[vsnet-grb-info 10783] GRB 110726A: ROTSE-III refined analysis, fast decay in early phase

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12205
SUBJECT: GRB 110726A: ROTSE-III refined analysis, fast decay in early phase
DATE:    11/07/27 00:49:50 GMT
FROM:    Weikang Zheng at U.of Michigan  <zwk at umich.edu>

W. Zheng (U Mich), B. E. Schaefer (Louisiana State), H. Flewelling
(IfA/Hawaii), report on behalf of the ROTSE collaboration:

Further analysis to the early optical observations of GRB 110726A from
ROTSE-IIId (Schaefer et al. GCN 12197) shows that, the OT decayed
quickly in early time after ~140s. The OT is detected in our first
co-added of 10 images (14s -142s) with magnitude ~16.1 +/- 0.2. However,
in our second co-added of 10 images (150s - 429s), and afterward
observations, the OT had faded to below our limiting magnitude of ~18.0,
this gives a decay index larger than -1.7, which is much steeper than
the later decay index reported by Melandri et al. (GCN 12198) of ~-0.4
15 minutes after the burst. We summarize the result below:

t_start t_stop mag    err detection?     number of co-added images

 14.0    74.0  16.1   0.3 Yes            5
 82.0   142.0  16.1   0.3 Yes            5
150.0   285.0  17.8   -   Upper limit    5
293.0   429.0  17.8   -   Upper limit    5