TITLE:   GCN CIRCULAR
NUMBER:  27678
SUBJECT: No optical bursts detected from SGR J1935+2154 by 24 fps observations with Tomo-e Gozen
DATE:    20/05/03 03:06:16 GMT
FROM:    Yuu Niino at University of Tokyo  <yuuniino@ioa.s.u-tokyo.ac.jp>

Niino, Y., Morokuma, T., Sako, S., Ohsawa, R., Beniyama, J (U. of Tokyo), 
Kokubo, M (Tohoku U), 
on behalf of the Tomo-e Gozen collaboration

We performed monitoring observations of SGR J1935+2154, from which intense burst activities have been found in the last few days (GCN #27657, #27659, #27661, #27663, #27664, #27665, #27667, #27668, #27669, #27675, ATel #13675, #13678, #13679, #13681, #13682, #13684, #13685, #13686, #13687, #13688, #13692, #13693, #13697), for 7 hrs (3.5 hrs starting UTC 2020-04-30 15:28 + 3.5 hrs starting UTC 2020-05-01 15:28) using the Tomo-e Gozen camera (optical CMOS imager, Sako et al. 2018, SPIE, 10702, 107020J) mounted on the 105-cm Kiso Schmidt telescope. 

The observations were conducted in a high-speed imaging mode with a frame rate of 24.4 fps (time resolution ~ 0.041 sec) and a 4.8x8 arcmin^2 FoV. Our quicklook analysis which degrades S/N of images by a factor of  ~ 10 shows no apparent optical bursts above a 5-sigma limit of ~ 1 Jy ms.