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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EP

Regime transitions of dynamos driven by fingering double-diffusive convection

Wei Fan, YufengLin

Long-term cooling of planetary interiors is expected to progressively establish thermally stable stratification in the liquid outer core, yet its influence on dynamo action remains incompletely understood. Here we present three-dimensional numerical simulations of fingering double-diffusive convection-driven dynamos to investigate how progressively strengthening thermally stable stratification, modifies compositional convection driven flows and dynamos. Our results show that dynamo evolution is…

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astro-ph.GA

Galaxy sizes in the early Universe

P. Cataldi, S. Pedrosa, L. J. Pellizza, D. Ceverino, L. A. Bignone

We present preliminary results of a study of galaxy sizes at redshift $z \gtrsim 5$ using the high-resolution, zoom-in \textsc{FirstLight} simulations. We obtain a redshift-independent, chevron-shaped stellar mass--size relation with a peak at $M^{\star} \approx 10^{8.5}~\mathrm{M}_\odot$. This relation is shaped by the individual evolution of galaxies, which undergo a phase of contraction at this mass scale triggered by a strong central starburst.

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astro-ph.SRastro-ph.GA

The protostar FU Orionis may not be bursting: dramatic accretion suppression in embedded young eccentric binaries

Rajika L. Kuruwita

In 1936, the protostar FU Orionis began to brighten. Two years later, it was 100 times brighter and has not dimmed since. This object defined the class of FUor-type accretion bursts in protostars. Previous attempts to model FUors simulate isolated protostellar discs, thereby limiting the mass available to drive the burst and shortening its duration. However, these protostars are embedded within the interstellar medium, from which they actively accrete via accretion streamers. This work seeks the…

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astro-ph.GA

A Galactic-scale extreme-precision radial velocity survey

Sukanya Chakrabarti, Jack Wagner, Robert J. de Rosa, Henrique Reggiani, Jason T. Wright, Peter A. Craig, Jacob K. Luhn, Francesco Pepe et al.

We describe the first Galactic-scale extreme-precision radial velocity (EPRV) survey and outline our goals of measuring Galactic accelerations and deriving constraints on the dark matter distribution in our Galaxy. We are targeting quiet subgiant stars within a kiloparsec in radius of the Sun and about 2 kiloparsec in vertical height relative to the Galactic mid-plane. The observations described here were carried out using the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Ob…

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astro-ph.HEphysics.plasm-ph

A Linear Instability and Damping in the Acoustic Dispersion Relation of Fluids Subject to Inverse Compton Drag

Yiting Wang, Sebastian Heinz, Vladimir Zhdankin

Radiation drag from inverse-Compton scattering of an external radiation field changes the acoustic dispersion relation of a relativistic fluid. We derive the linear dispersion relation and show that, depending on the electron distribution and fluid sound speed, radiation drag either damps both modes or damps one while driving the other unstable. The unstable growth is robust at short wavelengths but slow and overdamped at long wavelengths, where the linear analysis is limited by the background a…

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astro-ph.SR

Linear Spectropolarimetry of the 2011 Eruption of the Recurrent Nova T Pyx

Alban Lamy-Rundstadler, Alessandro Ederoclite

ABRIDGED We investigate the temporal evolution of the intrinsic polarization of the 2011 eruption of the recurrent nova T Pyxidis and use its continuum and line-polarization signatures to constrain the geometry and kinematic structure of the ejecta. We analyzed nine epochs of VLT/FORS2 optical linear spectropolarimetry obtained between 24 and 70 days after discovery, from shortly before optical maximum to the early decline. The instrumental and interstellar polarization contributions were remove…

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astro-ph.SRastro-ph.EP

Hydrogen Line Emission in Accreting Low-Mass Objects I: Spectral Analysis of Shock-Origin Narrow Component

Yuhiko Aoyama, Jun Hashimoto, Gabriel-Dominique Marleau, Carlo F. Manara, Juan Manuel Alcalá, Gregory Herczeg, Camille Bergez-Casalou, Masahiro Ikoma et al.

Hydrogen lines are widely used as tracers of stellar and planetary accretion. In classical T~Tauri stars, hydrogen lines are usually interpreted as arising from magnetospheric accretion columns, whereas in lower-mass counterparts (subsolar-mass objects including brown dwarfs and gas giant planets), the post-accretion-shock region can directly emit a substantial fraction of the hydrogen-line luminosity. However, the boundary between non-shock-dominated and shock-dominated cases has remained uncle…

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astro-ph.SR

Morphology of Solar Filaments During the Solar Maximum of Cycle 24: A Study of 35 Filaments Focusing on Chirality, Barb Orientation, Skewness, and Eruptive Behavior

Jain Jacob P. T., Ram Ajor Maurya

Filaments in the solar atmosphere are plasma structures held aloft by magnetic fields, counteracting the pull of gravity. Analyzing their magnetic structure is challenging due to the lack of direct observations of their magnetic fields. However, through multi-wavelength intensity observations, one can infer their morphology. We identified 35 solar filaments during the maximum period of the solar cycle 24. In order to ascertain their chirality, we analyzed H$α$ intensity observations. Using coron…

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astro-ph.HE

Spectral Analysis of the Egress and Ingress Phases of Cen X-3 with XRISM/Resolve

J. Planelles-Villalva, L. Gu, J. J. Rodes-Roca, G. Sanjurjo-Ferrín, J. de Plaa, J. M. Torrejón, F. S. Porter, Y. Mochizuki et al.

We investigate the phase-resolved X-ray spectral evolution of the high-mass X-ray binary Cen X-3 across eclipse ingress and egress, using two out-of-eclipse intervals as references, to constrain the absorbing material and Fe K emitting regions with high-resolution XRISM/Resolve spectroscopy. We model the spectra with SPEX, including interstellar and local wind absorption, a power-law and blackbody continuum, disk reflection, and Gaussian components for Fe XXV and Fe XXVI. We compare the orbital…

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astro-ph.HE

Spectral Analysis of the Egress and Ingress Phases of Cen X-3 with XRISM/Resolve

J. Planelles-Villalva, L. Gu, J. J. Rodes-Roca, G. Sanjurjo-Ferrín, J. de Plaa, J. M. Torrejón, F. S. Porter, Y. Mochizuki et al.

We investigate the phase-resolved X-ray spectral evolution of the high-mass X-ray binary Cen X-3 across eclipse ingress and egress, using two out-of-eclipse intervals as references, to constrain the absorbing material and Fe K emitting regions with high-resolution XRISM/Resolve spectroscopy. We model the spectra with SPEX, including interstellar and local wind absorption, a power-law and blackbody continuum, disk reflection, and Gaussian components for Fe XXV and Fe XXVI. We compare the orbital…

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astro-ph.GA

Age and Mass Signatures in the Multiband Second-order Image Structure of Young Star Clusters in M31

Yuan Liang, Chao-Wei Tsai, Jingwen Wu

The ages and masses of star clusters may leave systematic signatures in the second-order spatial structure of semi-resolved photometric images. To test this hypothesis, we analyze the images using the Hessian matrix and identify basic luminous structures, termed peak cores. Applying this analysis to six-band PHAT/AP images of 1249 M31 clusters with CMD-based ages of 10--300 Myr and masses of $10^{2.2}$--$10^{4.5}\,M_{\odot}$, we examine the correlations of age and mass with the peak-core structu…

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physics.space-phastro-ph.EPastro-ph.SRphysics.geo-ph

Predicting low-latitude ionospheric Total Electron Content (TEC) over the Indian sector under variable space weather conditions using solar wind parameters

Sumanjit Chakraborty, Gopi K. Seemala, A. P. Dimri

Accurate prediction of ionospheric Total Electron Content (TEC) during geomagnetically disturbed conditions remains challenging, particularly when empirical models perform poorly during storms and neural network (NN) approaches rely explicitly on geomagnetic indices such as Kp/Ap or Dst/SYM-H. In this study, we develop an NN-based model to predict TEC variations over the Indian longitude sector without incorporating geomagnetic indices as inputs. The model is trained on the full-year (2024) Glob…

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physics.space-phastro-ph.EPastro-ph.SRphysics.geo-ph

Interhemispheric differences in field-aligned currents, ground magnetic perturbations, and TEC during the geomagnetic storms of May and October 2024

Sumanjit Chakraborty, Gopi K. Seemala

This study investigates storm-to-storm variability and hemispheric differences in magnetosphere-ionosphere (MI) coupling during the extreme (G5) geomagnetic storm of May 10-11 and the severe (G4) storm of October 10-11, 2024. Global field-aligned current (FAC) patterns derived from the Active Magnetosphere and Planetary Dynamics Response Experiment (AMPERE), together with conjugate observations from ground-based magnetometers within the SuperMAG network and Global Positioning System (GPS)-derive…

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astro-ph.GA

EP-FXT observations of the cool-core cluster Abell 478 out to R200: Thermodynamic properties and azimuthal asymmetry

J. X. Sun, Y. Chen, S. M. Jia, C. K. Li, J. Zhang, X. J. Yang, H. Yu, A. Liu et al.

We use deep observations from the Einstein Probe Follow-up X-ray Telescope (EP-FXT) to investigate the gas distribution and thermodynamic properties of the cool-core galaxy cluster Abell 478 (A478) from the center out to $R_{200}$, and to examine its azimuthal asymmetry and the influence of local dynamical disturbances on hydrostatic mass estimates. We derive the surface-brightness, temperature, electron-density, pressure, entropy, and total mass profiles. The surface-brightness distribution is…

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astro-ph.GAastro-ph.IM

XMST II: The spatial and kinematic structure of Galactic OB associations in Gaia DR3

Mark Gallaway

Stellar associations are difficult clustering targets because position, kinematics and extinction carry different physical units, different uncertainties and different discriminatory power. We extend the Extended Minimum Spanning Tree (XMST) framework without forcing these observables into a single metric. Three-dimensional spatial connectivity first defines candidate parent structures (XMST-S1), transverse kinematics then tests those parents for dynamically distinct populations (XMST-S3), and v…

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astro-ph.GA

On the Detectability and Measurement of Galactic Bars as a Function of Redshift

Yi-Xiao Lyu, Luis C. Ho, Zhao-Yu Li, Ming-Yang Zhuang

The cosmic evolution of galactic bars offers key insights into the dynamical history of disk galaxies. However, studies of high-redshift bars are severely hampered by observational effects such as resolution degradation and surface brightness dimming. To quantify these biases and establish a robust methodology of bar detection and measurement for high-redshift galaxies, we develop an automated pipeline integrating isophotal ellipse fitting and Fourier decomposition. We benchmark its performance…

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astro-ph.EPastro-ph.IM

Designing 3D transfers: application to Earth-Moon

Allan Kardec de Almeida Junior, Timothée Vaillant, João P. F. Agostinho, Antonio F. B. A. Prado, Leonardo B. T. Santos

Three dimensional Earth-Moon transfers usually consume more fuel than planar ones, but are needed depending on the latitude of the launch site and the desired inclination of the final lunar orbit. A systematic search of the optimal 3D transfers represents a true challenge due the dimension of the parameter set to span. In this paper, we propose a new method to design 3D transfers using a tangential velocity constraint for the burns, modeled using the overdetermined constraints technique based on…

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astro-ph.EP

Rosetta Earth Flyby Anomaly Revisited: Assessing Physical Contributions through Orbital Dynamics Analysis

Tobias Hoffmann, Frank Budnik

Background: During the navigation of Rosetta's first Earth flyby in 2005, a small yet unexplained asymptotic velocity increase was detected in the departing leg, necessitating inserting an artificial prograde delta-V at perigee in the orbit determination. Similar instances of this phenomenon have been observed in several missions. However, subsequent Rosetta Earth flybys did not exhibit this effect. Despite numerous investigations of the - so called Earth flyby anomaly - over the last decades, t…

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astro-ph.HE

The role of photon fields of local sources in the formation of the cosmic rays energy spectrum

S. E. Pyatovsky, S. K. Machavariani

The influence of photon fields of local sources (LS) on the formation of the cosmic ray (CR) energy spectrum (E0) is considered. A model for the formation of irregularities in the CR spectrum, based on the local source model, is proposed. It is shown that the CR spectrum can be formed as a sum of partial spectra formed near local CR sources during the passage of primary cosmic radiation (PCR) through the photon fields of the sources. Local sources can be the most active stars of various types of…

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physics.plasm-phastro-ph.EP

Plasma localization of charged debris

Bikramjit Joardar, Madhurjya P. Bora

We investigate whether the plasma disturbances generated by a charged debris object can be used to infer its position without directly sampling the object or its immediate sheath. A one-dimensional open-boundary electrostatic particle-in-cell (PIC) framework is used to model a continuously flowing electron-ion plasma containing an initially uncharged debris object. The debris charges self-consistently and produces an ion-ion counter-streaming instability (IICSI), which is sustained and reaches a…

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astro-ph.HEastro-ph.GA

Observational Evidence of an Internal Shock Collision in the Relativistic Jet of the Nearby Radio Galaxy 3C 111

Kenzo Kawamura, Motoki Kino, Mareki Honma, Kazuhiro Hada, Paul Tiede, Evgeniya Kravchenko, Marcello Giroletti, Rocco Lico et al.

We report 10 epochs of 22 GHz East Asia To Italy: Nearly Global VLBI (EATING VLBI) observations of the nearby radio galaxy 3C~111 obtained from 2020 to 2023. Combined with VLBA data at 15 and 43 GHz, these observations yield a 64-epoch, multi-frequency sequence of high-resolution radio images. We used high-resolution Bayesian Stokes~I imaging and Gaussian component modeling to derive light curves and knot kinematics. We find evidence that a faster, later-emitted knot catches up with a slower, ea…

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gr-qcastro-ph.IM

Optimal all-angle reconstruction of the Hellings-Downs curve

Jing-Hong Han, Zhi-Chao Zhao

Pulsar timing arrays (PTAs) detect nanohertz gravitational waves through spatial correlations between the timing residuals of different pulsars. For an isotropic, unpolarized stochastic background in general relativity, the ensemble-mean correlation follows the Hellings--Downs (HD) curve; measuring this angular pattern tests the gravitational-wave origin of the signal. Standard bin-by-bin reconstructions optimize the weights within each angular bin separately. We reconstruct the curve jointly us…

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astro-ph.GA

Growth from KiDS: Stellar mass assembly of galaxies since z=2 in the light of Kilo-Degree Survey

Qingshan Wang, Antonios Katsianis, Nicola R. Napolitano, Linghua Xie, Rui Li, Xiaohu Yang, Baitian Tang, Jiaxin Han et al.

We measure the galaxy stellar mass function at $z = 0-2$ using 28M galaxies from the KiDS DR4 which spans an effective survey area of 676.9 deg$^2$. Combining nine-band photometry ($u$--$K_s$) and redshifts derived using deep learning photometry, we use five SED fitting configurations, CIGALE/LePhare and CB19/BC03/M05 Stellar Population Synthesis (SPS). We present the impact of the systematics related to the code, SPS modeling and Star formation History (SFH) , which combined can introduce syste…

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astro-ph.HEastro-ph.EPastro-ph.SR

Eccentricity and Inclination Excitation of Stellar Orbits around merging Black-Hole Binaries

Hao Gao, Hanlun Lei

Identifying the formation channels of merging compact-object binaries remains a fundamental challenge in gravitational-wave (GW) astrophysics. Here, we formulate a generalized framework incorporating both third-body perturbations and post-Newtonian effects to investigate the resonance-driven excitation of eccentricity and/or inclination for stellar orbits around merging black-hole binaries (BHBs). We show that at the quadrupole level, inclination excitation is driven by adiabatic capture into a…

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astro-ph.GA

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

Suziye He, Yuehui Ma, Xuepeng Chen, Hongchi Wang, Miaomiao Zhang, Zhenyi Yue, Xiangyu Ou

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 r…

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astro-ph.GA

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

Arian Moghni, Timothy M. Heckman, Namrata Roy, Kyle B. Westfall, Kevin Bundy, Kate H. R. Rubin

For over two decades, Na I D ($λ\lambda5891.58, 5897.56$ Å) absorption has been the primary optical tracer of cool, neutral gas in galaxies. In contrast, Ca II H&K ($λλ$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 bisym…

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astro-ph.HEastro-ph.SR

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

Botao Li, Yongjie Jin, Shike Qu, Chaohua Gao, Wei Wang, Pei Wang, Shumei Jia, Jifeng Liu et al.

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 sourc…

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astro-ph.GA

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, I. Ferreras, I. Kolesnikov, V. M. Sampaio

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 sp…

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gr-qcastro-ph.HEhep-th

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…

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gr-qcastro-ph.HE

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

Ozodbek Abdurakhmonov, Javlon Rayimbaev, Inomjon Ibragimov, Sherzod Djumanov, Nuraliev Farhod, lkhomjon Makhmudov

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…

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