[vsnet-grb-info 17339] GRB 151216A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18705
SUBJECT: GRB 151216A: MAXI/GSC detection
DATE:    15/12/17 02:27:14 GMT
FROM:    Nobuyuki Kawai at Tokyo Tech  <nkawai at hp.phys.titech.ac.jp>

T. Kawamuro (Kyoto U.), H. Negoro (Nihon U.), S. Nakahira (JAXA), T. Sakamoto (AGU), 
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, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), 
A. Yoshida, Y. Kawakubo, H. Ohtsuki (AGU), 
H. Tsunemi, R.Imatani (Osaka U.), 
M. Nakajima, K. Tanaka, T. Masumitsu (Nihon U.), 
Y. Ueda, 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 nova alert system triggered a bright uncatalogued X-ray transient 
source at UT 2015-12-16T19:03:15.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (323.762 deg, 24.765 deg) = (21 35 02, +24 45 54) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.32 deg and 0.25 deg, respectively.
The roll angle of long axis from the north direction is 162.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 140 +- 25 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:
(322.253 deg, 24.688 deg) = (21 29 00, +24 41 17) (J2000)
(322.468 deg, 24.080 deg) = (21 29 52, +24 04 46) (J2000)
(324.455 deg, 24.613 deg) = (21 37 49, +24 36 46) (J2000)
(324.259 deg, 25.227 deg) = (21 37 02, +25 13 37) (J2000)

There was no significant excess flux in the previous transit at UT 17:30
and in the next transit at 20:35 UT with an upper limit of 20 mCrab for each.

Detection Information:
http://maxi.riken.jp/alert/novae/7372632950/7372632950.htm <http://maxi.riken.jp/alert/novae/7372632950/7372632950.htm>