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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 30 April

Astrophysics of Galaxies

A New Perspective on Galactic Evolution: Studying the Outskirts of the Abell S1063 Galaxy Cluster

L. Pecoraro, A. Mercurio, M.Annunziatella et al. (+14 more)

Galaxy physical properties are influenced by their environments, but the processes responsible for mass and environmental quenching and structural transformations remain debated. Galaxy clusters are ideal laboratories for investigating galaxy formation and evolution, offering a full range of galaxy properties and environments. Observations of large-scale structures, particularly filaments in cluster outskirts ($r \sim5r_{200}$), are currently constrained to the low-redshift Universe. To explore galaxy evolution at intermediate redshifts, deep photometric data, ideally combined with spectroscopic redshifts, are essential. Abell S1063 cluster ($z$ = 0.346) is observed within the Galaxy Assembly as a function of the Mass and Environment program with the VLT Survey Telescope (VST-GAME) combined VISTA Public Survey program Galaxy Cluster At Vircam. We investigate galaxy evolution across a wide range of stellar masses and environments. We release a multiwavelength photometric catalog with photometric redshifts for 64394 sources in $1x1 deg^2$. The analysis of overdensity regions provides insights for future studies on galaxy properties in cluster outskirts. The dataset is obtained through deep ($r<$24.65 mag) and wide optical ($u$, $g$, $r$, $i$, VST) and near-infrared ($Y$, $J$, $K_s$, VISTA) observations. The photometric catalog includes all detected sources, excluding nearby or overlapping objects, saturated stars, and image artifacts. The multiwavelength catalog enabled photometric redshift estimates and identification of cluster members. The density field allowed comparison of galaxy properties, colors, and masses across environments. We detect a very dense structure near the cluster center, and with such a large field of view, we find another dense region to the north-west, in the opposite direction to the cluster elongation. Filaments connecting the regions are also visible.
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All authors L. Pecoraro, A. Mercurio, M.Annunziatella, M. D'Addona, R. Ragusa, G. Angora, M. Girardi, G. Granata, C. Grillo, L. Limatola, P. Rosati, P. Bergamini, G. Caminha, F. Getman, A. Grado, M. Meneghetti, E. Vanzella

High Energy Astrophysical Phenomena

Probing the $\gamma$-ray Emission Origin of Two Star-forming Galaxies NGC 2403 and NGC 3424 with the Fermi-LAT

Linjie Liu, Wei Zhang, Xian Hou et al. (+1 more)

Star-forming galaxies (SFGs) are a subclass of $\gamma$-ray emitters and a correlation between their $\gamma$-ray luminosity ($L_{\rm \gamma}$) and the total infrared (IR) luminosity ($L_{\rm IR}$) has been established based on the Fermi Large Area Telescope (LAT) data. NGC 2403 and NGC 3424 have been reported as outliers in the $L_{\rm \gamma}$-$L_{\rm IR}$ correlation with light curves showing significant variability, which contrasts with the temporally stable $\gamma$-ray emission in other SFGs, originating primarily from cosmic rays interacting with interstellar medium. In this study, we reanalyze the $\gamma$-ray emission in the directions of NGC 2403 and NGC 3424 using more than 16.5 yr Fermi-LAT data. NGC 3424 is found to be spatially coincident with the detected $\gamma$-ray source, while NGC 2403 is significantly offset from the nearest $\gamma$-ray source, suggesting an implausible association. We confirm the previously reported variability of both $\gamma$-ray sources and the significant deviation from the $L_{\rm \gamma}$-$L_{\rm IR}$ correlation when assuming an association of both $\gamma$-ray sources with the two galaxies. Our findings lend further support to the interpretation that their $\gamma$-ray emission is driven primarily by alternative radiative processes-rather than by star formation activity-such as the ejecta of the Type IIP supernova SN 2004dj in NGC 2403 interacting with a surrounding high-density shell and an obscured active galactic nucleus in NGC 3424.
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All authors Linjie Liu, Wei Zhang, Xian Hou, Pierrick Martin

Cosmology and Nongalactic Astrophysics

Cosmological Observational Tests in the JWST Era. II: The Tolman Test

V. V. Tsymbal, A. A. Raikov and N. Yu. Lovyagin

In this work, we investigate a classical cosmological test - the dependence of galaxy surface brightness on redshift z (the Tolman test). We analyzed 6 860 galaxies with reliably determined spectroscopic redshifts from the ASTRODEEP-JWST photometric catalogue. We find that (a) the mean surface brightness of galaxies indeed decreases with increasing distance, and (b) the observed trend shows a significant departure from the prediction of the standard cosmological model, which expects the mean surface brightness to decline as ~ (1 + z)^-4.
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Astrophysics of Galaxies

Anisotropy of Satellite Galaxies-I: Contrasting Correlations with Central Galaxy, Host Halo, and Large-Scale Filament Structures

Zhuoming Zhang, Weiguang Cui, Yun Chen et al. (+2 more)

Using the SIMBA, EAGLE, and IllustrisTNG-100 galaxy formation simulations, we examine the anisotropy of the satellite distribution and its dependencies on central galaxies, host halos, and cosmic filaments. We find that in all simulations the satellite anisotropy is robustly aligned with the halo/central galaxy major axis. This correlation is both redshift- and halo-mass-dependent and also extends to filamentary structures outside the halo to several virial radii. The alignment persists up to $z=1.5$ at high redshifts, and the mass dependence remains down to $M_\mathrm{200c} \approx 10^{11}M_{\odot}$. We identify a clear $3\sigma$ scale-dependent transition in the structural tracers of satellite anisotropy: satellite distributions correlate with central galaxy morphology at small scales ($<0.3R_{\rm 200c}$), are governed by host halo triaxiality at halo scales ($0.3$-$2R_{\rm 200c}$), and align with cosmic filaments beyond $2R_{\rm 200c}$. By tracing satellite trajectories in SIMBA, we uncover the kinematic origin of this transition, demonstrating that satellites prefer halo major-axis aligned regions because their trajectories intersect this axis far more frequently and stay in it for a longer time under the host's gravitational potential. This dynamical processing effectively erases primordial filament-related signals upon accretion ($<2R_{\rm 200c}$), explaining the shift in dominant structural tracers across scales.
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All authors Zhuoming Zhang, Weiguang Cui, Yun Chen, Romeel Davé, Katarina Kraljic

Solar and Stellar Astrophysics

Asteroseismic modelling of main-sequence solar-like stars and Kepler exoplanet host stars with the FICO procedure I. Catalogue of fundamental stellar properties

Jérôme Bétrisey, Daniel R. Reese, Camilla Pezzotti et al. (+2 more)

We present detailed asteroseismic modelling of 95 main-sequence solar-like stars and Kepler exoplanet host stars using the FICO procedure, a three-step method that combines forward and inverse techniques that enables precise inference of fundamental stellar parameters such as mass, radius, age, and mean density. We applied the FICO procedure to a catalogue of stars with high-quality asteroseismic and classical observations, and compared its results against literature values. We also compared its performance with direct frequency fitting using semi-empirical surface corrections. The FICO procedure achieved statistical precisions of 2.3%, 0.82%, 6.9%, and 0.49% in mass, radius, age, and mean density, respectively on average, well within PLATO quality requirements. We reconfirmed that surface-independent methods more effectively mitigate biases inherent to semi-empirical surface corrections, particularly for stars more massive than 1.15 Msun or above 6050 K. Two regimes were identified: near-solar conditions, where both approaches perform similarly, and higher-mass stars, where surface-independent methods consistently outperform direct fitting methods. While our results are consistent with literature values, we observed age biases (~11.5% on average for the Kepler LEGACY sample) that are comparable to the PLATO accuracy requirement of 10% for a Sun-like star, and therefore not negligible in that context. The FICO procedure provides a robust framework for high-precision stellar characterisation in the PLATO era. Its hybrid architecture effectively addresses surface effects, making it a promising tool for the accurate determination of exoplanet host-star properties. Our findings also highlight the importance of carefully selecting and validating the physical assumptions embedded in stellar models, particularly in the context of next-generation space missions such as PLATO.
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All authors Jérôme Bétrisey, Daniel R. Reese, Camilla Pezzotti, Marie-Jo Goupil, Margarida S. Cunha

Solar and Stellar Astrophysics

TESS Asteroseismology of Red Giants in the Old Metal-Rich Open Clusters NGC 188 & NGC 6791

Madeline Howell, Jennifer A. Johnson, Marc H. Pinsonneault et al. (+5 more)

Open clusters are fundamental laboratories for investigating stellar and Galactic evolution, and serve as important benchmarks for asteroseismic analyses. Using a boutique method to analyze TESS photometry, we study red giants in two old metal-rich open clusters: NGC 188 & NGC 6791. By comparing Kepler and TESS observations for NGC 6791, similar oscillation mode frequencies are recovered, however we find a systematic offset of 2.2% with a scatter of 9% in the $\nu_{\text{max}}$ measurements. We attribute this discrepancy to the lower signal-to-noise of the TESS data for these relatively faint stars. For the brighter cluster NGC 188, we present new seismic measurements in 17 red giants. We estimate average seismic masses for the RGB of $M_{\text{RGB,NGC188}} = 1.13\pm0.04$(rand)$^{+0.12}_{-0.19}$(sys) $M_{\odot}$ and RC of $M_{\text{RC,NGC188}} = 1.11\pm0.01$(rand)$^{+0.11}_{-0.19}$(sys) $M_{\odot}$, consistent with independent mass estimates for this cluster and with similar precision to previous Kepler studies. From the difference between the average evolutionary phase masses, we estimate an integrated RGB mass loss of $\Delta M = 0.02 \pm 0.04$(rand)$\pm0.01$(sys) $M_{\odot}$, supporting the evidence for lower mass loss at higher metallicities. Using asteroseismology and chemical abundances, we identify three binary interaction candidates: two under-massive stars and one over-massive star potentially exhibiting dipole-mode suppression. Finally, we derive an average seismic cluster age of $7.0\pm0.9$ Gyrs, in good agreement with previous literature ages. Our analysis demonstrates the strong potential of TESS asteroseismology for open clusters, and motivates extending this investigation to other TESS clusters that span a wider range of ages and metallicities.
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All authors Madeline Howell, Jennifer A. Johnson, Marc H. Pinsonneault, Leslie M. Morales, Jamie Tayar, John D. Roberts, Dennis Stello, Madeleine McKenzie

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Stochastic Axion Mixing: A General Mechanism Beyond Decay Constant Constraints

Hai-Jun Li

We propose a novel and generalized mechanism, dubbed stochastic axion mixing. In a multi-axion framework, this mixing occurs naturally provided that the masses of all ultra-light axion-like particles (ALPs) are distinct and lighter than the zero-temperature mass of the QCD axion. Crucially, this mechanism is independent of the relative magnitudes of the axion decay constants. In contrast to the conventional maximal mixing scenario – which strictly relies on specific decay constant hierarchies – stochastic mixing represents a significantly broader formalism. Notably, maximal mixing emerges as a specific subset of stochastic mixing under restrictive conditions. This new mechanism offers profound implications for axion cosmology.
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Astrophysics of Galaxies

Robust AGN and host-galaxy decomposition in optical spectral fitting

C. Aydar, A. Merloni, G. Zeltyn et al. (+24 more)

Unraveling the growth of supermassive black holes and their connection to host galaxies requires disentangling the Active Galactic Nuclei (AGN) emission from that of the stellar populations. When an AGN spectrum is observed at different activity phases, if the spectral decomposition properly recognizes the nuclear and stellar components, key physical properties - such as black-hole mass, stellar mass, and stellar velocity dispersion - should remain consistent. We present a novel optical spectral-fitting approach that combines pPXF and PyQSOFit to robustly decompose spectra into stellar and AGN components. We apply this technique to three SDSS samples with repeated optical spectra of the same objects at z<0.55: 32 changing-look AGN in bright and dim states, and 15 quasars and 15 galaxies with three single-epoch and one stacked spectrum each. To compare with the literature, we use SDSS spectra and photometric data from AGN in the eFEDS field, as well as Gemini and VLT observations of some of our changing-look AGN. We evaluate the reliability of stellar mass, velocity dispersion, and black-hole mass measurements, especially in relation to the AGN-to-total continuum contribution (fAGN). For host-derived properties, especially when fAGN<0.8, our method yields consistent results. For single-epoch black-hole mass estimates from Ha and Hb, 3-sigma confidence in the broad-line flux and FWHM provides effective criteria for selecting reliable measurements. After applying these quality cuts, measurements across different epochs agree within uncertainties, and their reliability is confirmed by the alignment with previously established scaling relations. Many changing-look AGN in our sample exhibit "breathing" broad-line regions, as determined from Ha analysis, while some deviate significantly, suggesting non-virialized systems across the spectral transition.
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All authors C. Aydar, A. Merloni, G. Zeltyn, C. Andonie, B. Trakhtenbrot, S. Bernal, Q. Wu, J. Buchner, M. Salvato, T. Dwelly, S. F. Anderson, R. J. Assef, F. E. Bauer, W. N. Brandt, S. LaMassa, M. L. Martínez-Aldama, A. L. Rankine, D. P. Schneider, Y. Shen, J. R. Brownstein, H. Javier Ibarra-Medel, A. M. Koekemoer, M. Krumpe, S. Morrison, K. Nandra, C. A. Negrete Peñaloza, S. F. Sanchez

Cosmology and Nongalactic Astrophysics

A Cosmological Uncertainty Relation and Late-Universe Acceleration

Savvas M. Koushiappas

We propose that the size of the universe and its expansion rate cannot be simultaneously specified with arbitrary precision–a quantum mechanical uncertainty encoded via a deformed commutation relation for the scale factor. This deformation introduces a geometric correction to the Friedmann equation, where the resulting cosmological dynamics are governed entirely by the sign and magnitude of a single free exponent. For a positive exponent, the model predicts late-time dark energy with $w>-1$, leaving a distinct expansion history that is testable by current and next-generation large-scale structure surveys. Conversely, a sufficiently negative exponent yields a nonsingular classical bounce, resolving the big bang singularity. Notably, the model requires no exotic particles or fields and preserves a scale-invariant primordial power spectrum. Rather than operating at the Planck length, this deformation naturally manifests as a horizon-scale phenomenon set by the cosmological horizon. Within this framework, cosmic acceleration emerges as the macroscopic imprint of quantum gravity at the cosmological horizon.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Theoretical and Experimental Constraints in the $\mu$–$\tau$ Four-Lepton Sector of the SMEFT: implications to neutrino self interactions

Aadarsh Singh, G. D'Ambrosio and Sudhir K. Vempati

We study the dimension-six SMEFT four-lepton operators in the $\mu$–$\tau$ sector. These operators control both charged-lepton scattering and neutrino self-interactions, the latter being weakly constrained by direct laboratory probes despite their importance for cosmological tensions. We compare three classes of constraints on the Warsaw-basis coefficients $[C_{\ell\ell}]_{2222}$, $[C_{\ell\ell}]_{2233}$, and $[C_{\ell\ell}]_{2332}$. We use perturbative unitarity from $2\!\to\!2$ partial-wave analysis, spin-summing positivity sum rules, and the experimental bounds from NA64$\mu$ and the global fit~\cite{Falkowski:2017pss}. We find that the global fit dominates for $[C_{\ell\ell}]_{2222}$ and $[C_{\ell\ell}]_{2332}$, while NA64$\mu$ provides the leading bound on $[C_{\ell\ell}]_{2233}$, with the unitarity line for this direction entering the range of collider energies near $200~\mathrm{GeV}$. Renormalization-group running between $1~\mathrm{GeV}$ and $30~\mathrm{TeV}$ modifies these coefficients by up to $10\%$. Translating these bounds onto the effective four-neutrino coupling $G_\mathrm{eff}$, we find values many orders of magnitude smaller than the strongly interacting regime motivated by the Hubble tension; this excludes heavy-mediator UV completions of strong $\nu_{\mu}$–$\nu_{\mu}$ and $\nu_\mu$–$\nu_\tau$ self-interactions within the validity of the dimension-six SMEFT and in the absence of tuned cancellations between operators, while leaving the cosmologically motivated light-mediator scenarios unconstrained by this analysis. Finally, we comment on the bounds these coefficients place on a leptophilic $L_\mu - L_\tau$ $Z'$ UV completion. Our SMEFT-based current and projected NA64$\mu$ bounds reproduce the dedicated $Z'$ analyses already available in the literature.
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Instrumentation and Methods for Astrophysics

Radio signal generation in milliseconds: enabling multi-parameter reconstruction of ultra-high-energy cosmic rays

Arsène Ferrière

In recent years, radio detection of ultra-high-energy cosmic rays (UHECRs), with energies above $10^{18}$ eV, has become an established technique. The radio emissions can be simulated with high accuracy using Monte Carlo codes such as ZHAireS and CoREAS. These simulations are essential but are computationally intensive. In this work, we present a machine-learning-based emulator that reproduces radio signal simulations with high accuracy in milliseconds rather than hours. Primary particle properties can then be reconstructed by comparing measured signals to emulated traces using a Markov Chain Monte Carlo approach. Using ZHAireS simulations carried out over the GRANDProto300 experiment layout, the method achieves an 8.9% resolution on electromagnetic energy and a 0.08{\deg} angular resolution, matching state-of-the-art reconstruction performance. Finally, we apply the method on real data, successfully reconstructing cosmic-ray candidates detected by the GP300 prototype.
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High Energy Astrophysical Phenomena

Long-term study of the gamma-ray emission of Cygnus X-3 with MAGIC and Fermi-LAT

K. Abe, S. Abe, J. Abhir et al. (+185 more)

Cygnus X-3 is a microquasar composed of a compact object of unknown nature closely orbiting around a Wolf-Rayet star. The particularities of this source make it a unique case among microquasars. This fact, together with its recent establishment as a PeV particle accelerator, makes Cygnus X-3 a very interesting target for the investigation of the physical processes leading to gamma-ray production. In this work, the TeV and GeV gamma-ray emission of Cygnus X-3 is studied in order to determine its origin and constrain the properties of the system. For that purpose, a point-like analysis of 130 h of data taken with the MAGIC telescopes between 2013 and 2024 was performed, which represents the largest available sample for Cygnus X-3 at $\sim$TeV energies. Additionally, contemporary data from Fermi-LAT were also analysed to better contextualize the MAGIC observations. For a more detailed investigation of the source physics, the data were divided into three subsets according to the flaring state of the source and orbital phase. No significant detection of Cygnus X-3 is found between 0.1 and 7 TeV for any of the datasets, and differential and integral flux upper limits are reported over the long-term monitoring of the source. The Fermi-LAT fluxes can be considered compatible with previous results, taking into account the different data samples used across studies. The MAGIC upper limits presented in this work represent the most constraining ones up to date at $\sim$TeV energies. An eventual detection of Cygnus X-3 at these energies would significantly constrain the source properties, and is not unreasonable to expect given that the source has already been detected in both the GeV and PeV regimes during flaring states. Further observations of Cygnus X-3 at energies above tens of GeV would be valuable for this purpose.
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All authors K. Abe, S. Abe, J. Abhir, A. Abhishek, V. A. Acciari, A. Aguasca-Cabot, I. Agudo, I. Albanese, T. Aniello, S. Ansoldi, L. A. Antonelli, A. Arbet Engels, C. Arcaro, T. T. H. Arnesen, A. Babić, C. Bakshi, U. Barres de Almeida, J. A. Barrio, L. Barrios-Jiménez, I. Batković, J. Baxter, J. Becerra González, W. Bednarek, E. Bernardini, J. Bernete, A. Berti, J. Besenrieder, C. Bigongiari, A. Biland, O. Blanch, G. Bonnoli, P. Bordas, Ž. Bošnjak, E. Bronzini, I. Burelli, C. Campa, A. Campoy-Ordaz, A. Carosi, R. Carosi, M. Carretero-Castrillo, A. J. Castro-Tirado, D. Cerasole, G. Ceribella, A. Cerviño, A. Chilingarian, G. Chon, A. Cifuentes Santos, J. L. Contreras, J. Cortina, S. Covino, G. D'Amico, P. Da Vela, F. Dazzi, A. De Angelis, B. De Lotto, M. Delfino, J. Delgado, F. Di Pierro, R. Di Tria, L. Di Venere, A. Dinesh, D. Dominis Prester, A. Donini, D. Dorner, M. Doro, L. Eisenberger, D. Elsaesser, L. Foffano, L. Font, F. Frías García-Lago, S. Fröse, Y. Fukazawa, S. García Soto, M. Gaug, J. G. Giesbrecht Paiva, N. Giglietto, F. Giordano, P. Gliwny, N. Godinović, T. Gradetzke, R. Grau, J. G. Green, P. Günther, D. Hadasch, A. Hahn, G. Harutyunyan, T. Hassan, J. Herrera Llorente, D. Hrupec, D. Israyelyan, J. Jahanvi, I. Jiménez Martínez, J. Jiménez Quiles, S. Kankkunen, J. Konrad, P. M. Kouch, H. Kubo, J. Kushida, M. Láinez, A. Lamastra, E. Lindfors, S. Lombardi, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, L. Lulić, E. Lyard, P. Majumdar, M. Makariev, G. Maneva, M. Manganaro, S. Mangano, M. Mariotti, M. Martínez, P. Maruševec, D. Mazin, S. Menchiari, J. Méndez Gallego, S. Menon, D. Miceli, J. M. Miranda, R. Mirzoyan, M. Molero González, E. Molina, H. A. Mondal, A. Moralejo, C. Nanci, A. Negro, V. Neustroev, M. Nievas Rosillo, C. Nigro, L. Nikolić, S. Nozaki, A. Okumura, J. Otero-Santos, S. Paiano, D. Paneque, R. Paoletti, J. M. Paredes, M. Peresano, M. Persic, M. Pihet, F. Podobnik, P. G. Prada Moroni, E. Prandini, W. Rhode, M. Ribó, J. Rico, A. Roy, N. Sahakyan, F. G. Saturni, F. Schiavone, K. Schmitz, T. Schweizer, A. Sciaccaluga, G. Silvestri, A. Simongini, J. Sitarek, D. Sobczynska, A. Stamerra, J. Strišković, D. Strom, M. Strzys, Y. Suda, R. Takeishi, J. Tartera Barberà, P. Temnikov, T. Terzić, M. Teshima, A. Tutone, S. Ubach, M. Vazquez Acosta, S. Ventura, G. Verna, I. Viale, A. Vigliano, C. F. Vigorito, E. Visentin, V. Vitale, M. Vorbrugg, I. Vovk, R. Walter, C. Walther, F. Wersig, P. K. H. Yeung, V. Bosch-Ramon

Solar and Stellar Astrophysics

Probing dust properties through polarized scattered-light images of a sample of ring-shaped protoplanetary disks

Maxime Roumesy, François Ménard, Gaspard Duchêne et al. (+2 more)

The evolution of protoplanetary disks, especially in the early stages of planetary formation, as dust grows, is the cornerstone of the birth of planets. The mechanisms involved in the growth of sub-micrometric dust grains into planetesimals within a very short time frame are a challenging field of study, while the initial conditions remain relatively undefined. One of the main challenges is to unambiguously identify the dust properties within the disk, and our goal is to break this barrier by investigating the light scattered by dust particles lying on the protoplanetary disk surface from many recent promising observations. In this study, we used a set of 30 polarized light images composed of new VLT/SPHERE observations to examine the light scattered by dust grains. For each ring-shaped system, we used the new DRAGyS tool to estimate the disk geometry using the substructures visible on the surface and to extract the limb-brightening-corrected scattering phase function, which encodes the dust grains' physical properties. Finally, we compared our results with the AggScatVIR database of numerical scattering phase functions of nonspherical dust. We combined our measurements of disk geometry to estimate an average disk flaring of about 1.357. First, we recovered the two categories of scattering phase functions based on their shape, as determined in previous studies. Category I is monotonically decreasing and can be explained by fractal organic aggregates with small monomers of 100nm, or compact aggregates with medium porosity and big monomers of 400nm. Category II is defined by a bell-shaped scattering phase function and can be explained by sub-micrometric irregular grains or compact aggregates with low porosity. This statistical study offers general trends about dust populations, but the degeneracy is too strong to apply this method to a unique disk analysis.
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All authors Maxime Roumesy, François Ménard, Gaspard Duchêne, Ryo Tazaki, Christian Ginski

High Energy Astrophysical Phenomena

Blazar flares from plasma blobs crossing the broad-line region

Sébastien Le Bihan, Anton Dmytriiev and Andreas Zech

The blazar 3C 279 is well known for its rapid and large-amplitude variability. On 20 December 2013, the source exhibited an orphan {\gamma}-ray flare characterized by a flux-doubling timescale of a few hours, a very hard spectrum, a time-asymmetric light curve with a slow decay, and no significant optical variability. We propose a new interpretation of this event based on a two-zone scenario in which a stationary emission region produces the quiescent emission, while a second zone accelerates within the broad-line region(BLR). We compute the time-dependent radiative output of both zones with the EMBLEM code, including synchrotron, synchrotron self-Compton, and external inverse-Compton processes, as well as bulk acceleration, adiabatic expansion, and a Fokker-Planck treatment of the electron distribution. This is the first attempt to precisely model the asymmetric {\gamma}-ray flux evolution during this flare. A model with a stationary region outside the dusty torus and an accelerating plasma blob reproduces the main features of the event: a short and intense {\gamma}-ray flare with a hard spectrum and no optical counterpart. The flare results from the variation of the external photon field in the blob frame as the blob crosses the BLR and reaches its terminal Lorentz factor not far from the inner radius of the BLR. Bulk acceleration and the propagation of a plasma blob within the jet provide a natural mechanism for producing high-energy flares and asymmetric light curves without requiring an ad hoc time-dependent particle injection. The model predictsa delayed EUV/X-ray enhancement once the blob exits the BLR. No very-high-energy data are available for this event, but if {\gamma}-rays were emitted in this band, a delay would be expected with respect to the Fermi-LAT flare.
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High Energy Astrophysical Phenomena

On the Difference Between Pulsar Radio Emission Beams from the Two Poles

Xiancong Wu, Hongguang Wang, Hao Tong et al. (+4 more)

The long-standing assumption of symmetric radio emission beams from the two magnetic poles of pulsars is challenged by observational evidence of asymmetry and underfill. Direct testing of this symmetry remains difficult for most pulsars. As an indirect test, we collected polarization profiles of 11 interpulse pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope, MeerKAT, and Parkes. We developed a rotating vector model incorporating aberration and retardation effects to fit the position angle swings of selected pulsars, thereby determining the intrinsic emission region corresponding to the observed pulse windows. Based on both the conal and fan beam models, we compared three key parameters-beam radius, magnetic azimuth width, and emission intensity-between the intrinsic emission regions of the main pulse and interpulse. Among the eight pulsars with a confirmed double-pole geometry, none exhibits similarity in the azimuth width. Only two show potentially similar beam radii, while six demonstrate comparable emission intensities within specific parameter spaces. These results indicate that the emission beams from the two magnetic poles of a pulsar may be generally dissimilar in size, suggesting that the physical conditions governing pair production and particle acceleration differ between the two poles. The random distribution of active emission regions further implies inhomogeneity within the polar cap, which may originate from the differences in local magnetic field structure or surface properties.
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All authors Xiancong Wu, Hongguang Wang, Hao Tong, Rui Luo, Pengfei Wang, Chengbing Lyu, Hai Lei

Solar and Stellar Astrophysics

Eclipsing time variations in close binaries produced by azimuthal dynamo waves

Felipe H. Navarrete, Dominik R.G. Schleicher, Petri J. Käpylä et al. (+1 more)

The nature of eclipsing time variations (ETVs) in post-common-envelope binaries (PCEBs) is still unknown. Circumbinary planets routinely fail the test of time and the Applegate mechanism has energetic constraints and problems in reproducing observations. Based on recent analytic models of magnetically-induced ETVs and stellar dynamo simulations, we aim at explaining ETVs via non-axisymmetric magnetic fields that drift in the azimuthal direction of the star, know as azimuthal dynamo waves (ADWs). We implement a time-varying non-axisymmetric quadrupole moment ($Q$) in a binary system. We solve for the dynamics of the system, compute the resulting eclipsing times, and construct O-C, diagrams. We perform several simulations with different amplitudes of $Q$, periods, stellar masses and binary separations. ADWs naturally give rise to characteristic shapes in the O-C diagram that resemble observations. Depending on how fast $Q$ changes, the solutions can have a sharp decrease in O-C producing amplitudes such as the one obtained in QS Vir, or sinusoidal-like shapes such as in V471 Tau or NN Ser. We also find that the amplitude of the eclipsing times varies from tens to hundreds of seconds. ADWs offer a self-consistent explanation for ETVs as they are expected in dynamo theory. They can explain a variety of features in the observed O-C diagrams. As suggested by dynamo simulations, ADWs are easily excited in rapidly rotating stars, alleviating energetic constrains required in the context of the Applegate mechanism. They produce non-axis $Q$ that in turn produce ETVs that can account for the long-term variation of the O-C, diagrams. We expect in this case that the resulting O-C diagrams are not strictly periodic, unlike explanations based on a third body that would imply a strict periodicity unless additional mechanisms are being invoked.
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All authors Felipe H. Navarrete, Dominik R.G. Schleicher, Petri J. Käpylä, Marcel Völschow

High Energy Astrophysical Phenomena

Diffuse Gamma-ray Emission Around 4FGL J1626.0-4917

Ziwei Ou and Jie Wang

Extended gamma-ray sources provide significant information about particle propagation. 4FGL J1626.0-4917 was labeled as an unassociated source in 4FGL catalog without known counterparts at other wavelengths. We report an analysis on 4FGL J1626.0-4917 with 17 years Fermi Large Area Telescope data and archival Chandra X-ray Observatory data. We find extended GeV emission around this source, which can be modelled by a Gaussian disk of 0.28 degree radius with a significance of the extension of 7.2 sigma. The gamma-ray spectrum of 4FGL J1626.0-4917 has a photon index of 2.73. The gas content, including molecular, neutral and ionized gas, was investigated and the potential hadronic origin is discussed. The diffuse GeV gamma-ray emission may likely originate from the interaction between accelerated protons in 4FGL J1626.0-4917 and the target proton in surrounding gas, although the leptonic process cannot be ruled out. The X-ray spectral analysis was performed, which reveal a point source inside 4FGL J1626.0-4917. We investigate potential counterparts, including the stellar cluster NGC 6134 and the supernova remnant G335.2+0.1. Our results highlight the complexity of unidentified extended gamma-ray sources and the need for further observations.
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Instrumentation and Methods for Astrophysics

An Extended Evaluation Split for DeepSpaceYoloDataset

Olivier Parisot

Recent technological advances in astronomy, particularly the growing popularity of smart telescopes for the general public, make it possible to develop highly effective detection solutions that are accessible to a wide audience, rather than being reserved for major scientific observatories. Published in 2023, DeepSpaceYoloDataset is a collection of annotated images created to train YOLO-based models for detecting Deep Sky Objects, particularly suited for Electronically Assisted Astronomy. In this paper, we present an update to DeepSpaceYoloDataset with the addition of a new split, test2026, designed to evaluate detection models with a greater diversity of images.
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Astrophysics of Galaxies

Dense cores and filaments in M16: Enhanced formation efficiency in the stellar feedback-driven shell

Nageen Pervaiz, Guo-Yin Zhang, Alexander Men'shchikov et al. (+1 more)

We present a comprehensive analysis of dense cores and filamentary structures in the M16 Eagle Nebula using high-resolution ($11.7^{\prime\prime}$) surface density and temperature maps derived from Herschel observations. Using the hires algorithm for map construction and the getsf method for source and filament extraction, we identified 233 cores and 111 filaments in this massive star-forming region. The filaments exhibit a median width of 0.4\,pc – and a median linear density of 61\,$M_\odot$\,pc$^{-1}$, with 76% being supercritical for gravitational fragmentation. Our radial analysis of the $\sim$60\,pc diameter shell driven by the central NGC 6611 cluster reveals strong enhancements in structure formation: filament formation efficiency (FFE) is 2.3 times higher within the shell (peaking at 22%), while core density shows a concurrent 1.5-fold enhancement. The moderate correlation between core density and FFE ($r=0.67$) indicates coupled formation processes. Theoretical analysis demonstrates that observed surface densities exceed the critical threshold for fragmentation by a factor of $\sim$8, with a fragmentation timescale ($\sim$1.5–2.0\,Myr) comparable to the shell's dynamical age ($\sim$1.0–1.3\,Myr), indicating we are observing fragmentation in progress. These results reveal a hierarchical fragmentation sequence – shell compression $\rightarrow$ filament formation $\rightarrow$ core formation – providing clear observational evidence for positive feedback where massive star formation triggers secondary structure formation in the surrounding molecular cloud.
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All authors Nageen Pervaiz, Guo-Yin Zhang, Alexander Men'shchikov, Jin-Zeng Li

Earth and Planetary Astrophysics

Thermal instability and rocky planetesimal formation in the inner regions of protoplanetary disks

Ryo Kato, Takahiro Ueda and Satoshi Okuzumi

The inner regions of protoplanetary disks are promising formation sites of rocky planetesimals. Theoretical studies have proposed that dust trapping at the magnetorotational instability (MRI) activation boundary, or the dead-zone inner edge, promotes planetesimal formation. However, the inner disk may be thermally unstable, in which case the dead-zone inner edge may not remain steady, and the associated pressure maximum and dust trap may not be maintained. In this study, we propose a scenario in which planetesimals form in a thermally unstable inner disk through dust self-accumulation driven by the coevolution of dust and disk temperature. To this end, we simultaneously calculate the non-equilibrium thermal evolution, the evolution of the gas and dust surface densities, dust growth, and planetesimal formation. Our results show that thermal instability triggers cyclic MRI activation and deactivation, during which planetesimals form. The MRI is activated in the inner disk, and thermal instability causes the active region to expand outward and then return to an inactive state, producing a periodic cycle. Triggered by a local enhancement in the dust surface density, dust undergoes self-accumulation while migrating inward during the MRI-inactive phase, resulting in planetesimal formation. Once the MRI is reactivated at a smaller radius, the next cycle begins. For a typical accretion rate of $10^{-8}M_{\odot}~{\rm yr^{-1}}$, a planetesimal belt forms near 1 au. Depending on the model parameters, approximately 10$-$80% of the dust flowing into the planetesimal-forming region is converted into planetesimals. This mechanism produces sufficient planetesimal mass for the formation of multiple super-Earths. The resulting planetesimal distribution can serve as a physically motivated initial condition for subsequent planet formation simulations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Gravitational wave constraints on the Paneitz operator

Robin Valtin, Alexander Ganz and Guillem Domènech

The Paneitz operator is a dimension-4 conformally invariant fourth-order differential operator that has recently attracted attention for possible cancellations of the vacuum energy. We show that, in four dimensions, the Paneitz operator acting on a scalar field falls within the class of extended mimetic gravity theories. Thus, it exhibits the usual instabilities of mimetic gravity. Assuming such instabilities are cured by higher derivative terms, we derive constraints on the Paneitz operator from a modified propagation speed of gravitational waves, after including the Einstein-Hilbert action in the mimetic gravity formulation.
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Instrumentation and Methods for Astrophysics

Finding Strongly Lensed Supernovae from Blended Light Curves

Sangwoo Park, Arman Shafieloo, Alex G. Kim et al. (+2 more)

We present a model-independent, photometry-only framework for identifying strongly lensed supernovae when multiple images are unresolved and blended into a single point source. Building on the simulation-based methodology of Bag et al. (2021), we apply this approach to real Zwicky Transient Facility (ZTF) data using a validation sample of spectroscopically confirmed Type Ia supernovae. The method models the observed flux as a superposition of two time-shifted components, and Bayesian inference is used to estimate the relative scaling and time delay. Applying this framework to 445 well-converged supernovae, we find that only a single object satisfies the selection criteria when adopting a conservative threshold of $\Delta t \ge 12$ days, corresponding to a false positive fraction of $1/445 \approx 0.22\%$. A laxer threshold of $\Delta t \ge 10$ days yields fourteen objects, for a false positive fraction of $3.15\%$. The method provides a scalable and model-independent first-stage filter for identifying lens-like candidates in large time-domain surveys such as the Rubin Observatory's Legacy Survey of Space and Time (LSST).
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All authors Sangwoo Park, Arman Shafieloo, Alex G. Kim, Eric V. Linder, Xiaosheng Huang

High Energy Astrophysical Phenomena

Detection of optical quasi-periodic oscillation in the blazar 3C 454.3

Karan Dogra, Alok C. Gupta, C. M. Raiteri et al. (+83 more)

We analyzed 19 years of $R$-band data of the blazar 3C 454.3 from the Whole Earth Blazar Telescope (WEBT) archive, along with new data from its members and from public archives such as those provided by the Small and Moderate Aperture Research Telescope System (SMARTS) and the Steward Observatory projects to search for quasi-periodic oscillations (QPOs). We detected a QPO of $\sim$ 433 days using Lomb-Scargle periodogram, which lasted from MJD 54980–58450 as detected by the weighted wavelet Z-transform technique, making it one of the most persistent QPOs ever detected in the optical regime. The phase dispersion minimization technique was also performed to further validate this QPO claim. We detected this signal at a global significance of $2.53\sigma$ across all methodologies. To explain the observed QPO, we have considered both models focused on the accretion disk around the super-massive black hole (SMBH), and those based purely on jet emissions. Plausible jet-based models involve a shock moving down the jet in a helical magnetic field, whereas the SMBH models could involve Lense-Thirring effect-induced jet precession or dual jets in a binary SMBH system. We introduce a novel approach to distinguish genuine QPOs from spurious signals arising from annual seasonal gaps, a common limitation of ground-based observations.
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All authors Karan Dogra, Alok C. Gupta, C. M. Raiteri, M. Villata, Paul J. Wiita, Mauri J. Valtonen, S. O. Kurtanidze, S. G. Jorstad, R. Bachev, G. Damljanovic, C. Lorey, S. S. Savchenko, O. Vince, M. Abdelkareem, F. J. Aceituno, J. A. Acosta-Pulido, I. Agudo, G. Andreuzzi, S. A. Ata, G. V. Baida, L. Barbieri, D. A. Blinov, G. Bonnoli, G. A. Borman, M. I. Carnerero, D. Carosati, V. Casanova, W. P. Chen, Lang Cui, P. U. Devanand, E. G. Elhosseiny, D. Elsaesser, J. Escudero, J. H. Fan, M. Feige, K. Gazeas, T. S. Grishina, Minfeng Gu, V. A. Hagen-Thorn, F. Hemrich, H. Y. Hsiao, M. Ismail, R. Z. Ivanidze, M. D. Jovanovic, T. M. Kamel, G. N. Kimeridze, Shubham Kishore, E. N. Kopatskaya, D. Kuberek, O. M. Kurtanidze, A. Kurtenkov, V. M. Larionov, Elena G. Larionova, L. V. Larionova, H. C. Lin, K. Mannheim, A. Marchini, C. Marinelli, A. P. Marscher, D. Morcuende, D. A. Morozova, S. V. Nazarov, M. G. Nikolashvili, D. Reinhart, J. Otero-Santos, A. Scherbantin, E. Semkov, E. V. Shishkina, L. A. Sigua, A. K. Singh, A. Sota, R. Steineke, M. Stojanovic, A. Strigachev, A. Takey, Amira A. Tawfeek, Tushar Tripathi, I. S. Troitskiy, Y. V. Troitskaya, An-Li Tsai, A. A. Vasilyev, K. Vrontaki, Zhongli Zhang, A. V. Zhovtan, N. Zottmann, Wenwen Zuo

High Energy Astrophysical Phenomena

X-Ray Spectral Variability of the TeV HBL Blazar PG 1553+113 with XMM-Newton

P. U. Devanand, Alok C. Gupta, Paul J. Wiita et al. (+2 more)

We present an extensive X-ray spectral variability study of the TeV photon-emitting high-energy-peaked BL Lacertae object PG 1553+113, using the data from EPIC-PN camera of XMM-Newton, which observed the source during its operational period from Sep 2001 to Nov 2024. X-ray spectra in this energy range, $0.6-7.0$ keV, were fitted with absorbed Power-law (PL) and absorbed Log-Parabola (LP) models. We found with 99$\%$ confidence that 14 of them were fit well by LP models having parameters in the range $\alpha\simeq2.13-2.80$, and $\beta\simeq0.04-0.18$, one spectrum favours a LP model with $\beta<0$, while simple PL models with $\Gamma\simeq2.53-2.69$ were sufficient to describe the X-ray spectra of the remaining 15. Two of these 30 observations showed strong signatures of an additional inverse Compton component, while one showed weaker indications. On fitting joint Optical Monitor and EPIC-PN data with LP models, we found synchrotron peaks in the energy range of $\nu_s\simeq4.59-48.61$ eV. This indicates that the spectral evolution is probably caused by variations in particle acceleration or cooling conditions within the jet.
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All authors P. U. Devanand, Alok C. Gupta, Paul J. Wiita, V. Jithesh, Archana Gupta

Cosmology and Nongalactic Astrophysics

Revisiting primordial black hole dark matter from axion inflation

Gabriele Franciolini, Nadir Ijaz and Marco Peloso

We revisit the production of primordial black holes (PBHs) by a U(1) gauge field with a pseudo-scalar coupling to the inflaton. We improve upon the existing literature by working in the homogeneous backreaction regime with numerically computed gauge mode functions, adopting state-of-the-art PBH abundance calculations, and incorporating the uncertainty in the statistics of $\delta\rho$. We find that PBHs can account for all of the dark matter in the asteroidal mass range, even when the inflaton gradient energy density is highly subdominant ($10^{-4}$–$10^{-3}$ of the kinetic energy), supporting the validity of the backreaction scheme. This mechanism also unavoidably generates a stochastic gravitational wave background with an amplitude that will be measured at LISA and that will allow to indirectly discriminate between different statistics of $\delta \rho$.
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High Energy Astrophysical Phenomena

First Detection of Faraday Rotation in a Gamma-Ray Burst Afterglow: Low Polarization and High Rotation Measure in GRB 260310A Reveal Jet Magnetic Structure and Environment

Collin T. Christy, Tanmoy Laskar, Kate D. Alexander et al. (+10 more)

We report the detection of linear polarization in the radio afterglow of GRB 260310A, representing the first centimeter-wavelength polarization detection of a gamma-ray burst (GRB) afterglow and the first measurement of Faraday rotation in a GRB environment. We detect linearly polarized emission across $11-25$ GHz, with a polarization fraction decreasing monotonically from $(3.18 \pm 0.18)\%$ at 25 GHz to $(0.69 \pm 0.22)\%$ at 11 GHz. Interpreting the radio data as emission from a reverse shock in a structured, relativistic jet, the observed depolarization toward lower frequencies is consistent with suppression by synchrotron self-absorption, while the low observed polarization at high frequencies relative to the theoretical maximum suggests a patchy magnetic field in the jet with a coherence scale, $\theta_{\rm B}\approx10^{-2}$ rad. We identify a frequency-dependent rotation of the polarization angle consistent with Faraday rotation, with a rotation measure of ${\rm RM} = -(8300 \pm 90)~\rm{rad/m^2}$ at the GRB redshift. The magnitude of the rotation measure is consistent with propagation through a dense, magnetized environment, such as a progenitor HII region. These findings demonstrate that GRB afterglows exhibit measurable linear polarization at centimeter wavelengths, and that their polarimetric properties probe both intrinsic jet magnetization and the surrounding medium. Future multi-frequency polarimetric monitoring over timescales of days to weeks will enable detailed studies of the evolution of magnetic field structure and provide new constraints on the role of magnetic fields in GRB afterglows.
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All authors Collin T. Christy, Tanmoy Laskar, Kate D. Alexander, Noah Franz, Jonathan Granot, Ryan Chornock, Raffaella Margutti, Ramandeep Gill, Jeniveve Pearson, Edo Berger, Wen-fai Fong, Coleman Rohde, Patricia Schady

Astrophysics of Galaxies

The Critical Mass in Galaxy Evolution

Preetish K. Mishra, Changbom Park, Jaehyun Lee et al. (+4 more)

We investigate the physical origin of critical mass, a threshold where many galaxy properties and scaling relations undergo fundamental transitions, using the Horizon Run 5 simulation. Focusing on massive ($M_{\rm tot} \geq 10^{12}{\rm M_\odot}$) central galaxies, we examine the mass-dependent turnover of the stellar-to-total mass ratio (STR) and the physical processes driving it. We decompose STR into the stellar-to-baryon mass ratio ($M_*/M_{\rm bar}$) and baryon retention fraction ($M_{\rm bar}/M_{\rm tot}$) to examine galaxies' ability to retain baryons and convert them into stars. We find that STR evolution is dominated by variation in $M_*/M_{\rm bar}$, which changes by over a factor of three, peaking within a narrow range of $M_{\rm tot} \sim 10^{12.4\text{--}12.7}{\rm M_\odot}$ independent of redshift, while $M_{\rm bar}/M_{\rm tot}$ varies by at most 30%. A redshift-independent critical mass at $M_{\rm tot} \sim 10^{12.5}{\rm M_\odot}$ ($M_* \sim 10^{10.7}{\rm M_\odot}$) arises from the changing nature of gas accretion. At this scale, a dynamically stable hot gas halo develops that suppresses cool gas inflow, reducing in-situ star formation efficiency such that $M_{\rm tot}$ growth exceeds in-situ $M_{*}$ growth. Consequently, the hot gas reservoir grows while $M_{*}$ growth slows, producing upturns in $M_{\rm gas}/M_{\rm tot}$ and $M_{\rm bar}/M_{\rm tot}$ and a downturn in $M_{*}/M_{\rm bar}$ that ultimately drives the STR turnover. We also identify a secondary critical mass at $M_{\rm tot} \approx 10^{11}{\rm M_\odot}$ (or $M_{*} \approx 10^{9\text{--}9.5}{\rm M_\odot}$) where gas retention fraction peaks, above which increasing hot gas fraction gradually suppresses in-situ star formation efficiency.
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All authors Preetish K. Mishra, Changbom Park, Jaehyun Lee, Yohan Dubois, Christophe Pichon, Juhan Kim, Brad Gibson

Cosmology and Nongalactic Astrophysics

Foreground Mitigation and Power Spectrum Analysis for Tianlai Full-Sky 21 cm Survey Observation

Yikai Deng, Shifan Zuo, Jixia Li et al. (+2 more)

We present a comprehensive analysis of the 21 cm intensity mapping (IM) data from the Tianlai Cylinder Pathfinder Array (TCPA), focusing on multi-scale foreground mitigation and three-dimensional power spectrum estimation. Utilizing 20 days of drift-scan observations (714.4-781.7 MHz, corresponding to HI emission at redshift $z \approx 0.82-0.99$), we reconstruct high-fidelity sky maps by incorporating a high-precision, drone-measured primary beam model. This in-situ calibration significantly enhances reconstruction accuracy over previous analytical approximations. To address astrophysical foregrounds, which exceed the cosmological signal by approximately five orders of magnitude, we implement a robust multi-scale subtraction strategy–mPCA-UWTS–which combines an isotropic Undecimated Wavelet Transform on the Sphere (UWTS) with independent Principal Component Analysis (PCA) within each wavelet domain. We subsequently estimate the 3D power spectrum via Spherical Fourier-Bessel (SFB) decomposition, providing a mathematically rigorous treatment of wide-angle and line-of-sight curvature effects inherent in wide-field surveys. Our analysis demonstrates that the SFB framework effectively isolates systematic contaminants and recovers the clustering signal without the biases introduced by conventional flat-sky approximations. This work represents the first application of the SFB formalism to observational 21 cm IM data, establishing it as a computationally efficient and scalable diagnostic tool for the next generation of wide-field 21 cm surveys, including the Square Kilometre Array (SKA) and the full Tianlai array.
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All authors Yikai Deng, Shifan Zuo, Jixia Li, Yougang Wang, Xuelei Chen

High Energy Astrophysical Phenomena

Indication of gamma-Ray Quasi-periodicity in GB6 J1037+5711 from Multi-technique Timing Analysis

Zahoor Malik, Sikandar Akbar, Zahir Shah et al. (+1 more)

We report the indication of a long-term quasi-periodic oscillation (QPO) in the $\gamma$-ray emission of the BL Lac object 4FGL J1037.7+5711 (GB6 J1037+5711) using more than 17 years of monthly binned Fermi-LAT observations. Since blazar $\gamma$-ray variability is typically dominated by stochastic red-noise processes from turbulent jet activity and accretion fluctuations, we applied multiple independent timing techniques to test periodic modulation. These include the Lomb–Scargle periodogram (LSP), weighted wavelet $Z$-transform (WWZ), first-order autoregressive red-noise modeling (REDFIT), and epoch-folding analysis. The LSP reveals a significant periodic signal at $478.74 \pm 17.55$ days, exceeding the $99.99\%$ confidence level from Monte Carlo simulations. The WWZ analysis independently recovers a comparable period of $474.72 \pm 27.24$ days at $99.7\%$ significance, while the REDFIT analysis identifies a similar periodic feature at $481.67 \pm 35.41$ days above the $99\%$ confidence level. The epoch-folding analysis further confirms the same modulation timescale. The small differences in period estimates across methods are expected given the distinct mathematical frameworks and sensitivity functions. The long-term flux distribution of the source is better described by a lognormal profile than a Gaussian, suggesting that the underlying variability arises from multiplicative processes. The indication of a $\sim$478 day QPO, independently confirmed across all four timing techniques, may be associated with the orbital dynamics of a supermassive binary black hole system driving Newtonian jet precession or periodic Doppler-factor modulation, Lense–Thirring precession of the inner accretion disk around a rapidly spinning SMBH, or accretion-driven instabilities at the disk–jet interface amplified through relativistic beaming.
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All authors Zahoor Malik, Sikandar Akbar, Zahir Shah, Seemin Rubab

Instrumentation and Methods for Astrophysics

A benchmark for binary star interaction with a supermassive black hole in general relativity

Megha Sharma, Alexander Heger, Daniel J. Price et al. (+4 more)

Most galaxies have supermassive black holes (SMBH) at their centres, surrounded by stars with binary systems also present in this environment. We use two schemes - post-Newtonian (PN) and a scalar perturbation to a background metric to numerically solve the three-body problem of a binary with a SMBH. We test three different PN formulations for the PN scheme: The Einstein-Infeld-Hoffman equation, pair-wise implementation of two-body PN-terms for three bodies and the Arnowitt-Deser-Misner Hamiltonian. We compare these approaches for one million solar mass and one billion solar mass black holes, and find a statistical match between the two approximations for stellar mass binary interacting with a million solar mass black hole. We also perform a statistical study for encounters with this black hole, and find that the higher order PN formulation matches with metric-with-perturbation scheme. However, we find a decrease in separation of the binary, and eccentricity variations between different schemes around the billion solar mass black hole. This behaviour is not present if binary has a large separation or is further away from the black hole due to decreased general-relativistic effects. We find that the pair-wise PN method results in a decrease in separation at pericentre in all test cases irrespective of the distance from the black hole or mass of the black hole, making this the least reliable method for solving this problem. Our work highlights the need for caution when interpreting the results in different formulations around SMBHs. This also shows that when understanding extreme mass ratio inspirals (EMRIs) using simulations, one should beware as the binary gets closer to the black hole.
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All authors Megha Sharma, Alexander Heger, Daniel J. Price, Emilio Tejeda, Evgeni Grishin, Luis A. Manzaneda, Alessandro A. Trani