2020MNRAS.492.2335L -
Mon. Not. R. Astron. Soc., 492, 2335-2346 (2020/February-3)
The large amplitude X-ray variability in NGC 7589: possible evidence for accretion mode transition.
LIU Z., LIU H.-Y., CHENG H., QIAO E. and YUAN W.
Abstract (from CDS):
We report the discovery of large amplitude X-ray variability in the low-luminosity active galactic nucleus NGC 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/X-Ray Telescope and XMM-Newton over 17 yr. Results of long-term monitoring data in the UV, optical, and infrared bands over ∼20 yr are also presented. The Eddington ratio λEdd increased from 10–3 to ∼0.13, suggesting a transition of the accretion flow from an advection dominated accretion flow 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 (∼19+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 ∼107M☉. These results may indicate that NGC 7589 had experienced accretion mode transition over a time-scale of a few years, suggesting the idea that similar accretion processes are at work for massive BH and BH X-ray binaries.
Abstract Copyright:
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
accretion, accretion discs - galaxies: active - X-rays: individual: NGC 7589
Simbad objects:
8
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