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.
Agnieszka Janiuk (CFT PAN)
Federico Gonzalez (Universidad Nacional de San Juan)
Radek Poleski (OAUW)
Christian Ikechukwu Eze (CAMK PAN)
Leatitia Gibaud (University of Białystok)
Mikołaj Korzyński (CFT PAN)
Sebastian Trojanowski (Astrocent)
Dorottya Szesci (Nicolaus Copernicus University, Toruń)
The metal-poor, irregular dwarf galaxy called I Zwicky 18 has been suggested to harbor (theorized) progenitors of Gravitational-Wave emitting mergers. The galaxy emits an unprecedented amount of hard ionizing radiation together with certain emission features in its spectrum. To explain this, a theorist like me has to put together a complex hypothesis based on reliable computer models of those stars, and compare its predictions to all available observations in the literature. Sounds easy, right? But what if she finds that the observations *themselves* actually contradict each other? Then she has no choice but go down the rabbit hole of learning how observational astronomers work, speak, and think – a scientific challenge in itself. In this talk, I share my curious story of the past 12 years tackling the case of I Zwicky 18, and my hunt for finding observational evidence for the existence of a certain type of GW progenitors, which have just come to an end. (Relevant paper: A&A 703 A131)
Parikshit Biswas (CAMK, Warsaw)
