TITLE:   GCN CIRCULAR
NUMBER:  31037
SUBJECT: GRB 211024A: MITSuME Akeno optical observation
DATE:    21/11/04 06:14:14 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

Y. Imai, R. Hosokawa, K. L. Murata, N. Ito, Y. Takamatsu, M. Takaku, M.
Niwano, R. Noto, S. Sato, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 211024A (The Fermi GBM team GCN Circular
#30962, V. Lipunov et al. GCN Circular #30963, S. Xiao et al. GCN Circular
#30974, Aaron Tohuvavohu et al. GCN Circular #31006, P. A. Evans et al. GCN
Circular #31007, S. Poolakkil et al. GCN Circular #31011, M. Perri et al.
GCN Circular #31013, H. Kumar et al. GCN Circular #31014, H. Kumar et al.
GCN Circular #31017) 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 was carried out from 2021-10-27 13:34:50 UT
(~3.5 days after the Fermi trigger) to 2021-10-31. We stacked the images
with good conditions.

We detected the Source 4 reported by the Swift ToO observation (Perri et
al. GCN Circular #31013) and performed aperture photometry. The magnitudes
of the Source 4 and the 5-sigma limits of the stacked images are as follows.

T0+[day] | MID-UT | T-EXP[sec] | Source 4 magnitude | 5-sigma limits
------------------------------------------------------------------------------------------------
3.6 | 2021-10-27 15:18:55 | 4200 | g'=19.2 +/- 0.2, Rc=18.2 +/- 0.1,
Ic=17.6 +/- 0.1| g'>19.9, Rc>20.4, Ic>19.8
4.4 | 2021-10-28 11:42:32 | 10380 | g'=19.3 +/- 0.2, Rc=18.2 +/- 0.1,
Ic=17.7 +/- 0.1 | g'>19.9, Rc>20.2, Ic>19.9
5.4 | 2021-10-29 11:41:30 | 9240 | g'=19.1 +/- 0.2, Rc=18.2 +/- 0.1,
Ic=17.6 +/- 0.1 |g'>19.8, Rc>20.4, Ic>19.9
6.4 | 2021-10-30 10:34:24 | 960 |g'=18.5 +/- 0.3, Rc=18.1 +/- 0.1, Ic=17.5
+/- 0.1 | g'>18.6, Rc>19.1, Ic>18.5
7.4 | 2021-10-31 10:41:48 | 540 | g' no detection, Rc=17.9 +/- 0.2, Ic=17.7
+/- 0.2 | g'>18.6, Rc>18.9, Ic>18.3
------------------------------------------------------------------------------------------------
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).