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GCN Circular 6295

Subject
GRB 070411: TLS data shows plateau, flares
Date
2007-04-13T00:48:22Z (18 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann, U. Laux, S. Klose, H. Meusinger, S. Schulze (TLS 
Tautenburg) and J. Greiner (MPE, Garching) report:

The afterglow of the Swift GRB 070411 (Moretti et al., GCN 
6267) was observed with the Tautenburg 1.34m Schmidt 
telescope in RRM mode starting 342 seconds after the trigger 
(Kann et al., GCN 6268).

A total of 18 observations were obtained before the afterglow 
become unobservable. We performed aperature photometry 
vs. two unsaturated and isolated USNO B1.0 stars (R1 
magnitudes):

RA = 07:09:17.16, Dec. = +01:04:35.9, assuming R = 15.55

RA = 07:09:28.54, Dec. = +01:03:57.1, assuming R = 16.25

We derive the following magnitudes (mean exposure times 
after the burst have been derived logarithmically):

dt      Start   Exposure        R mag   dR
(days)  (SOD)   (seconds)

0.0049994       73095   180     18.03   0.05
0.0076498       73324   180     18.12   0.03
0.0103234       73555   180     18.18   0.03
0.0129739       73784   180     18.17   0.05
0.0156244       74013   180     18.43   0.07
0.0182864       74243   180     18.79   0.05
0.0209485       74473   180     18.83   0.07
0.0235989       74702   180     18.95   0.08
0.0262494       74931   180     19.23   0.07
0.0288999       75160   180     19.38   0.09
0.0315503       75389   180     19.75   0.12
0.0342008       75618   180     20.00   0.16
0.0368512       75847   180     19.83   0.12
0.0395017       76076   180     19.88   0.15
0.0421522       76305   180     20.13   0.19
0.0472965       76540   600     20.64   0.23
0.0548081       77189   600     19.91   0.14
0.0623197       77838   600     19.96   0.15

Adding further R and CR data (Rykoff et al., GCN 6269, 
Gomboc et al., GCN 6271, Jelinek, Nuez, & Castro-Tirado, 
GCN 6272, Berger et al., GCN 6278, Mikuz, Skvarc, & 
Dintinjana, GCN 6288), we find:

The afterglow may be rising early on, looking at the earliest 
detections from Crni Vrh, ROTSE and Tautenburg.

The afterglow then goes over into a plateau phase (decay 
alpha= 0.14 +/- 0.1). In our data, we do not see the strong 
rebrightening detected by ROTSE (Rykoff et al., GCN 6269).

At 0.014 +/- 0.001 days, the afterglow breaks and begins a 
decay with alpha = 1.54 +\- 0.16 up to about 0.03 days, where a 
possible flare occurs.

At about 0.05 days, the afterglow seems to rebrighten strongly, 
our data here are in full accordance with those of the Liverpool 
telescope (Gomboc et al., GCN 6271) and the IAC80 (Jelinek, 
Nuez, & Castro-Tirado, GCN 6272).

Further photometric follow-up of this GRB is warranted.

This message may be cited.
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