[vsnet-grb-info 5187] GRB 071010B: Bright OT confirmed with TLS

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6884
SUBJECT: GRB 071010B: Bright OT confirmed with TLS
DATE:    07/10/11 14:56:36 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

D. A. Kann, C. Hoegner & R. Filgas (TLS Tautenburg) report:

We observed the field of GRB 071010B (Markwardt et al., GCN 6871) with the 
TLS 1.34m Schmidt telescope under bad weather conditions (low 
transparency, passing clouds). We obtained 9 600 second integrations in 
the Rc Filter starting at UT 1:26:44 (0.2 days after the GRB). The 
afterglow (Oksanen, GCN 6873) is clearly detected on several frames, the 
others were lost to passing clouds.

We measure a refined OT position (J2000) in comparison to the USNO-B1.0 
catalog:

RA   =  10:02:09.24
Dec. = +45:43:49.7

with errors of 0".7.

This is in accordance with the position of Oksanen (GCN 6873) and the 
Swift XRT detection (Kennea et al., GCN 6878).

Preliminary photometry on raw images yields a decaying afterglow. Assuming 
the USNO-B1.0 star at RA = 10:02:06.71, Dec. = +45:42:34.2 (J2000) to have 
R2 = 17.26, we find the following magnitudes:

Date		Mid-Time	Rc	Rc error

11.06361	0.19848		18.61	0.07
11.07113	0.20600		18.73	0.05
11.07865	0.21352		18.87	0.06
11.13149	0.26637		19.21	0.05

Oksanen (GCN 6873) reported the OT to have R > 18 mag already in the first 
hour, therefore our bright detections may indicate a slow decay or a 
rebrightening. This GRB was a bright, soft FRED (Markwardt et al., GCN 
6877; Golenetskii et al., GCN 6879) with a well determined peak energy. 
This may indicate an event at relatively low redshift. Further photometric 
and especially spectroscopic follow-up is encouraged.

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