Abstract Details
| Name: Saikruba Krishnan Affiliation: The Inter-University Centre for Astronomy and Astrophysics (IUCAA) Conference ID: ASI2024_433 Title : Multi-wavelength study of an X-ray flaring event and a variable soft X-ray excess in Seyfert galaxy detected with eROSITA Authors and Co-Authors : S. Krishnan1⋆, A.G. Markowitz1, 2, M. Krumpe3, D. Homan3, R. Brogan3, S. Haemmerich4, M. Gromadzki5, T. Saha1, M. Schramm6, H. Winkler7, S. Waddell8, J. Wilms4, A. Rau8, Z. Liu8, and I. Grotova8 Abstract Type : Poster Abstract Category : High Energy Phenomena, Fundamental Physics and Astronomy Abstract : Active Galactic Nuclei (AGN) are powered by accretion of gas onto supermassive black holes. There are open questions regarding how the X-ray corona, disk, and BLR evolve in response to changes in the global accretion supply. We are using eROSITA's all-sky X-ray surveys to identify extragalactic X-ray transients. I present multi-wavelength observations of a candidate AGN transient event detected with eROSITA. Its X-ray flux increased by ~6 over six months; concurrent optical photometric monitoring data with ATLAS showed a simultaneous increase by 4. We triggered a multi-wavelength follow-up monitoring program (XMM-Newton, NICER; optical spectroscopy) to study the evolution of the accretion disk, broad-line region, and X-ray corona. We witnessed a likely sudden strong increase in local accretion rate, which manifested itself via an increase in accretion disk emission and thermal Comptonization emission in the soft X-rays, followed by a decrease in accretion and Comptonized luminosity. The physical processes (e.g., disk instabilities) leading to such substantial variations are still an open question, and future continuous monitoring along with multi-wavelength studies will shed some light on it. |