Discovery and state transitions of the new Galactic black hole candidate MAXI J1535−571. (11th September 2018)

• Record Type: Journal Article
• Authors: Nakahira, Satoshi; Shidatsu, Megumi; Makishima, Kazuo; Ueda, Yoshihiro; Yamaoka, Kazutaka; Mihara, Tatehiro; Negoro, Hitoshi; Kawase, Tomofumi; Kawai, Nobuyuki; Morita, Kotaro
• Is Part Of: Publications of the Astronomical Society of Japan. Volume 70:Number 5(2018:Oct.)
• Publication Date: 2018-09-11
• Subjects: accretion, accretion disks -- black hole physics -- X-rays: binaries -- X-rays: individual (MAXI J1535−571); Astronomy -- Periodicals; 520.5
• DOI: 10.1093/pasj/psy093
• Languages: English
• ISSNs: 0004-6264

Abstract

Abstract: We report on the detection and subsequent X-ray monitoring of the new Galactic black hole candidate MAXI J1535−571 with the Gas Slit Camera onboard Monitor of All-sky X-ray Image (MAXI/GSC). After the discovery on 2017 September 2, made independently with MAXI and the Swift/BAT, the source brightened gradually, and in a few weeks reached the peak intensity of ∼5 Crab, or ∼1.6 × 10 −7 erg cm −2 s −1 in terms of the 2–20 keV flux. On the initial outburst rise, the 2–20 keV MAXI/GSC spectrum was described by a power-law model with a photon index of ≲ 2, while after a hard-to-soft transition, which occurred on September 18, the spectrum required a disk blackbody component in addition. At around the flux peak, the 2–8 keV and 15–50 keV light curves showed quasi-periodic and anti-correlated fluctuations with amplitudes of 10%–20%, on a time scale of ∼1 d. Based on these X-ray properties obtained with the MAXI/GSC, with additional information from the Swift/BAT, we discuss the evolution of the spectral state of this source, and give constraints on its system parameters.