TITLE: GCN CIRCULAR NUMBER: 27405 SUBJECT: LIGO/Virgo S200316bj: Upper limits from CALET observations DATE: 20/03/18 09:29:18 GMT FROM: Yuta Kawakubo at Louisiana State U./CALET Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka, S. Torii (Waseda U), T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time of S200316bj T0 = 2020-03-16 21:57:56.157 UT (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 27388). No CGBM on-board trigger occurred around the event time. Based on the LIGO-Virgo localization sky map, the summed LIGO probabilities inside the CGBM HXM (7 - 3000 keV) and SGM (40 keV - 28 MeV) fields of view are 52 % and 72 %, respectively (and 82 % credible region of the initial sky map was above the horizon). The HXM and SGM fields of view were centered at RA = 136.4 deg, Dec = +56.1 deg and RA = 144.6 deg, Dec = +47.5 deg at T0, respectively. Based on the analysis of the light curve data with 0.125 sec time resolution from T0-60 sec to T0+60 sec, we found no significant excess around the trigger time in either the HXM or the SGM data. The CALET Calorimeter (CAL) was operating in the high energy trigger mode at the trigger time of S200316bj. Using the CAL data, we have searched for gamma-ray events in the 10-100 GeV band from -60 sec to +60 sec from the GW trigger time and found no candidates in the overwrap region with the LIGO-Virgo high probability localization region. The 90% upper limit of CAL is 2.8 x 10^-6 erg/cm^2/s (10-100 GeV) when the summed LIGO-Virgo probability reaches 35%. The CAL FOV was centered at RA = 144.7 deg, DEC = +47.5d deg at T0.