129 citations · 1.7k across the 78 of their papers we have counts for
29 papers · 1 filter
Low-angular-momentum accretion shocks can power weak-to-moderate X-ray flares from SgrA*
Samik Mitra, Bożena Czerny, Michal Zajaček +1
X-ray flares from Sgr~A* span broad ranges in duration, fluence, and luminosity, but their origin remains unsettled. We test whether standing shocks in low-angular-momentum magneti…
What is the reason for the lack of cool evolved stars near the center of the Galaxy?
Petr Kurfürst, Michal Zajaček, Norbert Werner +2
The observed deficit of bright late-type giants in the central parsec of the Milky Way remains an open problem. We investigate whether repeated passages of red giants (RGs) through…
Observations of X-ray quasi-periodic eruptions
Thomas Wevers, Joheen Chakraborty, Erwan Quintin +2
Quasi-periodic eruptions (QPEs) are a novel class of repeating nuclear transients, discovered exclusively in the X-ray band to date. Since their initial discovery in 2019, the QPE…
Tidal disruption of a low-mass star in an active galactic nucleus as the origin of the PS16dtm outburst
Marzena Śniegowska, Bożena Czerny, Michal Zajaček +7
The event PS16dtm, which occured in the center of the Narrow Line Seyfert 1 (NLS1) galaxy SDSS J015804.75-005221.8 (z = 0.080440), is one of the few candidates for a tidal disrupti…
Evolution of Quasi-Periodic Eruptions in the post-TDE Accretion Disk Perturbed by an Orbiting Star
Martin Mondek, Michal Zajaček, Henry Best +3
Quasi-periodic eruptions (QPEs) are a recently discovered class of highly variable X-ray bursts originating in galactic nuclei. These high-amplitude bursts exhibit periodicity rang…
Non-orbital particle trapping in binary black holes through dynamic stability
Ali Kurmus, Michal Zajacek, Greg Kestin +1
We present an interdisciplinary comparison between binary black hole systems and Radio Frequency (RF) Paul Traps, modeling the gravitational binary system as a rotating saddle near…
Repeated Partial Tidal Disruptions and Quasi-Periodic Eruptions in SwJ023017.0+283603
Dheeraj Pasham, Eric Coughlin, Chris Nixon +5
SwJ023017.0+283603 (SwJ0230) exhibited soft X-ray (0.3-1.0 keV) eruptions recurring roughly every 22 days. We present results from an extended monitoring campaign of SwJ0230 using…
Repeating Nuclear Transients as Candidate Electromagnetic Counterparts of LISA Extreme Mass Ratio Inspirals
Shubham Kejriwal, Vojtech Witzany, Michal Zajacek +2
Extreme-mass-ratio inspirals (EMRIs) are one of the primary targets for the recently adopted millihertz gravitational-wave (GW) observatory LISA. Some previous studies have argued…
A Case for a Binary Black Hole System Revealed via Quasi-Periodic Outflows
Dheeraj R. Pasham, Francesco Tombesi, Petra Sukova +33
Binaries containing a compact object orbiting a supermassive black hole are thought to be precursors of gravitational wave events, but their identification has been extremely chall…
Alive but Barely Kicking: News from 3+ years of Swift and XMM-Newton X-ray Monitoring of Quasi-Periodic Eruptions from eRO-QPE1
Dheeraj R. Pasham, Eric R. Coughlin, Michal Zajacek +11
Quasi-periodic Eruptions (QPEs) represent a novel class of extragalactic X-ray transients that are known to repeat at roughly regular intervals of a few hours to days. Their underl…
Lense-Thirring Precession after a Supermassive Black Hole Disrupts a Star
Dheeraj R. Pasham, Michal Zajacek, C. J. Nixon +8
An accretion disk formed around a supermassive black hole (SMBH) after it disrupts a star is expected to be initially misaligned with respect to the black hole's equatorial plane.…
MAD UFOs: Magnetically Arrested Discs with persistent Ultra-Fast Outflows
Petra Suková, Michal Zajaček, Vladimír Karas
General-relativistic magneto-hydrodynamical (GRMHD) simulations of accreting black holes suggest that the accretion flows form toroidal structures embedded in a large scale compone…
X-ray eruptions every 22 days from the nucleus of a nearby galaxy
Muryel Guolo, Dheeraj R. Pasham, Michal Zajaček +15
Galactic nuclei showing recurrent phases of activity and quiescence have recently been discovered, with recurrence times as short as a few hours to a day -- known as quasi-periodic…
Precession-induced Variability in AGN Jets and OJ 287
Silke Britzen, Michal Zajaček, Gopal-Krishna +5
The combined study of the flaring of Active Galactic Nuclei (AGN) at radio wavelengths and pc-scale jet kinematics with Very Long Baseline Interferometry (VLBI) has led to the view…
Science with a small two-band UV-photometry mission III: Active Galactic Nuclei and nuclear transients
M. Zajaček, B. Czerny, V. K. Jaiswal +14
In this review (the third in the series focused on a small two-band UV-photometry mission), we assess possibilities for a small UV two-band photometry mission in studying accreting…
Science with a small two-band UV-photometry mission I: Mission description and follow-up observations of stellar transients
N. Werner, J. Řípa, C. Thöne +33
This is the first in a collection of three papers introducing the science with an ultra-violet (UV) space telescope on an approximately 130~kg small satellite with a moderately fas…
Spectral Energy Distribution profiles from AGN accretion disc in multi-gap setup
Marcel Štolc, Michal Zajaček, Bożena Czerny +1
Spectral Energy Distribution (SED) of the broad-band continuum emission from black-hole accretion discs can serve as a tool to measure parameters of the central body and constrain…
Radio jet precession in M81*
S. D. von Fellenberg, M. Janssen, J. Davelaar +5
We report four novel position angle measurements of the core region of M81* at 5GHz and 8GHz, which confirm the presence of sinusoidal jet precession of the M81 jet region as sugge…
Non-thermal emission from fall-back clouds in the Broad-Line Region of Active Galactic Nuclei
Ana Laura Müller, Mohammad-Hassan Naddaf, Michal Zajaček +3
The spectra of active galactic nuclei exhibit broad-emission lines that presumably originate in the Broad-Line Region (BLR) with gaseous-dusty clouds in a predominantly Keplerian m…
Electromagnetic signatures of strong-field gravity from accreting black holes
Vladimir Karas, Michal Zajacek, Devaky Kunneriath +1
Observations of galactic nuclei help us to test General Relativity. Whereas the No-hair Theorem states that classical, isolated black holes eventually settle to a stationary state…
Stellar transits across a magnetized accretion torus as a mechanism for plasmoid ejection
Petra Suková, Michal Zajaček, Vojtěch Witzany +1
The close neighbourhood of a supermassive black hole contains not only the accreting gas and dust but also stellar-sized objects, such as late-type and early-type stars and compact…
Depletion of bright red giants in the Galactic center during its active phases
Michal Zajaček, Anabella Araudo, Vladimír Karas +2
Observations in the near-infrared domain showed the presence of the flat core of bright late-type stars inside from the Galactic center supermassive black hole…
Current and future applications of Reverberation-mapped quasars in Cosmology
Swayamtrupta Panda, Mary Loli Martínez-Aldama, Michal Zajaček
Reverberation mapping technique is an important milestone in AGN demographics, kinematics and the structure of the Broad Line Region (BLR) based on the time-delay response between…
Super-Massive Black Hole mass estimation from bright flares
Vladimir Karas, Michal Bursa, Michal Dovciak +4
Super-Massive Black Holes reside in galactic nuclei, where they exhibit episodic bright flares due to accretion events. Taking into account relativistic effects, namely, the boosti…