TITLE: GCN CIRCULAR NUMBER: 6329 SUBJECT: GRB 070419A: MITSuME Okayama Observations DATE: 07/04/20 06:48:04 GMT FROM: Michitoshi Yoshida at Okayama Astrophysical Obs M. Yoshida, K. Yanagisawa, Y. Shimizu, S. Nagayama (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We performed optical imaging observation (g', Rc, and Ic) of the field of GRB 070419A (Stamatikos et al. GCN 6302) with 50cm MITSuME telescope at Okayama Astrophysical Observatory from UT 10:53 to UT 13:06 on Apr.19 2007. We coadded 106 CCD frames for each band. Exposure time of each frame is 1 minute. We made flux calibration using a USNO B1.0 star close to the XRT position (12:10:57.57, +39:55:40.2, B=16.14, R=15.22, I=14.37; see Williams et al. GCN 6328, Cenko et al. GCN 6306). We detected a faint source in g' band at the position of the optical transient reported by Chornock et al. (GCN 6304). The g' band magnitude and three sigma limiting magnitudes for Rc and Ic bands of this source are listed below. --------------------------------------------------------------- band mid-UT exp.time brightness g' Apr. 19 12:00 106 x 1 min. 20.9 +- 0.2 mag Rc Apr. 19 12:00 106 x 1 min. > 21.5 mag (upper limit) Ic Apr. 19 12:00 106 x 1 min. > 19.4 mag (upper limit) ---------------------------------------------------------------