The Colloquium takes place every Wednesday at 11:15 AM - Warsaw Copernicus Astronomical Centre online by means of Zoom platform. The Colloquium is given in English and chaired by dr Stanisław Bajtlik (contact mail seminar@camk.edu.pl). People from outside of the Copernicus Center are very welcome to participate. For technical detailes please contact Dr. Stanislaw Bajtlik (bajtlik@camk.edu.pl).
Scott Hagen (SISSA Trieste)
Active galactic nuclei (AGN) are powered by accretion onto a supermassive black hole (SMBH). Observations show that these vary on week-year timescales in the optical/UV and day-weeks in the X-ray. This is in stark contrast to standard accretion theory which predicts that they can only vary on ~10^5 year timescales, suggesting significant limitations in our understanding of accretion onto SMBHs. In this talk I will discuss how AGN variability provide an opportunity to study the physical conditions and structure of the accretion flow; from the central flow near the SMBH to outer large scale height structures such as the broad line region (BLR) and winds. I will show how modelling assuming a modified, intrinsically variable, disc structure can qualitatively match the observed variability properties; albeit with some limitations. I will further show results from a number of recent monitoring campaigns that highlight not only intrinsic variability, but also extrinsic variations caused by obscuring winds and variations in the BLR. Finally, I will briefly discuss the prospects for the upcoming ESA flagship mission NewAthena to probe the link between the inner flow and large scale structures (e.g. winds, the BLR) through a subset of sources displaying extreme variations in their inner structure.
Journal Club takes place on Mondays at 11:15 AM in the Seminar Room. The presentation is given in English and is chaired by Journal Club Coordinators. Anyone interested in giving a Journal Club talk is encouraged to contact the email: journalclub(@camk.edu.pl).
Sudhagar Suyamprakasam (NCAC, Warsaw)
Based on Collection of papers. TBA
