The complex time behaviour of the microquasar GRS 1915+105 in the \rho-class observed with BeppoSAX. III: The hard X-ray delay and limit cycle mapping

TL;DR

This study analyzes the timing delays between hard and soft X-ray emissions in the microquasar GRS 1915+105 during ho-class bursting, revealing a variable delay correlated with count rate using limit cycle mapping and cross-correlation methods.

Contribution

It introduces a systematic approach to measure and analyze hard-soft X-ray delays in GRS 1915+105, combining limit cycle mapping with cross-correlation techniques for the first time.

Findings

Hard-soft X-ray delay varies from 3 to 10 seconds.

Delay correlates with baseline count rate.

Limit cycle mapping effectively characterizes delay behavior.

Abstract

The microquasar GRS1915+105 was observed by BeppoSAX in October 2000 for about ten days while the source was in \rho-mode, which is characterized by a quasi-regular type I bursting activity. This paper presents a systematic analysis of the delay of the hard and soft X-ray emission at the burst peaks. The lag, also apparent from the comparison of the [1.7-3.4] keV light curves with those in the [6.8-10.2] keV range, is evaluated and studied as a function of time, spectral parameters, and flux. We apply the limit cycle mapping technique, using as independent variables the count rate and the mean photon rate. The results using this technique were also cross-checked using a more standard approach with the cross-correlation methods. Data are organized in runs, each relative to a continuous observation interval. The detected hard-soft delay changes in the course of the pointing from about 3 s to about 10 s and presents a clear correlation with the baseline count rate.