[vsnet-grb-info 6067] GRB 080507: Optical Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7701
SUBJECT: GRB 080507: Optical Afterglow
DATE:    08/05/08 23:16:01 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

D. A. Kann, C. Hoegner, S. Ertel and S. Schulze (TLS Tautenburg) report:

We observed the field of the AGILE GRB 080507 (Lapshov et al., GCN 7697) 
with the Tautenburg 1.34m Schmidt telescope after twilight in good 
conditions. We obtained 12 usable 180 second images in the Rc band, with a 
mid-exposure time of 1.54 days after the GRB.

At the position of the brightest X-ray source (Mangano et al., GCN 7699), 
we detect an optical source that is not visible in the DSS (but is 
significantly below the limiting magnitude) or the SDSS (which has a 
comparable limiting magnitude to our image). We consider this the optical 
afterglow of GRB 080507 due to the coincidence with the bright X-ray 
source. At the moment, we can't make any claims of variability.

Assuming the USNOB1.0 star just to the north of the afterglow position, at 
R.A. = 15 34 43.7, Dec. = +56 26 21, has R1 = 14.96 (R2 = 15.08), we find 
a magnitude for the afterglow of:

time (days)	Rc	dRc

1.5383		22.10	0.11

Further follow-up is encouraged to confirm a fading nature for this 
source.

We note that the error circle of the second faint X-ray source at R.A. = 
233.662500, Dec. = 56.420972 (Mangano et al., GCN 7699) also contains an 
optical source clearly visible in the SDSS and in our images, implying 
that this is a persistent source.

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