[vsnet-grb-info 6062] GRB 080506: TLS 2nd Epoch - possible light curve break

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7696
SUBJECT: GRB 080506: TLS 2nd Epoch - possible light curve break
DATE:    08/05/08 03:18:02 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

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

We observed the afterglow of Swift GRB 080506 (Baumgartner et al., GCN 
7685) with the Tautenburg 1.34m Schmidt telescope 1.33 days after the GRB, 
again in good conditions. We obtained a four 300 sec exposures in the Rc 
band before twilight shut us down. The afterglow is faintly detected in 
the stacked image.

Using the same comparison star as Kann et al. (GCN 7688), we find:

time (days)	Rc	dRc

1.3346		22.23	0.33

An extrapolation of the decay in the first 0.4 days (~0.63, Kann et al., 
GCN 7688, de Ugarte Postigo et al., GCN 7690) yields an expected magnitude 
of Rc ~ 21.8 at 1.33 days after the GRB. Our measured value lies below the 
extrapolation, indicating a break (possibly a jet break) may have occured. 
We caution that the detection is rather marginal and the high sky 
background may falsify the measurement.

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