91 citations · 615 across the 31 of their papers we have counts for
9 papers · 1 filter
Changing Look AGN: An X-ray Look
Lev Titarchuk, Elena Seifina, Yegor Mishin
To date, a number of changing-look (CL) active galactic nuclei (AGNs) are known. We studied, in detail what happens to the X-ray spectrum during the CL events using the example of…
Active galaxy nuclei: current state of the problem
Elena Seifina
This review presents the main points of current advances in the field of active galactic nuclei (AGN). A brief historical excursion about the search for the nature of AGN is given.…
Spectral index-mass accretion rate correlation and evaluation of black hole masses in AGNs 3C~454.3 and M87
Lev Titarchuk, Elena Seifina, Alexandre Chekhtma +1
We present the discovery of correlations between the X-ray spectral (photon) index and mass accretion rate observed in active galactic nuclei (AGNs) 3C~454.3 and M87. We analyzed s…
Scaling of X-ray spectral properties of a black hole in the Seyfert 1 galaxy NGC~7469
Elena Seifina, Lev Titarchuk, Lyubov Ugolkova
We present our analysis of X-ray spectral properties observed from the Seyfrert 1 galactic nucleus NGC~7469 using the RXTE and ASCA observations. We demonstrate strong observationa…
NGC 4051: Black hole mass and photon index-mass accretion rate correlation
Elena Seifina, Alexandre Chekhtman, Lev Titarchuk
We present a discovery of the correlation between the X-ray spectral (photon) index and mass accretion rate observed in AGN NGC 4051. We analyzed spectral transition episodes obser…
Swift J164449.3+573451 and Swift J2058.4+0516: Black hole mass estimates for tidal disruption event sources
Elena Seifina, Lev Titarchuk, Enrico Virgill
A tidal disruption event (TDE) is an astronomical phenomenon in which a previously dormant black hole (BH) destroys a star passing too close to its central part. We analyzed the fl…