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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GAastro-ph.IMgr-qc

Milky Way Structure from Double White Dwarf Gravitational-Wave Sources

Shao-Dong Zhao, Xue-Hao Zhang, Qun-Ying Xie, Yu-Xiao Liu, Soumya D. Mohanty

The millihertz gravitational-wave sky will be dominated by $\sim10^{4}$--$10^{7}$ resolved double white dwarf binaries in the Milky Way, whose three-dimensional spatial distribution traces the Galaxy's structural parameters. We present \textsc{Galena}, a hierarchical Bayesian pipeline that recovers these parameters from a double white dwarf catalogue through an inhomogeneous Poisson-process likelihood. Each source's $3\times3$ Galactic position covariance is computed from the waveform Fisher inf…

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astro-ph.GAastro-ph.IMgr-qc

Milky Way Structure from Double White Dwarf Gravitational-Wave Sources

Shao-Dong Zhao, Xue-Hao Zhang, Qun-Ying Xie, Yu-Xiao Liu, Soumya D. Mohanty

The millihertz gravitational-wave sky will be dominated by $\sim10^{8}$ double white dwarfs while $\sim10^{4}$ be resolvable in the Milky Way, whose three-dimensional spatial distribution traces the Galaxy's structural parameters. We present \textsc{Galena}, a hierarchical Bayesian pipeline that recovers these parameters from a double white dwarf catalogue through an inhomogeneous Poisson-process likelihood. Each source's $3\times3$ Galactic position covariance is computed from the waveform Fish…

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astro-ph.SRastro-ph.GA

Long-slit spectroscopy of the bipolar planetary nebula ESO\,428$-$05

Alexei Kniazev

The results of detailed long-slit spectroscopy of the bipolar planetary nebula \ESO\ are presented. The observations were obtained with the facility spectrograph RSS of the SALT telescope. The total measured extent of the nebula reaches $\approx$55$^{\prime\prime}$, and the kinematics along the slit directly confirms its bipolar structure. The inclination of the nebula to the line of sight is estimated as $i\approx 45^{\circ}$, and the kinematic ages of two morphological structures are measured:…

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gr-qcastro-ph.HE

Prospects of electromagnetic follow-up of neutron star-black hole mergers in the LIGO-India era

Yogita Kumari, Kanchan Soni, Sanjit Mitra

Neutron star-black hole (NSBH) mergers are promising multimessenger sources, but only a subset is expected to produce detectable electromagnetic (EM) counterparts, depending on the binary mass ratio, black hole (BH) spin, and neutron star (NS) equation of state (EoS). We investigate the prospects for detecting kilonova counterparts to NSBH mergers in the LIGO-India era using the Vera C. Rubin Observatory (Rubin). We simulate GW230529-motivated NSBH populations with two effective tidal deformabil…

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astro-ph.HE

Time-Correlated Profile Variability in the MeerKAT Pulsar Timing Array

Bhavnesh Bhat, Michael J. Keith, E. Carli, R. M. Shannon, Benjamin W. Stappers

Long-term pulse-profile variability has emerged as a potentially important source of uncertainty for high-precision pulsar timing, as changes in the integrated pulse shape can bias pulse times of arrival and affect the sensitivity of pulsar timing arrays to nanohertz gravitational waves. We present a systematic search for long-term pulse-profile variability in the six-year MeerKAT Pulsar Timing Array data, analysing observations of 84 millisecond pulsars using a two-dimensional Gaussian-process…

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astro-ph.GA

The magnetic field in M16: new results from the JCMT BISTRO survey

R. M. R. Tulloh, D. Ward-Thompson, J. Karoly, J. M. Kirk, K. Pattle

We present a study of the magnetic field (B-field) in the Eagle Nebula (M16) using data from the James Clerk Maxwell Telescope (JCMT) B-fields In STar-forming Region Observations (BISTRO) survey. We extend our previous study of the well-known `Pillars of Creation' region of the nebula to study two other structures in the region, the `Spire' and the bright-rimmed cloud (BRC) known as `SFO30'. These structures show similar B-field morphologies to the Pillars. We calculate B-field strengths using t…

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astro-ph.GA

The Dense Gas Structures Around MMS 2/OMC-3 Traced by C$^{18}$O Emission

Yuhua Liu, Satoko Takahashi, Masahiro N. Machida

We report the Atacama Large Millimeter/submillimeter Array observations of 1.3 mm continuum, C$^{18}$O ($J=2$$-$$1$), and N$_{2}$D$^{+}$ ($J=3$$-$$2$) toward the millimeter multi-system MMS 2 in the Orion Molecular Cloud-3 region, at an angular resolution of 1.59" ($\sim$620 au). MMS 2 is in the flat-spectrum phase, with its protostars in the late stage of the main accretion phase. We detect the centrally condensed structures traced by C$^{18}$O emission associated with the 1.3 mm continuum sour…

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astro-ph.EP

JWST-SUPER I: New insights into irradiated warm Neptunes atmospheres from MIRI observations of HD 106315 c

A. Dyrek, R. Waters, S. -M. Tsai, M. Holmberg, B. Edwards, J. Pye, M. Güdel, N. Crouzet et al.

Sulphur-bearing molecules have recently emerged as powerful tracers of atmospheric photochemistry in exoplanets observed with JWST. In several warm giant planets, SO$_2$ has been detected as a product of UV-driven chemical processing, suggesting a close connection between stellar irradiation, atmospheric metallicity, and sulphur chemistry. Whether these trends extend to Neptune-mass planets orbiting hotter stars remains largely unexplored. We investigate the atmospheric composition of the warm N…

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astro-ph.IM

First Very Long Baseline Interferometry Fringe Detection at 690GHz

Ming-Tang Chen, Geoffrey B. Crew, Dan Bintley, Alan Roy, Keiichi Asada, Johnson Han, Kuan-Yu Liu, Chin-Shin Chang et al.

We report the first very long baseline interferometry (VLBI) experiment conducted in the 690 GHz atmospheric window. On 2024 November 21, observations with the Atacama Large Millimeter/submillimeter Array, the Atacama Pathfinder EXperiment (APEX), and the James Clerk Maxwell Telescope (JCMT) were carried out using ALMA's newly developed Band 9 phasing capability. Fringes were detected on the ALMA-APEX baseline during a scan of the quasar J0423-0120, with a signal-to-noise ratio of ~12 and useful…

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astro-ph.GAastro-ph.SR

A Theoretical Study of the Stellar Parameters and Surface Nucleosynthesis of the Extremely Metal-Poor RGB Giant BD$-18^{\circ}$5550 - Part I: Effects of $α$-enhancement and Internal Mixing

Mrinmay Medhi, Upakul Mahanta, Swapnajyoti Sarma, Apurba Talukdar

We present a detailed stellar evolution study of BD$-18^{\circ}$5550, an extremely metal-poor red giant star in the Galactic halo. Such stars are among the oldest known objects and preserve chemical signatures of the earliest stages of Galactic history. BD$-18^{\circ}$5550 exhibits $α$-enhancement, $\rm[α/Fe]=+0.4$, typical of Population II halo stars, with enhanced abundances of oxygen, magnesium, and other $α$-elements relative to iron. Using the \texttt{MESA} stellar evolution code, we perfor…

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astro-ph.SR

Studies of Two Post Common Envelope Binary Stars

Chris Koen, Alexei Kniazev

New time series photometry of the short period ($P<0.2$~d) binary stars ZTF~J032906.36+070408.3 (ZTF~0329) and ATO~J090.7238+00.5996 (ATL~0602) is presented. The primary (hotter) stars in both systems are white dwarfs, while the cooler stars are M dwarfs. Archival photometry and new and archival spectra are used to derive the temperatures of the components in the two binaries. Both are single-lined binaries. Velocity curves are fitted to radial velocity measurements of the red dwarfs and used to…

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physics.ins-detastro-ph.IMhep-ex

Operation of a negative ion gas time projection chamber without electronegative fill gases

Lachlan J. McKie, Lindsey J. Bignell, Nicholas Adams, Victoria U. Bashu, Ferdos Dastgiri, Gregory J. Lane

The high fidelity reconstruction of particle tracks in micropatterned gaseous time projection chambers renders this technology ideal for future rare-event searches, including direction-sensitive dark matter experiments. Large drift distances are typically required for such experiments, so that the overall spatial resolution is limited by diffusion. Negative ion drift exhibits lower diffusion than electron drift and is thus an attractive option for realising a large-scale detector. The use of ele…

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astro-ph.SRphysics.atom-phphysics.comp-ph

Validity of the CRD limit for modeling scattering polarization in the photospheric Sr I 4607 Å line

Simone Riva, Gioele Janett, Franziska Zeuner, Luca Belluzzi, Fabio Riva, Pietro Benedusi

Context. Scattering polarization in the Sr I 4607 Å line is a key diagnostic for small-scale, unresolved magnetic fields in the quiet solar photosphere, inaccessible to Zeeman-based techniques. The complete frequency redistribution (CRD) limit is commonly used to model this line, but its validity and impact on magnetic sensitivity have not been systematically investigated. This is timely given new facilities observing this line with unprecedented accuracy, and future synoptic programs targeting…

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gr-qcastro-ph.IM

Clock-noise propagation and calibration for phase-locking configurations in space-based gravitational-wave detectors

Pan-Pan Wang, Cheng-Gang Shao

In space-based gravitational-wave detectors, laser phase locking transfers the phase of weak received light to a local laser and maintains the interspacecraft heterodyne frequencies within the phasemeter bandwidth. Fluctuations of the onboard ultrastable oscillators introduce clock noise into these heterodyne phase measurements, requiring additional calibration in time-delay interferometry (TDI). Existing formulations based on six independently formed one-way measurements do not explicitly descr…

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astro-ph.EPastro-ph.IM

Hybrid Spin-Orbit Tomography for Earth-like Planets: Simultaneous Mapping of Static Surfaces and Dynamic Clouds from Multicolor Light Curves

Atsuki Kuwata, Hajime Kawahara

Photometric variability of directly imaged exoplanets encodes information on both persistent surface features and time-variable phenomena such as clouds. We present Hybrid Spin-Orbit Tomography, a method that simultaneously retrieves multiple static components and a single dynamic component, together with their reflection spectra, from multiband photometric variability. The method integrates spectral unmixing and dynamic spin-orbit tomography by introducing a time-dependent component into the fo…

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astro-ph.SR

The changing optical and X-ray emission of the dormant $γ$ Cas star HD 45314

G. Rauw, Y. Nazé, E. Bryssinck, W. Vollmann, J. Guarro Fló, X. Dupont, M. A. Smith, C. Motch et al.

$γ$ Cas stars are Oe/Be stars that exhibit bright and hard X-ray emission. HD45314 belonged to this category, but lost its $γ$ Cas characteristics as its circumstellar disc started to fade away. The star was monitored in optical spectroscopy, optical photometry, and X-ray spectroscopy to follow its variability on timescales of hours to years. Time series of magnitudes, colours, line equivalent widths and violet over red peak intensity ratios were analysed with Fourier methods to uncover possible…

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astro-ph.SRphysics.plasm-ph

Connecting Dynamo Theory with DNS Data: A Computational Analysis of α and \b{eta} Effects

Kiwan Park

We investigate the influence of current helicity on the turbulent magnetic diffusivity $β$ using three complementary derivations of the $α$ and $β$ coefficients, based on the large-scale magnetic field $\overline{\mathbf{B}}$, the turbulent velocity $\mathbf{u}$, and the turbulent magnetic field $\mathbf{b}$. Applying these coefficients to raw DNS data, we reconstruct $\overline{\mathbf{B}}$ and compare the results with the original simulations. In the kinematic regime all models agree well with…

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astro-ph.SRphysics.plasm-ph

Connecting Dynamo Theory with DNS Data: A Computational Analysis of $α$ and $β$ Effects

Kiwan Park

We investigate the influence of current helicity on the turbulent magnetic diffusivity $β$ using three complementary derivations of the $α$ and $β$ coefficients, based on the large-scale magnetic field $\overline{\mathbf{B}}$, the turbulent velocity $\mathbf{u}$, and the turbulent magnetic field $\mathbf{b}$. Applying these coefficients to raw DNS data, we reconstruct $\overline{\mathbf{B}}$ and compare the results with the original simulations. In the kinematic regime all models agree well with…

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astro-ph.GAastro-ph.SR

Tracing M22's origins: Spatial and chemical constraints on its formation history

Emanuele Dondoglio, Antonino P. Milone, Randa Asa'd, Anna F. Marino, Alessandra Mastrobuono-Battisti, Fabrizio Muratore, Tuila Ziliotto, Emanuele Bortolan et al.

Globular clusters (GCs) are well known to host stellar populations characterized by light-element variations. A subset of Galactic GCs, beyond such 'canonical' populations, contains an additional group enriched in iron, s-process elements, and total C+N+O abundance (i.e., the anomalous stars). We combine multi-facility photometry with APOGEE spectroscopy to investigate the spatial distribution, chemical properties, and formation history of the stellar populations in M22, with particular focus on…

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astro-ph.HEastro-ph.SR

1LHAASO J1852+0050u: GeV-100TeV Gamma-ray emission Powered by Star-forming Region?

The LHAASO Collaboration

Star-forming regions (SFRs), including HII regions, have recently attracted significant attention as potential sites of particle acceleration capable of producing PeV cosmic rays, i.e. as potential Galactic PeVatrons. Yet, SFRs known as candidate PeVatrons are still very rare. Here we report a highly likely physical association between the UHE gamma-ray source 1LHAASO J1852+0050u and coincident star-forming regions. Using $\sim$4 years of LHAASO data, the extended source 1LHAASO J1852+0050u (cal…

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astro-ph.SRastro-ph.EPastro-ph.IM

Automated Detection of Double-Lined Spectroscopic Binaries in High-Resolution Spectra and a Probabilistic Analysis of Stellar Multiplicity

William B. Salazar, Steven Giacalone, Andrew W. Howard

The characterization of Sun-like stars, including determining whether those stars are single or have stellar companions, has become increasingly important for missions seeking planets beyond the Solar System. With upcoming missions like the Habitable Worlds Observatory (HWO) on the horizon, vetting stars for binarity and confirming potential targets as viable is essential precursor science. In this paper, we present an automated algorithm that searches for double-lined spectroscopic binaries (SB…

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astro-ph.GAastro-ph.CO

CROCODILE-SIDM: Tidal Formation of Dark Matter-Deficient Galaxies as a Test Case

Kenji Kihara, Kentaro Nagamine, Lissandre Bourrat, Leonard Romano, Yuri Oku, Daisuke Toyouchi

We introduce CROCODILE-SIDM, a framework for treating self-interacting dark matter (SIDM) with the $N$-body part of GADGET4-Osaka code, as part of CROCODILE simulation family. As a test case, we investigate the impact of SIDM on the tidal formation of dark matter-deficient galaxies (DMDGs) with velocity-dependent cross-section models. We demonstrate that our implementation reproduces the analytic scattering rate in isolated halos. Including dynamical friction self-consistently, we evolve a dwarf…

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astro-ph.HEastro-ph.GA

Aarmed with Data: Bumps, Outflows, and Disk-like Emission in TDE 2025aarm

Aysha Aamer, Kate D. Alexander, Charlotte R. Angus, Panos Charalampopoulos, Iair Arcavi, Giorgos Leloudas, Matt Nicholl, Jennifer Andrews et al.

The origin of the optical emission in tidal disruption events (TDEs) remains one of the major outstanding questions in the field, in part due to the limited number of nearby events with high-cadence monitoring to track their evolving photometric and spectroscopic properties. We present multi-wavelength observations of the nearby ($z=0.01368$) TDE\,2025aarm, including near-daily spectroscopic coverage prior to the optical peak. Its proximity makes it one of the brightest TDEs discovered, reaching…

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astro-ph.SR

The FU Ori outburst of PR Ori B

Carlos Contreras Pena, Zsofia Nagy, Gregory Herczeg, Jeong-Eun Lee, Agnes Kospal, Peter Abraham, Doug Johnstone, Bo Reipurth et al.

We report the discovery of a nearby FU Ori-type outburst (FUor), PR Ori B, in the L1641 cluster of the Orion star-forming region. The high-amplitude variability was first identified in the NEOWISE (3-5 $μ$m) photometry of the unresolved PR Ori binary system. Long-term, resolved optical photometric monitoring demonstrates that PR Ori B is the driver of a $ΔG=5~$mag outburst, while PR Ori A has remained constant over the last 20 years. The near-IR spectrum of PR Ori B changes from a late K-type sp…

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astro-ph.HE

The Evolution of Thermal and Non-thermal Emission Components in GRB 250920C

Jia-Ming Chen, Ke-Rui Zhu, Shan Chang, Dan Zhu, Yu-Lu Gong, Zhao-Yang Peng, Yong-Gang Zheng, Li Zhang et al.

We present a temporal and time-resolved spectral analysis of GRB 250920C using \textit{Fermi}/GBM and \textit{Swift}/BAT data. The prompt emission consists of two distinct episodes, EI and EII, separated by a significant quiescent interval. We perform Bayesian spectral fitting with empirical, thermal, composite, and physical synchrotron models. In EI, the spectra show clear evidence for an additional thermal component. The BB+PL model is preferred in most bright time bins, and joint \textit{Ferm…

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astro-ph.HE

Searching for Type Ia Supernovae in the Dark Energy Spectroscopic Instrument

Xiaoyu Zhuang, Song Ran, Dezheng Meng, Weiyu Ding, Ranfang Zheng, Yao Yao, Zheyu Lin, Bingxue Fu et al.

With the development of large-scale photometric surveys, an increasing number of supernova candidates are being discovered, leading to a rapidly growing demand for supernova spectra. In addition to equipping photometric surveys with follow-up spectroscopic facilities, archival spectra from large multi-object spectroscopic surveys can be mined to provide spectroscopic classifications for candidates and to find supernovae missed by previous surveys. In this work, we combine Principal Component Ana…

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astro-ph.HE

Pulse Signal Simulation of Pulsars

Jalormi Brahmachari, Mayuresh Surnis

The present thesis is a work in progress on improving the simulation of integrated pulse profiles of pulsars. Pulsars, highly magnetized rotating neutron stars, serve as precise cosmic clocks useful for studying gravity and the interstellar medium. Although periodic pulses from many pulsars are observed and modeled at differ- ent radio frequencies, a robust realistic simulation of their profiles utilizing their parameters remain underdeveloped. The present study focuses on developing a physicall…

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astro-ph.GAastro-ph.SR

High Resolution Spectroscopic Follow-up Observation Results for 13 EMP Candidates Selected by Narrow-band Photometry

Huiling Chen, Yang Huang, Huawei Zhang, Zhen Guo

Extremely metal-poor (EMP; [Fe/H] < -3.0) stars preserve key information about the earliest stages of Galactic chemical evolution. Based on a training set of spectroscopic metallicities, we constructed catalogs of more than 120,000 EMP candidates from large-scale narrow-band photometric surveys. To validate this approach, we obtained high-resolution CFHT/ESPaDOnS spectra for 13 candidates selected from the SkyMapper-based catalog. The follow-up observation confirms that the narrow-band photometr…

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

A pilot study on the CSST astrometric capability: Detecting astrometric binaries with Gaia synergy via simulated data

Shangyu Wen, Shilong Liao, Zhaoxiang Qi, Zhensen Fu, Xiyan Peng, Ye Ding, Qiqi Wu, Qi Xu et al.

Context. The China Space-station Survey Telescope (CSST) will provide deep, wide-field epoch astrometry during its 10-year mission. Astrometric binary orbits constrain the masses of stellar and compact-object components. Orbital recovery depends on astrometric precision and temporal coverage. Combining CSST and Gaia data extends the baseline and improves binary detection. Aims. We evaluate CSST, Gaia, and joint astrometry for binary-candidate selection and 12-parameter (12p) orbit fitting at fai…

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astro-ph.SRastro-ph.GA

Planetary Nebula Central Stars as Tracers of Planetary Nebula-Star Cluster Associations in the Galaxy

Vasiliki Fragkou, Luis Lomelí-Núñez, Dante Minniti, Arianna Cortesi, Denise R. Gonçalves

Planetary nebulae (PNe) that are physically associated with star clusters are rare but crucial for stellar evolution studies because they allow their initial and final stellar properties to be determined independently, contributing to constraints on the initial-to-final-mass relation (IFMR), which traces stellar mass loss. Although the identification of such pairs is essential, most reported cases have been identified incidentally rather than through systematic searches. Here, we attempt to unco…

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