Gamma-ray Burst 150428C

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Notice
  

  TITLE:           GCN/MAXI NOTICE
  NOTICE_DATE:     Tue 28 Apr 15 08:47:50 UT
  NOTICE_TYPE:     MAXI Unknown Source Position
  EVENT_ID_NUM:    140269683
  EVENT_RA:         60.25d {+04h 00m 59s} (J2000),
                    60.63d {+04h 02m 30s} (current),
                    59.02d {+03h 56m 05s} (1950)
  EVENT_DEC:       +67.82d {+67d 49' 04"} (J2000),
                   +67.86d {+67d 51' 36"} (current),
                   +67.68d {+67d 40' 38"} (1950)
  EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
  EVENT_FLUX:      161.0 +- 0.0 [mCrab]
  EVENT_DATE:      17140 TJD;   118 DOY;   15/04/28
  EVENT_TIME:      30269.00 SOD {08:24:29.00} UT
  EVENT_TSCALE:    1s
  EVENT_EBAND:     Low, 2-4 keV
  SUN_POSTN:        35.40d {+02h 21m 36s}  +14.10d {+14d 05' 50"}
  SUN_DIST:         56.20 [deg]
  MOON_POSTN:      154.55d {+10h 18m 12s}   +7.19d {+07d 11' 14"}
  MOON_DIST:        84.82 [deg]
  MOON_ILLUM:      72 [%]
  GAL_COORDS:      139.39, 11.23 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       74.36, 45.99 [deg] ecliptic lon,lat of the burst (or transient)       
  COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.
  

• GCN Circular #17772
  F. Honda, M. Fujita, H. Negoro (Nihon U.), M. Serino (RIKEN), S. Nakahira, S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA) T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana, Y. Ono (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), M. Nakajima, T. Namba, T. Masumitsu, K. Tanaka (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM) report on behalf of the MAXI team:
  The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 08:24:15 UT. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (60.247 deg, 67.818 deg) = (04 00 59, +67 49 03) (J2000) with a 90% C.L. statistical error of 0.29 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 161 +- 27 mCrab (4-10keV, 1 sigma error).
  Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners:

  (59.061 deg, 67.515 deg) = (03 56 14, +67 30 54) (J2000)
  (58.970 deg, 68.084 deg) = (03 55 52, +68 05 00) (J2000)
  (61.826 deg, 67.549 deg) = (04 07 18, +67 32 57) (J2000)
  (61.794 deg, 68.119 deg) = (04 07 10, +68 07 09) (J2000)
  

  There was no significant excess flux in the previous transit at 06:51 UT with an upper limit of 20 mCrab.
  We note that no significant X-ray flux above 10 keV was detected, and the spectrum was represented by a blackbody model with the temperature of approximately 1 keV. Thus, the burst might be an X-ray burst from an unknown source. We tentatively name the source MAXI J0401+678.
• GCN Circular #17786
  K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
  Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 150428C (Honda et al. GCN Circ. 17772) in a series of observations tiled on the sky. The total exposure time is 2.1 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 819 s. The data were collected between T0+16.2 ks and T0+28.9 ks, and are entirely in Photon Counting (PC) mode.
  No real uncatalogued sources have been detected. Although a low-significance source was reported by the automatic software, we believe this is an artifact caused by high background emission. In addition, a previously-catalogued X-ray source has been detected, however because it is a catalogued object it is unlikely to be the afterglow.
  The 3-sigma upper limit in the field ranges from ~0.01 to ~0.05 ct s^-1, corresponding to a 0.3-10 keV observed flux of 4e-13 to 2e-12 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
  The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/xrt_products/TILED_GRB00043/