Time lag in transient cosmic accreting sources

TL;DR

This paper presents a universal model for time lags between brightness peaks at different wavelengths in transient accreting cosmic sources, applicable to various systems like AGNs and binaries.

Contribution

It introduces a simple, general formula for time lag calculation in accreting sources, linking physical processes to observable delays across wavelengths.

Findings

Derived a universal formula for time lag estimation.

Validated models with examples from galactic and extragalactic sources.

Linked time lag mechanisms to physical properties like viscosity and free fall time.

Abstract

We develop models for time lag between maxima of the source brightness in different wavelengths during a transient flash of luminosity connected with a short period of increase of the mass flux onto the central compact object. We derive a simple formula for finding the time delay among events in different wavelengths, valid in general for all disk accreting cosmic sources, and discuss quantitatively a model for time lag formation in AGNs. In close binaries with accretion disks the time lag is connected with effects of viscosity defining a radial motion of matter in the accretion disk. In AGN flashes, the falling matter has a low angular momentum, and the time lag is defined by the free fall time to the gravitating center. We show the validity of these models by means of several examples of galactic and extragalactic accreting sources.