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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GAastro-ph.CO

Enabling Cosmic Web Analysis at Gigaparsec Scales: A Multi Block Approach for DisPerSE

Ankit Singh, Frazer Pearce, Meghan Gray, Gustavo Yepes

Cosmic filaments are the longest structures in the Universe and the dominant element of the cosmic web, channelling matter onto clusters and shaping the environments in which galaxies form and evolve. Accurate reconstructions of this network across gigaparsec volumes are increasingly important for cosmology and galaxy evolution. However, the most commonly used topological filament finder, DisPerSE (Discrete Persistent Structures Extractor), faces a memory bottleneck: it requires a Delaunay tesse…

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

DUET: Design of a simultaneous InGaAs--CCD split-beam imager for ultra-cool dwarf exoplanet transit survey

Peter P. Pedersen, Clark Baker, Karolina Dziewiecka, Mathias Beck, Michaël Gillon, Amaury H. M. J. Triaud, Didier Queloz

We present the design of DUET, a dual-channel imager being built for the SPECULOOS-Southern Observatory (SSO) to detect and characterise transiting terrestrial exoplanets orbiting ultra-cool dwarfs. A dichroic beamsplitter at 955\,nm directs visible light to a deeply-depleted silicon CCD and near-infrared light to a CMOS-based InGaAs detector, enabling fully simultaneous photometry with bandpasses from 0.4 to 1.7\,\textmu m. The near-infrared filters have been chosen to suppress sensitivity to a…

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physics.opticsastro-ph.IM

Empirical verification of principal mode orthogonality and relative phase calibration in photonic lanterns

Adam K. Taras, Barnaby R. M. Norris, Christopher Betters, Daniel S. Dahl, Andrew Ross-Adams, Peter G. Tuthill, Jin Wei, Sergio Leon-Saval et al.

Photonic lanterns efficiently map input spatial modes to single-mode outputs for applications like high angular resolution imaging and nulling interferometry. However, manufacturing limits prevent full control over the device's mode transfer matrix at the design stage, making empirical characterisation essential. In this work we further analyse a dataset of direct measurements of a photonic lantern's principal modes using digital off-axis holography over a 73 nm range near 1550 nm. By analysing…

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astro-ph.GA

The Mysterious Case of Iron in XMPs: Anomalous High log(Fe/O) Observed in Extremely Metal-Poor Galaxies HSCJ1631+4426 and SDSSJ0811+4730

Aaron Myszka, Themiya Nanayakkara, Karl Glazebrook, Sarah M. Sweet, Brent Groves, Nikole M. Nielsen, Jarle Brinchmann, Yuki Isobe et al.

We present integral field spectroscopic observations of two local extremely metal-poor galaxies (XMPs), HSCJ1631+4426 and SDSSJ0811+4730, obtained with the Keck Cosmic Web Imager (KCWI) over the wavelength range $3545-5529$ Å at a spectral sampling of 0.5 Å, capturing bright nebular emission lines essential for determining gas-phase metallicity and chemical enrichment measurements. Using integrated spectra, we derive oxygen abundances of $\rm12+\log(O/H)=7.079\pm0.010$ and $6.926\pm0.004$, and e…

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astro-ph.HE

Early Near-Infrared Excess and Rapid Disk-Corona Evolution in the Tidal Disruption Event 2024aepd

Yongxin Wu, Yanan Wang, Thomas M. Reynolds, Shuyuan Wei, Shiyan Zhong, Zikun Lin, Megan Newsome, Sebastian Gomez et al.

We present multi-wavelength observations of the tidal disruption event (TDE) 2024aepd, spanning primarily the first $\sim$300 days after discovery. The X-ray spectrum is initially dominated by a thermal disk component accompanied by a hard excess. From $\sim$178 days onward, the spectrum becomes power-law dominated and subsequently hardens, indicating the rapid emergence and strengthening of a hot corona. A prominent near-infrared (NIR) excess is detected as early as $\sim40$ days. Its nearly fl…

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astro-ph.HE

Cosmogenic photon fluxes at ultra-high energies

Marcus Niechciol, Chiara Jane Papior, Markus Risse

During their propagation, ultra-high energy cosmic rays produce cosmogenic photons. The expected flux level of these photons may vary by orders of magnitude depending on parameters such as the spectrum and composition of cosmic rays at injection or the source distance. We investigate the photon yields for various assumptions on injection parameters. The photon yield is largest for proton-emitting sources at about 15 Mpc distance for cosmogenic photons above $10^{18}$ eV. While the photon yield f…

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astro-ph.IM

Optical design of a direct fibre-fed MO-IFS for the NLOT

Nitish Singh, S. Sriram, Totan Chand, Jurgen Schmoll, Bharat Kumar Yerra, Savitha M S

The initial optical design and performance analysis of a dual-channel fibre-fed Multi-Object Integral Field spectrograph (Mo-IFS) being designed for a future National Large Optical/Infrared Telescope (NLOT) in India. The front end will be a moveable lenslet+fiber based integral field unit. The spectrograph is designed to directly accept an f/4 beam from the approximately 200 optical fibers, each with a 100 um core diameter without additional fore-optics. The instrument consists of two optimized…

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astro-ph.GA

On the reconstruction of the Rotation Curve for Milky Way and its spacetime implications: a Machine Learning approach

Aritra Sanyal, Swapan Das, Farook Rahaman, Saibal Ray

We propose a machine learning-assisted analytical reconstruction of the Milky Way rotation curve and discuss its implications in a relativistic spacetime context. The rotation curve is reconstructed using 73 observational data points over the range 0.1-95.56 kpc, and we compare the performances of Ridge regression, LASSO regression, and feed-forward neural networks using a physically motivated functional basis. Ridge regression yields the most stable prediction with R2 = 0.9824 +/- 0.0064 and RM…

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astro-ph.SRastro-ph.HEphysics.flu-dyn

Efficiency of Tidal Dissipation in Convective Flow Under Rapid Tidal Forcing

Hongzhe Zhou, Dong Lai

For close binaries and star-planet systems, tidal interactions mediate the energy transfer between the orbital motion and the internal flows of the bodies involved, thus playing a central role in their evolution. For equilibrium tides, the associated energy transfer is commonly modeled through an effective viscosity acting on the tidal flow. However, the scaling of viscous dissipation efficiency with tidal frequency $ω_\text{T}$ remains debated, particularly when $ω_\text{T}$ greatly exceeds the…

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astro-ph.SR

The coronal mass ejection productivity of solar active region 13664/8

Lijuan Liu, Yuming Wang, Quanhao Zhang, Jingnan Guo, Yutian Chi

In May 2024, NOAA active region (AR) complex 13664/8 was one of the most productive regions of the current solar cycle, producing 12 X-class flares and over 20 coronal mass ejections (CMEs) and triggering the strongest geomagnetic storm since 2003. We investigate why this AR complex was so CME-productive. Using primarily SDO/AIA and SDO/HMI observations, we analyzed its photospheric magnetic evolution, eruption sources, eruption waiting times, and magnetic parameters in comparison with five othe…

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astro-ph.SRastro-ph.GA

Runaway OB stars within 1 kpc of the Sun

Juan Martinez Garcia, Nicholas Wright, Alexis Quintana

Runaway stars are high-velocity stars ejected from their birth environments that can provide insights into the kinematic history of the stellar cluster they were ejected from. We derived runaway star probabilities for 40 O-type stars and $24,487$ B-type stars taken from a recently published volume-complete sample of OB stars within 1 kpc of the Sun. We fit a Galactic rotation model to the observed proper motions of these stars and identify runaway stars using both a fixed 2D peculiar velocity th…

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astro-ph.GAgr-qchep-ph

Relativistic Tidal Transitions of Saturated Kerr Boson Clouds

Yi-kun Li

Rotating black holes can bind ultralight bosons in macroscopic clouds whose level structure is swept by the tidal field of a binary companion. Existing estimates of the resulting resonant transitions have largely used hydrogenic wave functions, even where the cloud grows most efficiently and the Kerr geometry appreciably deforms its quasibound states. I compute tidal transition matrix elements on the numerically determined saturation branches of the $|211\rangle$, $|322\rangle$, and $|433\rangle…

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gr-qcastro-ph.HE

Random walks around black holes and low-frequency X-ray variability

Arthur G. Suvorov

The stochastic dynamics of a grain embedded within a turbulent fluid subject to strong gravitational fields can be formulated as a random walk on a Riemannian manifold. Such curvature-weighted walks provide a framework to model the intrinsic variability of accretion onto compact objects. By solving the relevant Fokker-Planck equation on a black hole background, we find the counterintuitive result that the escape probability of a grain is actually higher compared to flat space. This is a conseque…

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astro-ph.EPastro-ph.IM

Observational planning for the 2026 August 5 Falcon 9 Upper Stage lunar impact

Benjamin Fernando, Jennifer Heldmann, Bill Grey, John Ortiz, Bryan Euser, Darryl Z. Seligman, Eunhyeuk Kim, Anthony Colaprete et al.

On 2026 August 5, at approximately 06:35 UT, a spent Falcon 9 upper stage will impact the lunar surface near Einstein Crater. This event will occur on sunlit terrain near the eastern limb as seen from Earth. The impact flash and resultant ejecta plume from this event are potentially observable from ground- and space-based observational facilities. This event provides an opportunity to attempt the recording of an artificial impact in real-time; although many of the properties of the event (such a…

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astro-ph.GA

A Catalog of Compact High-Velocity Clouds from the FAST All-Sky HI Survey (FASHI) DR2

Jin-Long Xu, Chuan-Peng Zhang, Xiao-Lan Liu, Nai-Ping Yu, Mei Ai, Ming Zhu

High-velocity clouds (HVCs) -- especially compact HVCs (CHVCs) -- are thought to serve as gaseous tracers of dark-matter-dominated subhalos, providing a crucial empirical link between the predicted dark matter substructure and observed satellite galaxies. In this paper, we present a new catalog of 192 CHVCs identified from the FAST All-Sky HI Survey (FASHI) Data Release 2 (DR2). Among these, 108 are ultra-compact HVCs (UCHVCs), the majority of which are new discoveries. We find that 185 of the 1…

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astro-ph.GA

Features of the distribution of absorbing matter in the local system

V. I. Sorokina, V. V. Bobylev, G. A. Gontcharov, A. T. Bajkova

V. I. Sorokina$^1$\footnote [99]{e-mail: vasilisushka05@gmail.com}, V. V. Bobylev$^2$, G. A. Gontcharov$^{2}$, A. T. Bajkova$^2$A detailed study of the dust distribution in the Local System was conducted. Using the latest map by Gontcharov et al., smoothed distributions of dust matter were obtained in projection onto the galactic plane $XY$ using various smoothing parameters. Within the 2-kpc radius region around the Sun under study, key structural features associated with the Radcliffe Wave, Sp…

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astro-ph.IM

Design and Development of a Lab Prototype of a Fiber-Based Integral Field Spectrograph

Nitish Singh, S Sriram, Jurgen Schmoll, Bharat Kumar Yerra

Integral Field Spectroscopy provides simultaneous spatial and spectral information, making it a powerful technique for studying both point like and extended astronomical sources. As part of our effort to develop a compact Integral Field Spectrograph (IFS) for optical astronomy, we have designed and realized a fiber based prototype with a resolving power of ~800 at the H-$α$ wavelength. The front end optics, including the fore optics and lenslet based integral field unit (IFU), have been designed…

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astro-ph.COastro-ph.IM

Probabilistic redshift estimation of unresolved galaxies from multi-band background light maps

Shun-Sheng Li, Hendrik Hildebrandt, Ludovic Van Waerbeke

Accurate knowledge of the redshift distributions of unresolved galaxy populations is essential for extracting the cosmological information encoded in the cosmic optical background. We present the first framework for estimating these distributions directly from multi-band maps of unresolved background light, using conditional normalising flows trained on realistic image simulations. For imaging qualities comparable to those expected from the synergy between the Euclid and Rubin LSST surveys, our…

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astro-ph.GAastro-ph.HEastro-ph.SRgr-qchep-th

Revisiting Data Quality Control and Multiple-star Modeling in Wide Binary Gravity Tests: Confirmation of MOND-type Gravitational Anomaly at Low Acceleration

Kyu-Hyun Chae, Youngsub Yoon

Wide binary stars provide natural laboratories for directly probing gravity in the low-acceleration regime, as dark matter inferred from any viable gravity has negligible effects on their internal dynamics. Various recent studies including Bayesian 3D analyses have shown that wide binaries with separations greater than several thousand astronomical units experience MOND-type gravity with a boost factor of $γ\approx 1.3-1.6$. However, results claiming preference for, or no deviation from, standar…

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astro-ph.GA

Accurate proper motions of the protostellar system VLA1623-2417

Ricardo Hernández Garnica, Laurent Loinard, Carlos Carrasco-González, Jazmín Ordóñez-Toro, Johanan Ramírez-Arellano, María José Maureira, Isaac C. Radley, Eleonora Bianchi et al.

We present a detailed astrometric analysis of the quadruple protostellar system VLA1623-2417, deriving accurate absolute proper motions for components A, B, and W, as well as, for the first time, individual motions for the compact binary components of A (Aa and Ab). Our study combines 37 archival interferometric observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA) at centimeter and millimeter wavelengths, supplemented with additi…

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