[vsnet-grb-info 2047] GRB050824: First 2 hours of power low optical decay?

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3886
SUBJECT: GRB050824: First 2 hours of power low optical decay?
DATE:    05/08/26 17:27:26 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <gcncirc at observ.inetcomm.ru>

V. Lipunov,  V.Kornilov,  N.Tyurina, A.Belinski,
E.Gorbovskoy, D.Kuvshinov

Sternberg Astronomical Institute, Moscow Union "Optic"

We have analysed all photometric points obtained during first 2 hours (see 
picture http://observ.pereplet.ru/images/GRB050824/2.jpg ) from ROTSE
(GCN Circ 3867), MASTER (GCN Circ 3883), J. Gorosabel et al. (GCN Circ 
3865) and Swift UVOT(GCN Circ 3880) in similar colors .

The upper limits of ROTSE and MASTER for 500-750 sec (GRB time) are in 
agreement. Both instrumental systems are more or less similar.
There is some contradiction with J. Gorosabel  et al. (GCN 3865) and 
MASTER data (GCN Circ 3880)  for 24 - 47 minutes.
But there is no error bar in  J. Gorosabel et al.(GCN 3865).
The SWIFT UVOT V-band  is  most closed to MASTER in color sense.
If we include only 2 MASTER points and Swift UVOT V-point we can obtain 
next  power low:


m = 2.1(+-0.2) log (t) + 19.5  ,

t in hours. This corresponds to usual flux  power law

  F ~ t^-0.9

However there is strong contradiction with  ROTSE (11 min) uper limit and
J. Gorosabel et al. (GCN 3865) point.




JPG-images are available at 
http://observ.pereplet.ru/images/GRB050824/2.jpg  .

This work is supported by RFFI  04-02-16411 grant.
This message can be cited.
Mailto: lipunov at sai.msu.ru