MAXI/GSC detection of increased flux in a region including 4U 0923-31, CXO J092418.2-314217, and 3MAXI J0924-316

ATel #15583; T. Kawamuro, T. Mihara (RIKEN), H. Negoro (Nihon U.), M. Serino (AGU), M. Nakajima, K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.), S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, J. Kohara (Chuo 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 2 Sep 2022; 14:48 UT
Credential Certification: Taiki Kawamuro (kawamuro@kusastro.kyoto-u.ac.jp)

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The MAXI/GSC nova alert system triggered on a significant 4--10 keV enhancement of 20 +- 4 mCrab (1 sigma error) averaged over scans on 2022 August 31. Its position was constrained to be (R.A., Dec) = (141.003 deg, -31.700 deg) = (09h24m00s, -31d41m59s) (J2000) with a 90% C.L. elliptical error region, whose long and short radii are 0.62 deg and 0.42 deg, respectively. The roll angle of long axis from the north direction is 134.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). In the error region, there are 4U 0923-31, CXO J092418.2-314217 (Tomsick et al. 2017, ApJS, 230, 25), and 3MAXI J0924-316 (Kawamuro et al. 2018, ApJS, 238, 32), whose separation angles from the detected source are ~ 0.58 deg, 0.06 deg, and 0.04 deg, respectively. Given that the Chandra source and the 3MAXI source are possibly identical, judging from their separation angle of 0.02 deg, it is inferred that the detected emission was associated with either the 4U source, or the other two sources. Or, all of the three candidates are independent and MAXI captured a flare from a source among the three. As an alternative and intriguing possibility, a new source might have appeared in the region. To conclude the origin of the event, followup observations in the X-ray are encouraged. Also, for characterizing the nature, observations at different wavelengths, for example, in optical and radio, should be important.