Long term X-ray variability characteristics of the narrow-line Seyfert 1 galaxy RE~J1034+396

TL;DR

This study analyzes long-term X-ray variability in the NLS1 galaxy RE J1034+396 using multi-instrument data, revealing increased variability at longer time scales and estimating the black hole mass around 3 million solar masses.

Contribution

It provides a comprehensive analysis of the galaxy's X-ray variability across multiple time scales and instruments, and estimates the black hole mass based on QPO characteristics.

Findings

Variability is slightly larger in the hard X-ray band.

X-ray variability increases sharply at longer time scales.

Black hole mass estimated at approximately 3 million solar masses.

Abstract

We present the results of our study of the long term X-ray variability characteristics of the Narrow Line Seyfert 1 galaxy RE J1034+396. We use data obtained from the AstroSat satellite along with the light curves obtained from XMM-Newton and Swift-XRT. We use the 0.3 - 7.0 keV and 3 - 20 keV data, respectively, from the SXT and the LAXPC of AstroSat. The X-ray spectra in the 0.3 - 20 keV region are well fit with a model consisting of a power-law and a soft excess described by a thermal-Compton emission with a large optical depth, consistent with the earlier reported results. We have examined the X-ray light curves in the soft and hard X-ray bands of SXT and LAXPC, respectively, and find that the variability is slightly larger in the hard band. To investigate the variability characteristics of this source at different time scales, we have used X-ray light curves obtained from XMM-Newton data (200 s to 100 ks range) and Swift-XRT data (1 day to 100 day range) and find that there are evidences to suggest that the variability sharply increases at longer time scales. We argue that the mass of the black hole in RE J1034+396 is likely to be $\sim$3 $\times$ 10$^6$ M$_\odot$, based on the similarity of the observed QPO to the high frequency QPO seen in the Galactic black hole binary, GRS 1915+105.