{
  "format": "text/plain",
  "submitter": "Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>",
  "circularId": 46074,
  "createdOn": 1793241200748,
  "eventType": [
    "GRB",
    "X-ray Transient"
  ],
  "body": "S. Ogawa (TUS), M. Serino, Y. Kawakubo (AGU),\nH. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.),\nT. Mihara, A. Aoyama, M. Ota, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),\nT. Sakamoto, S. Sugita,  H. Hiramatsu, T. Kato, A. Yoshida (AGU),\nY. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.),\nM. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (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),\nreport on behalf of the MAXI team:\n\nThe MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 16:32:33 UT on 28 October 2026.\n\nThe source was detected in two transit scans at 16:32 UT and 18:05 UT on October 28, \nwith X-ray fluxes of 382  +- 42 mCrab and 531 +- 49 mCrab (4.0-10.0keV, 1 sigma error), respectively.\n\nWe obtain the source position at\n(242.237 deg, -48.765 deg) = (16 08 56, -48 45 54) (J2000)\nwith a circular statistical error region of radius 0.12 deg at the 90% confidence level.\nThere is an additional systematic uncertainty of 0.1 deg (90% containment radius).\n\nThere was no significant excess flux in the previous transit at 14:59 UT\nand in the transit at 19:38 UT with an upper limit of 20 mCrab for each.\n\nWe tentatively name the source MAXI J1609-487 because the position of the source is \nclose to the galactic plane and the behavior of the source is different from a typical GRB.\n\nThis report will also be cross-posted to The Astronomer's Telegram (ATel).",
  "eventId": "GRB 261028B",
  "submittedHow": "web",
  "subject": "GRB 261028B / MAXI J1609-487: MAXI GSC detection"
}