[vsnet-grb-info 27505] GRB 210306A: MITSuME Akeno optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29608
SUBJECT: GRB 210306A: MITSuME Akeno optical observation
DATE:    21/03/07 06:38:39 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa at hp.phys.titech.ac.jp>

R. Hosokawa, R. Adachi, K. L. Murata, M. Niwano, F. Ogawa, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210306A (D'Elia et al. GCN #29597, Watson
et al. GCN 29598, Romanov GCN #29599, Strausbaugh et al. GCN #29600,
Ohno et al. GCN #29602, Hentunen et al. GCN #29603, Stecklum et al.
GCN #29604, Veres et al. GCN #29605, Lipunov et al. GCN #29606, Zhu et
al. GCN #29607) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope of Akeno Observatory,
Yamanashi, Japan. The observation with a series of 60 sec exposures
started at 2021-03-06 09:12:03 UT (5.3 hours after Swift BAT trigger).
We stacked the images with good conditions. We marginally detected the
point source at the position consistent with the afterglow detected
previously(D'Elia et al. GCN #29597, Watson et al. GCN 29598, Romanov
GCN #29599, Strausbaugh et al. GCN #29600, Hentunen et al. GCN #29603,
Stecklum et al. GCN #29604, Zhu et al. GCN #29607).
We measured the magnitudes as follows.

T0+[hour] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
5.3 11:38:10 8160 g'=20.0+/-0.4, Rc=20.2+/-0.4, Ic=19.0+/-0.3
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used PS1 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU
reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages
4-24; https://github.com/MNiwano/Eclaire).