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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 11 November

Astrophysics of Galaxies

A warm ultra-luminous infrared galaxy just 600 million years after the Big Bang

T. J. L. C. Bakx, Laura Sommovigo, Yoichi Tamura et al. (+24 more)

We present an Atacama Large Millimeter/submillimeter Array (ALMA) Band 9 continuum detection ($3.3 \sigma$) of MACS0416_Y1 that confirms the suspected warm dust (91$^{+62}_{-35}$ K) of this Lyman-Break Galaxy (LBG) at $z = 8.3$ with $\log_{10} M_{\ast}/$M$_{\odot} = 9.0 \pm 0.1$. A modified black-body fit to the ALMA Bands 3 through 9 data of MACS0416_Y1 finds an intrinsic infrared luminosity of 1.0$^{+1.8}_{-0.6} \times{} 10^{12}\ \mathrm{L_{\odot}}$, placing this UV-selected LBG in the regime of Ultra Luminous Infrared Galaxies (ULIRGs). Its luminous but modest dust reservoir (1.4$^{+1.3}_{-0.5} \times{} 10^{6}\ \mathrm{M_{\odot}}$) is co-spatial to regions with a UV-continuum slope $\beta_{\rm UV} \approx -1.5$ as seen by James Webb Space Telescope (JWST) imaging. Although this implies some dust obscuration, the JWST photometry implies less obscured star formation than seen in the complete characterization by ALMA, implying some spatial separation of dust and stars on scales below 200 pc, i.e., smaller than those probed by JWST and ALMA. This source is an extreme example of dust-obscured star formation contributing strongly to the cosmic build-up of stellar mass, which can only be revealed through direct and comprehensive observations in the (sub)mm regime.
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All authors T. J. L. C. Bakx, Laura Sommovigo, Yoichi Tamura, Renske Smit, Andrea Ferrara, Hiddo Algera, Susanne Aalto, Duncan Bossion, Stefano Carniani, Clarke Esmerian, Masato Hagimoto, Takuya Hashimoto, Bunyo Hatsukade, Edo Ibar, Hanae Inami, Akio K. Inoue, Kirsten Knudsen, Nicolas Laporte, Ken Mawatari, Juan Molina, Gunnar Nyman, Takashi Okamoto, Andrea Pallottini, W. M. C. Sameera, Hideki Umehata, Wouter Vlemmings, Naoki Yoshida

Astrophysics of Galaxies

Thermodynamic blocking in self-gravitating systems

Barnabás Deme and Jean-Baptiste Fouvry

Building upon a thermodynamic formalism, we show that self-gravitating systems in hydrostatic equilibrium with a uniform density are maximal entropy states when submitted to perturbations which are slow on dynamical timescale. We coin this phenomenon "thermodynamic blocking", given its similarity with the more general "kinetic blocking". This result underlines the importance of the thermodynamic formalism which proves useful when kinetic equations break down.
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Earth and Planetary Astrophysics

Remanent crustal strain on Mars in non-poikilitic olivine of NWA 7721

Yaozhu Li, Szilvia Kalácska, Phil McCausland et al. (+5 more)

We present a multiscale microstructural analysis of olivine from the non-poikilitic lithology of the poikilitic shergottite NWA 7721, using dark-field X-ray microscopy (DFXM), electron backscatter diffraction (EBSD), and context in situ 2D micro-XRD. A single olivine crystal contains two distinct subgrain populations. Type 1 subgrains are fine (1-5 micrometers), randomly oriented, and nearly strain-free, whereas Type 2 subgrains are coarse (greater than 30 micrometers), aligned, and strongly strained. Layered DFXM data reveal slip-band features in Type 2 that are absent in Type 1. We interpret Type 1 as products of shock-induced recrystallization, whereas Type 2 preserves remnants of a highly deformed parent grain. This bimodal microstructure, not observed in other Martian meteorites including the paired NWA 1950 and ALH A77005, points to a heterogeneous response to impact influenced by pre-existing strain in the olivine grain. We propose that NWA 7721 olivine experienced substantial crustal or magmatic stress before impact. The subsequent shock wave imposed a rapid load-release cycle that mobilized dislocations and produced low-angle boundaries in Type 2, while driving recrystallization of Type 1. Grain-growth constraints limit the post-shock heating duration to approximately 2.3 s, consistent with rapid quenching. These results provide the first evidence that non-poikilitic olivine in NWA 7721 preserves dynamic crustal deformation on Mars in the Late Amazonian.
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All authors Yaozhu Li, Szilvia Kalácska, Phil McCausland, Roberta L. Flemming, Callum Hetherington, Bo Zhao, Can Yildirim, Carsten Detlefs

Solar and Stellar Astrophysics

Coordinated Space- and Ground-based Monitoring of Accretion Bursts in a Protoplanetary Disk: The Orbital and Accretion Properties of DQ Tau

Hala Alqubelat, Carlo F. Manara, Justyn Campbell-White et al. (+9 more)

Multiplicity in pre-main-sequence (PMS) systems shapes circumstellar and circumbinary disks, often producing features such as inner cavities, spiral arms, and gas streamers that facilitate mass transfer between the disk and stars. Consequently, accretion in eccentric close binaries is highly variable and synchronized with their orbits, producing bursts near periastron passages. In this study, we examine the orbital and accretion properties of the eccentric Classical T-Tauri binary DQ Tau using medium- to high-resolution spectroscopy from the Very Large Telescope (VLT) X-Shooter and UVES instruments. The data were taken during a monitoring of inner disk chemistry with JWST, and our analysis is needed for correct interpretation of JWST data. We refine the orbital parameters and report an increment in the argument of periastron of 30 degrees. This apsidal motion may be caused by the massive disk acting as a third body. We also explore the possibility that it is due to a still undetected additional (sub-)stellar companion, estimating a lower limit of 15 MJ for its mass at the cavity edge (a=3 abin). We investigate accretion of the primary and secondary using the Ca II 849.8 nm emission line. The primary accretes more at periastron than in previous quiescent phases, while the secondary dominates post-periastron. Additionally, we report elevated Lacc at apastron, possibly due to interaction with irregularly shaped structures near the closest approach to the circumbinary disk. Finally, we derive each star's accretion luminosity across disentangled epochs and compare it to UV-excess-based results, finding good agreement. The individual Lacc values can be used as input for chemical models.
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All authors Hala Alqubelat, Carlo F. Manara, Justyn Campbell-White, Monika G. Petr-Gotzens, Benjamin M. Tofflemire, Andrea Banzatti, Enrico Ragusa, Emma T. Whelan, Guillaume Bourdarot, Catherine Dougados, Eleonora Fiorellino, Sean I. Mills

Earth and Planetary Astrophysics

The MATISSE view of the inner region of the RY Tau protoplanetary disk

J. S. Martin, J. Kobus, J. Varga et al. (+44 more)

The T-Tauri type young stellar object RY Tau exhibits a dust depleted inner cavity characteristic of a transition disk. We constrain the spatial distribution and mineralogy of dust in the RY Tau protoplanetary disk in the inner few astronomical units using spectrally resolved interferometric observations in the L, M, and N bands obtained with VLTI/MATISSE. Employing a 2D temperature gradient model we estimate the orientation of the inner disk finding no evidence of significant misalignment between the inner and outer disk of RY Tau. Successively, we analyze the chemical composition of silicates depending on spatial region in the disk and identify several silicate species commonly found in protoplanetary disks. Additionally, a depletion of amorphous dust grains toward the central protostar is observed. Monte Carlo radiative transfer simulations show that hot dust close to the protostar and in the line of sight to the observer, either in the uppermost disk layers of a strongly flared disk or in a dusty envelope, is necessary to model the observations. The shadow cast by a dense innermost disk midplane on the dust further out explains the observed closure phases in the L band and to some extent in the M band. However, the closure phases in the N band are underestimated by our model, hinting at an additional asymmetry in the flux density distribution not visible at shorter wavelengths.
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All authors J. S. Martin, J. Kobus, J. Varga, A. Matter, S. Wolf, M. Abello, F. Allouche, J.-C. Augereau, P. Berio, F. Bettonvil, R. van Boekel, P. A. Boley, P. Cruzalèbes, W. C. Danchi, J. Drevon, C. Dominik, V. Fleury, V. Gámez Rosas, A. Glindemann, L. N. A. van Haastere, M. Heininger, Th. Henning, K.-H. Hofmann, M. Hogerheijde, M. Houllé, J. W. Isbell, W. Jaffe, L. Labadie, S. Lagarde, J. H. Leftley, M. Lehmitz, M. Letessier, B. Lopez, F. Lykou, J. Ma, A. Meilland, F. Millour, C. Paladini, E. Pantin, R. G. Petrov, P. Priolet, S. Robbe-Dubois, D. Schertl, M. Scheuck, J. Scigliuto, G. Weigelt, J. Woillez

Cosmology and Nongalactic Astrophysics

A Strong Gravitational Lensing Model of PSZ2 G118.46+39.32

Isaac Smith, Catherine Cerny, Keren Sharon et al. (+4 more)

We present the first strong gravitational lensing model for the cluster PSZ2 G118.46+39.32 (z = 0.3967) using new NIRCam imaging from the Strong LensIng and Cluster Evolution (SLICE) JWST program. We leverage the broad coverage of the SLICE ultrawide JWST filters to identify new lensed galaxies, some of which are not visible in HST, to model the cluster's mass distribution. The model was constructed with a total of 11 multiply imaged systems, decomposed into 30 images with 60 clumps used as strong lensing constraints. PSZ2 G118.46+39.32 shows a clear bimodal structure, indicating that it may be undergoing a merger. The predicted mass distribution of the model aligns with the X-ray gas in the cluster, suggesting it is in a pre-merger state.
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All authors Isaac Smith, Catherine Cerny, Keren Sharon, Guillaume Mahler, Gourav Khullar, Benjamin Beauchesne, The SLICE Collaboration

Earth and Planetary Astrophysics

An Overview of Exocomets

Daniela Iglesias, Isabel Rebollido, Azib Norazman et al. (+8 more)

We give a general overview of what the scientific community refers to as "exocomets". The general definition of exocomets, as presented in this work, is discussed and compared with Solar System comets and interstellar objects, addressing their detection around main-sequence stars as well as orbiting white dwarfs. We introduce the different types of exocomet observations, highlighting the difference between exocometary 'bodies' and exocometary 'material'. We provide a census of all exocometary system candidates detected so far, both via spectroscopy and photometry, including detections around white dwarfs.
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All authors Daniela Iglesias, Isabel Rebollido, Azib Norazman, Colin Snodgrass, Darryl Z. Seligman, Siyi Xu, H. Jens Hoeijmakers, Matthew Kenworthy, Alain Lecavelier des Etangs, Michele Bannister, Bin Yang

Cosmology and Nongalactic Astrophysics

Euclid preparation: LXXXVII. Non-Gaussianity of 2-point statistics likelihood: Precise analysis of the matter power spectrum distribution

Euclid Collaboration, J. Bel, S. Gouyou Beauchamps et al. (+281 more)

We investigate the non-Gaussian features in the distribution of the matter power spectrum multipoles. Using the COVMOS method, we generate 100\,000 mock realisations of dark matter density fields in both real and redshift space across multiple redshifts and cosmological models. We derive an analytical framework linking the non-Gaussianity of the power spectrum distribution to higher-order statistics of the density field, including the trispectrum and pentaspectrum. We explore the effect of redshift-space distortions, the geometry of the survey, the Fourier binning, the integral constraint, and the shot noise on the skewness of the distribution of the power spectrum measurements. Our results demonstrate that the likelihood of the estimated matter power spectrum deviates significantly from a Gaussian assumption on nonlinear scales, particularly at low redshift. This departure is primarily driven by the pentaspectrum contribution, which dominates over the trispectrum at intermediate scales. We also examine the impact of the finiteness of the survey geometry in the context of the Euclid mission and find that both the shape of the survey and the integral constraint amplify the skewness.
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All authors Euclid Collaboration, J. Bel, S. Gouyou Beauchamps, P. Baratta, L. Blot, C. Carbone, P.-S. Corasaniti, E. Sefusatti, S. Escoffier, W. Gillard, A. Amara, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco, V. F. Cardone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, S. de la Torre, G. De Lucia, F. Dubath, C. A. J. Duncan, X. Dupac, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, B. Kubik, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, O. Marggraf, K. Markovic, M. Martinelli, N. Martinet, F. Marulli, R. Massey, E. Medinaceli, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, F. Rizzo, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, G. Seidel, M. Seiffert, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, Y. Wang, J. Weller, G. Zamorani, E. Zucca, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, D. Di Ferdinando, J. A. Escartin Vigo, L. Gabarra, J. Martín-Fleitas, S. Matthew, N. Mauri, R. B. Metcalf, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, S. Alvi, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, D. Bertacca, M. Bethermin, A. Blanchard, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, S. Contarini, A. R. Cooray, S. Davini, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, C. C. Kirkpatrick, S. Kruk, M. Lattanzi, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, L. Leuzzi, T. I. Liaudat, J. Macias-Perez, G. Maggio, M. Magliocchetti, F. Mannucci, R. Maoli, C. J. A. P. Martins, L. Maurin, M. Miluzio, P. Monaco, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, L. Pagano, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, P. Reimberg, P.-F. Rocci, G. Rodighiero, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, F. Vernizzi, G. Verza, P. Vielzeuf, N. A. Walton

High Energy Astrophysical Phenomena

Fill the gaps: continuous in time interpolation of fluid dynamical simulations

Jonas Pronk, Oliver Porth and Jordy Davelaar

Flexible and accurate interpolation schemes using machine learning could be of great benefit for many use-cases in numerical simulations and post-processing, such as temporal upsampling or storage reduction. In this work, we adapt the physics-informed token transformer (PITT) network for multi-channel data and couple it with Fourier neural operator (FNO). The resulting PITT FNO network is trained for interpolation tasks on a dataset governed by the Euler equations. We compare the performance of our machine learning model with a linear interpolation baseline and show that it requires $\sim6-10$ times less data to achieve the same mean square error of the interpolated quantities. Additionally, PITT FNO has excellent mass and energy conservation as a result of its physics-informed nature. We further discuss the ability of the network to recover fine detail using a spectral analysis. Our results suggest that loss of fine details is related to the decreasing correlation time of the data with increasing Fourier mode which cannot be resolved by simply increasing Fourier mode truncation in FNO.
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Astrophysics of Galaxies · Cross-listed from gr-qc

Constraining modified theories of gravity through the detection of one extremely large mass-ratio inspiral

Hui-Min Fan, Alejandro Torres-Orjuela, Verónica Vázquez-Aceves et al. (+2 more)

Extremely large mass-ratio inspirals (XMRIs), formed by brown dwarfs inspiraling into a massive black hole, emit gravitational waves (GWs) that fall within the detection band of future space-borne detectors such as LISA, TianQin, and Taiji. Their detection will measure the astrophysical properties of the MBH in the center of our galaxy (SgrA$^\ast$) with unprecedented accuracy and provide a unique probe of gravity in the strong field regime. Here, we estimate the benefit of using the GWs from XMRIs to constrain the Chern-Simons theory. Our results show that XMRI signals radiated from the late stages of the evolution are particularly sensitive to differences between Chern-Simons theory and general relativity. For low-eccentricity sources, XMRIs can put bounds on the Chern-Simons parameter $\zeta$ at the level of $10^{-1}$ to an accuracy of $10^{-3}$. For high-eccentricity sources, XMRIs can put bounds on the parameter $\zeta$ at the level of $10^{-1}$ to an accuracy of $10^{-6}$. Furthermore, using the time-frequency MCMC method, we obtain the posterior distribution of XMRIs in the Chern-Simons theory. Our results show that almost all the parameters can be recovered within $1\sigma$ confidence interval. For most of the intrinsic parameters, the estimation accuracy reaches $10^{-3}$. For the brown dwarf mass, the estimation accuracy reaches $10^{-1}$, while for $\zeta$, the estimation accuracy reaches $\Delta\log_{10}\zeta=0.08$ for high eccentricity sources and 1.27 for low eccentricity sources.
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All authors Hui-Min Fan, Alejandro Torres-Orjuela, Verónica Vázquez-Aceves, Tian-Xiao Wang, Tai-Fu Feng

Instrumentation and Methods for Astrophysics

Emulating Radiative Transfer in Astrophysical Environments

Rune Rost, Lorenzo Branca and Tobias Buck

Radiative transfer is a fundamental process in astrophysics, essential for both interpreting observations and modeling thermal and dynamical feedback in simulations via ionizing radiation and photon pressure. However, numerically solving the underlying radiative transfer equation is computationally intensive due to the complex interaction of light with matter and the disparity between the speed of light and the typical gas velocities in astrophysical environments, making it particularly expensive to include the effects of on-the-fly radiation in hydrodynamic simulations. This motivates the development of surrogate models that can significantly accelerate radiative transfer calculations while preserving high accuracy. We present a surrogate model based on a Fourier Neural Operator architecture combined with U-Nets. Our model approximates three-dimensional, monochromatic radiative transfer in time-dependent regimes, in absorption-emission approximation, achieving speedups of more than 2 orders of magnitude while maintaining an average relative error below 3%, demonstrating our approach's potential to be integrated into state-of-the-art hydrodynamic simulations.
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Cosmology and Nongalactic Astrophysics

Galaxy cluster temperature maps from joint X-ray and SZ maps with The Three Hundred hydrodynamical simulations

R. Wicker, M. De Petris, A. Ferragamo et al. (+8 more)

Galaxy clusters can be used as powerful cosmological probes, provided one can obtain accurate mass estimates, which requires a precise knowledge of the underlying astrophysics of galaxy clusters. For these purposes, spatially resolved measurements of the thermodynamic properties of intra-cluster medium (ICM), such as density and temperature, are necessary. In particular, temperature estimates are traditionally obtained through spatially resolved X-ray spectroscopy. Such measurements suffer from their sensitivity to the chosen energy calibration, may exhibit inherent biases, and are especially hard to perform at high redshift as they require deep observations. In recent years however, millimetre wavelength data with high spatial resolution, comparable to the one of current X-ray telescopes, have begun to be available. This has enabled the implementation of new methods to infer and map the cluster temperature in individual clusters, using the combination of density maps from X-ray data and pressure maps from millimetre data. In this paper, we present the first systematic validation of this approach on a large sample of synthetic clusters generated in The Three Hundred hydrodynamical simulations. We show that we are able to recover theoretical estimates of the temperature, namely the mass-weighted and spectroscopic-like temperatures, within biases of the order of $\lesssim 1\%$ in the best cases, up to $\sim 10\%$ in average, with scatters of the order of $10\%$. To prepare the application of this approach to observed data, we discuss the modelling of the effective length $l_\mathrm{eff}$, a key quantity necessary for the combination of X-ray and SZ projected data. In particular we provide templates calibrated on simulations for this quantity, and investigate their impact in the recovery of the temperature map, compared to other standard models.
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All authors R. Wicker, M. De Petris, A. Ferragamo, I. Bartalucci, G.Yepes, E. Rasia, R. Adam, W. Cui, F. Mayet, L. Perotto, M. Muñoz-Echeverría

Astrophysics of Galaxies

Investigating star formation scenarios in the Milky Way using YSO distributions – A pilot study

Annarien G. Headley and James O. Chibueze

We investigated the distributions of classified young stellar object (YSO) in nine star-forming regions associated with Hii regions, namely Sh2-22, Sh2-19, Sh2-17, M16, M8, IC5070, Sh2-252, NGC2467 and M42, as a means of exploring the star formation scenarios (triggered or spontaneous) in the various regions. The YSO distributions of nine regions along the galactic longitudes and across different spiral arms were explored. It is noted that Sh2-22 and Sh2-19 may have evidence of localized triggered star formation, whereas Sh2-17 may be a spontaneous star forming region. The results showed that the location within the Milky Way may influence localized triggered star formation within individual regions. There is strong evidence that there are fewer older stars (Transition Disks) within the Outer regions of the Galaxy (2.91 +- 1.74%), accompanied by a higher number of Class I (32.49 +- 10.77%). This is different from the Inner Galactic regions where the Transition Disks are higher (32.93 +- 13.78%) as compared to low Class I sources (11.01 +- 4.81%). The number of Class II stars is relatively high and increases from the Inner regions (52.64 +- 10.07%) to Outer regions (64.54 +- 11.09%). These nine star-forming regions are not an accurate representation of locations throughout the Galaxy and the results may be biased.
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High Energy Astrophysical Phenomena

Study of Flat Spectrum Radio Quasars and BL Lacertae Objects as Sources of Diffusive Ultra High-Energy Cosmic Rays

Swaraj Pratim Sarmah and Umananda Dev Goswami

We examine whether Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BL Lacs) can act as plausible astrophysical sources of diffuse ultra-high-energy cosmic rays (UHECRs). Using realistic luminosity-dependent density evolution (LDDE) functions derived from observed gamma-ray luminosity functions for FSRQs and BL Lacs, we calculate the redshift evolution of the cosmic ray source population through integrated luminosity functions. The diffuse UHECRs flux from these sources is modelled by propagating nuclei through extragalactic space, including energy losses from interactions with cosmic photon backgrounds. The resulting UHECRs spectra are compared with observational data from the Pierre Auger Observatory and the Telescope Array, with fluxes normalised at reference energies. We also construct illustrative full skymaps of the integral UHECRs flux from $10$ EeV to $100$ EeV using the HEALPix framework, assuming a uniform distribution of synthetic sources and including energy dependent magnetic diffusion. Our results show that although both FSRQs and BL Lac objects can reproduce the observed UHECR flux, the FSRQ scenario is disfavoured by anisotropy and inconsistent source density, while BL Lacs remain consistent with observations.
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Solar and Stellar Astrophysics

Stellar spin in young star clusters: comparison between simulations and observations

Giacomo Cordoni, Sajay Sunny Mathew and Christoph Federrath

The angular momentum evolution of stars is crucial for understanding the formation and evolution of stars and star clusters. Using high-resolution magnetohydrodynamical (MHD) simulations of star formation in clouds with different physical properties, we study the initial distribution of stellar rotation periods in young clusters. We compare these results with observations of young Galactic clusters. Simulations qualitatively reproduce the observed trend of increasing rotation period with stellar mass. Additionally, simulations with lower virial parameter (ratio of turbulence to gravity) or solenoidal turbulence driving produce period-mass distributions that more closely match the observed ones. These simulations also recover the break in the mass-period relation. However, the break appears at higher masses than in observations and is absent in the youngest simulated clusters. This suggests that the emergence of the break is an important diagnostic of angular momentum evolution during the earliest stages of cluster formation. The simulations yield stars that rotate about an order of magnitude faster than those observed. This discrepancy mainly reflects the earlier evolutionary stage of the simulations, while unresolved physical interactions between stars and discs might also contribute. This conclusion is supported by simulations showing a significant period increase within 0.1-1 Myr. We quantify the required angular-momentum loss by rescaling simulated rotation periods to match observations, finding that 80-95% of the initial angular momentum must be removed within the first Myr. Our results highlight that understanding the earliest stages of star cluster formation is fundamental to addressing the angular momentum problem.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Extreme mass ratio inspirals into black holes surrounded by matter: Resonance crossings

Michal Stratený, Georgios Lukes-Gerakopoulos and Ondřej Zelenka

The forthcoming space-based gravitational-wave observatory Laser Interferometer Space Antenna (LISA) should enable the detection of Extreme Mass Ratio Inspirals (EMRIs), in which a stellar-mass compact object gradually inspirals into a supermassive black hole while emitting gravitational waves. Modeling the waveforms of such systems is a challenging task, requiring precise computation of energy and angular momentum fluxes as well as proper treatment of orbital resonances, during which two fundamental orbital frequencies become commensurate. In this work, we perform a systematic comparison of fluxes derived from three approaches: the quadrupole formula, post-Newtonian approximations, and time-domain solutions of the Teukolsky equation. We show that quadrupole-based fluxes remain in good agreement with Teukolsky results across a broad range of orbital configurations, including perturbed orbits. Building on these insights, we explore the dynamical impact of resonance crossings within the adiabatic approximation. By introducing novel numerical methods, we reduce computational costs and uncover diverse resonance-crossing behaviors. These results contribute to the effort to understand theoretically and model adequately resonance crossings during an EMRI.
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Earth and Planetary Astrophysics

HyperScout-H: the hyperspectral imager for the ESA Hera mission

Marcel M. Popescu, Julia de León, George Pantelimon Prodan et al. (+16 more)

The HyperScout-H (HS-H) instrument is one of the payloads aboard ESA's Hera spacecraft. Hera is a planetary defence mission that aims to provide a detailed characterization of the near-Earth binary asteroid (65803) Didymos-Dimorphos after the NASA/DART mission impact. HS-H is a versatile dual-use payload, functioning as a hyperspectral imager that captures both images and spectral data within the 0.65–0.95 $\mu$m wavelength range. The observations from this instrument will offer key insights regarding the composition of the two bodies Didymos and Dimorphos, space weathering effects, and the potential presence of exogenous material on these asteroids. Thanks to its wide field of view ($\approx 15.5^\circ \times 8.3^\circ$ in paraxial approximation), HS-H will be able to monitor the system's orbital dynamic and dust environment. At the same time, both components of this binary asteroid remain in the field of view for most of the asteroid phase of the mission. These results also complement the data obtained from other instruments in characterizing the geomorphological units. The data that will be obtained by HS-H will enable the creation of maps highlighting key spectral features, such as taxonomic classification, spectral slope, and band parameters. This article presents the pre-flight calibration of the instrument, outlines the science objectives, and discusses the expected investigations. The instrument's capabilities are demonstrated through laboratory observations of two meteorite samples and a dedicated software toolbox was developed specifically for processing the instrument's data.
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All authors Marcel M. Popescu, Julia de León, George Pantelimon Prodan, Michael Küppers, Gábor Kovács, Balázs Vince Nagy, Björn Grieger, Hannah Goldberg, Marco Esposito, Nathan Vercruyssen, Eri Tatsumi, Lisa Krämer Ruggiu, Özgür Karatekin, Seiji Sugita, Monica Lazzarin, Paul A. Abell, Jean-Baptiste Vincent, Iulian Petrişor, Patrick Michel

Instrumentation and Methods for Astrophysics · Cross-listed from eess.SY

Spacecraft Angular Rate Estimation via Event-Based Camera Sensing

Vittorio Franzese and Matteo El Hariry

This paper presents a method for determining spacecraft angular rates using event-based camera sensing. This is achieved by analyzing the temporal distribution of brightness events triggered by the apparent motion of stars. The location and polarity of the events are used to infer the apparent motion field of the stars, which is, in turn, employed to estimate the observer angular velocity in the camera frame. This can be converted to the spacecraft angular rates provided an attitude reference. The method is validated through numerical simulation for a synthetic dataset of event streams generated on random spacecraft pointing and rates conditions. The accuracy of the method is assessed, demonstrating its potential to complement or replace conventional rate sensors in spacecraft systems using event camera sensing.
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Cosmology and Nongalactic Astrophysics

CSST Strong Lensing Preparation: Cosmological Constraints Forecast from CSST Galaxy-Scale Strong Lensing

Hengyu Wu, Yun Chen, Tonghua Liu et al. (+6 more)

Strong gravitational lensing by galaxies is a powerful tool for studying cosmology and galaxy structure. The China Space Station Telescope (CSST) will revolutionize this field by discovering up to $\sim$100,000 galaxy-scale strong lenses, a huge increase over current samples. To harness the statistical power of this vast dataset, we forecast its cosmological constraining power using the gravitational-dynamical mass combination method. We create a realistic simulated lens sample and test how uncertainties in redshift and velocity dispersion measurements affect results under ideal, optimistic, and pessimistic scenarios. We find that increasing the sample size from 100 to 10,000 systems dramatically improves precision: in the $\Lambda$CDM model, the uncertainty on the matter density parameter, $\Omega_m$, drops from 0.2 to 0.01; in the $w$CDM model, the uncertainty on the dark energy equation of state, $w$, decreases from 0.3 to 0.04. With 10,000 lenses, our constraints on dark energy are twice as tight as those from the latest DESI BAO measurements. We also compare two parameter estimation techniques – MultiNest sampling and Bayesian Hierarchical Modeling (BHM). While both achieve similar precision, BHM provides more robust estimates of intrinsic lens parameters, whereas MultiNest is about twice as fast. This work establishes an efficient and scalable framework for cosmological analysis with next-generation strong lensing surveys.
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All authors Hengyu Wu, Yun Chen, Tonghua Liu, Xiaoyue Cao, Tian Li, Hui Li, Nan Li, Ran Li, Tengpeng Xu

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Gravitational-wave dispersion over inhomogeneous space-times: General relativity, screened theories of gravity and non-minimal dark energy

Nicola Menadeo, Serena Giardino and Miguel Zumalacárregui

Gravitational waves (GWs) are direct probes of cosmological gravity, sensitive to space-time inhomogeneities along their propagation. The presence of massive objects breaks homogeneity and isotropy, allowing for new interactions between different GW polarizations, and opening up the intriguing opportunity to test modified gravity theories. This setup generalizes the notion of gravitational deflection and lensing, revealing novel phenomena in modified theories. Any non-minimal theory introduces effective mass terms for GWs, causing lens-induced dispersion (LID), a frequency-dependent phase shift on the waveform. We compute GW dispersion in Einstein's general relativity (GR) for a spherical matter distribution, finding a small but non-zero phasing that is potentially accessible to next-generation detectors. We then extend our analysis to scalar-tensor theories, focusing on symmetron gravity as an example of screened theory, combining cosmological deviations and consistency with local gravity tests. We find enhanced GW dispersion in a large region of the symmetron parameter space, compared to both GR and Brans-Dicke theory. We argue that dispersion, associated to an effective mass for the metric fluctuations, can in some cases prevent the propagation of GWs through some astrophysical bodies, turning them into reflectors. Our analysis shows that the Earth becomes an efficient GW shield for a hitherto unconstrained region of the symmetron parameter space, leading to a $\sim 50\%$ fraction of events becoming unobservable or at least displaying a dramatic modification of the detector antenna response. The richness and universality of dispersive phenomena in non-minimal theories open a new avenue to test theories of dynamical dark-energy, relevant in light of recent observational results challenging the $\Lambda$CDM paradigm.
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High Energy Astrophysical Phenomena

Entropy-based classification of core-collapse supernova gravitational waves for nuclear equation-of-state inference

Aknur Sakan, Nurzhan Ussipov, Y. Sultan Abylkairov et al. (+6 more)

Gravitational waves from core-collapse supernovae provide a unique probe of the physical processes occurring during stellar collapse and of the properties of dense nuclear matter. In this work we investigate the classification of supernova gravitational-wave signals associated with different nuclear equations of state using an entropy-based machine learning framework. The analysis combines signal decomposition, feature extraction, and feature selection techniques to identify informative characteristics of the waveforms and distinguish between different equation of state models. We evaluate the performance of several machine learning classifiers using a compact set of selected features and assess their robustness in the presence of detector noise. We find that entropy-based representations capture the underlying differences between waveform classes and enable accurate classification while maintaining better performance compared to raw data under noisy conditions. These results demonstrate the potential of complexity-based feature extraction as an efficient and interpretable approach for gravitational wave studies of core-collapse supernovae.
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All authors Aknur Sakan, Nurzhan Ussipov, Y. Sultan Abylkairov, Marat Zaidyn, Alisher Zhunuskanov, Almat Akhmetali, José A. Font, Matthew C. Edwards, Ernazar Abdikamalov

Instrumentation and Methods for Astrophysics

Towards direct imaging and orbital parameter estimation of supermassive black hole binaries with spaceborne VLBI

B. Hudson, L. I. Gurvits, E. Mooij et al. (+2 more)

Direct observation of the orbital motion of a sub-parsec supermassive black hole binary (SMBHB) would provide the first conclusive electromagnetic proof of such systems existing. Widely considered to be the source of gravitational waves, binaries are expected to form as a natural consequence of galactic mergers, and determining the processes that drive their evolution is essential to understanding cosmological evolution. In this work, we evaluate the prospects of using ground and spaceborne Very Long Baseline Interferometry (VLBI) to observe SMBHBs and estimate their orbital parameters. The Black Hole Explorer (BHEX) is considered the primary case study. Achieving unprecedented resolution, BHEX will provide access to a new volume of binary parameter space, potentially enabling the first confident detection of an SMBHB. We present an orbit-fitting approach that uses relative astrometry and Bayesian dynamic nested sampling, and demonstrate its efficacy on a set of example binary systems. For simulating observations, we use a binary image model based on post-Newtonian orbit propagation and find that for BHEX, binary detection requires a total flux density of 40 mJy and a minimum separation of $\sim$2 $\mu$as. With three annual observations, BHEX could constrain the semi-major axis and the eccentricity of binaries with orbital periods of $\leq$10 years to within 0.06 dex of the true values under specific noise assumptions. We have also evaluated the benefits provided by BHEX for binary detection compared to ground-only observations by arrays such as the next generation Event Horizon Telescope (ngEHT). Finally, we constrained the requirements of a future spaceborne VLBI system capable of performing a statistically significant survey of SMBHBs.
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All authors B. Hudson, L. I. Gurvits, E. Mooij, A. Ricarte, D. Palumbo

Cosmology and Nongalactic Astrophysics

Spectral distortions in the decaying QCD dark matter scenario

Jorge Mastache and Raúl Henriquez-Ortiz

We study the QCD–DM scenario by analyzing the imprint of energy injection from decaying dark-sector particles on the spectral distortions (SDs) of the Cosmic Microwave Background (CMB). We adopt a unified framework capable of describing both relativistic and non-relativistic particles, as well as fast and slow decay regimes. Within this approach, we model exponential, power-law, oscillatory, and two-step decays, computing the resulting $\mu$- and $y$-type distortions across the parameter space spanned by the confinement scale $a_c$, decay rate $\Gamma_\chi$, energy-transfer efficiency $\Sigma_\chi$, and velocity $v_{\chi c}$. We find that power-law, oscillatory, and cascade decays can be effectively mapped onto exponential models with appropriate rescaling. The dominant factors controlling SDs are the decay epoch and lifetime, with $v_{\chi c}$ becoming relevant only in the ultra-relativistic limit. FIRAS observations impose tight constraints on early energy injection, with $\mu$-type distortions placing the strongest bounds on $\Sigma_\chi$. Simultaneous matching of both $\mu_{\rm firas}$ and $y_{\rm firas}$ breaks the degeneracy between $\Gamma_\chi$ and $\Sigma_\chi$, localizing preferred decay rates around $\Gamma_\chi \lesssim (3.3-4.4)\times10^{-3}~{\rm yr}^{-1}$ and $\Sigma_\chi \lesssim 8.5\times10^{-4}$ for relativistic particles, while fast decays with $\Gamma_\chi \gtrsim 6.5~{\rm yr}^{-1}$ become observationally negligible. Our results show that CMB spectral distortions are a powerful probe of dark-sector dynamics. Future missions such as PIXIE or PRISM could extend current limits by several orders of magnitude and test previously inaccessible regions of parameter space.
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Instrumentation and Methods for Astrophysics

In-Orbit GRB Identification Using LLM-based model for the CXPD CubeSat

Cunshi Wang, Zuke Feng, Difan Yi et al. (+12 more)

To validate key technologies for wide field-of-view (FOV) X-ray polarization measurements, the Cosmic X-ray Polarization Detector (CXPD) CubeSat series has been developed as a prototype platform for the Low-Energy X-ray Polarization Detector (LPD) onboard the POLAR-2 mission. The wide-FOV design significantly increases the complexity of the background environment, posing notable challenges for real-time gamma-ray burst (GRB) identification. In this work, we propose an in-orbit GRB identification method based on machine learning, using simulated spectral data as input. A training dataset was constructed using a Geant4-based simulator, incorporating in-orbit background and GRB events modeled within the 2-10 keV energy range. To meet the computational constraints of onboard processing, we employ a multimodal large language model (MLLM), which is fine-tuned using low-rank adaptation (LoRA) based on miniCPM-V2.6 and quantized to 4-bit precision. The model achieves perfect classification accuracy on validation data and demonstrates strong regression performance in estimating GRB spectral indices, with an RMSE of 0.118. Furthermore, we validate the feasibility of onboard deployment through a simulated satellite data processing pipeline, highlighting the potential of our approach to enable future real-time GRB detection and spectral analysis in orbit.
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All authors Cunshi Wang, Zuke Feng, Difan Yi, Yuyang Li, Lirong Xie, Huanbo Feng, Yi Liu, Qian Liu, Yang Huang, Hongbang Liu, Xinyu Qi, Yangheng Zheng, Ali Luo, Guirong Xue, Jifeng Liu

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Detecting Parity-Violating Gravitational Wave Backgrounds with Pulsar Polarization Arrays

Qiuyue Liang, Kimihiro Nomura and Hidetoshi Omiya

Pulsar timing arrays probe isotropic stochastic gravitational wave (GW) backgrounds in the nanohertz band but are insensitive to its parity-violating component. Motivated by recent progress in pulsar polarization arrays, we study the response of pulsar polarimetry to GWs and evaluate its potential to detect circular polarization in isotropic stochastic GW backgrounds, which characterizes parity violation. Based on geometric optics, we derive the rotation of the polarization of electromagnetic waves induced by propagation through a GW background. We show that the cross-correlation between pulsar timing and polarimetry signals isolates the circular polarization component from the GW intensity, sharing the same Hellings-Downs angular pattern. With future facilities such as the SKA, timing-polarimetry correlations could reach sensitivities to the circular polarization of GWs comparable to those of the current astrometric methods.
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Astrophysics of Galaxies

A Modified 3D Biconical Outflow Model: Spatial Constraints on AGN-driven Outflows

Changseok Kim and Jong-Hak Woo

We present a modified outflow model and its application to constrain ionized outflow properties of active galactic nuclei (AGNs). By adding a rotating disk component to the biconical outflow model of Bae & Woo, we find that models with a rotating disk require faster launching velocities ($\lesssim$ 1500 km s$^{-1}$) than outflow-only models to be consistent with the observed gas kinematics of local type 2 AGNs. We perform Monte Carlo simulations to reproduce the observed distribution of gas kinematics of a large sample ($\sim$ 39,000), constraining the launching velocity and opening angle. While the launching velocity is moderate for the majority of the local AGNs, the notable cases of 2 - 5 % show strong outflows with $V_{max} \sim 1000-1500$ km s$^{-1}$. By examining the seeing effect based on the mock integral field unit data, we find that the outflow sizes measured based on velocity widths tend to be overestimated when the angular size of the outflow is comparable to or smaller than the seeing. This result highlights the need for more careful treatments of the seeing effect in the outflow size measurement, yet it still supports the lack of global feedback by gas outflows for local AGNs.
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High Energy Astrophysical Phenomena

Could the stochastic gravitational wave background from newborn magnetars be detected by the advanced LIGO and Einstein Telescope?

Yu-Long Yan, Quan Cheng, Xiao-Ping Zheng et al. (+1 more)

Newborn magnetars are important gravitational wave sources due to their ultra-strong magnetic fields and fast spins, and the entire population in the Universe may significantly contribute to the stochastic gravitational wave background (SGWB). In this work, we investigate the SGWB from newborn magnetars and assess its detectability by the advanced LIGO (aLIGO) and Einstein Telescope (ET) based on three typical formation mechanisms of magnetars, i.e., the $\alpha-\Omega$ dynamo, convective dynamo, and magnetic flux conservation. For the two dynamo scenarios, when calculating the SGWB, we creatively incorporate the anti-correlations between the magnetic fields and initial spin periods $P_{\rm i}$ with the initial dipole-field distribution of newborn magnetars. For the flux-conservation scenario, a bimodal lognormal form is adopted to describe the distribution of initial dipole fields, and all magnetars are assumed to have the same $P_{\rm i}$. Our results show that the SGWB from newborn magnetars may be undetectable by the aLIGO and ET if the magnetars are formed due to these mechanisms since the signal-to-noise ratio of the SGWB with respect to the ET for an observation time of one year is only 0.37 for the $\alpha-\Omega$ dynamo, $3\times10^{-4}$ for the convective dynamo, and at most 0.21 for the flux conservation.
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All authors Yu-Long Yan, Quan Cheng, Xiao-Ping Zheng, Xiao-Yue Yu

Cosmology and Nongalactic Astrophysics

JWST Lensed Quasar Dark Matter Survey III: Dark Matter Sensitive Flux Ratios and Warm Dark Matter Constraint from the Full Sample

R. E. Keeley, A. M. Nierenberg, D. Gilman et al. (+24 more)

We present the full sample of measurements of the warm dust emission of 31 strongly-lensed, multiply imaged quasars, observed with JWST MIRI multiband imaging, which we use to constrain the particle properties of dark matter. The strongly lensed warm dust region of quasars is compact and statistically sensitive to a population of dark matter halos down to masses of $10^6$ M$_\odot$. The high spatial resolution and infrared sensitivity of MIRI make it uniquely suited to measure multiply imaged warm dust emission from quasars and thus to infer the properties of low-mass dark halos. We use the measured flux ratios to test for a warm dark matter turnover in the halo mass function. To infer the dark matter parameters, we use a forward modeling pipeline which explores dark matter parameters while also accounting for tidal stripping effects on subhalos, globular clusters, and complex deflector macromodels with $m=1, m=3, \text{ and } m=4$ elliptical multipole moments. Adopting a comparable prior on the projected density of substructure to our previous analyses, the data presented here provide a factor of 2 improvement in sensitivity to a turnover in the halo mass function. Assuming subhalo abundance predicted by the semi-analytic model galacticus we infer with a Bayes factor of 10:1, a half-mode mass $m_{\rm{hm}} < 10^{7.8} M_{\odot}$ (m>5.6 keV for a thermally produced dark matter particle). If instead we use a prior from N-body simulations, we infer $m_{\rm{hm}} < 10^{7.6} M_{\odot}$ (m>6.4 keV). This is one of the strongest constraints to date on a turnover on the halo mass function, and the flux ratios and inference methodology presented here can be used to test a broad range of dark matter physics.
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All authors R. E. Keeley, A. M. Nierenberg, D. Gilman, T. Treu, X. Du, C. Gannon, P. Mozumdar, K. C. Wong, H. Paugnat, S. Birrer, M. Malkan, A. J. Benson, K. N. Abazajian, T. Anguita, V. N. Bennert, S. G. Djorgovski, S. F. Hoenig, A. Kusenko, H. R. Larsson, T. Morishita, V. Motta, L. A. Moustakas, W. Sheu, D. Sluse, D. Stern, M. Stiavelli, D. Williams

Earth and Planetary Astrophysics

The formation and structure of iron-dominated planetesimals

Terry-Ann Suer, Edgar S. Steenstra, Simone Marchi et al. (+2 more)

Metal-rich asteroids and iron meteorites are considered core remnants of differentiated planetesimals and or products of oxygen-depleted accretion. Investigating the origins of iron-rich planetesimals could provide key insights into planet formation mechanisms. Using differentiation models, we evaluate the interior structure and composition of representative-sized planetesimals (approx. 200 km diameter) while varying oxygen fugacity and initial bulk meteoritic composition. Under the oxygen-poor conditions that likely existed early in the inner regions of the Solar System and other protoplanetary disks, core fractions remain relatively consistent across a range of bulk compositions (CI, H, EH, and CBa). Some of these cores could incorporate significant amounts of silicon (10-30 wt percent) and explain the metal fractions of Fe-rich bodies in the absence of mantle stripping. Conversely, planetesimals forming under more oxidizing conditions, such as beyond snow lines, could exhibit smaller cores enriched in carbon, sulfur (more than 1 wt percent), and oxides. Sulfur-rich cores, like those formed from EH and H bulk compositions, could remain partly molten, sustain dynamos, and even drive sulfur-rich volcanism. Additionally, bodies with high carbon contents, such as CI compositions, can form graphitic outer layers. These variations highlight the importance of initial formation conditions in shaping planetesimal structures. Future missions, such as NASA's Psyche mission, offer an opportunity to measure the relative abundances of key elements (Fe, Ni, Si, and S) necessary to distinguish among formation scenarios and structure models for Fe-rich and reduced planetesimals.
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All authors Terry-Ann Suer, Edgar S. Steenstra, Simone Marchi, John A. Tarduno, Ilaria Pascucci

High Energy Astrophysical Phenomena

Kerr Polarization Transport: Accuracy and Performance in General Relativistic Light Propagation

Shakibul Chowdhury

We present a compact and reproducible method for general relativistic polarization transport in the Kerr metric that achieves median electric vector position angle (EVPA) residuals of $\langle \Delta \mathrm{PA} \rangle \approx 0.09^\circ$, a 95th percentile of $0.31^\circ$, and a worst case $\Delta \mathrm{PA} \lesssim 0.32^\circ$ for spins up to $|a/M|=0.9$, while maintaining a fivefold or greater speedup relative to a strict reference integrator. Across the benchmark grid, typical residuals remain at the sub-tenth-degree level, with only modest degradation ($\Delta \mathrm{PA} \lesssim 2^\circ$) near the Thorne spin limit. Photon four-momenta $k^\mu$ and polarization four-vectors $f^\mu$ are advanced using a fourth order Runge-Kutta scheme with cached Christoffel symbols, maintaining the constraints $u\cdot f=0$ and $n\cdot f=0$, where $u^\mu$ is the ZAMO four-velocity and $n^\mu$ is the disk normal, while keeping $k\cdot f \simeq 0$. A physically motivated gauge is enforced by projecting the polarization into the local zero-angular-momentum observer (ZAMO) screen at every substep, ensuring numerical stability of the orthogonality constraints. Accuracy and performance are benchmarked over a representative grid in spin, inclination, image-plane azimuth, and radius. The method comfortably meets IXPE and NICER polarization tolerances and approaches EHT requirements. The approach provides a practical foundation for future general relativistic polarimetry and simulation pipelines.
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