Datum od | 15.05.2022 / 13:00 |
Datum do | 15.05.2022 / 15:00 |
Celodenní | Ne |
Pro studenty | Ano |
Pro veřejnost | Ano |
Jen pro zvané | Ne |
Author: Deepika Bollimpalli
Title: Variability in discs around black holes: Broadband variability and QPOs
Abstract:
Long-term observations have shown that black hole X-ray
binaries exhibit strong, aperiodic variability on time scales of a few
milliseconds to seconds. In addition, these systems also exhibit rapid
variability in their X-ray light curves termed quasi-periodic
oscillations (QPOs); also broadly classified into high-frequency and
low-frequency QPOs. Understanding the nature of these variabilities
and the underlying physical processes helps us probe the nature of the
compact object and its surroundings. In this talk, I shall give a
broad overview of the existing theoretical models for broadband
variability and different types of QPOs, with a focus on the findings
from the current state-of-art simulations of accretion discs in
reproducing such time variability phenomena. In particular, I will
discuss how the mass accretion rate fluctuations generated by the
turbulence in the simulations naturally explain the observed
broad-band variability in BHXRBs, and how the precession frequency of
the inner geometrically thick disc differs from the standard
Lense-Thirring precession frequency in truncated disc geometry and its
implications to Type-C QPOs.
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