GCN Circular 6206
Subject
GRB 070311: Tautenburg sees afterglow fading
Event
Date
2007-03-14T22:09:44Z (19 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann, R. Filgas & C. Hoegner (TLS Tautenburg) report:
We observed the position of the optical/NIR afterglow (Covino et al., GCN
6190, Bloom, GCN 6191, Halpern & Armstrong, GCN 6195) of GRB 070311
(Mereghetti et al., GCN 6189) with the 1.34m Schmidt Telescope of the
Thueringer Landessternwarte Tautenburg. Observing conditions were good but
the image depth was affected by light pollution.
We obtained 6 x 600 sec images with the Rc filter. Observation midtime was
March 14.80113 UT, which is 3.72277 days after the GRB.
At the position of the GRB afterglow, we detect a very faint source at the
limit of the image (which is Rc > 23.4, 2 sigma). Using the same USNO
comparison star that Halpern & Armstrong (GCN 6195) use, we derive the
following magnitude:
dt (days) Rc mag dmag
3.72277 23.35 0.37
We caution that the detection is marginal and may not represent a real
source. On the other hand, it is clear that the afterglow has faded,
probably around one magnitude, between the rebrightening seen by Halpern &
Armstrong (GCN 6203) and Greco et al. (GCN 6204). Thus, we conclude that
it is probably not a low redshift GRB exhibiting the early rise of SN
emission.
Still, the rebrightening is interesting and further deep photometric
follow-up is warranted. No further observations are planned at TLS as we
will not be able to reach deeper limiting magnitudes for this object.
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