The X-ray variation of M81* resolved by Chandra and NuSTAR. Issue 2 (13th April 2023)

• Record Type: Journal Article
• Authors: Niu, Shu; Xie, Fu-Guo; Wang, Q Daniel; Ji, Li; Yuan, Feng; Long, Min
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 522:Issue 2(2023)
• Page Start: 2644
• Page End: 2654
• Publication Date: 2023-04-13
• Subjects: accretion, accretion discs -- galaxies: active -- galaxies: individual: M81* -- galaxies: nuclei -- X-rays: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stad1080
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Despite advances in our understanding of low-luminosity active galactic nuclei (LLAGNs), the fundamental details about the mechanisms of radiation and flare/outburst in hot accretion flow are still largely missing. We have systematically analysed the archival Chandra and NuSTAR X-ray data of the nearby LLAGN M81*, whose L bol ∼ 10 −5 L Edd . Through a detailed study of X-ray light curve and spectral properties, we find that the X-ray continuum emission of the power-law shape more likely originates from inverse Compton scattering within the hot accretion flow. In contrast to Sgr A*, flares are rare in M81*. Low-amplitude variation can only be observed in soft X-ray band (amplitude usually ≲2). Several simple models are tested, including sinusoidal-like and quasi-periodical. Based on a comparison of the dramatic differences of flare properties among Sgr A*, M31*, and M81*, we find that, when the differences in both the accretion rate and the black hole mass are considered, the flares in LLAGNs can be understood universally in a magnetohydrodynamical model.