[vsnet-grb-info 21990] GRB 190404C: MITSuME Akeno and Okayama optical upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24089
SUBJECT: GRB 190404C: MITSuME Akeno and Okayama optical upper limits
DATE:    19/04/10 11:53:08 GMT
FROM:    Adachi Ryo at Tokyo Institute of Tech  <adachi at hp.phys.titech.ac.jp>

R. Adachi, M. Niwano, K. L. Murata, K. Iida, M. Oeda,
K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We performed tiling observation for the error region of GRB 190404C
(S. Yamada et al., GCN Circular #24049)
with an optical tri-color (g', Rc, and Ic) camera attached to
the MITSuME 50cm telescopes at Akeno Observatory
and Okayama Astrophysical Observatory, in Japan.

The follow up observation started at 2019-04-04 13:36:27 UT, 1,339 sec
after the trigger.
Our tiling observation covered almost 95% of the MAXI/GSC error box
(S. Yamada et al., GCN Circular #24049).

We did not find any new point source within the Swift XRT error circle
(P. D'Avanzo et al. GCN #24054, #24062) in all three bands.
Since the brightness source near the XRT error circle(~9 arcsec), the
obtained upper limit is very shallow.
The obtained 5 sigma upper limits of the optical counterpart are
summarize below:

T0+[sec]    MID-UT      T-EXP[sec]        g'       Rc        Ic
-------------------------------------------------------------------------------------------------------
1339      13:42:06          480              >13.1  >12.4    >11.9
-------------------------------------------------------------------------------------------------------


Furthermore, compared our co-added images with GSC2.3 catalog and
UCAC4 catalog, we found no bright optical transient in the observed
region.
Because the sky condition was unstable, the obtained upper limits are
different for each field.
The 5-sigma upper limits of the co-added images are listed below.

Field num.   center position(R.A., Dec.)   size of field(R.A.(arcmin)
x Dec.(arcmin))   5-sigma upper limit   start observation time(UT)
--------------------------------------------------------------------------------------------
Field 1    14:42:36, -22:46:14   25.7 x 25.9   g' > 17.0, Rc > 17.2,
Ic > 17.1   13:36:27
Field 2    14:43:08, -22:37:04   25.7 x 25.9   g' > 17.4, Rc > 17.6,
Ic > 17.4   13:47:51
Field 3    14:43:03, -22:14:27   26.0 x 25.0   g' > 17.8, Rc > 18.0,
Ic > 17.5   14:47:19
Field 4    14:44:50, -22:41:11   23.3 x 23.7   g' > 15.6, Rc > 15.6,
Ic > 15.7   14:47:06
Field 5    14:41:24, -22:15:23   23.3 x 24.3   g' > 18.0, Rc > 18.0,
Ic > 17.5   16:24:11
Field 6    14:42:17, -22:30:00   24.0 x 23.6   g' > 18.1, Rc > 18.1,
Ic > 17.5   17:57:11
Field 7    14:43:12, -22:17:05   25.4 x 25.7   g' > 17.2, Rc > 17.3,
Ic > 17.1   15:46:23
Field 8    14:44:14, -22:27:57   25.8 x 25.9   g' > 17.7, Rc > 17.3,
Ic > 16.9   18:25:06
Field 9    14:41:18, -22:20:50   25.4 x 25.7   g' > 17.6, Rc > 17.7,
Ic > 17.1   19:28:34
Field 10  14:43:18, -22:41:18   23.3 x 23.7   g' > 18.4, Rc > 18.4,
Ic > 17.7   15:25:47
--------------------------------------------------------------------------------------------

We used UCAC4 catalog for flux calibration.