[vsnet-grb-info 26679] GRB 201024A: MITSuME Akeno optical upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28779
SUBJECT: GRB 201024A: MITSuME Akeno optical upper limits
DATE:    20/10/26 09:38:09 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata at u.phys.nagoya-u.ac.jp>

M. Niwano, K. L. Murata, R. Hosokawa, R. Adachi, 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 201024A (F. E. Marshall et al.,GCN Circular
#28761) with the optical three color (g', Rc, and Ic) CCD cameras attached
to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.

We observed for two nights. The observation with a series of 60 sec
exposures started at 2020-10-24 16:04:04UT for the first night and
2020-10-25 15:56:17UT for the second night. We stacked the images with good
conditions each night. We did not detect the point source reported by other
telescopes (Lipunov et al. GCN Circular #28760, Fernandez-Garcia et al.
#28763, de Ugarte Postigo et al. #28764, Martin Jelinek et al. #28766). We
obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
13.78 2020-10-24T18:27:11 11520 g'>20.2, Rc>20.4, Ic>19.7
38.48 2020-10-25T17:17:59 1980 g'>19.4, Rc>19.6, Ic>18.8
------------------------------------------------------------------------------------------------
T0+: Elapsed time after the burst
T-EXP: Total Exposure time

We used the 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., accepted for publication in
PASJ, https://arxiv.org/abs/2008.11486; https://github.com/MNiwano/Eclaire).