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GCN Circular 17791

GRB 150430A: MAXI/GSC detection
2015-04-30T10:09:31Z (9 years ago)
H. Negoro at Nihon U. <>
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, F. Honda, 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 00:21:12 UT.

Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(326.501 deg, -28.137 deg) = (21 46 00, -28 08 12) (J2000)
(326.260 deg, -28.014 deg) = (21 45 02, -28 00 49) (J2000)
(326.513 deg, -27.682 deg) = (21 46 03, -27 40 55) (J2000)
(326.753 deg, -27.805 deg) = (21 47 00, -27 48 19) (J2000)

The position of GRB 150430A (D'Elia et al. GCN #17789) is inside
of the error box. The trigger time is 16 sec before the BAT trigger.
The data download was, however, delayed for about 8.8 hours 
probably because of the data tracking problem.

The X-ray flux averaged over the scan was 512 +- 45 mCrab
(4-10keV, 1 sigma error). A simple power-law fit to the GSC 2-20 keV
spectrum gives a power-law index of 1.08  +/- 0.20.

There was no significant excess flux in the previous transit at 4/29 22:48 UT,
and in the next transit at 4/30 03:26 UT with an upper limit of 20 mCrab for each.
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