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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GA

Turbulent gas-rich discs at high redshift: the origin of early massive stellar bars

Joss Bland-Hawthorn, Thor Tepper-Garcia, Chris Hamilton, Johan M. Villa-Alatorre, Oscar Agertz, Takafumi Tsukui, Ken Freeman

Recent observations combining the power of ALMA and JWST have revealed large ($3-7$ kpc), massive ($3-10\times10^{10}\,\mathrm{M}_\odot$) stellar bars at $z=4-5$ when the Universe was only 1.2-1.6 Gyr old. At this early epoch, the host galaxy was baryon-dominated (typically 75\% gas, 25\% stars) within the observed extent of the disc ($8-15$ kpc). Using NEXUS $N$-body/hydrodynamic simulations, we show that such bars can form promptly (400$-$800 Myr), provided the disc mass fraction is high ($f_{…

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astro-ph.HE

Radiative Efficiency Enhancement by Electromagnetic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black Holes

Hiroyuki R. Takahashi, Ken Ohsuga, Ryohei Kobayashi, Akihiro Inoue, Yuta Asahina, Akira Nukada, Taisuke Boku

We investigate how black hole spin and the amount of magnetic flux affect electromagnetic energy dissipation and radiation transport in supercritical accretion flows. For this purpose, we perform general relativistic radiation magnetohydrodynamic simulations of MAD and SANE accretion flows with different black hole spins. In the high-spin MAD model, we find that a fraction of the electromagnetic energy extracted by the Blandford--Znajek mechanism is dissipated near the disk surface in the vicini…

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gr-qcastro-ph.HE

Non-extensive entropy signatures in compact star

B. N. Jayawiguna, M. H. Al Ghifari, A. Rohim, A. Sulaksono

The non-extensive entropy models applied to the black-hole horizon are connected to the generalized Einstein--Hilbert action, $f(R)$, via the Wald entropy formalism. We demonstrate that quark star configurations characterized by the MIT bag model under this modified gravity approach conform to the observational lower and upper bounds established for compact objects linked to HESS J1731$-$347 and GW190814. Furthermore, we assess the effective energy conditions and corresponding speed of sound to…

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astro-ph.GA

CLAS+: A large catalog of Changing-Look AGN candidates selected through S-PLUS narrow-band photometry

L. Nakazono, L. L. Oliveira, R. R. Valença, P. Sánchez-Sáez, G. Oliveira-Schwarz, N. M. Cardoso, A. L. O'Mill, S. Panda et al.

Changing-look active galactic nuclei (CLAGN) exhibit rapid spectral transitions on timescales of months to years, challenging standard AGN unification models and providing unique insight into accretion-disk variability and obscuration processes. Despite their scientific importance, systematic searches for CLAGN remain limited by the scarcity of multi-epoch spectroscopy and the difficulty of constructing large samples efficiently. We introduce CLAS+, a catalog constructed by comparing synthetic p…

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astro-ph.GA

Multi-tracer exploration of molecular gas in main sequence galaxies at z~4.5

M. Dessauges-Zavadsky, M. Béthermin, M. Ginolfi, L. Vallini, A. Faisst, M. -Y. Xiao, F. Pozzi, P. Cassata et al.

Molecular gas masses in high-z galaxies are inferred from indirect tracers, whose respective reliability remains poorly constrained. In particular, the bright [CII] 158$μ$m line is now widely used as a molecular gas tracer at z>4, yet direct observational tests against CO remain scarce. We search for CO(4-3), CO(5-4), and [CI](1-0) lines in three of the most [CII]-luminous galaxies at z~4.5 from the ALPINE survey to assess the detectability of these lines in high-z main-sequence (MS) galaxies an…

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astro-ph.IM

The Accretion Explorer Interferometer (AEI) Phase I NASA Innovative Advanced Concepts Final Report

Kimberly A. Weaver, Jenna M. Cann, Kenneth Carpenter, Maurice Leutenegger, Takashi Okajima, Scott Rohrbach, Liz Matson, Craig Stevens et al.

We must create superb X-ray images to understand the detailed physical processes behind some of the most powerful astronomical objects. The need to achieve this capability has been known for decades. But as time proceeds, X-ray astronomy falls further behind other wavebands that are steadily increasing their imaging capacity. Radio astronomy in particular has reached an angular resolution on the order of micro arcseconds via aperture synthesis interferometry, using the interference of electromag…

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astro-ph.HEgr-qc

Observational selection effects on radio pulsars are minimal for masses, but significant for orbits and spins

Lisa V. Drummond, Katerina Chatziioannou, Emmanuel Fonseca

The masses of Galactic pulsars in binaries measured through radio timing point to structure in the mass distribution with implications for dense matter and astrophysical formation processes: a bimodal shape with peaks at ${\sim} 1.3\,M_\odot$ and ${\sim} 1.6\,M_\odot$, with a cutoff above ${\sim}2\,M_\odot$. However, this observed population of radio pulsars is shaped not only by intrinsic pulsar properties, such as birth masses, binary evolutionary pathways and dense-matter constraints, but als…

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astro-ph.EPphysics.ao-ph

Evolutionary pathways toward survival of a thick CO2- or SO2-rich atmosphere on the lava world TOI-561 b

Emma Postolec, Tim Lichtenberg, Johanna K. Teske, Harrison Nicholls, Mara Attia, Anjali Piette, Lisa Dang, Nicole L. Wallack et al.

Rocky planets evolve through the exchange of volatiles between their interiors and atmospheres, an interplay still poorly constrained by observations. Remarkably, highly irradiated ultrashort-period (USP) exoplanets may offer a window into this exchange -- some retain low bulk densities compatible with volatile-rich envelopes surrounding rocky interiors, indicating possible secondary atmospheres. TOI-561 b is a prime example, with a bulk density of $4.3\pm0.4$ g cm$^{-3}$ and recent JWST observa…

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astro-ph.HE

Thermal and non-thermal emission from supermassive black hole circumbinary disks: Disks, Coronae, Streams, and Cavities

Chris Nagele, Julian H. Krolik, Brooks E. Kinch, Jeremy D. Schnittman, Scott Noble

The search for electromagnetic signals from supermassive black hole (SMBH) binary systems is one of the cornerstones of multi-messenger astrophysics, complementing gravitational wave observations of such systems by pulsar timing arrays and LISA. Although extensive simulations have been run to understand the time variability of the bolometric luminosity from accreting binary SMBH systems, comparatively few spectral predictions have been made, and none that go beyond simple emission models. In thi…

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

Infrared-excess sources in VVV: candidate debris discs, SED characterization, and variability analysis

P. Esteves, R. K. Saito, C. Chavero, V. Fermiano, D. Minniti, B. W. Borges, C. Cáceres, Z. Guo et al.

Debris disks around main-sequence stars provide important insights into planetary formation and evolution; however, identifying these systems in the Galactic plane, where high interstellar extinction and source crowding are significant, remains challenging. Deep, wide-area surveys such as the VISTA Variables in the Via Lactea (VVV) ESO Public Survey provide multi-epoch infrared observations, enabling systematic searches in these environments. We present a method to construct a refined sample of…

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astro-ph.IM

Optimizing Field Geometry for Modular Micropore-Optics Soft X-ray Time-Domain Surveys

Nicholas E. White, Massimiliano Galeazzi, Russell Roberts, Kip D. Kuntz

Wide-field micropore (lobster eye) optics enable focusing soft X-ray instruments with fields of view of hundreds of square degrees, but square-format modules require careful geometric arrangement to support both wide-area surveys and sensitive pointed observations. We examine this design problem using the X-ray TRansient Array / Micropore Optics X-ray Imager trade study, developed for a NASA Small Explorer mission concept, as a worked example. Single-module performance scaling is combined with g…

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astro-ph.COastro-ph.GA

TDCOSMO XXIX: JWST/NIRSpec IFU Spatially Resolved Kinematics of Three Time-delay Lenses

Shawn Knabel, Pritom Mozumdar, Anowar J. Shajib, Tommaso Treu, Devon M. Williams, Michele Cappellari, David Law, Simon Birrer et al.

Spatially resolved stellar kinematics are critical to the high precision achieved by cosmological probes utilizing time delays of strongly lensed quasars. Combined with high-resolution imaging and lens modeling, dynamical models of the 2D resolved kinematics of the deflector galaxy tightly constrain the mass profile and break the mass-sheet degeneracy, in turn providing tight constraints on the Hubble constant when the time delays are included. We extract stellar kinematics of the deflector gala…

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physics.space-phastro-ph.SR

Direct Four-Spacecraft Measurement of Reconnection Exhaust Thickness in the Solar Wind

Mani K Chettri, Rupak Mukherjee, Hemam D. Singh

The thickness of a reconnecting solar wind current sheet is normally inferred from a single spacecraft as the product of the boundary-normal speed and the crossing duration. Multipoint measurements have tested this method for generic solar wind current sheets and constrained the geometry of reconnection exhausts, but a direct comparison with single-spacecraft thickness estimates for the same reconnection-associated crossings is still lacking. We analyze four current-sheet crossings observed by M…

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astro-ph.GA

Same galaxy, different CGM: how the metal loading of galactic winds regulates the baryon cycle in Milky Way-mass galaxies

Prachi Khatri, Freeke van de Voort, Rebekka Bieri, Rüdiger Pakmor, Robert J. J. Grand, Thomas A. Rintoul, Maria Werhahn, Rosie Y. Talbot et al.

The circumgalactic medium (CGM) is both the reservoir of gas that fuels star formation and galaxy growth, and the repository for the mass, energy, and metals expelled through stellar evolution and feedback. We present a controlled experiment using a suite of five cosmological magnetohydrodynamical simulations of a Milky Way-mass halo from the Auriga suite, where we vary the metal content and energy loading of galactic winds driven by stellar feedback. We chose these parameters in combination suc…

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astro-ph.EP

Low-energy ring particle accretion as the origin of Pan's equatorial ridge

Marco Baj, Iosto Fodde, Lucia Francesca Civati, Fabio Ferrari

Pan is a small Saturnian satellite embedded within the planet's A ring, characterized by a polygonal equatorial ridge whose formation mechanism remains debated. A proposed explanation is ring particle accretion, yet previous simplified models could not address the ridge's complex multi-lobed morphology without ad hoc assumptions, and the cause of its latitudinal spread remains unclear. This work studies the complex low-energy dynamics around Pan to verify whether the ring particle accretion path…

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

Single-pulse reanalysis of the 2024 Vela glitch and new observations of PSR~J0437$-$4715 and PSR~J1644$-$4559

Carlos O. Lousto, Ruby Shrestha, Ezequiel Zubieta, Susana B. Araujo Furlan, Guillermo Gancio, Federico García, Santiago del Palacio, Ryan Missel et al.

The Pulsar Monitoring in Argentina (PuMA) collaboration systematically monitors southern glitching pulsars, maintaining high-cadence single-pulse records of the Vela pulsar. We present a pulse-per-pulse reanalysis of the 2024 major glitch of Vela (PSR~J0835$-$4510) with the 400~MHz-bandwidth ROACH backend of the Argentine Institute of Radioastronomy, and extend our machine-learning single-pulse pipeline---Isolation Forest outlier rejection, $β$-Variational-AutoEncoder denoising, and Self-Organiz…

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astro-ph.EP

New and Updated Rossiter-McLaughlin Measurements for Three Hot Jupiter-Hosting M Dwarfs

Drew Weisserman, Ryan Cloutier, Alexandra Rochon, Ze'ev Vladimir, Bertram Bitsch, Ritvik Basant, Jacob L. Bean, Tanya Das et al.

Evidence suggests that Kozai-Lidov high-eccentricity migration (HEM) is the dominant migration channel for short-period Giant Exoplanets around M dwarf Stars (GEMS). However, it is unlikely that all short-period GEMS form via HEM, given that most systems lack known massive companions capable of driving HEM. Characterizing the stellar obliquities of GEMS via the Rossiter-McLaughlin (RM) effect can help shed light on the dynamical histories of GEMS. We present RM effect detections for the GEMS TOI…

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astro-ph.EP

JWST MIRI reveals a potential atmosphere on the ultra-hot rocky planet TOI-431b

Cole Smith, Brandon Park Coy, Megan Weiner Mansfield, Rafael Luque, Anjali A. A. Piette, Qiao Xue, Michael Zhang, Jacob L. Bean et al.

An open question in exoplanet science is whether rocky exoplanets extremely close in to their host stars, `lava worlds', can retain significant atmospheres. Thermal emission observations via secondary eclipse can be used to determine whether a rocky exoplanet possesses an atmosphere. It is expected that an atmosphere could increase the planet's albedo and/or redistribute heat away from the dayside, reducing the secondary eclipse depth measured. Recent eclipse observations of lava planets, rocky…

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astro-ph.IM

A fast, wide-field, and real-time imaging prototype for large aperture arrays

Nithyanandan Thyagarajan, Jishnu Thekkeppattu, David Humphrey

Real-time processing on sub-millisecond timescales is essential for detecting fast astrophysical transients such as fast radio bursts (FRBs) and prompt electromagnetic counterparts to gravitational-wave mergers. Immediate localisation enables rapid multi-wavelength follow-up and maximises scientific return. As a result, real-time capability has become a key requirement for modern wide-field aperture arrays, which are increasingly being deployed at scales of thousands to tens of thousands of ante…

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gr-qcastro-ph.HEastro-ph.IM

DANSur_HM: Modularly incorporating higher modes in a deep learning based gravitational-wave surrogate

Osvaldo Gramaxo Freitas, Anastasios Theodoropoulos, Nino Villanueva, José A. Font, Antonio Onofre, Alejandro Torres-Forné, José D. Martin-Guerrero

Numerical relativity (NR) simulations provide the most faithful representation of the gravitational waves (GWs) emitted by binary black hole (BBH) systems during merger. In the context of GW astronomy, tasks such as parameter estimation can require vast numbers of waveform evaluations per second across the entire parameter space. Since performing full NR simulations for each evaluation is not computationally feasible, interpolating methods for existing NR waveforms, known as surrogate models, ha…

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astro-ph.GA

Evolution of bar-induced dark gaps in galaxy discs: evidence of strong bar-driven effects already at $z > 2$

Susnata Chattopadhyay, Soumavo Ghosh, Dimitri A. Gadotti, Zoe A. Le Conte, Taehyun Kim, Virginia Cuomo, Camila de Sá-Freitas, E. Athanassoula et al.

The properties of stellar bars play a crucial role in determining the bar-driven secular evolution in disc galaxies. However, a systematic observational study of the evolution of several bar properties (such as strength and length) across cosmic time is largely missing. In this paper, using a sample of $625$ barred galaxies, taken from SDSS, HST COSMOS, and JWST CEERS surveys, we systematically investigate the evolution of bar properties over redshifts ($0.02 \lesssim z < 3$) by making a novel u…

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astro-ph.HEastro-ph.GA

Multi-epoch Detection of an Ultra-fast Inflow in ESP 39607: Evidence for an Accretion Cascade

Alessandro Peca, Michael J. Koss, Roberto Serafinelli, C. Megan Urry, Claudio Ricci, Keigo Fukumura, Massimo Gaspari, Elias Kammoun et al.

We present simultaneous XRISM, XMM-Newton, and NuSTAR observations of ESP 39607, a Seyfert 2 galaxy at $z = 0.201$. XRISM/Resolve reveals two absorption features near 4.7 and 4.9 keV in the observed frame, consistent with redshifted Fe XXV He-$α$/Fe XXVI Ly-$α$ absorption from gas inflowing at $v_{\rm in} \simeq 0.16c$. The high velocity identifies the absorber as an ultra-fast inflow (UFI), which is detected at $\sim 3$-$3.7σ$ across different methods and continuum models. Photoionization model…

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astro-ph.SRastro-ph.GA

The scarcity of white dwarf-brown dwarf binaries in the solar neighbourhood: A population synthesis study

Alejandro Santos-García, Santiago Torres, Alberto Rebassa-Mansergas, Sarah L. Casewell, Zhangliang Chen, Hongwei Ge

White dwarf--brown dwarf (WD--BD) binaries are intrinsically rare systems that provide a unique opportunity to study binary evolution and the formation of substellar companions. Despite recent observational progress, only a small number are known in the solar neighbourhood. We investigate whether their scarcity can be explained by binary formation and evolution together with observational selection effects. We extend the MRBIN binary population synthesis code into the substellar regime by incorp…

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hep-phastro-ph.HE

Strong Constraints for Line Signals from Dark Matter Annihilation in Sub-halo

Asier Salces Pérez, Thong T. Q. Nguyen, Pedro De la Torre Luque, Tim Linden

We present a dedicated search for monochromatic gamma-ray emission from a recently proposed nearby dark matter subhalo candidate. Using nearly 15 years of Fermi-LAT Pass 8 data, we perform a sliding-window search for gamma-ray lines between 10 and 300 GeV. We do not find any statistically significant evidence for a line signal. The largest excess occurs at $E_γ\simeq 28 \, {\rm GeV}$ with a local significance of $2.5σ$. We therefore derive 95% confidence level upper limits on the annihilation cr…

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astro-ph.GA

Classical Cepheids in the Nuclear Stellar Disk: membership via dynamical analysis

M. De Leo, M. Zoccali, R. Albarracin, B. Acosta-Tripailao, J. Minniti

(abridged) Four classical Cepheids have been associated to the Nuclear Stellar Disk (NSD), suggesting a burst of star formation 20 Myrs ago. In this work, we analyse all available data for these four Cepheids in order to gauge if they are bona fide members of the NSD or interlopers in the region. This allows to confirm or rule out the star formation burst hypothesised in the literature. Our dynamical analysis is based on an updated MWpotential that includes all components of the inner Galaxy. We…

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hep-phastro-ph.HE

Strong Constraints on Line Signals from Dark Matter Annihilation in a Nearby Subhalo

Asier Salces Pérez, Thong T. Q. Nguyen, Pedro De la Torre Luque, Tim Linden

We present a dedicated search for monochromatic gamma-ray emission from a recently proposed nearby dark matter subhalo candidate. Using nearly 15 years of Fermi-LAT Pass 8 data, we perform a sliding-window search for gamma-ray lines between 10 and 300 GeV. We do not find any statistically significant evidence for a line signal. The largest excess occurs at $E_γ\simeq 28 \, {\rm GeV}$ with a local significance of $2.5σ$. We therefore derive 95% confidence level upper limits on the annihilation cr…

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astro-ph.HE

Unlocking the QPE Mystery: Star-Disk Collisions in Realistic AGN Disks

Zhaohuan Zhu, Xiaoshan Huang, Yan-Fei Jiang, Shunquan Huang

Quasi-periodic eruptions (QPEs) are luminous, recurring soft X-ray outbursts observed in the nuclei of low-mass galaxies. They display two remarkable trends: outburst durations are $\sim$10-20% of the recurrence timescale, and longer bursts are more luminous. A promising theory that naturally explains the quasi-periodicity invokes collisions between a star on an extreme mass-ratio inspiral (EMRI) orbit and the accretion disk around the supermassive black hole. However, it remains unclear how thi…

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astro-ph.GA

Bridging integrated-light and resolved-star studies of Local Group dwarf spheroidals. A novel use of deep imaging based on amateur telescopes

Sergio Guerra Arencibia, Ignacio Trujillo, Mireia Montes, Ignacio Ruiz Cejudo, Carlos Marrero-de la Rosa, Vicente Fontana, Aleix Roig

Low-mass galaxies beyond the Local Group can only be studied through their integrated light, yet it remains unclear whether structural parameters inferred from integrated light are directly comparable to those obtained from resolved-star studies. Using new deep imaging obtained with small-aperture amateur telescopes, we analyse the classical dwarf spheroidals Leo II, Sculptor, and Fornax, whose stellar distributions have been extensively characterised through resolved-star studies. We find that…

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gr-qcastro-ph.HEhep-phhep-thnlin.CD

Tidally-enhanced resonances in extreme-mass-ratio inspirals: A tertiary path to chaos

Kyriakos Destounis, Takuya Katagiri, Sajal Mukherjee, Kostas D. Kokkotas

Extreme-mass-ratio inspirals (EMRIs) provide a unique laboratory for probing strong-field gravity and complex relativistic dynamics. We study a tidally deformed EMRI composed of a stellar-mass secondary orbiting a supermassive (non-)rotating black hole embedded in an external, adiabatically varying tidal environment. These systems provide a restricted, yet astrophysically motivated, realization of the relativistic three-body problem, expected to appear in active galactic nuclei, with a clear hie…

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astro-ph.EP

Radial velocity detection of the TRAPPIST-1 planetary system with SPIRou and NIRPS

Alexandrine L'Heureux, René Doyon, Charles Cadieux, Pascal Petit, Olivia Lim, Étienne Artigau, Neil J. Cook, Eric Agol et al.

The TRAPPIST-1 system is well-known for its seven transiting Earth-sized exoplanets. It has been extensively studied and characterized, notably with transit timing variations (TTVs) to precisely measure the mass of the planets. Using near-infrared spectroscopic observations obtained as part of the SPIRou Legacy Survey and the NIRPS Guaranteed Time Observation programs, we aimed to verify those values through radial velocity (RV) measurements of the system. Our RV analysis reveals that the curren…

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