Pulsars, transients and relativistic astrophysics

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Uniting the Observed Dynamical Dark Energy Preference with the Discrepancies in Ωm and H0 across Cosmological Probes

The Astrophysical Journal Letters American Astronomical Society 983:1 (2025) l27

Authors:

Xianzhe TZ Tang, Dillon Brout, Tanvi Karwal, Chihway Chang, Vivian Miranda, Maria Vincenzi
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Cosmic ray transport and acceleration with magnetic mirroring

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf562

Authors:

AR Bell, JH Matthews, AM Taylor, G Giacinti
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A MeerKAT survey of nearby dwarf novae: I. New detections

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf556

Authors:

J Kersten, E Körding, PA Woudt, PJ Groot, DRA Williams, I Heywood, DL Coppejans, C Knigge, JCA Miller-Jones, GR Sivakoff, R Fender
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Prompt gravitational-wave mergers aided by gas in Active Galactic Nuclei: The hydrodynamics of binary-single black hole scatterings

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025)

Authors:

Connar Rowan, Henry Whitehead, Gaia Fabj, Pankaj Saini, Bence Kocsis, Martin Pessah, Johan Samsing

Abstract:

Abstract Black hole binary systems embedded in AGN discs have been proposed as a source of the observed gravitational waves (GWs) from LIGO-Virgo-KAGRA. Studies have indicated binary-single encounters could be common place within this population, yet we lack a comprehensive understanding of how the ambient gas affects the dynamics of these three-body encounters. We present the first hydrodynamical simulations of black hole binary-single encounters in an AGN disc. We find gas is a non-negligible component of binary-single interactions, leading to unique dynamics, including the formation of quasi-stable hierarchical triples. The gas efficiently and reliably dissipates the energy of the three-body system, hardening the triple provided it remains bound after the initial encounter. The hardening timescale is shorter for higher ambient gas densities. Formed triples can be hardened reliably by 2 − 3 orders of magnitude relative to the initial binary semi-major axis within less than a few AGN orbits, limited only by our resolution. The gas hardening of the triple enhances the probability for a merger by a minimum factor of 3.5 − 8 depending on our assumptions. In several cases, two of the black holes can execute periapses of less than 10 Schwarzschild radii, where the dynamics were fully resolved for previous close approaches. Our results suggest that current timescale estimates (without gas drag) for binary-single induced mergers are an upper bound. The shrinkage of the triple by gas has the prospect of increasing the chance for unique GW phenomena such as residual eccentricity, dephasing from a third object and double GW mergers.
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Anomaly Detection and Radio-frequency Interference Classification with Unsupervised Learning in Narrowband Radio Technosignature Searches

The Astronomical Journal American Astronomical Society 169:4 (2025) 206

Authors:

Ben Jacobson-Bell, Steve Croft, Carmen Choza, Alex Andersson, Daniel Bautista, Vishal Gajjar, Matthew Lebofsky, David HE MacMahon, Caleb Painter, Andrew PV Siemion
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