GCN Circular 18666

GRB 151205C: MAXI/GSC detection

M. Nakajima, H. Negoro (Nihon U.), M. Serino (RIKEN), T. Sakamoto (AGU),
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, 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.),
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 (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 2015/12/05 23:54:06.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (329.725 deg, 77.705 deg) = (21 58 54, +77 42 17) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.24 deg and 0.2 deg, respectively.
The roll angle of long axis from the north direction is 102.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 152 +- 24 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:
(326.621 deg, 76.996 deg) = (21 46 29, +76 59 46) (J2000)
(328.465 deg, 76.767 deg) = (21 53 51, +76 46 02) (J2000)
(333.174 deg, 78.383 deg) = (22 12 41, +78 23 00) (J2000)
(331.143 deg, 78.636 deg) = (22 04 34, +78 38 08) (J2000)

There was no significant excess flux in the previous transit at UT 22:21
and in the next transit at 12/6 01:26 UT with an upper limit of 20 mCrab for each.

Detection Information:
http://maxi.riken.jp/alert/novae/7361767105/7361767105.htm