Discovery of the Black Hole X-Ray Binary Transient MAXI J1348–630

Tominaga, Mayu and Nakahira, Satoshi and Shidatsu, Megumi and Oeda, Motoki and Ebisawa, Ken and Sugawara, Yasuharu and Negoro, Hitoshi and Kawai, Nobuyuki and Sugizaki, Mutsumi and Ueda, Yoshihiro and Mihara, Tatehiro (2020) Discovery of the Black Hole X-Ray Binary Transient MAXI J1348–630. The Astrophysical Journal, 899 (1). L20. ISSN 2041-8213

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Abstract

We report the first half-year monitoring of the new Galactic black hole candidate MAXI J1348–630, discovered on 2019 January 26 with the Gas Slit Camera on board the Monitor of All-sky X-ray Image (MAXI). During the monitoring period, the source exhibited two outburst peaks, where the first peak flux (at T = 14 days from the discovery of T = 0) was ∼4 Crab (2–20 keV) and the second one (at T = 132 days) was ∼0.4 Crab (2–20 keV). The source exhibited distinct spectral transitions between the high/soft and low/hard states and an apparent "q"-shape curve on the hardness-intensity diagram, both of which are well-known characteristics of black hole binaries (BHBs). Compared to other bright black hole transients, MAXI J1348–630 is characterized by its low disk temperature (∼0.75 keV at the maximum) and high peak flux in the high/soft state. The low peak temperature leads to a large innermost radius that is identified as the innermost stable circular orbit, determined by the black hole mass and spin. Assuming the empirical relation between the soft-to-hard transition luminosity (Ltrans) and the Eddington luminosity (LEdd), Ltrans/LEdd ≈ 0.02, and a face-on disk around a non-spinning black hole, the source distance and the black hole mass are estimated to be D ≈ 4 kpc and $\sim 7\left(D/4\,\mathrm{kpc}\right){M}_{\odot }$, respectively. The black hole is more massive if the disk is inclined and the black hole is spinning. These results suggest that MAXI J1348–630 may host a relatively massive black hole among the known BHBs in our Galaxy.

Item Type: Article
Subjects: Universal Eprints > Physics and Astronomy
Depositing User: Managing Editor
Date Deposited: 20 May 2023 03:54
Last Modified: 15 Jan 2024 03:50
URI: http://journal.article2publish.com/id/eprint/1985

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