Paper

The Large Amplitude X-ray Variability in NGC 7589: Possible Evidence for Accretion Mode Transition

Liu, Zhu, He-Yang, Liu, Qiao, Erlin, Yuan, Weimin, Cheng, Huaqing

2019

Overview

We report the discovery of large amplitude X-ray variability in the low luminosity AGN (LLAGN) MGC 7589, and present possible observational evidence for accretion mode transition in this source. Long-term X-ray flux variations by a factor of more than 50 are found using X-ray data obtained by Swift/XRT and XMM-Newton over 17 years. Results of long-term monitoring data in the UV, optical and infrared bands over ~20 years are also presented. The Eddington ratio increased from \\(10^{-3}\\) to \\(\\sim0.13\\), suggesting a transition of the accretion flow from an ADAF to a standard thin accretion disc. Further evidence supporting the thin disc in the high luminosity state is found by the detection of a significant soft X-ray component in the X-ray spectrum. The temperature of this component (\\(\\sim19^{+15}_{-7}\\)eV, fitted with a blackbody model) is in agreement with the predicted temperature of the inner region for a thin disc around a black hole (BH) with mass of \\(\\sim10^{7}\\,M_{\\mathrm{Sun}}\\). These results may indicate that NGC 7589 had experienced accretion mode transition over a timescale of a few years, suggesting the idea that similar accretion processes are at work for massive black hole and black hole X-ray binaries.

• Publisher: Cornell University Library, arXiv.org
• Subject: Accretion disks / Active galactic nuclei / Amplitudes / Blackbody / Deposition / Luminosity / Soft x rays / X ray binaries / X ray stars / XMM (spacecraft)