{
  "circularId": 35721,
  "bibcode": "2024GCN.35721....1N",
  "eventId": "GRB 240214A",
  "subject": "GRB 240214A/1H 0451-560: MAXI/GSC detection",
  "body": "H. Negoro, M. Nakajima (Nihon U.), W. Iwakiri (Chiba U.), T. Mihara (RIKEN),\nK. Kobayashi, M. Tanaka, Y. Soejima, Y. Kudo (Nihon U.),\nT. Kawamuro, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),\nT. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU),\nY. Tsuboi, S. Urabe, S. Nawa, N. Nemoto, E.Goto (Chuo U.), M. Shidatsu, \nY. Niida (Ehime U.), I. Takahashi, M. Niwano, S. Sato, N. Higuchi, Y. Yatsu (Tokyo Tech),\nS. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, T. Kurihara (JAXA),\nY. Ueda, K. Setoguchi, T. Yoshitake, Y. Nakatani, Y. Okada (Kyoto U.),\nM. Yamauchi, Y. Hagiwara, Y. Umeki, Y. Otsuki (Miyazaki U.),\nK. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), and M. Sugizaki (NAOC)\n\nThe MAXI/GSC nova alert system triggered on an uncatalogued soft X-ray transient source at\n01:43:39 UT on February 14, 2024. Assuming that the source flux was constant over the transit,\nwe obtain the source position at\n(R.A., Dec) = (73.197 deg, -55.923 deg) = (04 52 47, -55 55 22) (J2000)\nwith a 90% C.L. statistical error of 0.42 deg and an additional systematic uncertainty of\n0.1 deg (90% containment radius).\nThe X-ray flux averaged over the scan was 109 +- 24 mCrab (4.0-10.0keV, 1 sigma error).\nWithout assumptions on the source constancy, we obtain a rectangular error box \nfor the transient source with the following corners:\n(73.301, -55.429) deg = (04 53 12, -55 25 44) (J2000)\n(72.444, -56.103) deg = (04 49 46, -56 06 10) (J2000)\n(74.543, -56.916) deg = (04 58 10, -56 54 57) (J2000)\n(75.381, -56.228) deg = (05 01 31, -56 13 40) (J2000)\n\nThe burst showed a spectral softening during the burst duration of about 30 sec (in the MAXI \nscan window), and the average spectrum is characterized by a power-law with a photon index \nof 2.3 (+0.8, -0.6)  at a 90% confidence level.\n\nAn X-ray flux of about 20 mCrab at 2-10 keV was also recognized in the next transit at 03:16 UT.\nThere was no significant excess flux in the previous transit at 00:10 UT, and in the transit \nat 04:49 UT with an upper limit of 20 mCrab for each.\n\nWe note that 1H 0451-560 is located near the center of the error region. \n1H 0451-560 is a short-lived transient X-ray source with a Crab-like spectrum (Kaluzienski 1978, \nIAUC 3174).  Thus, 1H 0451-560 is most likely. We also tentatively name the source MAXI J0452-559.\n\nSwift/XRT followup observation is requested.\n\nWe crosspost this content to the Astronomer's Telegram because of the possible nature of the source.\n",
  "submittedHow": "web",
  "submitter": "Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi@nihon-u.ac.jp>",
  "createdOn": 1707893403739
}