Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 33087

GRB 221218A: MITSuME Akeno optical upper limits
2022-12-20T10:21:15Z (a year ago)
Ichiro Takahashi at Tokyo Tech <>
I. Takahashi, M. Niwano, R. Hosokawa, K. L. Murata, Y. Imai, N. Ito,
S. Sato, N. Higuchi, M. Tateda, M. Sasada, Y. Yatsu, and N. Kawai
(Tokyo Tech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 221218A (S. Mereghetti et al. GCN
Circular #33082, WeiKang Zheng et al. GCN Circular #33085, Y.-D. Hu et
al. GCN Circular #33086) with the optical three color (g', Rc, and Ic)
CCD cameras attached to the MITSuME 50 cm telescope Akeno.

The observation with a series of 60 sec exposures started at
2022-12-18 08:37:35 UT (1405 seconds after the INTEGRAL trigger). We
stacked the images with good conditions. We did not detect any
uncatalogued sources within the error region (S. Mereghetti et al. GCN
Circular #33082). We obtained the 5-sigma limits of the stacked images
as follows.

T0+[sec] | MID-UT | T-EXP[sec] | 5-sigma limits
1405 | 2022-12-18 08:51:23 | 1140.0 | g'>19.1, Rc>19.0, Ic>18.4
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;
Looking for U.S. government information and services? Visit