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GCN Circular 18062

Subject
GRB 150725A: MAXI/GSC detection
Date
2015-07-25T09:50:41Z (9 years ago)
From
H. Negoro at Nihon U. <negoro@phys.cst.nihon-u.ac.jp>
T. Masumitsu, H. Negoro, (Nihon U.), T. Sakamoto (AGU),
S. Ueno, H. Tomida, S. Nakahira, 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, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R.Imatani (Osaka U.), 
M. Nakajima, 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 UT 08:45:00 UT. 
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (220.422 deg, -2.421 deg) = (14 41 41, -02 25 15) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.11 deg and 0.09 deg, respectively. 
The roll angle of long axis from the north direction is 117.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 1491 +- 107 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) = (220.229 deg, -2.781 deg) = (14 40 55, -02 46 51) (J2000)
(R.A., Dec) = (220.058 deg, -2.639 deg) = (14 40 14, -02 38 20) (J2000)
(R.A., Dec) = (220.615 deg, -2.060 deg) = (14 42 27, -02 03 36) (J2000)
(R.A., Dec) = (220.786 deg, -2.201 deg) = (14 43 08, -02 12 04) (J2000)
There was no significant excess flux in the previous transit at 07:12 UT
with an upper limit of 20 mCrab.
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