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Physics Astrophysics

astro-ph Watch Astrophysics

Sunday 20 September

Astrophysics of Galaxies

Hierarchical Dynamics within Molecular Clouds: Type 4 Scaling Relations of Molecular Clouds in the Second Galactic Quadrant

Suziye He, Yuehui Ma, Xuepeng Chen et al. (+4 more)

We present a statistical study of the hierarchical structure of molecular clouds in the second quadrant of the Galactic midplane (139.75 deg <= l <= 159.75 deg, -5.25 deg <= b <= 8.25 deg), based on high-sensitivity 12CO and 13CO J = 1-0 data from the Milky Way Imaging Scroll Painting survey. Using DBSCAN and a non-binary Dendrogram algorithm, we identify 2,912 13CO clouds. Type 2 (multicloud, single-tracer) scaling relations show arm-dependent trends: the power-law index of the linewidth-size relation is about 0.32 in the Local Arm and about 0.42 in the Perseus and Outer Arms. The classical Keto-Heyer relation is weak in the Local Arm but present in the Perseus and Outer Arms, with a slope of about 0.3. The virial parameter is anti-correlated with cloud size, mass, and surface density, consistent with previous surveys. Type 4 (single-cloud, single-tracer) scaling relations exhibit stronger internal correlations. The linewidth-size index spans about 0.3-0.8 and correlates positively with sonic Mach number, indicating that the relation is not universal but depends on cloud compressibility. While substructures do not follow the conventional surface-density-based Keto-Heyer relation, a volume-density formulation restores a clear virial scaling, with evolutionary tracks aligning along lines of constant virial parameter. Moreover, the structural complexity of molecular clouds, characterized by the relationship between the number of substructures and the min_delta parameter, correlates with surface density rather than sonic Mach number, contrary to results from turbulence-only magnetohydrodynamic simulations. Together, these results are more consistent with a gravity-regulated hierarchical dynamical picture than with a purely turbulence-supported scenario.
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All authors Suziye He, Yuehui Ma, Xuepeng Chen, Hongchi Wang, Miaomiao Zhang, Zhenyi Yue, Xiangyu Ou

Astrophysics of Galaxies

Tracing Interstellar Gas in Quiescent Galaxies Using Na I D and Ca II H&K Absorption

Arian Moghni, Timothy M. Heckman, Namrata Roy et al. (+3 more)

For over two decades, Na I D ($\lambda \lambda5891.58, 5897.56$ Å) absorption has been the primary optical tracer of cool, neutral gas in galaxies. In contrast, Ca II H&K ($\lambda \lambda$3934.78, 3969.59 Å), which traces both neutral and ionized gas, has been comparatively unexplored. Here, we present a comparative study of the Na I D and Ca II H&K interstellar absorption lines using spatially resolved MaNGA IFU spectroscopy of 140 red geyser galaxies (local quiescent systems hosting low-luminosity AGN with bisymmetric ionized outflows) and a control sample of 140 quiescent galaxies. Using Gaussian fits to the Na I D and Ca II K lines, we measure gas velocity and dispersion. We find that the Ca II reservoirs are up to ~ 6 times larger in area, twice as radially extended, and have ~ 1.7 - 1.8x broader line widths than Na I D. Furthermore, Na I D shows a direct dependence on dust reservoir size, but the correlation vanishes for Ca II. In only ~ 20% of galaxies do the Na I D detections extend beyond dust regions, but this fraction jumps to ~70% for Ca II. Using these findings, we argue that dust plays a significant role in shielding Na I D from ionizing radiation, whereas Ca II, with its higher ionization potential, is not as dependent on shielding and can more easily survive beyond regions of dust. Na I D and Ca II trace distinct gas components, and studying both together provides a more complete picture of gas flows in galaxies.
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All authors Arian Moghni, Timothy M. Heckman, Namrata Roy, Kyle B. Westfall, Kevin Bundy, Kate H. R. Rubin

High Energy Astrophysical Phenomena

A dynamic magneto-ionic environment around a long-period radio transient

Botao Li, Yongjie Jin, Shike Qu et al. (+5 more)

Faraday rotation provides one of the most direct probes of magnetized plasma along the line of sight, from the large-scale Galactic magnetic field to compact plasma environments local to radio sources. In particular, temporal variations in rotation measure can trace changes in the density, magnetic-field strength, or geometry of the Faraday-rotating medium, as observed in radio pulsars and fast radio bursts. Long-period radio transients (LPTs), a recently identified class of coherent radio sources with periods of hundreds to thousands of seconds, remain poorly explored because their physical nature is still uncertain. Here we present full-Stokes observations of the 421-s LPT source CHIME J0630+25 and report, for the first time, extreme rotation measure (RM) variability from approximately -400 to -1630 rad m^-2. The rapid RM changes occur on short timescales, including a difference of approximately 50 rad m^-2 between two consecutive rotation periods and a sudden change of approximately 536 rad m^-2 within approximately 2500 s. Compared with other radio-emitting sources, CHIME J0630+25 occupies an unusual region of the DM-RM plane: despite its very small DM of approximately 22 pc cm^-3, |RM| reaches over 1.6 x 10^3 rad m^-2, far exceeding that expected from the interstellar medium and pulsars. The fast and large-amplitude RM variations should arise from a compact, structured, and rapidly evolving magneto-ionic environment local to the source, possibly associated with a compact binary system.
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All authors Botao Li, Yongjie Jin, Shike Qu, Chaohua Gao, Wei Wang, Pei Wang, Shumei Jia, Jifeng Liu

Saturday 19 September

Astrophysics of Galaxies

The assembly of bulge-dominated galaxies: two evolutionary channels traced through morphology, kinematics, and environment with a hybrid classification pipeline

R. Flores-Freitas, R. R. de Carvalho, K. V. Nedkova et al. (+3 more)

We investigate the physical origin of the bimodality in bulge-dominated galaxies, originally identified by Sampaio et al. (2025), by combining non-parametric morphological metrics, structural scaling relations, stellar kinematics, and environmental trends across a wide redshift range ($0.2 < z < 2.4$). Using the MEGG-based hybrid classification pipeline applied to CANDELS imaging, we examine the distributions of morphological metrics for two families of bulge-dominated galaxies: G1, with high specific star formation rate (sSFR) distributions, similar to discs, and G2 with lower sSFR. We find that G1 galaxies occupy an intermediate position between discs and G2 spheroids in morphological metrics, and this behaviour persists up to $z = 1.4$. Fitting the Kormendy relation separately for each family, we find a persistent offset in the zero-point across all redshifts: G2 galaxies are systematically brighter in mean effective surface brightness at fixed effective radius, likely indicating higher central stellar densities. This offset is present in both observed and rest-frame magnitudes, and we argue that it reflects a genuine difference in assembly history. A cross-match with MUSE observations reveals that G1 galaxies have higher projected angular momentum than G2 galaxies, with G1 galaxies overlapping with the disc population, while G2 galaxies are more dispersion-dominated. The redshift evolution of morphological fractions shows that, at high stellar masses, the G2 fraction grows, while discs follow the opposite trend. In parallel, G1 remains a stable, lower-mass population consistent with secular bulge growth. Finally, within galaxy clusters, G1 galaxies are preferentially found at larger cluster-centric radii, suggesting that high-density environments amplify the bimodality by accelerating quenching.
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All authors R. Flores-Freitas, R. R. de Carvalho, K. V. Nedkova, I. Ferreras, I. Kolesnikov, V. M. Sampaio

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Renormalized Dynamical Friction in Black-Hole Spacetimes

Jordan Wilson-Gerow

We derive the renormalized local equation of motion for the gravitational self-force on a compact object moving through matter in a black-hole spacetime. We integrate out the environment and metric perturbations on a Schwinger–Keldysh contour, obtaining a causal effective action given by a sum of curved-spacetime Feynman diagrams organized by powers of the mass ratio and environmental density. At leading order, an environmental wake gravitationally backreacts on the worldline. The corresponding diagram contains a logarithmic ultraviolet divergence that renormalizes the leading dissipative fluid–particle coupling. We isolate the divergence with a local large-momentum expansion, in which the curved-spacetime retarded Green's function reduces to its flat tangent-space form. We translate the resulting singularity into a Barack–Ori mode-sum scheme, deriving an analytic puncture and regularization parameters for an ideal-fluid environment. Mode subtraction fixes the divergent part but not the finite Wilson coefficient. For collisionless dust, we determine this coefficient by matching to an exact near-zone calculation for a black hole moving through the medium. This gives a complete renormalization prescription suitable for numerical self-force calculations.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Charged particles and QPO constraints in tidal charge black hole magnetosphere sourced by a current loop

Ozodbek Abdurakhmonov, Javlon Rayimbaev, Inomjon Ibragimov et al. (+3 more)

We investigate the dynamics of charged particles in the dipolar electromagnetic field generated by a stationary current loop around a static black hole in the Randall–Sundrum braneworld model. The current loop is located at the innermost stable circular orbit (ISCO) of the tidal charged black hole, and the azimuthal electromagnetic four-potential is obtained as an exact analytical solution of the Maxwell equations in the curved background. Starting from the Hamilton–Jacobi equation, we derive the effective potential for charged particle motion in both the interior and exterior regions of the current loop, and analyze the dependence of the ISCO radius, angular momentum, energy, and orbital frequency on the tidal charge parameter $b$ and the magnetic coupling parameter $\omega$. We further compute three fundamental frequencies and show that the dipolar loop field revives a nonzero nodal precession frequency even though the background is static and non-rotating. Using these frequencies we construct five twin-peak QPO models (RP, WD, and ER2–ER4) and perform a Markov chain Monte Carlo (MCMC) analysis to constrain the braneworld parameters $(b,\omega)$ from the observed twin-peak QPO frequencies of six black hole sources spanning three mass regimes: GRO~J1655–40, XTE~J1550–564, GRS~1915$+$105, H~1743$+$322, M82~X-1, and Sgr~A$^{*}$. Adopting the epicyclic-resonance ER4 model as the representative framework, we find moderate, non-negligible tidal charges $b\simeq0.3$–$1.0$, while the magnetic coupling remains consistent with zero, $|\omega|\lesssim0.05$. Our results therefore place upper bounds on the tidal charge and on the magnetic coupling strength from astrophysical QPO data.
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All authors Ozodbek Abdurakhmonov, Javlon Rayimbaev, Inomjon Ibragimov, Sherzod Djumanov, Nuraliev Farhod, lkhomjon Makhmudov

Astrophysics of Galaxies · Cross-listed from physics.plasm-ph

Scalar Dissipation Criticality in Compressible Magnetized Turbulence

Svitlana Mayboroda, David N. Spergel and Camillo De Lellis

We extend the Obukhov-Corrsin theory of scalar turbulence to compressible flows with spatially variable, anisotropic diffusivity. Combining density and diffusivity into a single positive matrix field, a transport landscape, permits an exact scale-by-scale balance in which the sign-indefinite commutator between filtering and diffusion is eliminated rather than estimated. If the density-weighted third-order velocity and scalar increments scale as $\ell^\alpha$ and $\ell^\beta$, respectively, we prove that anomalous scalar dissipation is impossible when $\alpha+2\beta>1$. Remarkably, this threshold is independent of the anisotropy and spatial regularity of the diffusivity, provided it remains uniformly elliptic. Codimension-one shocks in both velocity and scalar have $\alpha=\beta=1/3$ and therefore lie exactly at the critical threshold. For statistically stationary turbulence we further obtain an exact density-weighted constant-flux relation, providing a compressible analogue of the relation underlying Yaglom's law. The results apply directly to passive-scalar transport in both gases and magnetized plasmas and provide testable diagnostics for simulations of compressible magnetohydrodynamic turbulence. Because the same operator governs anisotropic heat conduction, the results carry over to the electron temperature of a magnetized plasma, and they imply that gradient statistics in such flows must be contracted with the transport landscape rather than with the density.
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Earth and Planetary Astrophysics

Marginalized planet-to-star radius ratio posteriors for low-SNR transiting planets via dimensionality reduction

Oryna Ivashtenko and Barak Zackay

Occurrence rate estimates of small long-period planets rely on the radii of low signal-to-noise ratio transit candidates whose posteriors should be propagated into the population inference. These posteriors should include the error budget from all latent parameters and account for the effects of the correlated noise. Full Markov chain Monte Carlo fits with Gaussian processes take days of runtime per target, and provide information on latent parameters that will be marginalized over anyway. We present a method that computes the marginalized posterior of the planet-to-star radius ratio while sampling only a lower-dimensional effective parameter space. The 11-dimensional problem reduces to a 4-dimensional one, while the posterior retains the uncertainty budget of all the nuisance parameters, including eccentric orbits, stellar parameters, and limb darkening. The method operates on whitened light curves, mitigating biases due to correlated noise. We show that the posteriors are calibrated on simulated systems: the true radii have uniformly distributed p-values. Applied to 419 faint long-period Kepler Objects of Interest, the method yields radius ratios broadly consistent with the KOI table, although their differences exceed those expected from the reported uncertainties.
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Astrophysics of Galaxies

Surveying the Universe in 4D: Beating Cosmic Variance with Wide-Field Slitless Spectroscopy from HST, JWST, Euclid, Roman, and Beyond

Andreea Petric, Gaël Noirot, Stacey Alberts et al. (+71 more)

We summarize strategies, lessons learned, and future directions from the Space Telescope Science Institute workshop Surveying the Universe in 4D: Beating Cosmic Variance with Wide-Field Slitless Spectroscopy from HST, JWST, Euclid, Roman, and Beyond, held August 24–28, 2026. The workshop examined scientific results, observational and data analysis challenges, extraction tools, and future opportunities. Discussions highlighted (1) the transformative potential of WFSS for the study of transient phenomena, galaxy evolution –both spatially-resolved and within the broader context of the cosmic web–, and rare populations and (2) the synergies among Euclid and Roman surveys, Rubin-LSST monitoring, JWST WFSS, and high-resolution integral-field observations. Participants identified advances in forward modeling and physics-informed machine learning as essential for addressing spectral overlap, crowded fields, and upcoming, very large data volumes. Realizing WFSS's full potential will require community-wide infrastructure, science-ready data products, accessible cloud-based analysis tools, and robust benchmarking of reduction pipelines. Crucially, participants called for systemic changes to properly recognize early-career researchers who invest significant efforts in pipeline, code, and calibration developments that enable WFSS science, and stressed that progress requires collaborative, multidisciplinary practices that optimize the participation and benefits of the next generation.
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All authors Andreea Petric, Gaël Noirot, Stacey Alberts, Russell Ryan, Louis-Gregory Strolger, Vicente Estrada-Carpenter, Mainak Singha, Adrian E. Bayer, Olivier Gilbert, Farhanul Hasan, Mason Huberty, Bingcheng Jin, Xiangyu Jin, Anika Kumar, Kasra Mokhtarpour, Preethi Nair, Eleni Tsiakaliari, Vivian U, Brittany N. Vanderhoof, Arshia Akhtarkavan, Natalia Alvarez-Ibanez, Roman Fernandez Aranda, Tri L. Astraatmadja, Clive Binu, Claire Bolda, Westley Brown, Guillermo Romero Cruz, Mohamed H. Abdullah, Jeremy Favaro, Mason Footh, Helen Fraser, Yuming Fu, Annie Giman, Nicolas Gomez, Massimo Griggio, Peter Gwartney, Aryana Haghjoo, Fabian Hervas-Peters, Jiamu Huang, Sandra Jaison, Jeyhan S. Kartaltepe, Sarah Kendrew, Ivan Kramarenko, Sahana Kumar, Zhaoran Liu, Arianna S. Long, Sangeeta Malhotra, Faezeh Manesh, Jasleen Matharu, Vihang Mehta, Edward M. Molter, Ivelina Momcheva, Zhiwei Pan, Yuxuan Pang, Pallavi Patil, Rachel Plesha, Marc Rafelski, Mitchell Revalski, Jyotika Roychowdhury, Gregory Rudnick, Swetha Sankar, Maya Seagraves, Lu Shen, Sabnam Shrestha, Manuchehr Taghizadeh-Popp, Jo Taylor, Wei Leong Tee, Scott Tompkins, Feige Wang, Xin Wang, Isak Wold, Jerry J.-Y. Zhang, Qianqiao Zhou, Zihao Zuo

Astrophysics of Galaxies

Star formation and morphological trends in the Antlia cluster: Probing environmental influence out to 5R200

Ciria Lima-Dias, Antonela Monachesi, Gissel P. Montaguth et al. (+48 more)

Galaxy evolution in dense environments such as clusters is strongly affected by environmental processes that can alter both morphology and star formation activity. We investigate these effects in the Antlia cluster out to 5R200 using Southern Photometric Local Universe Survey (S-PLUS) data. We derive H-alpha-based star formation rates from the J0660 band and Sersic indices with GALFITM. Our analysis focuses on 154 spectroscopically confirmed galaxies brighter than mr = 16. We classify galaxies as early- or late-type systems using colour and Sersic index, and as quenched or star-forming using specific star formation rate. We examine their dependence on clustercentric distance, projected phase-space, substructure, and local density. We find that star-forming galaxies dominate from 1 to 5R200, while quenched galaxies are more common within 1R200. Early- and late-type galaxies show similar radial trends, with comparable fractions within 1R200 and a higher late-type fraction at larger radii. Quenched galaxies dominate at log(Sigma10 [Mpc^-2]) >= 1.5, whereas late-type galaxies dominate at log(Sigma10 [Mpc^-2]) <= 1.0. We identify substructures extending from the cluster centre to the outskirts. Substructures outside the central region are dominated by star-forming and late-type galaxies, with fractions similar to those of galaxies not associated with detected substructures. However, when the massive central structure is included, the fraction of star-forming galaxies in substructures decreases, indicating a more environmentally processed population in the central region. Altogether, the presence of a massive central substructure together with additional substructures detected out to 5R200 indicates that Antlia is still undergoing mass assembly through group accretion, consistent with a dynamically active and young cluster that is still assembling its galaxy population.
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All authors Ciria Lima-Dias, Antonela Monachesi, Gissel P. Montaguth, Rodrigo F. Haack, Daniela E. Olave-Rojas, Hugo Méndez-Hernández, Sergio Torres-Flores, Luis Otárola, Juan Pablo Calderón, Analía V. Smith Castelli, Yara L. Jaffé, Christopher P. Haines, Diego Pallero, Vitor M. Sampaio, Cristóbal Sifón, Alvaro Alvarez-Candal, María Argudo-Fernández, Simón Véliz Astudillo, Maiara S. Carvalho, Letizia P. Cassarà, Cheng Cheng, Arianna Cortesi, Ricardo Demarco, Alexis Finoguenov, Marcos Fonseca-Faria, Thiago S. Gonçalves, Eduardo Ibar, Iván Lacerna, Elismar Lösch, Angela C. Krabbe, Ulrike Kuchner, Erik V. R. Lima, Amanda R. Lopes, Vitor H. Lopes-Silva, Amrutha B. Manjunatha, Natanael M. Cardoso, Sebastián Ortiz-Gómez, Gustavo B. Oliveira Schwarz, Umberto Rescigno, Boudewijn F. Roukema, Nicolás Tejos, Eduardo Telles, Benedetta Vulcani, Stephane V. Werner, Laerte Sodré Jr, Fábio R. Herpich, Felipe Almeida-Fernandes, Antonio Kanaan, Tiago Ribeiro, William Schoenell, Claudia Mendes de Oliveira

Earth and Planetary Astrophysics

Searching for Embedded Protoplanets with the Keck/NIRC2 Vortex Coronagraph: Confirmation of a Core-accretion Planet in the Narrow Gap of the Elias 2-24 Disk

Andrea Bernardi, Alice Zurlo, Lucas A. Cieza et al. (+8 more)

We present high-contrast imaging observations of seven stars obtained with the Keck/NIRC2 vortex coronagraph between 2018 May and June in the $L'$ and $M_s$ bands. All targets host protoplanetary disks with substructures such as gaps and cavities, potentially tracing ongoing planet formation. Our aim is to assess whether these embedded planets can be directly detected. We reduced the observations with a custom pipeline based on the VIP Python package. Postprocessed images were obtained using angular differential imaging and reference differential imaging combined with principal component analysis. Finally, 5$\sigma$ contrast curves and detection limits were derived for all targets. We confirm the planetary candidate around Elias 2-24, previously proposed in the literature, at a separation of 394$\pm$31 mas (54.9$\pm4$.3 au) and a position angle of 298.8$\pm$3.2$^\circ$, within the narrow gap of the protoplanetary disk. Comparing the derived photometry with 1 Myr isochrones, we infer a mass between 1.9 and 4.0 Jupiter masses for Elias 2-24 b, without considering accretion effects, in agreement with estimates considering the properties of the gap and planet-disk interactions. For all the systems in the survey, the 5$\sigma$ detection limits reach sensitivities down to 1-11 Jupiter masses at separations $\gtrsim$0.25". Since Elias 2-24 b (age $\lesssim$1 Myr) is the youngest exoplanet discovered to date, its confirmation has important implications for planet formation timescales and the origin of the gaps observed in very young disks.
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All authors Andrea Bernardi, Alice Zurlo, Lucas A. Cieza, Garreth Ruane, Valentin Christiaens, Anuroop Dasgupta, Greta Guidi, Dimitri Mawet, Dino Mesa, Sebastián Pérez, Jonathan P. Williams

Earth and Planetary Astrophysics

Super-Earth Interiors Shrink by About 10% as They Crystallise

Tim Lichtenberg, Mara Attia, Harrison Nicholls et al. (+26 more)

Super-Earth exoplanets are among the most abundant planets known, yet their bulk densities leave the interior state degenerate. The static structure models used to interpret them, and the interior retrievals built on them, typically describe the cold, solidified end state of an evolution that begins hot and molten. During this magma ocean stage the interior, the outgassed atmosphere, and the surface co-evolve and set the long-term climate and geophysics of super-Earths. We develop and validate a fully coupled model for the structural and thermal evolution of super-Earth exoplanets within the PROTEUS framework, including new and upgraded models of the interior structure, mantle energetics, and volatile outgassing. In volatile-poor super-Earths of 1 to 10 Earth masses, the silicate interior contracts by about 10 % of its molten radius through cooling and crystallisation, nearly independent of planet mass and driven by the thinning silicate shell alone. The solidified radius is set by planetary mass and core fraction, insensitive to the host star, irradiation, and initial thermal state. In contrast, volatile-rich super-Earths at and above about 5 Earth masses may not solidify: their thick outgassed atmospheres throttle the surface heat loss until the interior settles into a deep magma ocean, keeping the planet inflated and limiting the contraction to about half its volatile-poor value. Mantle contraction alone thus shapes the low-mass exoplanet transit population, motivating joint interpretation of atmospheric and geophysical signatures in upcoming exoplanet surveys.
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All authors Tim Lichtenberg, Mara Attia, Harrison Nicholls, Mariana Sastre, Dan J. Bower, Karen Stuitje, Flavia C. Pascal, Laurent Soucasse, Daniel Apai, Patrick Bos, Robb Calder, Lorenzo Cesario, Lisa Dang, Emeline Decocq, Marijn van Dijk, Mohammad Farhat, Kaustubh Hakim, Tadahiro Kimura, Imre Kisvárdai, Sebastiaan Krijt, Yamila Miguel, Ioannis Panagiotou, Emma Postolec, Martin Schlecker, Sara Seager, Anat Shahar, Oliver Shorttle, Paolo A. Sossi, Wim van Westrenen

Astrophysics of Galaxies

Sulfur-bearing molecules in a sample of active star-forming cores

R. D. Taboada, N. C. Martinez, S. Paron et al. (+3 more)

Astrochemical processes involving sulfur are not yet well understood because cosmic sulfur reservoirs and the production pathways of sulfur-bearing species remain elusive. Addressing this, requires high-resolution interferometric observations capable of probing individual molecular cores. Following our previous study focused on early molecular cores, we are motivated to expand this investigation toward a sample of evolved cores to understand their chemical transition. We analyzed data from ALMA toward 16 molecular cores in massive star-forming regions associated with methanol masers, targeting the same six sulfur-bearing species studied in a previous work toward early molecular cores: SO, SO2, H2CS, SO+, NS, and 34SO. Column densities and abundances were derived assuming LTE, and temperatures were estimated from methanol transitions. Comparisons were made between the results obtained for the evolved cores and those previously obtained for the early ones. We find that the abundances of the sulfur-bearing molecules are higher in the evolved cores than in the early ones, confirming a general time-dependent enrichment of sulfur in the gas phase. While abundances increase within the 100-220 K range, their correlation with temperature weakens, suggesting that gas kinematics become increasingly more important in the sulfur chemistry. This evolutionary transition involves a chemical reorganization where SO2 becomes dominant. We confirm the validity of SO2/SO as a chemical clock, though chemical modeling reveals a discrepancy in sources with more pronounced kinematic processes, namely a steeper increase in the SO2/SO ratio. The line-width analysis of the molecular species indicates that core evolution and kinematics lead to a well-mixed gas, erasing the spatial stratification where different species trace distinct layers in the cores at earlier stages.
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All authors R. D. Taboada, N. C. Martinez, S. Paron, A. Petriella, M. E. Ortega, L. Supán

Cosmology and Nongalactic Astrophysics

Thermal-acoustic fermionic dynamics and primordial perturbations in warm Yukawa inflation

Xi-Bin Li, Ke Fu, Ya-Ting Wang et al. (+2 more)

We investigate fermion production and its cosmological consequences in a warm inflationary scenario with a Yukawa interaction between the inflaton field and Dirac fermions. Treating the produced fermions as a thermalized relativistic fluid, we derive the coupled perturbation equations incorporating dissipative effects and thermal fluctuations. By solving the resulting system through Green's function methods, we identify distinct contributions from thermal noise, thermal-acoustic propagation, and higher-order scattering processes to the scalar perturbations. We show that acoustic propagation of fermionic fluctuations becomes significant in the relativistic regime, where the competition between gravitational attraction and Pauli degeneracy pressure allows collective fermionic modes to influence the primordial spectrum. Furthermore, we calculate the fermion number density and acoustic velocity, revealing that strong Yukawa interactions enhance non-adiabatic fermion production and modify the thermodynamic properties of the fermion bath. The sourced scalar and tensor perturbations are calculated, indicating that fermion production can substantially amplify primordial fluctuations, particularly in the strong-coupling regime. Since scalar perturbations receive more efficient enhancement than tensor modes, the tensor-to-scalar ratio is suppressed relative to the standard single-field warm inflation prediction. Our results show that thermalized fermions provide an additional mechanism for modifying primordial perturbations and offer new insights into the role of particle production in warm inflationary cosmology.
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All authors Xi-Bin Li, Ke Fu, Ya-Ting Wang, De-Tian Zhao, Xiao-Min Zhang

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Energy-momentum-squared gravity: charged quark star solutions with unified interacting matter

Ayan Banerjee, Bobur Turimov, Javlon Rayimbaev et al. (+3 more)

We investigate the equilibrium structure of electrically charged quark stars within the framework of energy-momentum-squared gravity (EMSG), adopting a unified interacting quark-matter equation of state that incorporates perturbative QCD corrections, color superconductivity, and finite-strange-quark-mass effects. By solving the modified Tolman-Oppenheimer-Volkoff equations over a broad range of EMSG coupling strengths and interaction parameters, we show that the inclusion of electric charge substantially increases both the maximum mass and radius compared with neutral configurations. For strong negative couplings and pronounced interaction strengths, the resulting stellar models reach masses close to $3,M_{\odot}$ with compactness ratios of order $0.34$, placing them within the mass range inferred for the secondary component of GW190814, whose nature remains observationally undetermined. The presence of charge reduces the central density at maximum mass by approximately $10$–$15\%$ while maintaining full compliance with causality requirements. Furthermore, comparisons with observational constraints from PSR J1614$-$2230, J0348$+$0432, J0740$+$6620, J0952$-$0607, and recent NICER radius measurements indicate that charged EMSG configurations remain consistent with current astrophysical bounds over a wide parameter space. These results demonstrate that a moderate electric charge, when combined with nonlinear matter-geometry coupling, can support quark stars that are significantly more massive than those predicted in general relativity, underscoring the potential observational relevance of charged compact objects in modified gravity and multimessenger astrophysics.
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All authors Ayan Banerjee, Bobur Turimov, Javlon Rayimbaev, Faisal Javed, Gulnoza Palvanova, Sulton Usanov

Earth and Planetary Astrophysics

Optical Constants of Photochemical Haze Analogs in N2-CH4-CO Atmospheres from 0.4 to 28.6 {\mu}m

Zhengbo Yang, Chao He, Haixin Li et al. (+4 more)

Photochemical hazes play an important role in shaping the spectra and radiative balance of N2-dominated planetary atmospheres. We present newly acquired FTIR and retrieved optical constants (N=n+ik) of laboratory-generated haze analogs from N2/CH4 and N2/CH4/CO gas mixtures under plasma discharge conditions. The retrievals use particle densities newly measured for the CH4-series and previously published particle densities for the CO-series. The experiments systematically explored CH4 concentrations from 0.5% to 10% and CO concentrations from 0% to 5% with fixed 5% CH4. Using measured particle densities together with the Beer-Lambert law and subtractive Kramers-Kronig (SKK) relation, we derived optical constants over the 350-25000 cm-1 (0.4-28.6 {\mu}m) spectral range, with the 0.4-25 {\mu}m results presented in the main text. The infrared spectra reveal prominent absorption features associated with hydrocarbon-, nitrogen-, and oxygen-bearing functional groups. Increasing CH4 abundance enhances aliphatic hydrocarbon features and corresponds to decreasing particle density, whereas increasing CO abundance promotes oxygen incorporation, broader mid-infrared absorptions, and higher particle density. The derived k spectra exhibit strong absorptions near ~3 {\mu}m, ~4.6 {\mu}m, and ~6-10 {\mu}m, while the real refractive index n generally ranges from ~1.2 to 1.7. The controlled CH4- and CO-series establish composition-dependent variations in haze optical properties. A benchmark comparison among Titan-, Pluto-, and Triton-like haze analogs then uses these experimentally identified trends to interpret the optical differences among N2-dominated planetary haze compositions. The density and optical constants provide laboratory constraints for atmospheric radiative transfer models and for interpreting planetary and exoplanetary spectra from spacecraft and telescopes.
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All authors Zhengbo Yang, Chao He, Haixin Li, Sai Wang, Xiao'ou Luo, Yu Liu, Sarah M. Hörst

Earth and Planetary Astrophysics

Characterization of the Compact Multi-planet System TOI-789: Validation of Three Terrestrial Planets, Dynamical Characterization, and Detection of a Fourth Temperate Candidate

Juan F. Pagés Navarrete

We present the validation and dynamical characterization of TOI-789 (TIC 300710077), a compact multi-planet system around an M3 dwarf at 43 pc. Using ~7 yr of TESS photometry (42 sectors), public ground-based follow-up (LCOGT, MEarth), and high-resolution imaging (Gemini/Zorro, SOAR), we statistically validate three terrestrial planets with TRICERATOPS: TOI-789 b (Rp = 1.18 Rearth, P = 5.45 d), c (1.15 Rearth, 8.04 d), and d (1.40 Rearth, 12.97 d), with false-positive and nearby-false-positive probabilities below the validation thresholds once resolved neighbours are excluded using the on-target ground-based photometry. Through an iterative Transit Least Squares search we identify a fourth, previously uncatalogued planet candidate (P = 19.74 d, Rp ~ 0.88 Rearth), the outermost and most temperate member (S = 1.71 Searth, Teq ~ 292 K); its low signal-to-noise ratio precludes formal validation, so we report it as a candidate pending confirmation. A dynamical analysis (SPOCK and N-body integrations) indicates a dynamically cold, near-resonant system, stable only for low eccentricities (e < 0.05), eccentricity rather than mass limiting stability; including the fourth candidate tightens this further. The four objects span the Earth-Venus transition across the Venus zone, two validated planets falling in the temperate regime under the equilibrium-temperature criterion, making the system a potential comparative-planetology laboratory anchored on confirmed planets. The low TSM (~3-5) and moderate host brightness place atmospheric characterization beyond reach. TOI-789 exemplifies the numerically dominant population of compact terrestrial-planet systems around M dwarfs whose characterization is limited by host brightness, for which dynamical characterization offers a complementary route.
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Solar and Stellar Astrophysics

Distinct Population of Wolf-Rayet Stars in the Low-Metallicity Galaxy NGC 6822. Quantitative analysis of optical and UV spectra of the complete sample

R. Trigg, L. M. Oskinova, W.-R. Hamann et al. (+9 more)

Context: Wolf-Rayet (WR) stars are particularly rare in low-metallicity galaxies and remain poorly understood. Detailed studies of the presumably complete population of WR stars in the nearby Small Magellanic Cloud (SMC) galaxy led to perplexing results. Aims: The nearby galaxy NGC 6822 has a similar metallicity to the SMC, and hence provides an excellent laboratory for a comparative study. We aim to derive the stellar and wind parameters of each known WR star in NGC 6822 by means of quantitative spectroscopy. The results are compared with the WR population of the SMC. Methods: New optical and UV spectroscopic observations have been obtained with the Very Large Telescope (VLT) and Hubble Space Telescope (HST). We employ the Potsdam Wolf-Rayet (PoWR) model atmosphere code for our analysis, consistently fitting synthetic spectra to the observed spectral energy distribution, and optical and UV spectra. Results: We spectroscopically confirm all four stars in our sample belong to the nitrogen sequence with early subtypes (WN3-WN6). All stars show indications of binarity. Only one star in our sample has a high fraction of hydrogen in its atmosphere, as typical for the WN population in the SMC, and two other stars in our sample are hydrogen-free. Finally, the spectrum and parameters of the fourth object closely resemble those of the qWR-type strongly magnetic merger-product star in the HD 45166 binary. Conclusions: The stellar properties of our sample are diverse. We have identified the first H-free WN-type stars at metallicities $\sim$ 1/7Z$_\odot$. According to evolutionary calculations, the WR stars in NGC 6822 stem from progenitors with initial masses below 40 M$_\odot$. We report a discovery of a low luminosity stripped qWR star in NGC 6822, and conclude that the WR star population in NGC 6822 and the SMC are distinct despite similar metallicities of their host galaxies.
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All authors R. Trigg, L. M. Oskinova, W.-R. Hamann, H. Todt, D. Pauli, T. Shenar, A.A.C. Sander, M. Chatzis, A. Mang, R.R. Lefever, V. Ramachandran, D. Massa

High Energy Astrophysical Phenomena

Dark matter self-annihilation as a hidden energy source in white dwarfs

Alvin Cheuk-Nam Chu, Cheuk-Man Yiu, Ching-Hui Lam et al. (+3 more)

White dwarfs (WDs) are compact remnants of stars, supported by electron degeneracy pressure, and their structures are generally considered to be well understood. Significant discrepancies exist between the theoretical and observed white dwarf mass-radius (MR) relations, especially for hot Q-branch white dwarfs with unexplained heating sources. In this study, we explore the potential of WDs as a portal to dark matter (DM) physics by investigating the effect of self-annihilating DM (SADM) admixed in WDs, solving the set of two-fluid hydrostatic equilibrium and heat diffusion equations self-consistently. We obtain empirical formulae for the WD luminosity $L$ and effective temperature $T_\text{eff}$ as functions of the DM mass fraction $f_d$, annihilation cross section $\langle\sigma v\rangle$, and particle mass $m_\chi$, as well as the WD's total mass $M_t$. We also compare the WD MR relations for various $L$, $f_d$, and both Fermionic and Bosonic DM particle statistics, with the observational data. We show that the majority of observed deviations in the WD MR relation can be accounted for by having SADM admixed with $f_d \le 10^{-5}$ and $\langle\sigma v\rangle \ll 3\times10^{-26}$ $\text{cm}^3$ $\text{s}^{-1}$, the thermal relic cross section. Therefore, our results suggest that WDs can be sensitive DM detectors, and DM self-annihilation could provide additional heating in WDs, accounting for their observed extra luminosities.
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All authors Alvin Cheuk-Nam Chu, Cheuk-Man Yiu, Ching-Hui Lam, Peter Siu-Hei Cheung, Fong-Ching Ho, Ming-chung Chu

Astrophysics of Galaxies

The interplay between active galactic nucleus photoionization, radio jet, and star formation in the z $\sim$ 3.5 radio galaxy 4C +03.24

Bruno Dall'Agnol de Oliveira, Dominika Wylezalek, Pranav Kukreti et al. (+9 more)

High-redshift radio galaxies (HzRGs) are among the most powerful radio sources, and are associated with the most massive galaxies and dense environments at redshifts z $\gtrsim$ 1. They are ideal laboratories for studying how active galactic nucleus (AGN) events can shape the evolution of galaxies, as intense radiation, jets, and star formation can be observed simultaneously in these galaxies. We present JWST/NIRSpec integral field spectroscopy ($\sim$ 1.6 kpc spatial resolution) of the 4C +03.24 system, a powerful HzRG at z $\sim$ 3.5 with a bolometric luminosity of $\sim 10^{47.6}$ erg s$^{-1}$. We identified kinematically disturbed regions in the warm ($\sim 10^4$ K) ionized gas by decomposing the emission-line spectra into multiple Gaussian components, which is crucial to avoid overestimating the outflow properties. The outflow power peaks at $\sim$ 2 kpc away from the nucleus, with a corresponding low kinetic coupling efficiency of $\sim 8_{-5}^{+7} \times 10^{-3}$ %. A combined analysis of the rest-frame optical and ultraviolet (from VLT/MUSE and HST imaging) continua revealed an extended emission (spanning $\sim$ 14 kpc), which we interpret as partially tracing star-forming regions. With a clearly delineated bipolar morphology, we show that the AGN photoionization dominates the ionization of the interstellar medium along the radio jet axis. The [C II]$\lambda$158$\mu$m emission gap in this region might be direct evidence of negative AGN feedback. We also discuss a possible scenario where 4C +03.24 could be situated in an overdense environment experiencing multiple galaxy interactions and the possibility of jet-induced star-formation.
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All authors Bruno Dall'Agnol de Oliveira, Dominika Wylezalek, Pranav Kukreti, Wuji Wang, Rogério Riffel, Rogemar A. Riffel, Andrey Vayner, Caroline Bertemes, Julian T. Groth, David S. N. Rupke, Carlos De Breuck, Joël Vernet

Astrophysics of Galaxies

Mid-Infrared Diagnostics of PAH Processing and Radiation Fields in M33 H II Regions with JWST/MIRI

Puja Porel, Archana Soam and Saikhom Pravash

We present JWST/MIRI (Proposal ID 4297) medium-resolution integral field spectroscopy of five H II regions in the nearby spiral galaxy M33, obtained from the Mikulski Archive for Space Telescopes (MAST). The fully calibrated Level-3 spectral cubes provide continuous wavelength coverage from 6.5 - 20.9~$\mu$m, enabling analysis of polycyclic aromatic hydrocarbon (PAH) emission, ionic fine-structure lines, and warm molecular hydrogen. The spectra show prominent PAH bands at 7.7, 8.6, and 11.3~$\mu$m, multiple H$_2$ rotational transitions, and hydrogen recombination lines. H$_2$ rotational diagrams yield warm molecular gas temperatures of $\sim316$ - $407$~K. The detected [Ne II], [Ne III], [S III], and [S IV] lines yield ionization indices of $-1.41$ to $+0.98$. The PAH ionization fraction shows no clear dependence on radiation hardness, consistent with previous Spitzer results. Unlike previous work, we find no clear correlation between the 7.7/11.2 and 8.6/11.2~$\mu$m PAH ratios, while the 7.7/11.2~$\mu$m ratio shows a moderate negative correlation with metallicity, possibly due to our small sample ($N=5$). The PAH-to-VSG ratio decreases with increasing radiation hardness. We derive the ionization parameter $\gamma$, far-ultraviolet radiation field, and PAH charge state, finding a predominantly cationic PAH population ($\sim75%$) despite [Ne III]/[Ne II] $<1$. The lack of a one-to-one correspondence between $\gamma$ and the 7.7/11.2~$\mu$m ratio suggests that PAH ionization is influenced by additional environmental factors. Given the limited sample, these trends are suggestive rather than statistically definitive.
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Astrophysics of Galaxies

The magnetic field in the multi-phase interstellar medium of NGC 6946

Amir Yarahmadi, Fatemeh Tabatabaei, Golshan Ejlali et al. (+3 more)

Magnetic fields regulate the multi-phase interstellar medium (ISM) of spiral galaxies, yet their behavior across ISM phases remains poorly constrained observationally. We present a comparative polarimetric study of the nearby spiral galaxy NGC 6946 using far-infrared (FIR) data at 154 $\mu$m from SOFIA/HAWC+ and radio continuum data at 6 cm from the VLA and Effelsberg telescopes, which probe magnetic fields in the cold dust-emitting and diffuse synchrotron-emitting phases of the ISM, respectively. The synchrotron polarization reveals a coherent large-scale spiral magnetic field, with high polarization fractions in interarm regions and strong depolarization in star-forming arms. The FIR polarization fraction is lower on average and shows stronger spatial variations. Both tracers decrease systematically with increasing star formation activity, indicating that star-formation-driven turbulence reduces magnetic field ordering; the synchrotron polarization fraction is strongly suppressed in the central kiloparsec but stable across the mid disk, with a tendency to increase beyond $R \approx 7$ kpc, while the FIR polarization fraction remains low ($\sim$2-3%) and approximately constant over the radial range where it can be reliably measured ($R \lesssim 5.4$ kpc). Our results indicate that NGC 6946 hosts a globally ordered magnetic field locally modulated by turbulence. This study highlights the complementary nature of FIR and radio polarimetry in probing magnetic fields across ISM phases and provides quantitative constraints on how magnetic field ordering varies between the cold and diffuse ISM components.
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All authors Amir Yarahmadi, Fatemeh Tabatabaei, Golshan Ejlali, Rainer Beck, Enrique Lopez-Rodriguez, Alejandro Borlaff

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Gamma-Ray Echo as a Probe of Supernova Neutrino Emission Anisotropy and Long-Baseline Effects

Garv Chauhan, Cecilia Lunardini and Yago Porto

During a core-collapse supernova (CCSN), the emitted electron antineutrino ($\bar{\nu}_e$) burst initiates inverse beta decay (IBD) in the outer hydrogen layer of the stellar envelope. This leads to the production of a characteristic 511 keV photon signal, termed the Gamma-Ray Echo. The same neutrino burst, when detected on Earth in large neutrino observatories such as Hyper-Kamiokande, will offer information about the $\bar{\nu}_e$ content of the neutrino flux reaching Earth. In this work, we show that comparing the $\bar{\nu}_e$ content inferred from the gamma-ray echo with that inferred from terrestrial neutrino observations during a nearby CCSN event can offer a promising probe of large neutrino emission anisotropies and long-baseline propagation effects. In the latter case, the combined SN-Earth observations effectively act as a near-far detector configuration for neutrino propagation over an astrophysical baseline. We find that, for a near-Earth supernova, anisotropies or non-standard propagation effects at the level of tens of percent can be tested using gamma-ray telescopes with effective areas of $\mathcal{O}(10^4)~\mathrm{ cm^2}$. Therefore, our results motivate the development of the next generation of large effective area gamma-ray telescopes operating in the MeV gap.
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Solar and Stellar Astrophysics

Hard X-Ray Quasi-Periodic Pulsations in X-Class Solar Flares Observed by Aditya-L1/HEL1OS

Sachin Rajkapoor Kanaujiya, Ram Ajor Maurya, Swetha Gopinathan et al. (+1 more)

We present the catalogue of quasi-periodic pulsations (QPPs) detected in hard X-ray (HXR) observations of X-class solar flares obtained with the HEL1OS instrument onboard Aditya-L1 during July 2024 - March 2026. The catalogue comprises 34 flares spanning GOES classes X1.1 - X7.1. QPPs are detected and studied using a uniform procedure based on Ensemble Empirical Mode Decomposition (EEMD) and wavelet analyses. Statistically significant QPPs are identified in 25 events (~74%), demonstrating that QPPs are a common property of X-class flares. The detected periods range from approximately 1 to 3 min, with a pronounced concentration between 1.3 and 1.7 min, suggesting the existence of a preferential timescale that may be associated with kink or slow magnetohydrodynamic oscillations in the flaring region. The dominant periods remain nearly independent of photon energy across the 8 - 20 keV range, while the modulation depth increases systematically with photon energy following a power-law relation with an exponent of about 1.5. QPPs detected in different HXR energy channels exhibit strong phase coherence and positive cross-correlation coefficients, indicating modulation by a common physical mechanism. Several intense flares display HXR modulation depths of up to 25%, providing evidence for nonlinear effects. The observed statistical properties support models in which QPPs are generated by repetitive magnetic reconnection, either spontaneous or periodically modulated by magnetohydrodynamic oscillations. This study establishes HEL1OS as a powerful instrument for quantitative studies of flare QPPs during Solar Cycle 25.
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All authors Sachin Rajkapoor Kanaujiya, Ram Ajor Maurya, Swetha Gopinathan, Valery M. Nakariakov

Cosmology and Nongalactic Astrophysics

Feeding the Void: Co-evolution of the SIDM-seeded Black Hole and the dark halo after core-collapse

Zhichao Carton Zeng, Annika H. G. Peter, Louis E. Strigari et al. (+3 more)

While the gravothermal collapse of self-interacting dark matter (SIDM) halos provides a compelling mechanism for seeding supermassive black holes (BHs), the post-collapse macroscopic co-evolution of the BH and its host halo remains largely unexplored. In this paper, we introduce a novel N-body framework to dynamically model the dark matter accretion onto the central BH. By bracketing the accretion rate with two complementary phenomenological schemes—a `multi-round core-collapse' scenario and a `continuous accretion' scenario—we establish bounds on the BH mass growth trajectory. We find that the BH mass reaches $5\%-12\%$ of the total halo mass within $\lesssim2$ Gyr post-collapse. Concurrently, this sustained mass depletion drives a `gravothermal supply chain' that forces outer dark matter inward, severely depleting the inner halo density ($\lesssim 2r_s$). This unique structural imprint qualitatively matches the recently detected anomaly in the strong lens JVAS B1938+666 (detection V), where the best-fit lens model consists of an unresolved central point mass and a shallow, uniform-surface-density extended disk, offering a distinct observational signature for SIDM-seeded BHs.
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All authors Zhichao Carton Zeng, Annika H. G. Peter, Louis E. Strigari, Andrew Benson, Xiaolong Du, Charlie Mace

Astrophysics of Galaxies

Dust Growth in Evolving Filamentary Molecular Clouds: Signatures in Ionization, Resistivity, and Infrared Scattering

Hayato Uchimura, Yoshiaki Misugi, Daisuke Takaishi et al. (+4 more)

Studies of dust growth in molecular clouds often prescribe the collapse history, leaving unclear how magnetic regulation of core formation shapes dust evolution and its observable and non-ideal MHD signatures. We address this problem by performing one-zone dust evolution and ionization calculations along time-dependent density and magnetic-field histories extracted from three-dimensional non-ideal MHD simulations of core formation through filament fragmentation. A stronger initial magnetic field delays contraction and thereby gives dust grains more time to grow at a given density. In our models, this delayed contraction leads to mass-weighted mean dust sizes of $1.2\,\mu\mathrm{m}$ and $3.1\,\mu\mathrm{m}$ at $n_{\mathrm{H}}=10^6\,\mathrm{cm^{-3}}$ for $B_{\mathrm{ini}}=20$ and $50\,\mu\mathrm{G}$, respectively. The associated depletion of very small dust grains reduces the adsorption of charged particles onto dust grain surfaces and lowers the conductivity: relative to models without dust growth, the ionization fraction increases from $\sim10^{-9}$ to $\sim10^{-8}$, the ambipolar resistivity increases, and the ion–neutral drift velocity rises to several $\mathrm{m\,s^{-1}}$ in the weak-magnetic-field model and approximately $10\,\mathrm{m\,s^{-1}}$ in the strong-magnetic-field model. These drift velocities remain below the observationally suggested range of $30$–$100\,\mathrm{m\,s^{-1}}$, indicating that still stronger magnetic fields may be required. The evolved dust populations also attain single-scattering albedos of order $\omega_\lambda\sim0.8$ at $3.6$–$4.5\,\mu\mathrm{m}$, with the stronger field shifting the onset of efficient infrared scattering toward lower densities. These results demonstrate that the magnetically controlled collapse timescale, rather than density alone, links dust growth to ionization, ambipolar diffusion, and infrared scattering in prestellar cores.
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All authors Hayato Uchimura, Yoshiaki Misugi, Daisuke Takaishi, Taishi Tsuchiyama, Tomoki Tokunaga, Rintaro Shibakawa, Yusuke Tsukamoto

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Kaluza–Klein Dark-Photon Mediation of Inelastic Dark Matter at LUX-ZEPLIN

Waqas Ahmed and George K. Leontaris

We study a five-dimensional realization of endothermic dark matter motivated by the recent high-recoil LUX-ZEPLIN event. A pseudo-Dirac Standard-Model singlet fermion is localized in the extra dimension and couples to a bulk $U(1)_D$ gauge field. The same localization that suppresses a distant-brane Majorana operator and generates the inelastic splitting also controls the couplings to the Kaluza–Klein (KK) dark-photon tower, producing a localization-filtered mediator propagator. We organize the phenomenology around two representative mass–splitting points: an LZ benchmark, $m_\chi=1.10~\TeV$ and $\delta=365~\keV$, and an IceCube-motivated comparison point, $m_\chi=1.08~\TeV$ and $\delta=566~\keV$. The latter is used only to compare terrestrial and solar kinematics; the published IceCube bound is Higgsino-specific and is not directly imposed on our singlet KK model. At the LZ benchmark with $R^{-1}=0.30~\GeV$ and $m_0=0.10~\GeV$, the KK tower enhances the high-recoil xenon rate by a factor of about four relative to a single dark photon at fixed microscopic coupling. The LZ point lies just below the terrestrial halo speed ceiling, whereas the $566~\keV$ comparison point is inaccessible to ordinary xenon scattering and instead lies in a kinematic regime accessible to solar capture; any neutrino constraint on the present singlet model remains dependent on its capture and annihilation dynamics. The characteristic prediction of the extra-dimensional construction is therefore a correlated interplay of localization, KK spectral distortion, and inelastic kinematics.
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High Energy Astrophysical Phenomena

Stereoscopic gravitational-wave probe: Gravitational lensing of a binary merger in active galactic nuclei

Paul Martens, Samson H. W. Leong, Ryan Zhang et al. (+1 more)

Recent work has shown that, if a large fraction of the LIGO-Virgo-KAGRA compact binary coalescences (CBCs) occur in accretion disks around active galactic nuclei (AGNs), many such AGN-CBC systems will likely experience lensing and produce multiple gravitational-wave (GW) "images" of the CBCs that will become detectable with current or future GW detectors. However, the waveforms produced by such lensed "images" will differ from those produced by other lensing systems because the binary source is orbiting the AGN's central supermassive black hole at a close distance. Here, we show that these systems produce 2 snapshots of the same binary source from 2 different viewing angles. These differences in the effective viewing angle between the images are encoded in the GWs they emit, such that GW detectors can effectively analyse the waveforms from 2 viewpoints. Beyond such "multi-view lensing", the GW images may also differ by their Doppler shift due to the expected relativistic orbital motion of the source around the AGN, an effect which is further amplified by the proximity to the lens. If the AGN's own angular momentum can be related to the binary's orbital angular momentum, we can describe the entire AGN-CBC system using only one additional free parameter compared with a typical point-mass lens system, or with 3 additional parameters when we do not make such an assumption. In this work, we establish a framework of transformation rules that describe both the angles in the 2 points of view, and the Doppler effect that comes from the source's motion around the lens. We also provide the framework to produce consistent AGN-lensed waveforms from any currently available GW waveform. These AGN-CBC systems give 2 unique points of view on a binary merger thus opening up a new window into the merger's properties unlike any other lens system.
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All authors Paul Martens, Samson H. W. Leong, Ryan Zhang, Otto A. Hannuksela

Friday 18 September

Earth and Planetary Astrophysics · Cross-listed from physics.class-ph

Short-term solar eclipse predictions using Euclidean geometry and dynamical systems

Alin-Doru Aluas, Valerian-Alin Fodor and Virgilius-Aurelian Minuta

We propose a computationally inexpensive algorithm to determine whether an opaque spherical body eclipses a luminous one, using only classical geometrical tools. We apply this method to the Sun-Earth-Moon system and predict solar eclipses, including their type, beginning, and duration, using the three-body problem. For predictions over a one-year period, the resulting errors are in the order of minutes.
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Earth and Planetary Astrophysics

The Science Potential of Characterizing Gas Giant Exoplanets with HWO

Beck Dacus, Jean-Baptiste Ruffio, Quinn Konopacky et al. (+19 more)

With the ability to directly image Earth-like exoplanets and search their atmospheres for biosignatures, the upcoming Habitable Worlds Observatory (HWO) will also collect high signal-to-noise ratio (S/N) reflected-light photometry and spectra of nearby gas giant exoplanets. Such high-quality data would allow novel investigations into gas giant atmospheric composition, formation, and kinematic properties, and could enable the detection of exomoons around these planets. We use the EXOSIMS direct imaging mission simulator to model HWO observations of Jupiter-radius gas giants at Earth-like and Jupiter-like instellations around the 164 stars in the ExEP target list. We find that HWO should be able to achieve S/N $\geq$ 5 broadband visible-light detections of gas giants in this instellation range within 5 minutes of integration. 10 hours of R=1000 near-IR spectroscopy with HWO should reveal water, methane, and ammonia absorption features in the atmospheres of Jupiter-like gas giants. HWO time-series photometry should exceed 1% flux precision in one hour for any Earth-instellation gas giants around ExEP stars, and for Jupiter-like gas giants at $d\leq$ 7 parsecs. Time-series light curves at this cadence and precision could, over tens of hours, reveal rotation-induced variability comparable to Jupiter's. Eclipses of Mars-sized exomoons may be detectable in high-cadence light curves of Jupiter sized planets in the habitable zones of ExEP stars at $d\leq$ 10 parsecs. For any hypothetical Earth-like exomoons with oxygen-rich atmospheres at $d\leq$ 7 parsecs from the Solar System, HWO might be able to detect the spectral signature of molecular oxygen amid the parent planet's photon noise in deep ($\sim$400 hour integration) spectroscopic HWO observations at R=1000. Such moons, if they exist, represent additional habitable worlds that HWO could investigate for biosignatures.
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All authors Beck Dacus, Jean-Baptiste Ruffio, Quinn Konopacky, Renyu Hu, Tyler D. Robinson, Mary Anne Limbach, Kielan Hoch, Katelyn Horstman, Bruce Macintosh, Dimitri Mawet, Michael W. McElwain, Bertrand Mennesson, Charley Noecker, Marshall D. Perrin, Laurent Pueyo, Dmitry Savransky, Corey Spohn, Sarah Steiger, Connor Vancil, Ji Wang, Nicole Wolff, Shelley Wright