Rms-flux relation of Cyg X-1 with RXTE: dipping and nondipping cases

TL;DR

This study investigates the linear rms-flux relation in Cyg X-1's X-ray variability using RXTE data, revealing differences between dipping and nondipping states across energy bands, explained by the propagating perturbation model.

Contribution

It provides the first detailed analysis of the rms-flux relation in Cyg X-1 during dipping and nondipping states across different energy bands.

Findings

Linear rms-flux relation observed in dipping states at 0.1-10 Hz.

Steeper rms-flux slope in nondipping low-energy regime.

Variable slopes in high-energy bands within errors.

Abstract

The rms (root mean square) variability is the parameter for understanding the emission temporal properties of X-ray binaries (XRBs) and active galactic nuclei (AGN). The rms-flux relation with Rossi X-ray Timing Explorer (RXTE) data for the dips and nondip of black hole Cyg X-1 has been investigated in this paper. Our results show that there exist the linear rms-flux relations in the frequency range 0.1-10 Hz for the dipping light curve. Moreover, this linear relation still remains during the nondip regime, but with the steeper slope than that of the dipping case in the low energy band. For the high energy band, the slopes of the dipping and nondipping cases are hardly constant within errors. The explanations of the results have been made by means of the ``Propagating Perturbation'' model of Lyubarskii (1997).