{
  "body": "H. Sugai (Chuo U.), D. Iijima, M. Serino (AGU), \nH. Negoro, M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.),\nT. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),\nT. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU),\nY. Tsuboi, N. Nagashima, Y. Ishihara (Chuo U.),\nM. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.),\nI. Takahashi, Y. Yatsu (Science Tokyo),\nS. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, 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)\n\nThe MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient \nsource at 06:43:02 UT on January 31, 2026.\nAssuming that the source flux was constant over the transit,\nwe obtain the source position at\n(R.A., Dec) = (24.348 deg, 34.351 deg) = (01 37 23, +34 21 03) (J2000)\nwith a statistical 90% C.L. elliptical error region\nwith long and short radii of 0.11 deg and 0.09 deg, respectively.\nThe roll angle of long axis from the north direction is 26.0 deg counterclockwise.\nThere is an additional systematic uncertainty of 0.1 deg (90% containment radius).\nThe X-ray flux averaged over the scan was 801 +- 56 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) = (23.945, 34.685) deg = (01 35 46, +34 41 06) (J2000)\n(R.A., Dec) = (23.826, 34.499) deg = (01 35 18, +34 29 56) (J2000)\n(R.A., Dec) = (25.021, 33.970) deg = (01 40 05, +33 58 11) (J2000)\n(R.A., Dec) = (25.142, 34.154) deg = (01 40 34, +34 09 14) (J2000)\nThere was no significant excess flux in the previous transit at 05:10 UT\nand in the next transit at 08:16 UT with an upper limit of 20 mCrab for each.",
  "circularId": 43580,
  "eventId": "GRB 260131B",
  "format": "text/plain",
  "submittedHow": "web",
  "createdOn": 1769849611514,
  "subject": "GRB 260131B: MAXI/GSC detection",
  "submitter": "Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>",
  "bibcode": "2026GCN.43580....1S"
}