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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.IM

3.5-meter Segmented-Mirror Robotic Space Telescope Mission White Paper I. Overall Architecture and Scientific Mission

Yong-Woo Kang, Sang Hyun Lee, Juhan Kim, Jeong-Yeol Han, Sungwook E. Hong, Bongkon Moon, Donguk Song, Juhyung Kang et al.

A 3.5-meter segmented-mirror robotic space telescope is under study as a space-based observatory for precision astrophysical observations and rapid-response transient astronomy in the 0.2-1.5 micron wavelength range. The telescope adopts a Cassegrain optical configuration optimized to deliver diffraction-limited performance across a wide, flat focal plane, achieving a Strehl ratio greater than 0.8 at 633 nm. The proposed scientific payload includes a Wide-field Camera (WC), a spectroscopic instr…

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astro-ph.EP

Photometric characterization of near-Earth asteroids: rotation, taxonomy, and candidate evidence for internal cohesion

A. Carbognani, A. Buzzoni, M. Barbetta, R. Gualandi

We present the results of a survey of previously uncharacterized near-Earth asteroids (NEAs) conducted between the second half of 2024 and the first months of 2026 using broadband $BVR_{c} I_{c}$ photometry and time-resolved lightcurve observations. Color indices were obtained for 14 NEAs of the 15 observed, with a dimension range between 0.11 and 2.5 km, and used to derive taxonomic classifications through comparison of a sample of reference reflectance curves. The sample appears to be dominate…

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astro-ph.GA

Constraining reionization-era Ly$α$ escape with JELS-MUSE: a highly complete H$α$-selected sample at $z\sim6.1$

A. L. Patrick, K. J. Duncan, Z. Li, C. A. Pirie, A. M. Swinbank, L. C. Keating, S. R. Flury, R. Begley et al.

The Ly$α$ escape fraction, $f_{\rm{esc}}^{\rm{Ly}α}$, probes both the interstellar medium (ISM) conditions governing ionizing photon escape and the rising neutral fraction of the IGM through the Epoch of Reionization (EoR). Characterising the intrinsic, ISM-driven distribution of $f_{\rm{esc}}^{\rm{Ly}α}$ before IGM attenuation becomes dominant is essential to interpret the observed decline in Ly$α$ visibility through the EoR. We present $f_{\rm{esc}}^{\rm{Ly}α}$ measurements for a highly comple…

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astro-ph.SR

Solar Soft X-ray Coronal Dimming in a Failed Eruption Associated with Plasma Cooling

Xinyue Wang, Astrid M. Veronig, Hechao Chen, Hui Tian

Coronal dimmings are observed as sudden and localized reductions in the extreme-ultraviolet and X-ray emission of the solar corona. Traditionally, significant dimmings of spectral lines formed at temperatures of 1-2 MK are regarded as indicators of coronal mass ejections (CMEs), reflecting the density depletion caused by plasma escaping into interplanetary space. In this Letter, we report a peculiar deep coronal dimming event predominantly observed in high-temperature spectral lines following an…

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astro-ph.HE

Are jet speeds governed by accretion modes?

Hong Tu, Xinwu Cao, Andrzej A. Zdziarski

Relativistic jets are observed in both stellar-mass black hole X-ray binaries (BHXRBs) and active galactic nuclei (AGNs), yet their bulk Lorentz factors differ systematically---those in black hole X-ray binaries are typically below $\sim2$, whereas AGN jets can reach $\sim50$. The origin of this discrepancy remains unclear. Searching the literature, we compile a sample of 333 AGNs with well-measured jet component motions, consisting of 270 quasars, 47 BL Lac objects, 10 FR I, and 6 FR II galaxie…

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astro-ph.HE

Are jet speeds governed by accretion modes?

Hong Tu, Xinwu Cao, Andrzej A. Zdziarski

Relativistic jets are observed in both stellar-mass black hole X-ray binaries (BHXRBs) and active galactic nuclei (AGNs), yet their bulk Lorentz factors differ systematically---those in black hole X-ray binaries are typically below $\sim2$, whereas AGN jets can reach $\sim50$. The origin of this discrepancy remains unclear. Searching the literature, we compile a sample of 333 AGNs with well-measured jet component motions, consisting of 270 quasars, 47 BL Lac objects, 10 FRI, and 6 FRII galaxies.…

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astro-ph.SR

Visual Discovery of Fading Events in the Wolf-Rayet Star WR 80

Rod Stubbings

Long-term visual and CCD V-band monitoring of the heavily reddened Wolf-Rayet star WR 80 from 2017-2026 reveals optical fading events that depart from its long-term stable baseline. On 26 April 2017 (JD 2457870), I discovered a deep minimum using a 22-inch (0.56-m) telescope, with the source plunging from a baseline of magnitude 14.6 down to magnitude 15.8. This 6-day event was subsequently verified via archival ASAS-SN V-band records. In July 2018, my visual observations identified a short dura…

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astro-ph.HEastro-ph.GA

Stars as triggers of interstellar gas entrainment in relativistic jets

B. Longo, M. Perucho, J. M. Martí, V. Bosch-Ramon, Y. Hoche

Low-power extragalactic jets are known to be decelerated and dissipate large amounts of energy within their host galaxies. However, the exact process by which this occurs is still elusive. The aim of this work is to probe the role of stars as triggers of jet mass-loading, deceleration and dissipation in Fanaroff-Riley type I radio galaxies. This is motivated by a theoretical model that proposes that stars interacting with the jet boundaries could facilitate entrainment of interstellar medium (IS…

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astro-ph.HE

Transient discs around isolated accreting neutron stars

Marina D. Afonina, Anton V. Biryukov, Sergei B. Popov, Arthur G. Suvorov

Mature, isolated neutron stars can accrete from the interstellar medium. Due to turbulence, the accreted gas can have a substantial angular momentum and form a disc around the compact object. In this paper, we perform a population synthesis of isolated neutron stars in the Milky Way that specifically tracks the possibility of disc formation, which typically requires a low spatial velocity of the compact object ($\lesssim 40$ km s$^{-1}$). In general, weak magnetic fields favour disc formation as…

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astro-ph.IM

CHARA/SPICA: The six-telescope visible combiner and near-infrared fringe tracker for the CHARA Array

D. Mourard, P. Bério, C. Bailet, A. Caci, J. Dejonghe, P. Geneslay, S. Lagarde, D. Lecron et al.

The suite called Stellar Parameters and Images with a Cophased Array (SPICA) has two interferometric instruments installed at the focus of the CHARA Array located at Mount Wilson, CA. SPICA is made of SPICA-VIS, a fiber-fed six-beam visible spectrograph with three spectral resolutions, and SPICA-FT, a six-beam near-infrared fringe tracker for the fast stabilization of the fringes. SPICA is opening access to imaging in the visible domain with an unprecedented angular resolution down to 0.2 millia…

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astro-ph.SRastro-ph.EPastro-ph.GA

Multiplicity of Cool Stars and their Evolution

Matthew I. Swayne, Leen Decin, Theo Khouri, Ayush Moharana, Léa Planquart, John Southworth, Nikki J. Miller, José A. Caballero et al.

Making up a sizeable portion of the galactic census, stellar multiples are experiencing a renaissance. Enabling the study of multiple strands of the study of cool stars, stellar multiples have been found and characterised in great numbers by the missions of the last decade, allowing the exploration of stellar parameters and populations, observation of stellar interactions, studies into stellar formation and evolution, and characterisation of circumbinary systems. This exciting explosion of scien…

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astro-ph.HE

Searching for optical pulsations from spider millisecond pulsars with the fast photometer SiFAP2

Christian Malacaria, Alessandro Papitto, Filippo Ambrosino, Caterina Ballocco, Riccardo La Placa, Giulia Illiano, Arianna Miraval Zanon, Luigi Stella et al.

Optical pulsations from millisecond pulsars (MSPs) have recently been discovered from a transitional MSP and an accreting MSP. Evidence for optical pulsations has also been found for a rotation-powered redback MSP. Observations suggest that optical pulsed emission is produced by different mechanisms depending on whether an accretion disk is present in the system or not. We explore a sample of rotation-powered MSPs in close binaries (P$_{orb}<1\,$day, redbacks and black widows), searching for opt…

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astro-ph.GA

Inside-out growth and the kiloparsec-scale star formation main sequence for low-surface-brightness disk galaxies in MaNGA

Bing-qing Zhang, Ze-hao Zhong, Yi-nan Zhu, Hong Wu

Low surface brightness galaxies (LSBGs) are very faint objects in the universe whose formation and evolution have long remained an unresolved problem. We selected a late-type, face-on, and disk-dominated galaxy sample from the MaNGA survey, composed of 38 LSBGs and 216 high surface brightness galaxies (HSBGs) by adopting a central surface brightness threshold $μ_{0}(g) = {\rm 22.0\ mag\ arcsec^{-2}}$. Based on maps derived from pipe3D products of star-forming areas in galaxies, we investigated t…

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astro-ph.SR

Surface brightness inhomogeneity on the helium-rich hot subdwarf in the X-ray binary HD 49798

C. Simon Jeffery, Gavin Ramsay

HD 49798 is an X-ray binary consisting of a hot helium-rich subdwarf primary and an accreting compact companion with an orbital period of 1.55 d. TESS observations of its optical light curve suggest short-period brightenings superimposed on a sinusoidal variation. The latter can be attributed to the tidal deformation of the primary, while frequency analysis of the additional variations shows up to eleven frequencies which form an harmonic series based on a period of 1.4 d, in excellent agreement…

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astro-ph.EP

The NC-CC dichotomy in ruthenium isotopes: Implications for the origin of the late veneer

Jonas Pape, Emily A. Worsham, Thorsten Kleine

High-precision mass-independent Ru isotope data for iron meteorites reveal that in three-isotope diagrams including the p-process Ru nuclides 96Ru or 98Ru, non-carbonaceous (NC) meteorites plot along an s-process mixing line, while the carbonaceous (CC) type irons plot as a cluster off the NC-line. As previously observed for Mo, this offset can be accounted for by an r-process excess in CC over NC materials. As a highly siderophile element, Ru in the bulk silicate Earth (BSE) is thought to predo…

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astro-ph.IMastro-ph.HE

Searching for Gravitational Wave Events Counterparts in X-Rays by Tilting the Multiple Shells of Wolter-I Optics

John Rankin, Daniele Spiga, Paolo Conconi, Sergio Campana, Giovanni Pareschi, Stefano Basso, Marta Maria Civitani, Vincenzo Cotroneo et al.

Current X-ray telescopes have a combination of field of view and angular resolution that makes it difficult to quickly localize the electromagnetic counterparts of gravitational wave events --- which will become increasingly important when the LIGO and Virgo experiment will work at full sensitivity or when the Einstein Telescope and the Cosmic Explorer observatories will come online in the next decades. We investigate what X-ray optical designs could provide --- in a small mission --- a field of…

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astro-ph.GA

An updated census of the Vast Polar Structure member galaxies

Alberto Manuel Martínez-García

The Vast Polar Structure (VPOS) is a thin, planar arrangement of dwarf galaxies oriented almost perpendicular to the Milky Way (MW) disc. Since its discovery, the census of VPOS member galaxies has progressively expanded thanks to continuous findings of new dwarfs in the vicinity of the MW and increasingly precise measurements of their phase-space coordinates. In this work, we present the largest census to date of VPOS member galaxies, building on a sample of 73 MW dwarfs for which positional an…

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physics.plasm-phastro-ph.HEastro-ph.SRphysics.flu-dyn

Instabilities in Cylindrical Geometry Using the Minimalist Approach: Formalism and Rotational Instabilities

Nektarios Vlahakis

The minimalist approach for linear stability analysis is applied to fluids and magnetized ideal plasmas in cylindrical geometry. In this approach, the dispersion relation is obtained by integrating a single first-order differential equation - referred to as the principal equation - subject to appropriate boundary conditions. We first derive the principal equation for a general unperturbed state with radially varying density and pressure, axial and azimuthal components of both the velocity and ma…

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astro-ph.IM

Scientific performances of the XGIS instrument on-board THESEUS

E. Arrigoni, S. Mereghetti, R. Campana, C. Labanti, A. Pisapia, P. Calabretto, G. Mattioli, E. Virgilli et al.

The Transient High Energy Sky and Early Universe Surveyor (THESEUS) satellite, currently undergoing a Phase-A study for the M7 ESA mission selection, will mainly rely on the XGIS (X and Gamma Imaging Spectrometer) instrument to discover and precisely localise gamma-ray bursts and other high-energy transients. The XGIS instrument has been designed to provide accurate sky images in a wide field of view (>2 steradians) in the 2-150 keV band, coupled to coverage of nearly half of the sky with good t…

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astro-ph.GA

Is the Nuclear Star Cluster a Bulge Fossil Fragment?

R. Michael Rich, Brian Thorsbro, Christian Johnson

The Milky Way nuclear star cluster (NSC) is unlike a conventional globular cluster: it contains a broad metallicity distribution and stellar populations formed over an extended interval, while its detailed abundances show a close connection to the inner Galactic bulge. We ask whether the NSC should instead be compared with the proposed "bulge fossil fragments" Terzan 5 and Liller 1, complex stellar systems interpreted as surviving remnants of massive structures involved in early bulge assembly.…

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astro-ph.IMastro-ph.HEastro-ph.SR

Demonstrating the Time-Domain Capabilities of the 4-m International Liquid Mirror Telescope: An Early Census of Transient and Variable Detections

Kumar Pranshu, Kuntal Misra, Bhavya Ailawadhi, Monalisa Dubey, Naveen Dukiya, Sara Filali, Paul Hickson, Priyanshi Kumari et al.

The PyLMT transient detection pipeline has been operational since November 2023, detecting transient and variable objects in the ILMT images in almost real time. Using the image subtraction technique, nearly 3700 CCD frames have been analyzed by the automated pipeline, generating nearly 23,000 alerts for the detection of verified transient candidates and cataloged variable sources. Around 21,000 of the alerts correspond to known MPC asteroids, nearly 2000 correspond to variable stars (including…

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astro-ph.SR

The relationship between solar and stellar tachoclines, dynamos, and spin-down

Loren I. Matilsky, Lydia Korre, Nicholas Brummell

The solar tachocline, a thin shear layer separating the differentially rotating convective zone (CZ) from the underlying rigidly rotating radiative zone (RZ), remains a dynamical mystery. Under the influence of "radiative spreading" (the process by which meridional circulation, baroclinicity, and differential rotation burrow through a stably stratified fluid), the tachocline should have spread significantly by the current age of the Sun. Some unknown torque must therefore rigidify the whole sola…

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astro-ph.EPastro-ph.IMmath-ph

Double Gravity-Assist Rendezvous Trajectory to Halley's Comet Using Deep-Space Low Thrust

Roberto Flores, Alessandro Beolchi, Chiara Pozzi, Mauro Pontani, Ivano Bertini, Cesare Barbieri, Elena Fantino

The perihelion of comet 1P/Halley in 2061 is an excellent chance to revisit this object of outstanding scientific and cultural relevance. During its 1986 approach to the Sun, it was targeted by several flyby missions. Due to its retrograde, highly-inclined orbit, the relative velocities during the encounter were large, limiting the scientific return due to the short time spent inside the coma. A rendezvous trajectory would overcome this limitation, but the design is challenging due to the limita…

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astro-ph.GAastro-ph.COhep-exhep-ph

Disc-Based Estimation of the Local Dark Matter Density and Velocity Distribution in IllustrisTNG50

Hatsume Chujo, Shogo Masaki, Keiko I. Nagao, Takuho Nakabayashi

We study the dark matter (DM) density and velocity distribution in the solar neighborhood of Milky Way-like galaxies using the TNG50-1 run of the IllustrisTNG simulation suite. Milky Way-like galaxies are selected according to both their halo mass and their bulge-to-total stellar mass ratio, and the solar-neighborhood region within each galaxy is identified from the positions and number density of stars, so that DM particles associated with the galactic disc are extracted while contributions fro…

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astro-ph.GA

Constraints on the Intranight Optical Variability of Intermediate-Mass Black Hole Candidates

Wenwen Zuo, Hengxiao Guo, Wanling Liu, Wenke Ren, Jingbo Sun, Patricia Arévalo, Luis C. Ho, Alok C. Gupta et al.

Intermediate-mass black holes (IMBHs) provide a unique regime for studying accretion variability at the low-mass end of the black hole population, yet their intranight optical variability (INOV) remains poorly constrained. We present a systematic investigation of INOV in an optically selected sample of IMBH candidates using high-cadence observations from the Zwicky Transient Facility (ZTF). From a parent sample of 1,447 broad H$α$-selected candidates, we identify 64 IMBH candidates (median $f_{\…

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astro-ph.GA

The Intermediate-Mass Black Hole Reverberation Mapping Project: Scientific Overview and Sample Characteristics

Hengxiao Guo, Jiancheng Wu, Wenwen Zuo, Ruining Tian, Xuechen Zheng, Meicun Hou, Paulina Lira, Philip G. Edwards et al.

Recent discoveries with the James Webb Space Telescope of massive black holes at high redshift have highlighted fundamental questions about black hole seed formation and the coevolution of black holes with their host galaxies. Because the initial seed population cannot yet be observed directly, nearby intermediate-mass black holes provide a complementary fossil record of black hole formation and early growth. Motivated by this opportunity, we present the Intermediate-Mass Black Hole Reverberatio…

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astro-ph.GAastro-ph.IM

Empirical Near-Infrared Spectral Templates from SPHEREx: Disentangling AGN and Host-Galaxy Emission

Wenke Ren, Hengxiao Guo, Zhenya Zheng, Minfeng Gu, Wenwen Zuo, Junxian Wang, Weida Hu, Zhen-Bo Su et al.

SPHEREx conducts the first all-sky near-infrared spectral survey over 0.75-5.0 $μ$m, spanning the transition from host-galaxy starlight to AGN-heated torus emission and enabling spectroscopic identification of active galactic nuclei (AGNs). We develop a data-driven framework combining weighted non-negative matrix factorization with forward modeling to learn empirical rest-frame templates from 2,777 normal galaxies and 1,064 AGNs in the North Ecliptic Pole (NEP) field. The resulting 14-component…

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astro-ph.IM

Simulation of the electron escape ratio for keV alpha-particle ionization tracks in liquid helium

Zihuai Hu, Junhui Liao, Zhuo Liang, Guangpeng An, Zhaohua Peng, Jian Zheng, Lifeng Zhang, Lei Zhang et al.

The electron escape ratio for 5.3 MeV alpha-particle ionization tracks in liquid helium under varying external electric fields has been measured in several experiments. However, to the best of our knowledge, the corresponding ratio for keV-scale alpha tracks in the same medium has not yet been reported. In this article, we demonstrate for the first time that this ratio can be accurately characterized using COMSOL-based simulations. Our simulation framework was developed in two stages. In Stage I…

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astro-ph.SRphysics.plasm-phphysics.space-ph

Electron acceleration by turbulent reconnection in solar flares

Zining Ren, Xin Cheng, Yulei Wang, Mingde Ding

Solar flares can release magnetic energy explosively in the corona and produce high-energy particles on short timescales. However, how and where these particles are accelerated remains an open question. Here, we investigate the acceleration and transport of electrons during self-developed three-dimensional turbulent reconnection of solar flares by solving Parker's transport equation in the framework of high-resolution MHD simulations. We find that thermal electrons at both the flare current shee…

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astro-ph.IM

Overview of multi-conjugate adaptive optics reconstructors

Clémentine Béchet

Multi-Conjugate Adaptive Optics (MCAO) systems aim at correcting for the atmospheric turbulence uniformly over wide-field observations. Compared to classical AO, this requires a tomographic reconstruction of the turbulence perturbations, that is to say a reconstruction of the atmosphere in its volume, and the control of several deformable mirrors optically conjugated to various altitudes. During the last two decades, many tomographic reconstructors have been proposed in the AO literature and som…

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