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Journal Club


"The disc vanishes"

Jean-Pierre Lasota (CAMK, Warsaw)

New observations are consistent with theoretical predictions that during the low states FO Aquarii, the accretion disk dissipates into a ring of diamagnetic blobs. The talk is based on


"Radio/X-ray correlation in black hole accretion systems"

Fu-Guo Xie (Shanghai Astronomical Observatory)

Jet is an unique feature of black hole BH) accretion systems. The linear relationship (in Log space) between radio and X-ray luminosities and BH mass provides a direct hint on the connection between accretion and ejection (jet). In this talk, I will address two projects. 1) The fundamental plane of BH activity for quiescent AGNs, where we gather from literature a sample of 73 sources, and confirm the radio/X-ray correlation slope steepens to 1.2 (compared to the normal 0.6). Such steepening is consistent with a jet origin in X-ray emission in quiescent AGNs. 2) The observations and theoretical interpretation of the so-called outlier sources with a hybrid radio/X-ray correlation.


"High-energy properties of young radio sources"

Dr. Malgosia Sobolewska (Smithsonian Astrophysical Observatory)

Formation of relativistic jets is one manifestation of black hole (BH) activity. Jets impact BH surrounding and in consequence affect BH feeding and growth. This coupling is believed to be essential to the AGN-galaxy feedback, which likely is present already at the stage of the initial jet launching. Contrary to theoretical predictions, young radio jets proved to be relatively faint and observing them has been challenging before the Chandra and XMM-Newton era. I will discuss the most recent X-ray results for a sample of Compact Symmetric Objects (CSO; radio structure sizes < 1kpc, ages < 3000 years) based on the high quality broadband spectra obtained with Chandra, XMM-Newton, and NuSTAR. We find evidence for a dichotomy of the CSO environment: X-ray obscured CSOs appear to have smaller radio sizes than X-ray unobscured CSOs with the same radio power. Thus, the environment may play a crucial role in regulating the early growth of the radio jets. Importantly, X-ray studies of the CSOs, in conjunction with the recent developments in lower energy bands, offer new insights for understanding the structure and size of the AGN obscuring torus.