[vsnet-grb-info 16671] GRB 150622A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17952
SUBJECT: GRB 150622A: MAXI/GSC detection
DATE:    15/06/22 12:42:11 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

Y. Kawakubo (AGU), S. Nakahira, S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, 
Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, 
T. Takagi, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), 
A. Yoshida, T. Sakamoto, H. Ohtsuki (AGU), H. Tsunemi, R.Imatani (Osaka U.), 
H. Negoro, M. Nakajima, K. Tanaka, T. Masumitsu (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 10:23:43 UT.  Assuming that the source flux was constant over the transit, 
we obtain the source position at

(R.A., Dec) = (252.028 deg, -52.768 deg) = (16 48 06, -52 46 04) (J2000) 

with a statistical 90% C.L. elliptical error region with long and short radii of 0.22 deg 
and 0.14 deg, respectively.  The roll angle of long axis from the north direction is 62.0 deg 
counterclockwise.  There is an additional systematic uncertainty of 0.1 deg (90% 
containment radius).  The X-ray flux averaged over the scan was 342 +- 40 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) = (251.874 deg, -52.244 deg) = (16 47 29, -52 14 38) (J2000)
(R.A., Dec) = (251.283 deg, -52.506 deg) = (16 45 07, -52 30 20) (J2000)
(R.A., Dec) = (252.300 deg, -53.392 deg) = (16 49 11, -53 23 29) (J2000)
(R.A., Dec) = (252.900 deg, -53.128 deg) = (16 51 36, -53 07 39) (J2000)

There was no significant excess flux in the previous transit at 8:48 UT.