MAXI/GSC detection of X-ray outburst probably from XTE J1901+014

ATel #15904; T. Kawamuro (RIKEN), H. Negoro, M. Nakajima, K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.), T. Mihara, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, J. Kohara, S. Urabe, S. Nawa, N. Nemoto (Chuo U.), W. Iwakiri (Chiba U.), M. Shidatsu, M. Iwasaki (Ehime U.), N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, T. Kurihara (JAXA), Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba (Kyoto U.), M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC)
on 15 Feb 2023; 08:44 UT
Credential Certification: Taiki Kawamuro (taiki.kawamuro@riken.jp)

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At UT 17:54 on February 14, the MAXI/GSC nova alert system triggered on a bright X-ray transient source spatially consistent with XTE J1901+014 at a 90% confidence level. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (285.410 deg, 1.393 deg) = (19 01 38, +01 23 34) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.16 deg and 0.11 deg, respectively. The roll angle of long axis from the north direction is 72.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 658 +- 75 mCrab (4.0-10.0keV, 1 sigma error). Historically, two outbursts were discovered from XTE J1901+014 based on RXTE/ASM data (ATel #88). The first and second outbursts in 1997 and 2002 reached 0.9 Crab and 0.4 Crab (2--12 keV), respectively. Later, the Swift/BAT captured an outburst from the object on 2010 January 8, and its 15--50 keV flux was estimated to be 0.25 Crab (ATel #2375). Thus, in terms of flux, the outburst detected this time by MAXI is similar to those found so far. The nature of XTE J1901+014 is not so clear. The outbursts found by RXTE look like the supergiant fast X-ray transient (Karasev, Lutovinov & Burenin 2008; Smith et al. 2012), often considered to be associated with a neutron star. However, with the RXTE data, Karasev, Lutovinov & Grebenev (2007) found a black-hole-like spectrum (i.e., a power-law without any cutoff between 20--30 keV) and then concluded that the primary object of XTE J1901+014 is a black hole. To better understand the nature, multi-wavelength follow-up observations would be helpful.