[vsnet-grb-info 4576] GRB070419a: Swift UVOT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6340
SUBJECT: GRB070419a: Swift UVOT observations
DATE:    07/04/20 21:57:46 GMT
FROM:    Wayne Landsman at GSFC/SSAI  <landsman at milkyway.gsfc.nasa.gov>

W. Landsman and M. Stamatikos (NASA/GSFC) report on behalf of the 
Swift/UVOT team

The Swift/UVOT began settled observations of GRB 070419A 115 seconds 
after  the BAT trigger (Stamatikos et al., GCN 6302).    The  afterglow 
first detected by Chornock et al. (GCN 6304) is weakly detected on the 
UVOT V-band image.  Photometry is difficult due to the presence of a 
diffraction spike from a 7th magnitude star 3' distant.    The bright 
star also precluded use of the UVOT broad-band white filter.     
Estimated magnitudes and 3-sigma upper limits are given below: 

Filter  Start(s)  End(s)   Exposure(s)    Magnitude
-----------------------------------------------------------------
V       115      515       394          20.2  ±   0.3
V       869     1204       330          20.0  ±   0.3
B       594      739        19          >18.7
U       569      861        58          >19.1

The magnitudes are not corrected for the Galactic reddening of E(B-V)=0.03

The  V band magnitudes are consistent with a brightening noted in 
previous reports (Williams et al. 6328, Wren et al. 6324, Cenko et al. 
6306).