Swadesh Chand (Inter-University Centre for Astronomy and Astrophysics, India)
Staszku, Podaję. Title: Accretion Geometry of Black Hole X-ray Binaries in the Hard State Abstract: Black hole X-ray binaries (BHXRBs) serve as ideal laboratories for studying the complex interplay between accretion and ejection processes in strong gravitational fields. Most of the low-mass BHXRBs are transient in nature and exhibit sporadic outbursts. During a typical outburst, these systems transition through various spectral states, from hard to soft, each associated with distinct spectral and timing properties. Despite decades of studies, the exact physical picture of these systems in the hard spectral state remains an open question, particularly regarding the geometry of the corona and extent of the inner accretion disk. While some studies argue for a disk that extends close to the innermost stable circular orbit (ISCO) in the hard state, others propose a significantly truncated disk scenario. In this talk, I will present findings from some of our recent broadband spectral and timing studies of BHXRBs in their hard state, which provide insights into the nature and evolution of the inner accretion flow.
Maciek Wielgus (Instituto de Astrofisica de Andalucia, Granada, Spain)
Very long baseline interferometry (VLBI) offers a way to study AGN jets with an exceptionally high angular resolution, zooming into the zone of the jet collimation and acceleration. In particular, a global array of the Event Horizon Telescope (EHT) offers unprecedented resolution with highest VLBI observing frequency of 230 GHz. During the first observing campaign of the EHT in 2017, observations of 16 AGN sources were carried out. Together with the previous measurements at lower radio frequencies, these new observations allow for a statistical study of the properties of AGN cores across the angular scales. We observe a persistent and statistically significant effect of brightness temperature increase with the distance from the central black hole, which indicates evolution of Doppler factors in accelerating jets and a gradual conversion of the magnetic energy into kinetic energy. I will describe these observations and discuss what they teach us about the AGN jets.
Sudhagar Suyamprakasam (CAMK, Warsaw)
he LIGO/Virgo/KAGRA (LVK) collaboration has discovered several dozen binary mergers since 2015; however, binary mergers are not the exclusive sources of gravitational waves. Asymmetric rotating neutron stars and planetary or asteroid mass-primordial BH (PBH) binaries during their in-spiral phase also emit quasi-monochromatic, long-duration gravitational waves. Detecting signals from these sources requires longer observation times due to their weak amplitude with respect to the current sensitivity of detectors, and thus far, the detection of those signals has not been confirmed yet. Suppose the massive object lies in the line of sight; the signal can undergo gravitational lensing. This presentation provides a brief overview of gravitational wave gravitational lensing, an emerging subdomain in gravitational wave astronomy, and the impact of the gravitational lensing signature in long-duration signals, which provides new possibilities for detecting the signals from those sources.
Luke Dones (Southwest Research Institute, Boulder, Colorado)
