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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EP

Dynamical formation of long-period exoplanets systems in evolving binary stars

Isabel J. Lima, Rafael R. Sousa, Silvia M. Giuliatti Winter, Diogo Belloni, Ernesto Vieira, Rosana A. N. Araújo, Eder Martioli

The dynamical formation and evolution of long-period giant exoplanets have not been well constrained due to the few observational parameters. In this study, we explore the dynamical effects in a multi-planetary system around one star of an evolving wide binary system. We used an interpolated result of a MESA stellar evolution inside REBOUND N-body integrations to perform simulations with a range of distinct planetary masses in a circumstellar configuration (S-type orbit), centered on a primary s…

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astro-ph.HE

Modes in Transitional Millisecond Pulsars: Evidence of Pulsar Wind-Induced Disk Heating from GRMHD and Radiative Transfer

Mignon-Risse Raphaël, Linares Manuel, Parfrey Kyle, Tchekhovskoy Alexander, Ressler Sean

Transitional millisecond pulsars (tMSPs) alternate between radio and X-ray pulsar states, and can represent the missing link between rotation- and accretion-powered neutron stars. Their disk state switches stochastically between the low and high X-ray modes, both of unknown physical origin and less luminous than low-mass X-ray binaries. To reveal the source of the X-ray emission, we carry out 2D axisymmetric general-relativistic magnetohydrodynamical simulations of the interaction between an acc…

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astro-ph.GA

An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN -- radiation-driven outflows in little red dots, quasars and variable stars

Ignas Juodžbalis, Xihan Ji, Francesco D'Eugenio, Jan Scholtz, Roberto Maiolino, Amanda Stoffers, Alessandro Marconi, Elena Bertola et al.

A notable achievement of the first generation of JWST surveys was the discovery of an abundance of faint high-redshift ($z > 4$) broad-line active galactic nuclei (AGN) in the $L_{\rm bol} < 10^{45}$~erg~s$^{-1}$ regime, previously only accessible at $z < 1$. The high prevalence of absorption features in their broad hydrogen lines is one of the peculiarities of a significant fraction of this new population. In this paper, we conduct a broad census of Balmer absorption in a sample of 47 Type-1 AG…

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astro-ph.SR

Consistent Multi-Wavelength Spectral Modeling of Cool White Dwarfs with Carbon-Polluted Atmospheres

Jay Farihi, Piotr M. Kowalski, Sandy K. Leggett, Hania Azzam, Jackson Headon, John P. Subasavage

This work presents atmospheric modeling of multi-wavelength spectra for eight cool white dwarfs with carbon-enriched atmospheres, with four each of spectral type DQ and DQp. The Deslanders-d'Azambuja bands of C2 are detected in all six DQ stars that have data covering wavelengths shorter than 4000A. These bands are blue shifted in the DQp types, consistent with that observed for the Swan bands, and reproduced with the same pressure distortion model. The coolest stars in the sample show significa…

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astro-ph.HEastro-ph.SR

Be/X-Ray Binaries: Phenomenology, Variability, and Accretion~Dynamics

Pablo Reig

Be/X-ray binaries constitute the largest and most diverse subgroup of neutron star high-mass X-ray binaries. These systems feature a rapidly rotating Be star surrounded by a circumstellar decretion disk that serves as the primary reservoir of accreted matter onto a strongly magnetized neutron star. While a few Be/X-ray binaries remain persistently active, the majority manifest as hard X-ray transient sources, becoming detectable only during X-ray outbursts. This review synthesizes current unders…

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astro-ph.GA

Molecular gas hidden in plain sight in the early Universe

Pasquier Noterdaeme, Jens-Kristian Krogager, Sergei Balashev

We report the discovery of an extreme intervening molecular absorber at zabs = 4.1 towards the z = 4.7 quasar SDSS J080023.02+305101.22 revealed through strong H2 absorption that had remained unnoticed in archival data for about two decades. The system, which we analysed with new VLT/X-shooter observations, has a metallicity of about one-fifth the solar value, in line with the moderate dust reddening AV~0.06 mag. More strikingly, it exhibits the highest molecular fraction, fH2 = 2N(H2)/(2N(H2) +…

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astro-ph.HEastro-ph.GA

A Type Ia Supernova Candidate at $z\sim4.3$: A Transient Interloper in the Search for $z\sim14$ Galaxies

Seiji Toshikage, Takahiro Morishita, Masaomi Tanaka, Kazumi Kashiyama, Charlotte A. Mason, Andrew J. Bunker, Matthew J. Hayes, George Helou et al.

The James Webb Space Telescope (JWST) is opening a new window into the distant Universe by discovering galaxies and transients in the early Universe. We investigate a high-redshift transient candidate, beacon_1420-5253_4770. This object was initially identified as a high-redshift galaxy candidate at $z\sim14$. However, the source was not detected in epochs before and after the detection epoch, suggesting that the object is a transient source rather than a persistent galaxy. We classify the sourc…

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astro-ph.SR

Influence of local and global solar magnetic fields on medium-term forecasting of the number and parameters of coronal mass ejections

Irina A. Bilenko

A study of cyclic variations in the number and parameters of coronal mass ejections (CMEs) in cycles 23-25 demonstrates differences in the behavior of strong and weak CMEs. Strong CMEs, unlike weak CMEs, follow the cyclic evolution of active regions. A method for separately predicting strong and weak CMEs is proposed. Based on global magnetic field (GMF) parameters, the timing of the minima of cycles 26 and 27 (CR~2375$\pm5$ and CR~2526$\pm5$), the duration of cycle 26 (151~CRs or 11.2838 years)…

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gr-qcastro-ph.GA

Accretion of multipolar massive complex scalar field packets by a Schwarzschild black hole

Flavio Rosales-Infante, Ivan Alvarez-Rios, Francisco S. Guzman

We study the finite-time accretion of complex massive scalar wave packets by a Schwarzschild black hole in the test-field regime, with parameters motivated by ultralight fuzzy dark matter around supermassive black holes. Our goal is to determine how the scalar content of a localized configuration is redistributed after interacting with the black hole, and which spectral and multipolar components are more efficiently absorbed. We decompose the Klein--Gordon field into independent multipolar secto…

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astro-ph.SR

Forward Modeling of the $δ$ Sct Star V1790 Ori: $Δν$, $Ω$, Resolution and Non-adiabatic Effects

Xiaoya Sun, Antonio García Hernández, Zhaoyu Zuo, Juan Carlos Suárez, Yifan Wang, Ruixuan Tang, Giovanni M. Mirouh, Taozhi Yang et al.

We investigate the role of large separation, rotational correction order, structural resolution, and non-adiabatic effects in modelling the rotating $δ$ Scuti star V1790 Ori. From TESS data, we extract 69 frequencies and determine $Δν\simeq 82$ $μ$Hz. Rotating MESA models are computed at low and high resolution; their pulsation frequencies are calculated with GYRE (adiabatic/non-adiabatic, first-order rotation) and FILOU (adiabatic, second-order rotation). Using $Δν$ as a structural constraint i…

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astro-ph.GA

Bright Galaxies at Cosmic Dawn: A Cloud-Scale Star Formation Model Unifying Variable SFE, IMFs, and Stochasticity

Elie Cueto, Anne Hutter

To investigate the origins of the high abundance of UV-bright galaxies at z > 10, we present a new semi-analytic model that bridges the gap between small-scale star formation physics and large-scale galaxy evolution by explicitly tracking discrete star-forming clouds within smoothly evolving dark matter potentials. Unlike conventional semi-analytic models, our approach naturally captures the stochasticity of star formation, allowing us to isolate how cloud properties, star formation efficiencies…

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astro-ph.SR

KIC 6464285: A Solar-type Eclipsing Binary in a Hierarchical Triple System with Quasi-periodic Out-of-eclipse Modulations

Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian, Ildar Asfandiyarov, Azizbek Matekov, Jaqsiliq Baltamuratov, Wen-Ping Liao, A-Li Luo et al.

We present the first detailed analysis of the solar-type triple system KIC 6464285. Combining long-term, high-precision photometry from Kepler, TESS, and ZTF with low-resolution spectra from LAMOST and near-infrared high-resolution spectra from SDSS/APOGEE, we performed a joint analysis of the light curves, eclipse timing variations (ETVs), and radial velocities. Spectroscopic analysis reveals the system to be triple-lined, with the inner binary's primary being a G-type main-sequence star and a…

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astro-ph.HE

Searching for $γ$-ray emission from a bona fide Compact Symmetric Object sample: a $γ$-ray signal near GB6 J0906+4124

Ying-Ying Gan, Kai Wang, Ji-Shun Lian, Run-Meng Wang

As a particular subclass of active galactic nuclei (AGNs), compact symmetric objects (CSOs) have attracted significant attention due to potential role as young AGNs. Several $γ$-ray emitting CSOs have been detected with Fermi Large Area Telescope (Fermi-LAT), which motivates further searches for more $γ$-ray emitting CSOs. We perform a systematic search for $γ$-ray emission from a bona fide CSO sample using 16 yr Fermi-LAT observation data. No significant $γ$-ray signal is found to be firmly ass…

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astro-ph.IM

Enhanced Astrometry of the Rapid ASKAP Continuum Survey: Mid and High Frequency Epochs

Akhil Jaini, Adam T. Deller, Yuanming Wang, Emil Lenc, Stefan W. Duschene, Marcin Glowacki

Accurate radio astrometry is essential for reliable cross-identification of sources across wavelengths, precision localisation of transient events, and the construction of stable all-sky reference catalogues. In this work we extend our astrometric correction framework for the Rapid ASKAP Continuum Survey (RACS) to its mid- and high-frequency epochs (RACS-Mid1 and RACS-High1), building on our previous corrections to the low-frequency surveys. Using a hierarchical crossmatching strategy with high-…

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astro-ph.HEastro-ph.GA

Semi-Analytical Model for the Evolution of Stellar Binaries in the Empty Loss Cone of Massive Black Holes

Samuel McGuire, Evgeni Grishin, Ilya Mandel, Yuri Levin

Binary star systems orbiting close to a supermassive black hole (SMBH) evolve through encounters with other stars, the SMBH's tidal forces, and the binary's internal dynamics, including general relativistic precession and tides. Many are driven onto highly eccentric inner binary orbits, potentially leading to stellar mergers; other possible outcomes include hypervelocity star ejections or tidal disruption events. We study the evolution of binaries in the empty loss cone regime, where the outer o…

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astro-ph.HEastro-ph.SR

The XMM-Newton Line Emission Analysis Program (X-LEAP) III: Earth's Magnetospheric X-ray Emission Revealed by 22-Year XMM-Newton Observations

Zeyang Pan, Zhijie Qu, Yuqi Gong, Tianran Sun, Joel N. Bregman, Yingjie Zhang, Li Ji, Jifeng Liu et al.

The magnetosphere, protecting the Earth from intense solar activity, is also shaped by the solar wind, while its structure is still uncertain in observation. In this study, we map the X-ray emission in the magnetosphere, which is induced by the charge exchange between the highly-ionized solar wind and the neutral gas around the Earth, known as the magnetospheric solar wind charge exchange (SWCX). In particular, we extract the magnetospheric SWCX in the O VII line emission data adopted from the X…

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astro-ph.GAastro-ph.SR

Estimating stellar metallicities from Gaia DR3 XP data using LAMOST DR10

Divyansh Srivastava, Andrzej Niedzielski, Rodolfo Smiljanic

Gaia DR3 provides astrophysical parameters for hundreds of millions of stars, but the metallicities [M/H] from its GSP-Phot module suffer from systematic biases. We estimate stellar metallicities from Gaia DR3 data using the homogeneous spectroscopic iron abundances [Fe/H] of LAMOST DR10 as training labels. We cross-matched LAMOST DR10 with Gaia DR3 and trained a gradient-boosted decision-tree regressor (XGBoost) on 1.20 million AFGK stars using only Gaia-derived inputs and proxies. We validated…

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astro-ph.HEhep-ph

Universal scaling between magnetar field and initial spin period for short gamma ray bursts

Qin-Mei Li, Qi-Bin Sun, Sheng-Bang Qian, Li-Yin Zhu, Fu-Xing Li, Si-Yuan Zhu, Ming Lian, Jing Li et al.

The $B_p$--$P_0$ correlation serves as a critical probe of magnetar engine physics. Although this scaling relation has been firmly established for long gamma-ray bursts (lGRBs), systematic investigations for short GRBs (sGRBs) remain absent, leaving the physical differences between the two populations poorly constrained. Here we analyze 33 Swift sGRBs exhibiting prominent X-ray plateaus from newborn millisecond magnetar spin-down, and derive their initial spin period $P_0$ and polar magnetic fie…

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astro-ph.GAastro-ph.COgr-qc

Resolving Galactic and Cluster Dynamics Without Dark Matter: Tsallis Entropy as the Unique Foundation of Emergent Gravity

S. Shamari, A. Sheykhi

While modified entropy models-such as Barrow, Tsallis, Kaniadakis,Power-law, Logarithmic, and Rényi entropies-have been widely explored in cosmological contexts, their implications on galactic scales remain largely untested. These generalizations of the Bekenstein-Hawking entropy encode quantum gravitational, nonextensive, or fractal spacetime effects and can alter the gravitational entropy-area relation. In this paper, we demonstrate that the entropic force framework, when applied to galactic r…

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astro-ph.EP

Azimuthal molecular variations in the AB Aur planet-forming disk

Haochang Jiang, Dmitry Semenov, Myriam Benisty, Vincent Piétu, Thomas Henning, Pablo Rivière-Marichalar, Lucas M. Stapper, Edwige Chapillon et al.

Late infall episodes are emerging as an important driver of disk evolution. Observed as filamentary streamers in molecular lines and scattered light, such accretion perturbs disk structures, yet its chemical consequences remain unconstrained. We present NOEMA 1.2 mm observations of AB Aur, a structured young Herbig disk showing evidence for ongoing infall and planet formation. We detect azimuthal chemical diversity: SO emission is enhanced in the northern disk near the inferred streamer-disk int…

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astro-ph.GA

Examining the stellar-merger origin of the blue main sequence in the open cluster NGC\,3532 with N-body simulations

Khushboo K. Rao, Sambaran Banerjee

Extended main-sequence turnoffs, extended main sequences, and split main sequences observed in the colour-magnitude diagrams of young and intermediate-age star clusters are now widely interpreted as the consequence of a distribution of stellar rotation rates among their intermediate-mass (1.5-1.8~M$_\odot$) members. However, the origin of the slowly rotating population that occupies the blue main sequence (bMS) remains uncertain, and stellar mergers have been proposed as one possible pathway. We…

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astro-ph.GA

Morphology-spin connection in the SAMI Galaxy Survey

Youngmin Baek, Sree Oh, Sukyoung K. Yi, Scott M. Croom, Matthew Colless, Jesse van de Sande, Stefania Barsanti, Sam P. Vaughan et al.

The spin parameter $λ_{\rm{R_e}}$ is a proxy for the specific stellar angular momentum of galaxies and is a useful metric for classifying kinematic morphology. This study aims to quantify the relative importance of galaxy properties in explaining $λ_{\rm{R_e}}$, using data from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) Galaxy Survey. We apply partial correlation analysis and partial least squares regression to assess the relative contributions of different parameters in expl…

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astro-ph.HEhep-ph

Time-Domain Axion Searches with Magnetic White Dwarfs

Hong-Yi Zhang, Heng Bian, Zhao-Yu Zuo

Magnetic white dwarfs can convert photons into axions in their strong magnetic fields, with the conversion probability modulating the light curve as the star rotates. However, this observable is degenerate with intrinsic stellar variability if the background is modeled too simplistically. We develop a controlled background-degeneracy framework that computes the axion-induced modulation from reconstructed stellar magnetic fields while fitting it simultaneously with a flexible Fourier model of the…

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astro-ph.SRastro-ph.HE

A multiwavelength light curve analysis of the very fast nova V1723 Sco

Izumi Hachisu, Mariko Kato

We have analyzed multiwavelength light curves of the very fast nova V1723 Sco, based on our fully self-consistent nova explosion models. The time-stretching method gives the distance modulus in the $V$ band of $(m-M)_V = 15.3\pm 0.2$. Then the absolute $V$ magnitude reaches $M_{V,\rm max}= m_{V, \rm max} - (m-M)_V= 6.77 - 15.3\pm 0.2 = -8.5\pm 0.2$. Using our fully self-consistent nova outburst model combined with the optically thick winds on a $1.25 ~M_\odot$ white dwarf accreted by a mass accr…

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astro-ph.SR

Stream-Driven Ignition of a Realistic Undisturbed Helium Shell on a White Dwarf

Nethra Rajavel, Dean M. Townsley, Ken J. Shen

The dynamically driven double degenerate double detonation (D$^6$) model has emerged as a promising progenitor scenario for Type Ia supernovae. In this model, a carbon-oxygen white dwarf (WD) in a close double WD binary undergoes a double-detonation triggered by dynamical mass transfer from its companion. The mass transfer stream directly impacts the surface of the primary WD, potentially igniting a helium detonation in the surface layer. The resulting shock converges in the core, triggering a c…

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astro-ph.EPastro-ph.GAastro-ph.SR

Capture of interstellar objects during stellar encounters

Sean N. Raymond, Nathan A. Kaib, Matthew J. Hopkins

As they orbit within the Galaxy, stars swim through a vast population of interstellar objects (ISOs). In this paper, we use N-body simulations to show that a fraction of ISOs within $\sim$1 pc of the Sun (its tidal radius) may be captured during the flyby of another star -- a mechanism that requires no planets. Capture is most efficient when the impulse imparted by the flyby is comparable to the escape speed at the widest stable orbit, which is roughly 0.1 km/s for the Sun. ISO capture is domina…

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astro-ph.EP

Chondrite Parent Bodies as Escaped Satellites of Proto-Planetary Embryos

Harold F. Levison, Rogerio Deienno, Kevin J. Walsh, Brandon C. Johnson, Harold C. Connolly, Shigeru Wakita, Robert E. Grimm

Chondrites are composed of formerly partially molten material, known as chondrules, surrounded by fine-grained matrix. They date from the earliest times in Solar System history. However, their role in the formation of the planets is uncertain because, in part, it is not clear how they were produced. Here, we show a robust pathway for forming meteorite-producing asteroids that contain chondrules through embryo-embryo collisions during the late stages of terrestrial planet formation. Melted materi…

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astro-ph.GA

Vz-GAL Dusty Star-Forming Galaxies: Revisiting the CO-H2 Conversion Factor Tension

Prachi Prajapati, Axel Weiss, Dominik Riechers, Tom J. L. C. Bakx, Leindert A. Boogaard, Diana Ismail, Pierre Cox, Andrew J. Baker et al.

The CO luminosity-to-H$_2$ mass conversion factor ($α_{CO}$) remains a debated uncertainty in determining molecular gas masses of high-redshift dusty star-forming galaxies (DSFGs). Dynamical mass constraints have often favored $α_{CO}=0.8$~$M_{\odot}~{(K~km~{s}^{-1}~{pc}^{2})}^{-1}$, whereas dust- and radiative-transfer-based methods imply higher values. We revisit this ``tension" using the largest homogeneous sample of 21 unlensed $z\sim1-4$ DSFGs, with securely measured \coonezero luminosities…

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astro-ph.GA

Clarifying Dead Quasars and Downsizing through the Evolution of Star-Forming Galaxies and Active Galactic Nuclei

Shingo Sumie

From the catalogs of visible emission lines of galaxies measured by the Subaru Fiber Multi-Object Spectrograph (Subaru-FMOS) and the KECK Multi-Object Spectrograph For InfraRed Exploration (KECK-MOSFIRE), galaxies were classified into Star-Forming Galaxies (SFGs) and Active Galactic Nuclei (AGNs) based on the Baldwin-Phillips-Terlevich (BPT) diagram. In the redshift (z) range 0.8 <= z <= 2.6, z dependence of their number densities was examined, and it was found that SFGs dominate at lower redshi…

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astro-ph.HE

Can We Find the Emission Mechanism Behind the Extremely Bright GRB 230812B?

Utkarsh Pathak, Sameer K. Patil, Hitesh Tanenia, Yashowardhan Rai, Viswajeet Swain, Anuraag Arya, Gaurav Waratkar, Anirudh Salgundi et al.

GRB 230812B is a bright long-duration GRB with a luminous, long-lived afterglow and an AstroSat/CZTI polarization measurement during the prompt phase, enabling a joint study of its prompt spectral evolution, polarization, and broadband afterglow. Time-resolved spectroscopy of the prompt emission shows that during the rising phase, the low-energy Band-function index exceeds the synchrotron line of death, favoring the presence of an additional thermal component. At later times, from $T_0+2$ s to $…

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