[vsnet-grb-info 17666] GRB 160227A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19103
SUBJECT: GRB 160227A: MAXI/GSC detection
DATE:    16/02/28 04:50:29 GMT
FROM:    H. Negoro at Nihon U.  <negoro at phys.cst.nihon-u.ac.jp>

T. Yoshii (Tokyo Tech), M. Nakajima, H. Negoro (Nihon U.),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, M. Arimoto, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, R. Imatani (Osaka U.),
K. Tanaka, T. Masumitsu (Nihon U.),
Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.),
Y. Tsuboi, S. Kanetou, Y. Nakamura, R. Sasaki (Chuo U.),
M. Yamauchi, D. Itoh, K. Furuya (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Morii (ISM)

report on behalf of the MAXI team:

The MAXI/GSC detected an uncatalogued X-ray transient source at 19:35:13 UT on 2016 February 27.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (192.924 deg, 78.686 deg) = (12 51 41, +78 41 09) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.39 deg and 0.38 deg, respectively.
The roll angle of long axis from the north direction is 46.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 130 +- 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:
(R.A., Dec) = (197.530 deg, 78.335 deg) = (13 10 07, +78 20 05) (J2000)
(R.A., Dec) = (194.899 deg, 77.788 deg) = (12 59 35, +77 47 15) (J2000)
(R.A., Dec) = (185.390 deg, 79.282 deg) = (12 21 33, +79 16 55) (J2000)
(R.A., Dec) = (187.705 deg, 79.931 deg) = (12 30 49, +79 55 52) (J2000)

The position is consistent with that of GRB 160227A (Siegel et al., GCN 19098),
and the detected time is 185 sec after the BAT trigger.

There was no significant excess flux in the previous transit at 
18:02 UT on 2016 February 27 and in the next transit at 
21:07 UT on 2016 February 27 with an upper limit of 20 mCrab for each.