TITLE: GCN CIRCULAR NUMBER: 26481 SUBJECT: LIGO/Virgo S191216ap: No transient candidates in CALET observations DATE: 19/12/18 04:06:07 GMT FROM: Yuta Kawakubo at Louisiana State U./CALET T. Sakamoto, A. Yoshida, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka, S. Torii (Waseda U), Y. Shimizu, 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 S191216ap T0 = 2019-12-16 21:33:38.473 UT (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 26454). No CGBM on-board trigger occurred around the event time. Based on the LVC high probability localization region, the summed LIGO probabilities inside the CGBM HXM (7 - 3000 keV) and SGM (40 keV - 28 MeV) fields of view are 0 % and 2 %, respectively (and 26 % credible region of the initial localization map was above the horizon). The HXM and SGM fields of view were centered at RA = 178.2 deg, Dec = 19.5 deg and RA = 186.8 deg, Dec = 13.9 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 (signal-to-noise ratio >= 7) around the trigger time in either the HXM or the SGM data. The CALET Calorimeter (CAL) was operating in the low energy trigger mode at the trigger time of S191216ap. Using the CAL data, we have searched for gamma-ray events in the 1-10 GeV band from -60 sec to +60 sec from the GW trigger time and found no candidates. There is no significant overlap with the LVC high probability localization region at T0+-60 sec. The CAL FOV was centered at RA=186.8 deg, Dec=13.9 deg at T0.