal modesAuthors: Mario Misas Arcos, Alberto T. Pérez, Carlos F. Sopuerta,Comments: 8 pages, 9 figures, revtex4-2Subjects: gr-qc astro-ph.HE hep-thCreated: 2026-10-21; Updated: 2026-10-26; Datestamp: 2026-10-26
Exceptional points (EPs) and eigenstate hysteresis, previously found in Kerr only with an auxiliary scalar field, arise intrinsically in the quasinormal-mode spectrum of Kerr-Newman BLACK HOLEs. Using a hyperboloidal formulation of the coupled gravito-electroMAGNETic Teukolsky equations and a Chebyshev pseudospectral method, we compute the $\ell=m=2$ spectrum and locate four EPs at up to $99.974\%$ of extremality, one from a new repulsion. The gaps close as a square root branch point, and quasistatic loops around one or more EPs exchange the coalescing modes, confirming hysteresis.
[abstract 25 / 32] (score: 2) - Title: Gravitational waves from inclined orbits around Kerr BLACK HOLEsAuthors: Yi-Han Huang, Sen Guo, Yu Liang, Lin Wen, Kai Lin,Comments: 26 pages, 11 figuresSubjects: gr-qc astro-ph.HECreated: 2026-10-21; Updated: 2026-10-26; Datestamp: 2026-10-26
Extreme mass ratio inspirals on generic inclined orbits provide a critical dynamical probe of strong field gravity, as they uniquely break the severe parameter degeneracies inherent to planar equatorial trajectories. To isolate the exact rotational signatures, we extend the periodic-orbit framework to three-dimensional inclined trajectories in the Kerr spacetime, specifically focusing on the $r$--$θ$ orbital resonances. By mapping the geodesic motion into a co-precessing spatial framework parameterized by Mino time, we compute the emitted quadrupole waveforms and evolve the local dynamics using circularity-preserving radiation reaction. It is demonstrated that frame-dragging induces a transient dynamical tilt at periastron, which directly splits the emitted radiation into an exact five-comb spectral architecture. When this resonant structure is resolved over a single coherence time, the statistical error on the dimensionless spin is reduced to $σ_a \approx 10^{-2}$, improving upon the equatorial baseline by up to two orders of magnitude. Because any bound orbit in a static, spherically symmetric spacetime generates a maximum of three frequency combs, the detection of this five-comb hierarchy establishes a rigorous, model-independent null test to strictly exclude spherical geometries.
[abstract 26 / 32] (score: 2) - Title: Newtonian I-Love-Q relations: An enthalpy-based approachAuthors: Athul Kunjipurayil, J. Piekarewicz,Comments: 13 pages, 3 figures Submitted to European Journal of PhysicsSubjects: astro-ph.HE astro-ph.SR gr-qc nucl-thCreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
We present a pedagogical introduction to the I-Love-Q relations within Newtonian gravity using an enthalpy-based formulation of stellar structure. Introducing the specific enthalpy converts Euler's equation into a first integral of hydrostatic equilibrium and recasts the equation of state as a relation between the mass density and the enthalpy. Together with Poisson's equation, these relations provide a unified description of spherical equilibrium and deformations induced by rotation and tides. We illustrate the formalism with polytropic equations of state and a RELATIVISTIC free FERMI gas. In Newtonian gravity, slow uniform rotation and a weak tidal field excite the same linear quadrupolar response, yielding the exact identity $\bar I^{\,2}\bar Q/\barλ\equiv1$ for the dimensionless (``bar'') observables---independently of the equation of state. This exact identity is distinguished from the approximate universality of the pairwise I-Love-Q relations, whose residual dependence on stellar structure is illustrated by the models considered in this work.
[abstract 27 / 32] (score: 2) - Title: The Galactic Center Reference Frame: A 30-Year SolutionAuthors: Jeremy Darling, Jennie Paine, Matthew Hosek, Shoko Sakai, Stefan Gillessen, Tatsuya Akiba-Lewis, Andrea Ghez, Frank Eisenhauer, Reinhard Genzel,Comments: 20 pages, 8 figures, 3 tables. Accepted by ApJSubjects: astro-ph.GA astro-ph.HE astro-ph.SR gr-qcCreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
Stellar orbits probe the metric of and mass around the Sgr A* massive BLACK HOLE. To enable study of the BLACK HOLE, the surrounding mass, and tests of gravity, a precise reference frame must be established and maintained. We present an updated stellar maser-based reference frame for the inner parsec of the Galactic Center, referenced to the radio continuum of Sgr A*. This work synthesizes 30 years of astrometric observations of 15 SiO stellar masers and the Sgr A* continuum at 43 GHz. The uncertainty in the mean offset of the maser ensemble from Sgr A* is 0.08 mas in the current epoch and will decay to 0.10 mas by 2030. At a distance of 8.2 kpc, these correspond to position uncertainties of 0.6 AU and 0.8 AU, respectively, which is similar to or smaller than the stellar SiO-emitting region. The mean maser proper motion uncertainties are 0.05 mas yr$^{-1}$ in RA and 0.08 mas yr$^{-1}$ in Dec, corresponding to 1.8 km s$^{-1}$ and 3.2 km s$^{-1}$. The reference frame stability between IR and maser astrometry is 10~$μ$as yr$^{-1}$ (0.40 km s$^{-1}$) in RA and 15 $μ$as yr$^{-1}$ (0.57 km s$^{-1}$) in Dec. The masers show substantial variability in flux density and velocity structure, most notably IRS~7, which shows a 30-fold brightening in a blueshifted component since 2022. This variability may set a floor on future astrometry improvements and especially measurements of radial acceleration.
[abstract 28 / 32] (score: 2) - Title: Overview of Enhanced D-alpha and Quasi Continuous Exhaust H-modes at DIII-DAuthors: N. Leuthold, Z. Li, M. Faitsch, A. Hyatt, C. F. B. Zimmermann, L. Gil, T. Osborne, T. Odstrcil, N. C. Logan, K. Barada, C. Chrystal, R. Gerru, S. Guizzo, R. Hood, L. Huse, S. K. Kim, C. J. Lasnier, A. O. Nelson, C. Paz-Soldan, R. Perillo, B. Victor, T. Wilks,Comments:Subjects: physics.plasm-phCreated: 2026-10-22; Updated: 2026-10-26; Datestamp: 2026-10-26
We review the Enhanced D-alpha (EDA) and Quasi-continuous Exhaust (QCE) H-modes that have recently been achieved in the DIII-D tokamak. These scenarios are free of large type-I edge-localized modes (ELMs) and achieved at high fueling compatible with divertor detachment. This makes them promising operational regimes as ELMs are a major risk for fusion pilot plants (FPPs). Access to EDA H-mode and the associated quasi-coherent mode (QCM) was observed at low heating power barely above the L-H power threshold, and increased density enabled access to EDA H-mode even at higher heating powers. The QCE H-mode was achieved at simultaneously high density and heating power, characterized also by a QCM and small ELMs with transient peaks of the total power into the divertor below about 3MW, in line with observations at ASDEX Upgrade. During the QCE H-mode, the turbulence parameter alpha_t at the separatrix is about 1 and does not separate ELMy or EDA from QCE H-modes well. Peeling ballooning stability calculations suggest that the EDA H-mode pedestal is limited by transport far away from ideal MAGNETohydrodynamic instability, and the QCE H-mode pedestal operates close to the ballooning branch of the stability boundary. BOUT++ simulations qualitatively reproduce the pressure collapse characteristics of the different regimes and suggest an important role of n ~ 50 resistive ballooning modes localized near the separatrix at the X-point during EDA and QCE H-modes. This work provides a foundation and guidance for further research on the access conditions and physics mechanisms of EDA and QCE H-modes necessary for the extrapolation of these regimes towards an FPP.
[abstract 29 / 32] (score: 2) - Title: Plasma transport by carrier electrons: delocalization length for heat-fluxAuthors: C. A. Walsh,Comments:Subjects: physics.plasm-phCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The delocalization length $λ_d=λ_{ei} Z/\sqrt{Z+4.45}$ is an improved heat-flux non-locality metric accounting for the localizing effect of electron-electron collisions on the electron population carrying heat-flux. Magnetization also localizes the carrier electrons; the delocalization Hall parameter $ψ_d=13.5 χZ/(Z+4.62)$ shows that this occurs at a faster rate than MAGNETization of thermal conductivity ($ψ_κ= 9.94χ(Z+0.17)/(Z+5.88)$). The traditional Knudsen number, which uses the electron-ion mean-free path, does not fairly represent non-locality across ionization and MAGNETization; $Kn_d = 8.28λ_{d\bot}/L_T$ should instead be used. The kinetic understanding of the three MAGNETized heat-flux components is unified in the linear regime with a full electron-electron collision operator and a converged harmonic expansion of the electron distribution (up to $f_6$). Righi-Leduc heat-flux is found to delocalize easier than its perpendicular counterpart, due to its carriers being higher energy electrons. This approach lays the groundwork for a consistent treatment of the kinetically-modified induction equation.
[abstract 30 / 32] (score: 2) - Title: Tracking the Evolution of Supermassive Black Hole Binaries with Pulsar TermsAuthors: Bence Bécsy, Magdalena Siwek,Comments: 15 pages, 6 figures, submitted to ApJSubjects: astro-ph.HE gr-qcCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
Pulsar timing arrays will soon be able to resolve the loudest supermassive BLACK HOLE binaries contributing to the stochastic gravitational wave background at nanohertz frequencies. While the few decades of observations are typically not enough to see these binaries evolve in frequency, the so-called pulsar terms offer a glimpse into the past and can help us map out the frequency evolution of these binaries over tens of thousands of years. Measuring this long-term frequency evolution can allow us to look for deviations from a vacuum binary evolution due to various environmental effects. We develop a Fisher-matrix approach to calculate how precisely the frequency can be tracked over time in this manner, and demonstrate its use on a realistic near-future pulsar timing array with a 30-year baseline. We find that the environmental effects predicted by 2-dimensional hydrodynamic simulations of circumbinary disks are unlikely to be detectable in the circular binaries we considered, however, in some cases they might result in biased chirp mass recovery if ignored. We also demonstrate how this approach allows one to test the orbital evolution predicted by general relativity in a purely gravitational-wave driven inspiral, and to put upper limits on additional generic environmental effects described by a power-law hardening model.
[abstract 31 / 32] (score: 2) - Title: Relativistic PlasticityAuthors: Joshua, Cadogan, Nils Andersson, Ian Hawke, Thomas Celora,Comments:Subjects: gr-qcCreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The elastic crust of a neutron star has long been established as a key player in relevant aspects of neutron star physics. However, the state-of-the-art theory of elasticity is restricted to the perturbative domain and does not account for permanent plastic deformations which should be relevant for pulsar glitches, MAGNETar flares, and the continuous emission of gravitational waves. Plasticity, however, is a historically challenging phenomenon to model - even in the Newtonian regime. This is owed mainly to its dissipative character and the multiscale methods required to consistently reproduce observed phenomena. In this work, we address this first challenge by making use of recent developments in the variational modelling of dissipative fluids to extend the theory of RELATIVISTIC elasticity to include plastic phenomenology. The resulting theory possesses the same freedoms as the modern Newtonian formalism, while now being compatible with general relativity. The second law of thermodynamics is then used to introduce the yield criterion of plasticity theory in the RELATIVISTIC setting.
[abstract 32 / 32] (score: 2) - Title: Three subpopulations of binary BLACK HOLEs in mass, spin magnitudes and tilts following GWTC-5Authors: Asad Hussain, Maximiliano Isi, Aaron Zimmerman,Comments: 33 pages, 23 figuresSubjects: astro-ph.HECreated: 2026-10-23; Updated: 2026-10-26; Datestamp: 2026-10-26
The mass and spin distributions of merging binary BLACK HOLEs offer clues to their formation pathways, which remain uncertain. In this work, we model the population of binary BLACK HOLEs using generic subpopulations with distinct mass-ratio, spin-magnitude, and spin-tilt distributions, whose relative contributions vary with primary mass. Using the 259 binary BLACK HOLEs in the fifth LIGO-Virgo-KAGRA catalog (GWTC-5), we resolve three subpopulations with low, medium, and high spins. The low-spin population dominates for primary masses near $35 M_\odot$, contributes roughly half of the binaries for primary masses of $10 M_\odot$, and favors nearly equal mass ratios overall; its spins are consistent with both BLACK HOLEs having negligible spin, with a log Bayes factor of $\log_{10}B =6.1^{+0.2}_{-0.3}$ in favor of vanishing spins. The medium-spin population accounts for the other half of the population around primary masses of $10 M_\odot$ and favors spin magnitudes $χ_i \approx 0.2$ for both components, preferentially aligned orientations, and comparable mass ratios. The high-spin population dominates above primary masses of $60 M_\odot$ and also contributes at lower masses $\sim 20 M_\odot$; it favors a rapidly spinning primary ($χ_1 \approx 0.7$), a broad range of secondary spins, widely distributed spin orientations, and a broad mass-ratio distribution. Allowing for a fourth subpopulation yields no distinct additional mass-ratio or spin distribution, as it becomes degenerate with existing features. To resolve highly concentrated features in spin, we control the variance of standard Monte Carlo likelihood estimators using truncated Gaussian mixture models. Taken together, our results add to a growing body of evidence for substructure in the population of LIGO-Virgo-KAGRA BLACK HOLEs, providing further clues to uncover their formation histories.
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