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Short X-ray Transient detected by MAXI/GSC

ATEL # 2842; M. Morii, N. Kawai, K. Sugimori, R. Usui (Tokyo Tech), K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA), T. Mihara, Y.E. Nakagawa, M. Sugizaki, M. Serino, T. Yamamoto, T. Sootome, M. Matsuoka (RIKEN), A. Yoshida, K. Yamaoka, S. Nakahira (AGU), H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, M. Nakajima H. Ozawa, F. Suwa (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), A. Uzawa, K. Yamazaki, K. Matsumura (Chuo U.), report on behalf of the MAXI team
on 13 Sep 2010; 8:26 UT
Password Certification: Mikio Morii (morii@hp.phys.titech.ac.jp)

Subjects: X-ray, Transients

At the scan transit centered at UT 2010-09-11 14:58:20, MAXI/GSC detected a transient X-ray source, which was present at least for 20 seconds within the 51 seconds triangular transit response of MAXI/GSC. The nominal location of the source, assuming that the source flux was constant over the transit, is determined as

(R.A., Dec) = (+103.41 deg, -70.43 deg) = (06 53 38, -70 25 53)(J2000)

with a rectangular 90% statistical error box with the following corners:

(R.A., Dec) = (+103.71 deg, -70.77 deg) = (06 54 50, -70 46 7)(J2000)
(R.A., Dec) = (+102.49 deg, -70.25 deg) = (06 49 57, -70 15 7)(J2000)
(R.A., Dec) = (+103.11 deg, -70.09 deg) = (06 52 28, -70 05 40)(J2000)
(R.A., Dec) = (+104.34 deg, -70.61 deg) = (06 57 21, -70 36 28)(J2000)

There is additional systematic uncertainty of 0.2 deg (90% containment radius).

If the source was only temporary bright during the scan, which is well expected for the case of a GRB/XRF or an X-ray burst, uncertainty along the scan direction becomes larger, as we cannot fit the light curve to the triangular transit response. Without assumptions on the source constancy, we obtain a rectangular error box with the following corners:

(R.A., Dec) = (+101.73 deg, -71.26 deg) = (06 46 55, -71 15 37)(J2000)
(R.A., Dec) = (+100.51 deg, -70.73 deg) = (06 42 4, -70 43 44)(J2000)
(R.A., Dec) = (+104.92 deg, -69.62 deg) = (06 59 40, -69 37 1)(J2000)
(R.A., Dec) = (+106.15 deg, -70.12 deg) = (07 04 37, -70 07 28)(J2000)

The nominal flux (4-10 keV) of the source was about 100 +-30 mCrab (1 sigma error) There was no significant detection at this location in the previous and following orbits (92 min before or after the detection) with an upper limit of 30 mCrab. There is no known bright X-ray binary source at the detected position.

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