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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.IM

Design and modeling of an oblique incidence dichroic mirror for a high contrast imaging system

Joanna Rosenbluth, Ramya Anche, Kyle Van Gorkom, Nikoli Cooper, William Melby, Daewook Kim, Ewan Douglas

The proposed Habitable Worlds Observatory (HWO) aims to detect and characterize Earth-like planets around Sun-like stars from the ultraviolet to the infrared using high-contrast imaging. A dichroic mirror is a natural choice for splitting light between multiple wavelength channels in such a system, but the coating must introduce minimal polarization aberrations and chromatic wavefront errors (WFE) to avoid limiting contrast. We present the design of a long-pass dichroic mirror operated at a $7^\…

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astro-ph.IM

Towards optimal photometric calibration of digital astronomical plates with deep learning

Mingyang Ma, Haibo Yuan, Lin Yang, Kai Xiao, Bowen Huang, Shiyin Shen, Zhengjun Shang, Yong Yu et al.

Photometric calibration of digitized photographic plates is commonly modeled with separable magnitude-, color-, and position-dependent terms, but this separability can break down when image quality varies across the field in a magnitude-dependent way, leaving coupled spatial systematics in the residuals. We introduce a deep-learning calibration framework, the Multi-Feature Fused Network (MFF-Net), which takes instrumental magnitude, color, and pixel coordinates as input and learns a single nonli…

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physics.plasm-phastro-ph.GAastro-ph.HE

Sub-sonic compressible magnetohydrodynamic turbulence I. Alfvénic and fast-magnetosonic injection, amplitude dependence, and compressibility effects

Eleonora Puzzoni, Silvio Sergio Cerri, Dimitri Laveder, Thierry Passot, Pierre-Louis Sulem

We investigate how sub-sonic compressible magnetohydrodynamic (MHD) turbulence properties that are relevant for cosmic-ray (CR) transport in the Galaxy are affected by the nature and amplitude of initial fluctuations, and by the plasma compressibility $β$. We perform 3D simulations of decaying compressible ideal-MHD turbulence at $1024^3$ resolution with the PLUTO code. The level of density fluctuations in fully developed turbulence is insensitive to whether this state is reached starting from A…

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astro-ph.HE

Propagation Diagnostics of Supernova Remnant Environments around Young Repeating FRBs. I. Hydrodynamic Evolution of the Source-Local Dispersion Measure

Xiang-Er Fang, Zhen-Yin Zhao, Yi-Qing Lin, Hao-Tian Lan, Fa-Yin Wang

Repeating fast radio bursts may reside in young supernova remnant (SNR) environments whose evolving plasma contributes to the observed dispersion measure (DM). We use two-dimensional axisymmetric hydrodynamic simulations to study the interaction between a continuous anisotropic wind from a young neutron star and homologously expanding supernova ejecta. We follow the evolution to approximately 160 yr and calculate the source-local DM along different viewing directions, using a passive tracer to s…

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astro-ph.GA

The physical mechanism for two rapid changing-look AGNs: SDSS J0225+0030 and SDSS J1723+5504

Shuang-Liang Li, Xinwu Cao, Wei-Min Gu

SDSS J0225+0030 and SDSS J1723+5504 are two turn-on changing-look active galactic nuclei (CL AGNs) with transition timescales shorter than one year. Such short timescales pose a challenge for the current physical models of CL AGNs. We investigate this issue by exploring two possible mechanisms in this work. First, we consider the effect of a large-scale magnetic field on the viscous timescale, which can increase the radial velocity of the accretion disk. However, it is found that the timescale g…

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astro-ph.HE

Deciphering the "Green Monster" in Cassiopeia A: Puncturing and sculpting a heterogeneous circumstellar shell

S. Orlando, H. -T. Janka, D. Milisavljevic, I. De Looze, T. Temim, R. Fesen, B. -C. Koo, M. Miceli et al.

JWST observations of Cassiopeia A have revealed the "Green Monster" (GM), a pockmarked region of shocked circumstellar medium (CSM) characterized by circular holes surrounded by bright rings. The origin of these structures remains debated, with proposed mechanisms including post-shock sculpting by ejecta fingers and pre-shock puncturing by fast-moving knots (FMKs). We investigate the physical viability of the FMK-driven scenario using three-dimensional hydrodynamic simulations of FMKs interactin…

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astro-ph.HE

The PSR J0435+3233 Triple System

Z. L. Yang, J. L. Han, Y. Yan, Bin Liu, Y. L. Guo, M. K. Yang, Bo Wang, W. M. Gu et al.

The detailed evolution of triple star systems is complicated and poorly known. Based on the optical/infrared and gamma-ray archived data, we identified that the pulsar, PSR~J0435+3233, is a gamma-ray pulsar in a hierarchical triple system, with a helium white dwarf (WD) as a close inner binary companion and a Sun-like star as the distant tertiary. PSR~J0435+3233 and the WD companion are in a circular orbit with a period of $P_{\rm orb1} = 8$~days and an eccentricity of $e=0.00016$.The tertiary i…

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astro-ph.HE

Simulations of Electromagnetic Cascades in the Intergalactic Medium with Plasma Instabilities: the grplinst Code

Rafael Alves Batista, Andrey Saveliev

Electromagnetic cascades initiated by TeV gamma rays from distant blazars provide one of the cleanest indirect probes of the intergalactic medium and, in particular, of intergalactic magnetic fields. However, their interpretation is not completely clear because of an open theoretical question: the extent to which the electron-positron beams generated in the cascade can lose energy through collective plasma processes. If this occurs before inverse Compton scattering produces secondary gamma rays,…

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astro-ph.COastro-ph.GAastro-ph.IM

AGN Reverberation Mapping with LITMUS: Fundamental Limits on lag Recovery Rates

Hugh McDougall, Tamara M. Davis, Benjamin J. S. Pope, Paul Martini, Zhefu Yu, Chris Lidman, Geraint F. Lewis

Reverberation mapping of active galactic nuclei provides one of the most direct probes of the geometry and kinematics of the broad-line region by measuring time delays between continuum and line variability. Modern RM surveys frequently suffer difficulties with lag measurements due to poor signal to noise and aliasing, whereby multimodal lag posterior distributions arise due to seasonal gaps in our data. These challenge the reliability of commonly used fitting tools such as JAVELIN, which can re…

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astro-ph.EP

CHEOPS photometry from 2024 reveals a reversal in the transit-timing variations of AU Mic c

Z. Garai, Gy. M. Szabó, D. Gandolfi, A. Brandeker, A. Bonfanti, N. Billot, W. Benz, A. Heitzmann et al.

We present new CHEOPS transit observations of AU Mic b and AU Mic c obtained between June and September 2024, extending the baseline of transit-timing measurements of this young planetary system. For AU Mic b, the timing signal is well established, with a semi-amplitude (10 $\pm$ 3 min) and a characteristic modulation timescale (1168 $\pm$ 20 d) consistent with previous determinations. By contrast, the new CHEOPS data show that the large transit-timing deviation of AU Mic c reported previously w…

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astro-ph.EPastro-ph.IM

Orbital Periods and Equilibrium Temperatures from Single TESS Transits with a Physics-Informed Neural Network

Muhammad Hassan Javed

Planets with orbital periods longer than a TESS sector produce a single transit, and no periodogram method can measure their period: with one transit, every trial period longer than the observing baseline fits the data identically. We show this is not a sensitivity limit but a structural one -- across 16 confirmed single-transit planets, Box Least Squares returns a power spectrum that is numerically constant over 95% of its search grid, and widening that grid from 27 to 200 days changes the medi…

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astro-ph.GA

Identification and Study of Irregular Radio Sources with SKA Continuum Surveys

Tapan K. Sasmal, Xuelei Chen, Baoqiang Lao, Soumen Kumar Bera, Yougang Wang, Soumen Mondal, Taotao Fang, Renyue Cen et al.

Radio galaxies show a wide range of morphologies, from regular double-lobed systems to more complex and distorted radio structures. In this chapter, we focus on irregular radio morphologies, defined as sources in which the radio jets and lobes deviate from a straight and symmetric structure. Bent-tail radio galaxies and winged radio galaxies are two important examples of such sources. Bent-tail radio galaxies show curved jets or lobes, mainly shaped by the interaction between radio plasma and th…

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astro-ph.GAastro-ph.IM

Investigations of MWISP Bubbles: Identification and Analysis of Enclosed Molecular Bubbles by Weight Fields

Yu Jiang, Xuepeng Chen, Ji Yang, Ke Wang, Zhibo Jiang, Sheng Zheng, Yan Sun, Yang Su et al.

Molecular bubbles are widely used as tracers of stellar feedback; yet, their identification in spectral-line surveys remains challenging because both cavity morphology and kinematic structure must be assessed consistently in position--position--velocity (PPV) space. We present the Bubble-Weight Fields (BWFields) framework, a PPV-based method that for the first time enables the automated and objective identification and analysis of enclosed molecular bubbles directly from spectral-line data cubes…

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astro-ph.HE

Day-timescale Quasi-periodic Oscillations of the Gev BL Lac RX J0805.4+7534 with TESS

Xin-Shun Jin, Ting-Feng Yi, Yangwei Zhang, Yuncai Shen, Junjie Wang, Lisheng Mao, Liang Dong

This paper reports for the first time the detection of quasi-periodic oscillations (QPOs) in the light curves of the BL Lacertae object RX J0805.4+7534. The Transiting Exoplanetary Survey Satellite (TESS) observed this source in seven sectors of the sky, and we extracted the light curves for these sectors using a custom method. The presence of QPO signals was found in these light curves. To detecte the periodicity and assess the statistical significance of the QPO signals, we employed two method…

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astro-ph.HE

Radio-Gamma-Ray Properties and High-Energy Implications for Fermi Blazars

Xu-Hong Ye, Wen-Xin Yang, Guo-Hai Chen, Zhi-Yuan Pei, Yong-Yun Chen, Yi Liu, Denis Bastieri, Jun-Hui Fan et al.

Radio and $γ$-ray emissions in blazars, a subclass of active galactic nuclei (AGNs), provide important insight into their high-energy radiation processes. We studied the relation between radio and $γ$-ray emissions using a large sample of 1687 \textit{Fermi} blazars, based on the Radio Fundamental Catalogue and the latest Third Data Release of the Fourth \textit{Fermi} AGN Catalogue. A clear correlation between radio and $γ$-ray fluxes for both BL Lacertae objects (BL Lacs) and flat-spectrum rad…

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astro-ph.EP

Öpik-type collision frequency for Kozai-driven projectiles: Target bodies on inclined circular orbits

Youpeng Liang, Junhai Huang, Xiaodong Liu

Existing Öpik-type collision-frequency methods already incorporate the Kozai-driven secular evolution of the orbital elements of high-inclination projectiles. However, these methods generally assume that the target body's orbit lies in the reference plane defined by the orbital plane of the perturbing body. The present paper extends the semi-analytical framework developed by Vokrouhlický et al. (2012) for a target body on a circular orbit in the reference plane to the case of a target body on a…

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astro-ph.GA

VLT/MUSE Study of Close AGN Pairs and Host Galaxies in the Local Universe. I. Overview of the Ionized Gas

Xiaoyu Xu, Zhiyuan Li, Meicun Hou, Junfeng Wang, Fuyan Bian, Yan-Mei Chen

Studying AGN pairs and their host galaxies is essential for understanding the interplay between galaxy mergers and key internal processes such as supermassive black hole fueling and feedback. We cross-match between the Big Multi-AGN Catalog (The Big MAC) and the public data archive of the VLT/MUSE, and obtain 12 AGN pair candidates in the local universe ($z\lesssim0.1$) with a projected distance $r_{\rm p}\leq 20\rm\,kpc$. Using the archival VLT/MUSE data, we present a spatially resolved study o…

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astro-ph.SR

First monitoring campaign of a Main-sequence Radio Pulse emitter: the case of CU Vir

Barnali Das, Hayley Bignall, Andrew Zic, Poonam Chandra, Joshua Pritchard, John Morgan, Ankita Ghosh, Bhaswati Bhattacharyya et al.

CU Vir, a magnetic hot star, is the first discovered Main-sequence Radio Pulse emitter (MRP) characterized by its ability to produce periodic radio pulses via electron cyclotron maser emission. Although significant advancements have been made in understanding MRPs, their temporal properties remain mostly unexplored. To overcome this limitation, we conducted a pilot study with the Australia Telescope Compact Array, in which we observed pulses from CU Vir at 36 epochs over $1-3$ GHz. In this frequ…

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gr-qcastro-ph.HE

Unified remnant models for aligned-spin, precessing, and eccentric binary black hole mergers

Tousif Islam, Digvijay Wadekar, Gaurav Khanna

Using approximately $5000$ numerical-relativity (NR) simulations spanning mass ratios up to $q=128$ and $1200$ black-hole-perturbation-theory (BHPT) simulations extending to $q=1000$, we present fully analytic models for the remnant properties of quasi-circular binary black hole mergers. The models gwModelRemS (for final mass, final spin, peak luminosity, and recoil kick) and gwModelRemP (for final mass, final spin, and peak luminosity) describe nonprecessing and precessing binaries, respectivel…

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astro-ph.COastro-ph.HEhep-exhep-ph

Measurement of the Hubble constant with high-energy neutrinos

Gonzalo Herrera, Nicholas Kamp, Carlos A. Argüelles

Measuring distances in the Universe is one of the hardest problems in physics and astronomy. Almost every distance probe relies on photons, whose propagation across cosmic distances introduces extinction, absorption, scattering, and radiative-transfer effects. Neutrinos suffer none of these and propagate unattenuated through dust, intergalactic medium, and dense source environments alike. We introduce a new distance-ladder method for measuring the Hubble constant $H_0$ using high-energy astrophy…

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astro-ph.GA

The HII Regions' Molecular Law of Star Formation

Daniela Calzetti, Drew Lapeer, Robert C. Kennicutt, Bruce Elmegreen, Sean T. Linden, Mark R. Krumholz, Angela Adamo, Daniel A. Dale et al.

We combine imaging data from the HST, JWST, and ground-based millimeter facilities to investigate the correlation between star formation rate (SFR) and molecular gas at the ~100 pc scale of HII regions in three nearby galaxies: NGC628, NGC5194 and NGC5236. The JWST 21 micron maps of the three galaxies offer a unique insight into the dust-absorbed SFR at high resolution. We find that the relation between the surface densities of SFR and molecular gas has a slope of ~1.85, in log-log scale, signif…

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astro-ph.IMastro-ph.HE

Black Hole Explorer Mission Development in Japan

Kazunori Akiyama, Mareki Honma, Akihiro Doi, Shoko Koyama, Kotaro Niinuma, Kazuhiro Hada, Yuto Akiyama, Rebecca Baturin et al.

The Black Hole Explorer (BHEX) is a next-generation space very-long-baseline interferometry (VLBI) mission concept that will extend existing ground-based millimeter/submillimeter VLBI arrays to space. The Japanese astronomical community has contributed to BHEX mission development through the BHEX Japan Consortium, established in 2023. This paper provides a high-level summary of progress in Japan since 2024, including the establishment of the Black Hole Explorer Working Group (BHEX WG) at the Ins…

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hep-phastro-ph.HE

Scalaron-driven Dark Matter during Warm Inflation via UV Freeze--in

F. Millo

We investigate the production of Dark Matter (DM) within the warm Higgs--Starobinsky (HS) inflation. By adopting the ultraviolet (UV) freeze--in mechanism -- where the DM number density is initially negligible but is populated over time through non-renormalizable interactions of defined mass dimensions -- we find that the DM production within the HS potential has a characteristic timing. For both DM masses, $m_χ=1$ MeV and $m_χ=100$ GeV, the yield of DM occurs close to the termination of inflati…

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astro-ph.IMphysics.optics

Qualification pathways for Photonic Integrated Circuits in Astrophotonic Space Missions

Kalaga Madhav, Aashia Rahman, Máté Ádámkovics

Photonic integrated circuits (PICs) promise order-of-magnitude reductions in the size, weight and power (SWaP) of optical subsystems for astronomy, planetary and Earth-observation missions, yet no PIC-specific space-qualification standard exists. This paper consolidates the principal NASA and ESA qualification documents that apply, or can be tailored, to astrophotonic PICs --- arrayed waveguide gratings, photonic lanterns, fibre Bragg gratings, and integrated beam combiners (ABCD, discrete beam…

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astro-ph.IMastro-ph.SR

webSME: An online tool to infer stellar parameters and abundances

Johannes Puschnig, Andreas J. Korn, Jonathan Remmert, Ivy Balkwill-Western, Chi Than Nguyen, Nikolai Piskunov

Stellar spectroscopy is a robust technique for determining fundamental stellar parameters such as effective temperature, surface gravity and metallicity. Spectroscopy Made Easy (SME) has long served as a framework for spectral synthesis and parameter inference. In this paper, we introduce webSME, a web-based extension of the Python implementation of SME. webSME integrates enhancements including a non-local thermodynamic equilibrium abundance correction mode, a precomputed grid of synthetic spect…

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astro-ph.HE

Submillimeter Detectability of Gravitational-Wave Counterparts from Neutron-Star Mergers with the Xue-shan-mu-chang 15-meter Telescope

Di Xiao

Submillimeter (sub-mm) follow-up of binary neutron star (BNS) mergers provides unique constraints on the early-time energetics and environments of relativistic outflows, capturing the spectral evolution at epochs where centimeter-band emission is often still optically thick or yet to peak. However, the practical scientific yield depends on instrument-specific thresholds, the observing cadence, and the distinct temporal contributions from isotropic ejecta versus beamed relativistic jets. With the…

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astro-ph.IM

Conceptual architecture of the detector infrastructure for WST

A. Meoli, O. Iwert, E. George, O. Squalli, M. Richerzhagen, A. Rüde, M. Seidel, S. Lévêque et al.

The Wide-field Spectroscopic Telescope (WST) is a proposed 12 m wide-field spectroscopic facility combining several multi-object spectrographs. It requires a yet unprecedented number of detectors. In this paper we present conceptual architecture for the detector controller and infrastructure required to operate a large number of detectors, potentially applicable to WST, focusing on the system-level, power distribution, and the associated data handling. We also consider how these elements may evo…

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astro-ph.GA

Supernova feedback in porous photoionized Giant Molecular Clouds

Cheryl S. C. Lau, Ian A. Bonnell, Yueh-Ning Lee, Ke-Jung Chen

We present a new suite of numerical simulations of Type II supernovae (SNe) detonating in Giant Molecular Clouds with a variety of density structures shaped by photoionization feedback. Ionizing radiation sculpts cavities and channels that guide SN energy to emerge from the cloud as shock-driven blowouts, rather than as a coherent spherically expanding shell as assumed in most sub-grid SN models adopted in galaxy or cosmological simulations. We investigate how such outflows differ to the 1-D des…

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astro-ph.GAastro-ph.SR

Spectral Microlensing of Extragalactic H II Regions by Stellar-Mass Black Holes

Dezi Liu

Most of the Milky Way's predicted stellar-mass black holes remain hidden, especially at high Galactic latitudes or in the Galactic halo, where traditional dense-field stellar microlensing is ineffective. We propose an alternative method to map this isolated population via the spectral microlensing of compact, extragalactic H II regions. Projected onto the source plane, the physical Einstein radius of a Galactic black hole can match the typical core sizes of H II regions in distant galaxies. Micr…

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astro-ph.EPastro-ph.IMastro-ph.SR

ESCAPE: a small explorer mission to study the stellar drivers of exoplanet evolution

Allison Youngblood, Kevin France, Brian Fleming, Tim H. Hellickson, Alan C. Hoskins, James Paul Mason, Dolon Bhattacharyya, Hannah Diamond-Lowe et al.

The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) photon and high-energy particle fluxes from the host star, which are poorly constrained. To address this key gap in our understanding of atmospheric retention, we present the Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission, a NASA Small Explorer concept proposed in 2026. ESCAPE employs extreme- and far-ultraviolet spectroscopy (80 - 1650 Ang)…

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