A Mass-Independent Damping Timescale in Black Hole Accretion Systems

TL;DR

This study uncovers a mass-independent damping timescale in black hole accretion systems, suggesting thermal conduction in disk-corona interactions influences X-ray variability, challenging previous scaling law expectations.

Contribution

It presents the first observational evidence of a mass-independent characteristic damping timescale in black hole systems, highlighting the role of thermal conduction in accretion disk variability.

Findings

Discovery of a mass-independent damping timescale in black hole accretion systems.

Thermal conduction from disk-corona interactions influences X-ray variability.

Implications for the disk--corona--jet connection in astrophysical systems.

Abstract

The scaling laws reveal the underlying structural similarities shared by astrophysical systems across vastly different scales. In black hole accretion systems, the scaling relations between the characteristic damping timescales (CDTs) of light curves and black hole mass offer valuable insights into the underlying physical structure of accretion disks. Here, we investigate the long-term hard X-ray CDTs of 106 black hole and neutron star accretion systems using light curves from the \textit{Swift} Burst Alert Telescope 157-month catalog. Unexpectedly, for the first time, we discover a mass-independent CDT in these black hole accretion systems, in contrast to well-established scaling laws. This puzzling phenomenon can be attributed to conductive timescales arising from disk--corona interactions, instead of the intrinsic accretion disk processes characterized by scaling laws, and it may further modulate jet emission in blazars. This result demonstrates thermal conduction as a key mechanism driving hard X-ray variability and offers new observational evidence for the disk--corona--jet connection.