Gamma-ray Burst 150311A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #17568
  M. Morii (RIKEN), H. Negoro (Nihon U.), M. Serino (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, D. Uchida (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki, T. Namba, M. Fujita, F. Honda (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, A. Kawagoe (Chuo U.), M. Yamauchi, Y. Morooka, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
  The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 2015-03-11T16:18:16 UT . Assuming that the source flux was constant over the transit, we obtain the source position at
  (R.A., Dec) = (235.099 deg, -15.809 deg) = (15 40 23, -15 48 32) (J2000)
  with a statistical 90% C.L. elliptical error region with long and short radii of 0.27 deg and 0.26 deg, respectively. The roll angle of long axis from the north direction is 79.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 93 +- 20 mCrab (4-10keV, 1 sigma error). There was no significant excess flux in the previous transit at UT 14:45 and in the next transit at 17:50 UT with an upper limit of 20 mCrab for each.
  According to GCN IPN_RAW Notices, The Konus-Wind instrument triggered at 16:16:24.88, which is 111s before the MAXI trigger.
  Therefore MAXI might have observed the afterglow of GRB 150311A triggered by Konus-Wind, while the position of this burst is not known.
• GCN Circular #17569
  D. Frederiks, on behalf of the Konus-Wind team, reports:
  The Konus-Wind trigger at 16:16:24.884 mentioned by Morii et al. (GCN 17568), which is 111 s before the MAXI trigger, is actually due to a X2.1 class solar flare. Therefore, taking into account the MAXI localization of the source, we suggest that the Maxi trigger is unrelated to the Konus-Wind trigger.