TITLE:   GCN CIRCULAR
NUMBER:  6341
SUBJECT: GRB070419A: Kuiper Optical detection
DATE:    07/04/20 23:23:49 GMT
FROM:    Peter A. Milne at Super-LOTIS  <pmilne@as.arizona.edu>

P.A. Milne and G.G. Williams (U Arizona) report on behalf of the
Super-LOTIS team:

The 1.54m Kuiper telescope began R and V-band observations of the error
region of GRB070419A (Swift trigger 276205) at 10:26:37 UT, 27 minutes
after the burst.  The OT detected by Chornock et al. (GCN 6304) and
observed by Cenko et al., Urata et al., Rol et al., Smith et al.,
Updike et al., Wren et al., Williams et al., Yoshida et al., Swan et al.
(GCN 6306/6322, 6308/6311, 6309, 6315, 6317, 6324, 6328, 6329, 6339)  is
clearly visible in the first image and all subsequent images until
11:36:36 UT.

We used the USNO-B star at RA=12:10:57.57, Dec=+39:55:40.2 to
derive the R and V magnitudes. For the R-band magnitude, we use R=15.22
(Cenko et al. GCN 6306). For the V-band magnitude, we used the
g=15.866 and r=15.447 magnitudes from Cool et al. (GCN 6318),
and derived a V magnitude of V=15.61 using the transformation
equations of Jester et al. (2005).

The R-band magnitude of the afterglow in the first image is:
UT Time       delta Time  R magnitude     error
10:26:37      60.0 s       19.12            0.09

The V-band magnitude of the afterglow in the first V-band image is:
UT Time       delta Time  V magnitude     error
10:35:35      60.0 s      19.66           0.14


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