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GCN Circular 24091

Subject
LIGO/Virgo S190408an: MAXI/GSC Observations
Date
2019-04-10T14:06:38Z (5 years ago)
From
Hitoshi Negoro at Nihon U <negoro@cygnus.phys.cst.nihon-u.ac.jp>
H. Negoro (Nihon U.), M. Serino, S. Sugita (AGU), M. Sugizaki, N. Kawai (Tokyo Tech),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
S. Nakahira, T. Mihara, M. Matsuoka (RIKEN), T. Sakamoto, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), 
Y. Tachibana, K. Morita, M. Oeda, K. Shiraishi (Tokyo Tech), 
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N.Isobe, R. Shimomukai,
M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, 
S. Ogawa (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara (Miyazaki U.), T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU)
report on behalf of the MAXI team:

At the LVC trigger time of S190408an, 18:18:02.29 UT on 2019 April 8 
(LIGO/Virgo Collaboration, GCN Circ. 24069), MAXI/GSC was scanning a part of 
the 50% credible region, centered around (R.A., Dec) = (333 deg, 20 deg),
but no flaring event was detected.
For one orbital period about 92 min, MAXI covered about 82% of the 90% 
credible region. Any enhancement was recognized in the region, and a typical 
(averaged) 1-sigma upper limit was 28 mCrab at 2-20 keV. MAXI observed 
the whole 90% credible region in 6 hours, and we put upper limits
of typically about 15 mCrab, and partially about 50 mCrab for the regions 
observed with the degraded GSC_3 camera.

Finally we note that MAXI detected GRB 190408A prior to the LVC trigger by 
12 min (Sugita et al. GCN Circ. 24072). The burst was relatively short 
(~ 10 sec) and soft, but the GRB location, (R.A., Dec) = (47.3 deg, 1.8 deg), 
is far from the GW localization region.
Thus, an association between these events is likely low.
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