Astronomical Institute of the Slovak Academy of Sciences

H.E.S.S. detection and multi-wavelength study of the $z \sim$ 1 blazar PKS 0346 $-$ 27

H. E. S. S. collaboration

PKS 0346-27 is a Low Synchrotron Peaked (LSP) blazar at redshift 0.991. The very-high-energy (VHE, E > 100 GeV) spectra of blazars are always affected by $γ γ$ absorption by the Ext…

astro-ph.HE2025★ 3 cited

Multiband optical variability on diverse timescales of the blazar Ton 599 from 2011 to 2023

O. Vince, C. M. Raiteri, M. Villata +72

(Shortened)Context: We analyze the optical variability of the FSRQ Ton 599 using BVRI photometry from the WEBT collaboration (2011-2023), complemented by photometric and spectrosco…

Pulsars identified in the LOFAR Two-metre Sky Survey at 144 MHz

G. A. C. Rijkers, C. G. Bassa, J. R. Callingham +1

We present the astrometric identification of 80 known radio pulsars as unresolved continuum sources detected at 144 MHz in the second data release of the LOFAR Two-metre Sky Survey…

The role of distant pulsars in the detectability of continuous gravitational waves

Kathrin Grunthal, Nataliya Porayko, David J. Champion +1

One of the imminent science goals of pulsar timing arrays (PTAs) is the detection of a continuous gravitational wave (CGW) emitted by an individual supermassive black hole binary (…

astro-ph.HE2025★ 4 cited

Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations

Saurabh, Hendrik Müller, Sebastiano D. von Fellenberg +282

We investigate the presence and spatial characteristics of the jet base emission in M87* at 230 GHz, enabled by the enhanced uv coverage in the 2021 Event Horizon Telescope (EHT) o…

Lost and Found - A gallery of overlooked optical nuclear transients from the ZTF archive

E. Quintin, E. Russeil, M. Llamas Lanza +12

Tidal disruption events (TDEs) correspond to the destruction of a star by the tidal forces around a black hole, leading to outbursts which can last from months to years. These tran…

astro-ph.HE2025★ 3 cited

Black-hole X-ray binary Swift J1727.8 $-$ 1613 shows simultaneous Type-B and Type-C quasi-periodic oscillations across the hard-intermediate and soft-intermediate states

Pei Jin, Mariano Méndez, Federico García +2

We present a timing analysis of \textit{Insight}-HXMT observations of the black-hole X-ray binary Swift J1727.8 $-$ 1613 across a bright soft X-ray flare on 2023 September 19 (MJD 60…

Pulse profile modelling of the accretion-powered millisecond pulsar SAX J1808.4-3658 using NICER data from its 2019 and 2022 outbursts

Bas Dorsman, Tuomo Salmi, Anna L. Watts +5

Pulse profile modelling is a relativistic ray-tracing technique that has provided constraints on parameters, with a focus on mass and radius, of five rotation-powered millisecond p…

The most distant optically polarised GRB afterglow: GRB 240419A at z = 5.178

R. Brivio, S. Covino, M. Ferro +31

Gamma-ray bursts (GRBs) are extremely bright phenomena powered by relativistic jets arising from explosive events at cosmological distances. The nature of the jet and the configura…

Double white dwarf ZTF J0538+1953 as the brightest verification binary for space laser interferometers

Serguey Antipin, Alexander Belinski, Leonid Berdnikov +4

A decrease in the orbital period of the ultrashort-period binary white dwarf \ZTF, which is one of the Galactic verification binaries in the millihertz frequency range for planned…

Aql X-1 from dawn 'til dusk: the early rise, fast state transition and decay of its 2024 outburst

A. Marino, F. Coti Zelati, K. Alabarta +36

Transient Low-Mass X-ray Binaries (LMXBs) are usually first detected by all-sky X-ray monitors when they enter new outbursts, typically at X-ray luminosities above $\sim$ 10 $^{36}$ …

astro-ph.HE2025★ 6 cited

The double neutron star PSR J1946+2052 I. Masses and tests of general relativity

Lingqi Meng, Paulo C. C. Freire, Kevin Stovall +28

We conducted high-precision timing of PSR J1946+2052 to determine the masses of the two neutron stars in the system, test general relativity (GR) and assessed the system's potentia…

VHE $γ$ -ray observations of bright BL Lacs with the Large-Sized Telescope prototype (LST-1) of the CTAO

The CTAO-LST Project, :, K. Abe +331

Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based gamma-ray observatory operating in the energy range from 20 GeV up to 300 TeV, with two sites in La…

Radiation-dominated polar emitting region of an accreting X-ray pulsar -- I. Polarization- and spectrum-dependent structure, and the emergent continuum

M. I. Gornostaev

The radiation-dominated polar emitting region of an accreting X-ray pulsar is simulated numerically in the framework of a three-dimensional (geometrically two-dimensional) model. T…

Violent mergers revisited: The origin of the fastest stars in the Galaxy

Rüdiger Pakmor, Ken J. Shen, Aakash Bhat +12

Binary systems of two carbon-oxygen white dwarfs are one of the most promising candidates for the progenitor systems of Type Ia supernovae. Violent mergers, where the primary white…

The very faint X-ray transient Swift J174610-290018 at the Galactic center

Giovanni Stel, Gabriele Ponti, Nathalie Degenaar +17

Very Faint X-ray Transients (VFXTs) are a class of X-ray binary systems that exhibit occasional outbursts with peak X-ray luminosities (L_X< 1e36 erg s^-1) much lower than typical…

astro-ph.HE2025★ 20 cited

Infrared Synchrotron Emission in the Soft State of GX 339-4 and the Mid-Infrared/X-ray Luminosity Plane of Black Hole X-ray Binaries

P. Gandhi, D. M. Russell, M. C. Baglio +33

Progress in understanding the growth of accreting black holes remains hampered by a lack of sensitive coordinated multiwavelength observations. In particular, the mid-infrared (MIR…

Horizon-scale variability of M87* from 2017--2021 EHT observations

The Event Horizon Telescope Collaboration

We report three epochs of polarized images of M87* at 230\,GHz using data from the Event Horizon Telescope (EHT) taken in 2017, 2018, and 2021. The baseline coverage of the 2021 ob…

Empirical correlation between masses of black holes and Wolf-Rayet stars derived from their mass distributions in spectroscopic binaries

Konstantin Postnov, Ivan Shaposhnikov, Anatol Cherepashchuk

We present observationally determined mass distributions of Wolf-Rayet (WR) stars in WR+OB binaries and black holes (BH) in spectroscopic binaries. Both WR and BH mass probability…

astro-ph.HE2025★ 4 cited

Can GRB 250702B be explained as the tidal disruption of a white dwarf by an intermediate mass black hole? Yes

Rob AJ Eyles-Ferris, Andrew King, Rhaana LC Starling +11

GRB 250702B is a unique astrophysical transient characterised by its nature as a repeating gamma-ray trigger. Its properties include possible periodicity in its gamma-ray light cur…

A HyperFlash and ÉCLAT view of the local environment and energetics of the repeating FRB 20240619D

O. S. Ould-Boukattine, A. J. Cooper, J. W. T. Hessels +16

Time-variable propagation effects provide a window into the local plasma environments of repeating fast radio burst (FRB) sources. Here we report high-cadence observations of FRB 2…

A multiwavelength study of the Galactic center black hole candidate MAXI J1744-294

Shifra Mandel, Kaya Mori, Paul A. Draghis +37

For the first time in nearly a decade, a bright transient was detected in the central parsec (pc) of the Galaxy. MAXI J1744-294, or -- as it was known in its previous life -- Swift…

Discovery and Analysis of Afterglows from Poorly Localised GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

Amit Kumar, B. P. Gompertz, B. Schneider +86

Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose a challenge for optical follow-up due to their large initial localisation…