{
  "submittedHow": "web",
  "submitter": "Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>",
  "circularId": 44746,
  "format": "text/plain",
  "body": "H. Aoe (Ehime U.), H. Negoro (Nihon U.), M. Serino, S. Sugita (AGU),\nM. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.),\nT. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),\nT. Sakamoto, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU),\nY. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.),\nM. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.),\nI. Takahashi, Y. Yatsu (Science Tokyo),\nS. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA),\nY. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.),\nM. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.),\nK. Yamaoka (Nagoya U.),\nM. Sugizaki (Kanazawa U.),\nW. Iwakiri (Chiba U.),\nT. Kawamuro (Osaka U.),\nS. Yamada (Tohoku U),\nS. Ogawa (TUS) \nreport on behalf of the MAXI team:\nThe MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source \nat 05:30:18 UT on 2026 May 31.\nAssuming that the source flux was constant over the transit,\nwe obtain the source position at\n(R.A., Dec) = (69.904 deg, -10.627 deg) = (04 39 36, -10 37 37) (J2000)\nwith a statistical 90% C.L. elliptical error region\nwith long and short radii of 0.23 deg and 0.17 deg, respectively.\nThe roll angle of long axis from the north direction is 64.0 deg counterclockwise.\nThere is an additional systematic uncertainty of 0.1 deg (90% containment radius).\nThe X-ray flux averaged over the scan was 230 +- 36 mCrab\n(4.0-10.0keV, 1 sigma error).\nWithout assumptions on the source constancy, we obtain a rectangular error\nbox for the transient source with the following corners:\n(R.A., Dec) = (69.234, -11.160) deg = (04 36 56, -11 09 36) (J2000)\n(R.A., Dec) = (69.533, -11.386) deg = (04 38 07, -11 23 09) (J2000)\n(R.A., Dec) = (70.598, -10.018) deg = (04 42 23, -10 01 04) (J2000)\n(R.A., Dec) = (70.300, -9.794) deg = (04 41 11, -09 47 38) (J2000)\nThere was no significant excess flux in the previous transit at 03:57 UT\nand in the next transit at 07:03 UT with an upper limit of 20 mCrab for each.\n\nNote that this position is consistent with the position of Seyfert Galaxy MCG-02-12-050,\nbut it is not clear if this transient is related to MCG-02-12-050 at this time.",
  "subject": "GRB 260531A: MAXI/GSC detection",
  "eventId": "GRB 260531A",
  "createdOn": 1780219733591
}