[vsnet-grb-info 6880] GRB 081102: MASTER prompt optical limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8471
SUBJECT: GRB 081102: MASTER prompt optical limit
DATE:    08/11/03 20:06:42 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <gcncirc at observ.inetcomm.ru>

MASTER-Net Team (http://observ.pereplet.ru):

V. Lipunov, V.Kornilov,  E.Gorbovskoy,
A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, A.Parkhomenko
Kislovodsk Solar Station of the Pulkovo observatory

V.Krushinski, I.Zalognikh
Ural State University, Kourovka


S.Yazev, K.Ivanov
Irkutsk State University


MASTER Very Wide Field Camera located at Kislovodsk (2000 m)
(http://apollo.sai.msu.ru/, D=50 mm, 4x1000 square degrees, 35'' per pix) 
has observed the Swift-BAT GRB081102 error box  (Ukwatta et al., GCN Circ 8642) 
with 5s exposures during all night without windows between images. 
There are two  separeted (~702m) mount with double cameras.

Now we present results from North camera.

These unfiltered images are calibrated relative to Tycho stars (V).
We do not detect any new source at the XRT position
reported in GCN Circ. 8467 ( Osborne et al.) brighter than 12.4 mag 
before and after trigger time.
The photometry results +-4 min around trigger time:


  T-T_trigger            m_lim (S/N=3)         Exposure         Coadd

-255s... 0... 255 s       11.6                  5s              no 
-2min...0...+2 min        12.2                 30s               6
-2min...0...+2 min        12.4                 60s              12

The optical fluence during the 60s-GRburst is limited by <= 6x10_-9 
erg/cm_2    including 2.5 magnitude  absorbtion (Ukwatta et al., Circ 
8462). The BAT-fluence is aboute 3 10_-6 erg/cm_2 (15-150 Kev) 
(http://gcn.gsfc.nasa.gov/notices_s/333427/BA/).
So

Optical Fluence/Gamma-Fluence ~ < 1/500

Same ratio for GRB080319B is ~ 1/200 (Naked Eye GRB).

The  light curve  is available at
http://observ.pereplet.ru/images/GRB081102/lc1.png


The  video  are available at
http://observ.pereplet.ru/images/GRB081102/grb.gif
You can see 200 sets.
Note: the GRB was at the edge of the FOW.

The reduction is continuing.

mailto: lipunov at sai.msu.ru