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GCN Circular 21555

LIGO/Virgo G298048, Fermi GBM trigger 524666471/170817.529: MAXI/GSC observations
2017-08-18T10:43:45Z (7 years ago)
Satoshi Sugita at Tokyo Inst. of Tech. <>
S. Sugita, N. Kawai (Tokyo Tech), M. Serino (RIKEN), H. Negoro (Nihon U.),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N.Isobe, R. Shimomukai (JAXA),
T. Mihara, M. Sugizaki, S. Nakahira, W. Iwakiri, M. Shidatsu, M.
Matsuoka (RIKEN),
T. Yoshii, Y. Tachibana, S. Harita, Y. Muraki, K. Morita (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka, T. Hashimoto (AGU),
H. Tsunemi, T. Yoneyama (Osaka U.),
M. Nakajima, T. Kawase, A. Sakamaki (Nihon U.),
Y. Ueda, T. Hori, A. Tanimoto, S. Oda (Kyoto U.),
Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.),
M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.),
T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.)
report on behalf of the MAXI team:

We examined the MAXI/GSC all-sky X-ray images (2-20 keV) obtained
in the orbits following LIGO/Virgo trigger G298048 and the Fermi GBM trigger
524666471/170817.529 at 2017-08-17 12:41:06.47 UTC (GCN 21506).

At the trigger time of Fermi GBM, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+173 sec.
The center of the Fermi GBM localization was located near the pole of
ISS orbital rotation, where the MAXI/GSC cannot cover the field.
The field of candidate optical counterpart (GCN 21529) was marginally
covered by MAXI and  was scanned at 12:23 UT (18 min before the trigger),
but the OT position was obscured by an ISS structure.

The OT candidate position was difficult to cover with MAXI/GSC due to
unfavorable orientation of the orbital plane of the ISS, and therefore
it was not observed for the following 8 orbits.
The first scan by MAXI/GSC was started at 08-18 02:19 UTC (818 min
after the LIGO trigger).
We did not detect a significant source at this position with a 3-sigma
upper limit of
54 mCrab.  This limit is higher than the typical value because of high
particle background flux.

For the remaining area of the G298048 preliminary-LALInference skymap,
we obtained a typical 1(3)-sigma upper limit of
11(33) mCrab in the orbit following the trigger.

If you require information of X-ray flux by MAXI/GSC at specific coordinates,
please contact the submitter of this circular by email.
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