UchUchU

Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GA

On the Jeans criterion in hydrostatic stratified media

Mahmood Roshan, Asiyeh Habibi

The classical Jeans stability criterion neglects spatial gradients in background physical quantities such as density and pressure. Here, we revisit the Jeans analysis for a non-rotating fluid in hydrostatic equilibrium, explicitly accounting for these gradients and deriving a modified dispersion relation governing perturbation propagation. Using physical arguments, we show why the Jeans swindle is not required to derive the Jeans criterion for perturbations that are small compared to the size of…

Read →
astro-ph.IM

Breakthrough Listen's Automated Commensal Technosignature Survey with MeerKAT

Daniel J. Czech, David H. E. MacMahon, Ian Heywood, Chenoa D. Tremblay, Matt Lebofsky, Kevin Lacker, Cherry Ng, Dave Horn et al.

The search for extraterrestrial intelligence (SETI) is an ongoing effort to detect technosignatures, evidence of technologically capable life beyond Earth. Conducting a comprehensive SETI programme requires a large amount of telescope time, which must be balanced with the science goals of a given observatory. Fortunately, many modern radio telescopes offer commensal access to the data they produce, allowing multiple scientific programmes to operate in parallel. The MeerKAT radio telescope in Sou…

Read →
astro-ph.GA

Disc Candidates in IC 2395: A WISE Survey of the Kinematically Confirmed Membership

Daniel Rose

Circumstellar disc dissipation timescales constrain the window available for planet formation. At approximately 9 Myr, IC 2395 lies at a critical epoch in primordial disc evolution, yet no kinematically selected disc census exists beyond the inner cluster core. A wide-field survey of IC 2395, extending to a 2 degree radius, establishes a kinematically selected disc census and evaluates the frequency of planet-forming environments in the outer cluster field. Using a high-purity catalogue of 173 m…

Read →
astro-ph.IMastro-ph.EP

ANDES, the high-resolution spectrograph of the ELT: simulated performance of the CORO module and overview of the high-contrast capabilities for exoplanet observations

M. N'Diaye, A. Simonnin, A. Spang, P. Berio, A. Chiavassa, G. Agapito, C. Bailet, G. Carlà et al.

We present the simulated performance of the coronagraph (CORO) module for ANDES, the Extremely Large Telescope (ELT) high-resolution spectrograph. ANDES aims to address a broad range of science cases, including the characterization of the atmosphere of exoplanets. With a first light envisioned by 2035, the instrument baseline features a modular fiber-fed echelle spectrograph with visible and near-infrared ultra-stable spectral arms to provide a simultaneous spectral range of 0.4-1.8\,$μ$m with a…

Read →
astro-ph.IM

Updating the SCExAO/CHARIS polarimetric calibration following the Nasmyth beam-switcher upgrade

Thomas McIntosh, Manxuan Zhang, Briley L. Lewis, Miles Lucas, Maxwell A. Millar-Blanchaer, Jaren Ashcraft, Kyohoon Ahn, Jeffrey Chilcote et al.

Subaru/SCExAO/CHARIS enables near-infrared integral field spectropolarimetry. Quantitative polarimetry is useful for a variety of science cases, particularly measurements related to dust grain properties in circumstellar disks. This capability requires correcting for polarization effects from the optical path via a Mueller matrix model. We present an updated model accounting for the recently installed SCExAO near-infrared wavefront sensor YJH50 dichroic beamsplitter and the major Subaru Nasmyth…

Read →
astro-ph.IMphysics.app-ph

Technologies and novel components for broadband splitting and coupling in pairwise and nulling interferometry

Harry-Dean Kenchington Goldsmith, Nemanja Jovanovic, Anusha Pai Asnodkar, Sanny Ahmed, Elsa Huby, Sylvestre Lacour, Michael Fitzgerald, Yoo Jung Kim et al.

Passive and active photonic components are central to the continued development of astronomical photonic integrated circuits (PICs), although achieving broadband achromatic performance remains a significant challenge. This work presents broadband evanescent tri-couplers, tapered directional couplers, and a chromatically controlled achromatic intensity modulator for astronomical interferometry in the J- and H-bands. Silicon nitride and silicon oxide provide complementary low-loss platforms, while…

Read →
astro-ph.COastro-ph.GA

Interpreting the stacked kinetic SZ effect I: velocity reconstruction and non-linear velocity effects

Lurdes Ondaro-Mallea, Raul E. Angulo, Boryana Hadzhiyska, Joop Schaye

The stacked kinetic Sunyaev-Zel'dovich (kSZ) signal probes the velocity-weighted projected gas momentum around galaxies, and is emerging as a powerful probe of gas fractions and baryonic feedback. Its interpretation, however, rests on several assumptions that we test in this pair of companion papers. Using the FLAMINGO hydrodynamical simulations and DESI-like galaxy mocks for luminous red galaxies (LRGs), the bright galaxy sample (BGS), and emission-line galaxies (ELGs), we identify the ingredie…

Read →
gr-qcastro-ph.HE

Dark matter imprints on a caustic encounter in an effective spinning black hole binary lens

Mohsen Fathi

We ask whether a cored dark matter (DM) correction can leave a resolved caustic trace after a spinning vacuum binary is allowed to imitate it. The vacuum comparison varies lens scale, common spin, separation, mass ratio, projected spin angle, and one phase offset fitted over the full orbit. Nearby unequal component spins and projected directions are also tested. The best high-resolution fit remains the equal-mass, common-spin model. In the selected encounter, the local root mean square residual…

Read →
astro-ph.GA

The ALMA-QUARKS Survey: Properties of Hot Molecular Fragments in the Massive Protocluster IRAS 17233-3606

Li Chen, Sheng-Li Qin, Dongting Yang, Wenyu Jiao, Tie Liu, Paul F. Goldsmith, Zhenying Zhang, Chuanshou Li et al.

To investigate the physical mechanisms of fragmentation within the hot molecular core of the massive protocluster IRAS 17233-3606 (G351.78-0.54), we carried out a detailed analysis of continuum and lines, using the ALMA Band 3 data from the ATOMS survey and Band 6 data from the QUARKS survey. The low-resolution 3 mm data reveal a massive hot core MM1 with a mass of ~81.3 Msun, and a prominent ultracompact (UC) HII region MM2, while the high-resolution data resolve MM1 into 11 hot molecular fragm…

Read →
astro-ph.GA

X-ray disc reverberation modelling of the X-ray/UV/optical spectral/timing properties of Fairall 9

M. Polioudakis, M. Papoutsis, I. E. Papadakis, C. panagiotou, E. Kammoun, M. Dovciak

Multiwavelength monitoring surveys of active galactic nuclei (AGN) have revealed correlated variability observed in the X-ray, UV, and optical bands. X-ray reverberation, arising from the absorption of X-rays illuminating the accretion disc, provides a self-consistent physical framework for interpreting these observations and imposing constraints on the geometry and energetics of accretion flows and X-ray coronae. We aim to apply the X-ray disc reverberation framework to the Seyfert 1 galaxy Fai…

Read →
hep-phastro-ph.HE

Testing selectively enhanced QCD axions couplings as an explanation of the RX J1856.5-3754 hard X-ray excess

Charul Rathod, Madhukar Mishra, P. K Das

We explore the possibility of explaining hard X-ray data obtained from one of the Magnificent Seven (M7) neutron-stars (NSs) employing QCD axion-converted photons. The emission of thermal axions along with neutrinos from the core has been considered. We adopt the nucleon-nucleon bremsstrahlung process as the baseline axion production mechanism and Cooper-pair breaking and formation (PBF) as an additional process. We investigate here whether the selectively enhanced QCD axion coupling model can b…

Read →
astro-ph.GA

Correlation between the two-armed $V_R$ spiral in the $Z$--$V_Z$ plane and moving groups

Yan Xu, Chao Liu, Chengdong Li, Heidi Neiberg, Hao Tian, Hua Jian Wang, Xiao Dian Chen, Li Cai Deng et al.

We use a cross-matched sample of 3.7 million stars from Gaia DR3 and LAMOST DR7 to investigate the velocity substructures in the Milky Way disk. The median radial velocity $V_R$ as a function of guiding-center radius $R_g$ exhibits alternating positive and negative stripes, which are strongly correlated with known moving groups. By examining the $V_R$ distribution in the $Z$--$V_Z$ phase space, we find that the D1, P2, D2, and P3 $V_R$ stripes display clear two-armed spirals. Among the moving gr…

Read →
astro-ph.HE

Diverse Morphologies of GRB X-Ray Plateaus within a Common Magnetar Framework

Xiao-Fei Dong, Yong-Feng Huang, Nurimangul Nurmamat, Chen Deng, Ze-Cheng Zou, Fan Xu, Abdusattar Kurban, Chen Du et al.

The origin of the X-ray plateau phase in gamma-ray bursts (GRBs) remains an open problem. In particular, it is unclear whether GRBs with different temporal morphologies (i.e., with a rising, flat, or decaying plateau) arise from a common underlying mechanism. Although magnetar energy injection is a leading explanation, previous studies have primarily inferred magnetar properties on a burst-by-burst basis and have not tested the model at the population level. Here we perform the first hierarchica…

Read →
astro-ph.HEastro-ph.CO

Constraining cosmological parameters from very-high-energy $γ$-ray attenuation in blazar spectra: Bayesian inference and systematic uncertainties

Patryk Liniewicz, Emmanuel Moulin

Very-high-energy $γ$ rays from active galactic nuclei are attenuated through pair production on the extragalactic background light (EBL), providing a probe of cosmic expansion. We develop a Bayesian inference analysis framework that uses an observationally driven, redshift-dependent EBL model and anchors intrinsic source spectra to the Fermi-LAT 3FHL catalogue while marginalising spectral-shape departures and dataset normalisations. The method is validated on realistic mock observations and appl…

Read →
astro-ph.IMphysics.ins-det

Output-Stage Design Optimization for High-Sensitivity SiSeRO CCDs and SiSeRO Active Pixel Sensors

Tanmoy Chattopadhyay, Sven Herrmann, Kevan Donlon, Ilya Prigozhin, Peter Orel, Steven W. Allen, Marshall W. Bautz, Michael Cooper et al.

The Single electron Sensitive Read Out (SiSeRO) technology is a new device class designed to support the needs of future X-ray and optical astronomical telescopes that will require fast, low-noise, megapixel spectro-imagers. Developed at MIT Lincoln Laboratory, in collaboration with Stanford University and MIT, the first generation SiSeRO-CCD (charge-coupled device) prototypes achieved a charge/current conversion gain of 700$-$800 pA per electron, an equivalent noise charge (ENC) of around 3.5 e…

Read →
astro-ph.GA

HETDEX: Star Formation Stochasticity Diagram of Lyman Alpha Emitting Galaxies at Cosmic Noon Confirms Three Archetypes

Nicole Firestone, Eric Gawiser, Kartheik G. Iyer, Charlotte Olsen, Antara Basu-Zych, Adam Broussard, Peter Kurczynski, Kyoung-Soo Lee et al.

In this work, we aim to measure the star formation stochasticity of Lyman Alpha Emitting Galaxies (LAEs) at Cosmic Noon. We identify 270 LAEs from the HETDEX Survey in the COSMOS field with rest-UV-through-NIR photometry from CANDELS\null. For each LAE, we perform non-parametric gaussian-process star formation history (SFH) reconstruction using the Dense Basis method. Our HETDEX LAE sample is described well by the three SFH archetypes defined for ODIN LAEs in Firestone et al. 2025 with comparabl…

Read →
astro-ph.SR

High-resolution spectroscopy of the bipolar proto-planetary nebula Hen 3-1475, the Garden Sprinkler Nebula

Ana Valeria Beltrán-Sánchez, Miriam Peña, Mudumba Parthasarathy

A detailed analysis of high-resolution spectra in the optical and near-infrared range of the central zone of the proto-planetary nebula Hen 3-1475, obtained in 2006 and 2024, is conducted. The spectrum primarily revealed stellar emission of H Balmer and Paschen series, lines of iron (Fe I, Fe II, and [Fe II]), and other significant lines of He I, Ca II, [Ca II], and O I. Several multiplets of Fe II, the H Balmer series, Ca II H and K, Na I D and He I lines exhibit P-Cygni profiles and bump-like…

Read →
astro-ph.EPastro-ph.SR

Asymmetrical shape of the Near-Infrared K 4p-5s doublet perturbed by He and H2

N. F. Allard, J. F. Kielkopf

The goal of this paper is to provide an exhaustive study of the K 4p-5s doublet at 1.243/1.252~$μ$m perturbed by He and H$_2$ in physical conditions of brown dwarfs. This work is applicable to analysis of the ESO SupJup Survey's J-band spectra such as for Luhman~16. Line profiles of this doublet computed within a unified line-shape theory exhibit a blue asymmetrical behavior. This effect is of increasing importance with He and H2 density, and as a result, the full treatment of the infrared K dou…

Read →
physics.space-phastro-ph.IMastro-ph.SR

For SIRs, CIRs, and Beyond: Polarization Ratio to Feature Location

Curt A. de Koning, Dusan Odstrcil, Sarah Gibson, Craig DeForest, Vic Pizzo, Christopher J. Scott

The Polarimeter to UNify the Corona and Heliosphere (PUNCH) mission will remotely observe solar wind transients with high signal-to-noise ratio, high-cadence, high-resolution polarized white-light images. Using different polarization states, an important PUNCH data product will be polarization ratio images. In the small-Sun limit, and using two simple line-of-sight density distributions with a finite angular width that can approximate a stream or corotating interaction region (SIR/CIR), we analy…

Read →
astro-ph.EP

Metal-Silicate Segregation During Planetary Accretion: Limited Iron Emulsification through intermediate Impacts

L. Honarbakhsh, G. Morra, P. Mora, CRM. Jackson

In this study, we investigate the post-collisional evolution of an impactor's iron core within a fully molten magma ocean using 2D numerical simulations with a novel Rothmann-Keller multiphase Lattice Boltzmann Method. The impactor's core diameter ranges from $152\;\text{km}$ to $552\;\text{km}$, with aspect ratios from $0.75$ to $5$. At Reynolds numbers up to $10^4$, our models reveal significant deformation and progressive fragmentation of the impactor into an iron cloud down to the smallest s…

Read →
astro-ph.GA

PhotoIFU: NIRCam as a Photometric Integral Field Unit for Mapping Feedback in Galaxies

Yongda Zhu, Marcia J. Rieke, Courtney Carreira, Yang Sun, Zhiyuan Ji, Jianwei Lyu, Christina C. Williams, Stacey Alberts et al.

We present PhotoIFU, a workflow that uses deep multi-band imaging as a low-resolution photometric integral field unit. Applied to PSF-matched JWST/NIRCam imaging, PhotoIFU treats each spatial pixel as a coarse SED element and fits the pixel SEDs with Prospector to map resolved stellar-population and ISM-related properties. We apply this approach to three galaxies at $z=1.3$--3.7 in JADES: two systems with extended ionized line emission and one post-starburst galaxy with an exceptionally strong n…

Read →
stat.MLcs.LGphysics.space-phstat.ME

Covariance-Boosted Gaussian Processes for Spatiotemporal Irregularities

Jeremy Ovadia

Nonstationary Gaussian process (GP) models are powerful tools for capturing input-dependent variability by adapting to observed data. However, with limited sampling and highly parameterized covariance structure, they are often prone to overfitting and overconfident uncertainty estimates, potentially leading to misleading predictions in safety-critical applications. Motivated by ionospheric modeling for satellite-based augmentation systems (SBAS), this paper proposes a Covariance-Boosted Gaussian…

Read →
eess.SYastro-ph.EPastro-ph.IMmath-ph

Drift-Aware Multi-Target Space Tug Logistics Using Natural Orbital Precession

Omer Burak Iskender, Leonard Felicetti, Kaan Gokturk, David Tellett, Adam Baker

Multi-rendezvous missions for active debris removal and in-orbit servicing incur prohibitive propellant costs when their targets differ in the orientation of their orbital planes, and classical mission design treats the nodal precession induced by Earth's oblateness as a perturbation to be cancelled. This paper presents a drift-aware trajectory optimisation framework that instead exploits that precession as a mission-design resource, benchmarked against the published winning solution to the Euro…

Read →
astro-ph.GA

A quasar hatching from a buried red phase at z = 3.7

Zheng Ma, Yongda Zhu, Zhiyuan Ji, Eiichi Egami, Marcia J. Rieke, Xiaohui Fan, Jianwei Lyu, George H. Rieke et al.

We present JADES-GS 209777, previously cataloged as CANDELS J033238.02-274626.2, hereafter "the Hatchling," a red quasar at $z=3.711$. While the source has been reported in earlier deep-field catalogs, our multiwavelength analysis reveals a visible active nucleus still embedded in a dense gas- and dust-rich environment. Red quasar continua are often attributed to dust attenuation, including non-standard extinction curves, but the highly comprehensive multiwavelength data for this source provide…

Read →
astro-ph.IM

SuperFIRE: Concept evolution of a seeing-limited broadband spectrograph for the GMT

Gustav M. Pettersson, Gábor Fűrész, Nathan P. Lourie, F. Elio Angile, Jill Juneau, Gerardo Berlanga Molina, Robert A. Simcoe

We are developing the SuperFIRE concept, which builds on the heritage of the FIRE spectrograph at Magellan, as a broadband (about 340 nm to 2.5 um) intermediate resolution (R=10,000) single-shot natural seeing spectrograph for the Giant Magellan Telescope (GMT) with support from the Kavli Foundation. This single-object spectrograph is envisioned as a first-light instrument that can operate in natural seeing and grow in long-term capability as the telescope and adaptive optics systems mature. Her…

Read →
astro-ph.EPastro-ph.SR

Tracing outer planetary systems through white dwarf pollution in wide binaries

Carolina Lizana-Vidal, Claudia Aguilera-Gómez, Laura K. Rogers, Amy Bonsor, María Ignacia Muñoz-Arriagada, Patrick Dufour, Constanza Bravo-Parra, Ema Salugova et al.

White dwarf (WD) atmospheric metal pollution provides strong evidence for the presence of remnant planetary material and it can be used as an indirect tracer of outer planetary systems. We analyze whether the presence of a wide stellar companion affects the occurrence of outer planetary systems by comparing the incidence of calcium (Ca) pollution in hydrogen-atmosphere WDs in wide binaries and in apparently single stars. We construct two sample pairs: a large homogeneous SDSS low-resolution spec…

Read →
astro-ph.EPastro-ph.GAastro-ph.SR

The JDISC Survey: Inner Disk Chemistry of Class I/FS Disks and Tentative Evidence for Early Pebble Drift

Ke Zhang, Andrea Banzatti, Colette Salyk, Abygail Waggoner, Klaus Pontoppidan, María José Colmenares, Ilaria Pascucci, Lucas A. Cieza et al.

We present the first chemical survey of Class I and Flat-Spectrum (I/FS) disks using JWST MIRI/MRS, targeting sixteen sources in the Ophiuchus star-forming region. Through empirical line luminosity measurements and multi-component slab modeling, we characterize the molecular reservoir of these young systems and compare them to twelve Class II disks of similar stellar mass. Water, HCN, C$_2$H$_2$, and CO$_2$ are frequently detected in I/FS sources with inclinations $i < 70^{\circ}$, whereas edge-…

Read →
astro-ph.GA

The role of filaments in the large-scale conformity signal

Daniela Palma, Ivan Lacerna, Noelia Pérez, Luis Pereyra, Antonio D. Montero-Dorta, Constanza A. Soto-Suárez, Laerte Sodré, M. Celeste Artale et al.

We investigate the large-scale conformity signal and its connection with the large-scale structure, focusing on low-mass central galaxies, after excluding galaxies that were satellites in the past. We measure the signal across different environments identified with the DisPerSE algorithm, including group outskirts, cluster outskirts, filaments, filament outskirts, and other environments (voids and walls) in order to assess how each population contributes to the large-scale conformity signal. We…

Read →
astro-ph.SR

1000 cataclysmic variables identified from DESI spectroscopy

K. Inight, B. T. Gänsicke, A. Aungwerojwit, P. Izquierdo, C. J. Manser, A. D. Myers, A. Swan, J. R. Thorstensen et al.

Most cataclysmic variables (CVs) are discovered when they have an outburst generating an inherent selection bias against CVs that rarely, or never, outburst. CVs discovered by virtue of their spectroscopic characteristics are particularly valuable to offset this bias and we have used an established machine-learning technique to assist in searching 98 966 000 spectra obtained by the Dark Energy Spectroscopic Survey (DESI) to find such CVs. DESI observations are much deeper than previous spectrosc…

Read →
astro-ph.GAastro-ph.IM

Unsupervised selection and characterisation of Little Red Dots in JWST surveys with manifold learning

Michele Ginolfi, Filippo Mannucci, Alessandro Marconi, Francesco D'Eugenio, Giacomo Venturi, Francesco Belfiore, Giovanni Cresci, Caterina Bracci et al.

Little Red Dots (LRDs) are compact, red sources discovered at high redshift by JWST whose physical nature and selection function remain debated. We investigate whether an unsupervised machine-learning approach applied to multi-band photometry can identify LRD-like objects, and other populations, without relying on predefined colour cuts. Using UMAP, a manifold-learning (dimensionality-reduction) method, we place ~242,000 isolated, well-measured sources from the ASTRODEEP-JWST catalogue on a two-…

Read →