[vsnet-grb-info 7698] GRB 090424: MASTER-Net prompt optical limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9252
SUBJECT: GRB 090424: MASTER-Net prompt optical limit
DATE:    09/04/25 20:29:42 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <gcncirc at observ.inetcomm.ru>

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

K.Ivanov, S.Yazev
Irkutsk State University

A. Tlatov, A.V. Parhomenko,
Kislovodsk Solar Station of the Pulkovo Observatory

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


There are 6 MASTER Very Wide Field cameras located at Kislovodsk and Irkutsk 
with common FOW = 6000 square degrees (http://observ.pereplet.ru/).

One of the two  MASTER Very Wide Field Cameras located at Irkutsk
(D=50 mm, 2x1000 square degrees, 11 Mpx, 72" per pix in binning regime) has 
observed  UVOT error box (Cannizzo et al., GCN 9223) with 1s exposure befoure, 
during and after GRB Time without time gap between images.
The error box is near at the center of our FOW.

Our unfiltered images are calibrated relative to Tycho stars (V) and very 
close to V band.
The magnitude limit of the each emage is  ~8 m at the center of FOW (some 
cloudy on the sky). The limit of coadded six images ~ 9 m.

We do not detect OT.

Our observations results:

----------------------------------------------------------------------
Fermi GRB Trigg.*     Exposure   Mag Limit   Optical Flux        Coadd?
time (sec)            (sec)        (m)       (erg/sm^2 s)
----------------------------------------------------------------------
     -2                  1          8.1        1.3x10^-8            No
     -1                  1          8.1        1.3x10^-8            No
      0                  1          8.0        1.4x10^-8            No
     +1                  1          8.0        1.4x10^-8            No
     +2                  1          8.0        1.4x10^-8            No
     +3                  1          7.9        1.5x10^-8            No
     +4                  1          8.0        1.4x10^-8            No
     +5                  1          8.0        1.4x10^-8            No
  -60 : +120             1          ~8        ~1.4x10^-8            No
     -6                  6          8.9        7.0x10^-9            Yes
     +0                  6          8.7        7.3x10^-9            Yes
     +6                  6          8.8        7.2x10^-9            Yes
    +12                  6          8.9        7.0x10^-9            Yes
    -60                 60          9.7        3.0x10^-9            Yes
      0                 60          9.7        3.0x10^-9            Yes
     60                 60          9.5        3.5x10^-9            Yes
-----------------------------------------------------------------------
*Fermi GBM Trigger Time = 14:12:08.67 (Connaughton, GCN 9230)  1% 
coincident with our start zero image time.

1). the optical fluence during  GRBurst is limited by

  0 up to +6 s                       ~<=  1 x 10E-7 erg/cm^2
  0 up to +60 s                       <=  5 x 10E-7 erg/cm^2

including  total absorbtion 1 magnitude in V band.
(The absorption column density NH = (0.20 +/-  0.01) x10^22 cm^-2
from Swift XRT spectrum data, Margutti, GCN 9237).

The event fluence (8-1000 keV) in this time interval is
(5.2 +/- 0.1)E-05 erg/cm^2 (Connaughton, GCN 9230).

So:

2).

Optical-Fluence(6s)/Gamma-Fluence (8-1000 keV)  ~ < 1/500
Optical-Fluence(60s)/Gamma-Fluence(8-1000 keV)  ~ < 1/100

The same ratio for  GRB080319B is

Optical-Fluence/Gamma-Fluence(8 - 1000 keV) ~ 1/140

(Naked Eye GRB, Racusin, Karpov et al., Nature, vol.455, 183, 2008).


The light curve and film  of our observations  is available at

http://observ.pereplet.ru/images/GRB090424/GRB090424.html


The reduction is continued.

The message may be cited.

mailto: lipunov at sai.msu.ru