[AAVSO-HEN] GRB 070520A: MITSuME Akeno optical upper limits

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  6430
SUBJECT: GRB 070520A: MITSuME Akeno optical upper limits
DATE:    07/05/21 04:19:51 GMT
FROM:    Nobuyuki Kawai at Tokyo Tech  <nkawai at hp.phys.titech.ac.jp>

T. Ishimura, T. Shimokawabe, N. Vasquez, Y. Yatsu, Y. Kudou and
N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
 
We observed the field of GRB070520A (Romano et al., GCN 6423)
with the 3-color 50cm MITSuME Telescope at Akeno, Japan starting 
at 13:15:15 UT, 10 min after the trigger, under a clear, but windy
condition.
In the co-added images of Ic, Rc, and g' bands, we did not detect
any new source in the XRT error circle.  The 3-sigma limiting
magnitudes based on USNO-B1.0 (I-band) and NOMAD (R-band,g'-band)
stars are following.

Filter   start time   end time    Exp(s)   Mag (3-sigma UL)  
-----------------------------------------------------------
Ic       13:15:15    15:06:06     60s * 91         20.3    
Rc       13:15:15    15:06:06     60s * 91         21.2    
g'       13:15:15    15:06:06     60s * 91         21.1    
-----------------------------------------------------------