[AAVSO-HEN] GRB 090306B: INTEGRAL SPI-ACS light curve

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
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TITLE:   GCN CIRCULAR
NUMBER:  8968
SUBJECT: GRB 090306B: INTEGRAL SPI-ACS light curve 
DATE:    09/03/10 14:23:05 GMT
FROM:    Volker Beckmann at ISDC  <Volker.Beckmann at obs.unige.ch>

V. Beckmann, M. Beck, C. Ferrigno, N. Produit, V. Savchenko (ISDC),
J. Borkowski (CAMK/Torun), D. Gotz (CEA/Saclay), S. Mereghetti 
(INAF/IASF-Milano), A. von Kienlin (MPE) report on behalf of the 
INTEGRAL SPI-ACS GRB team:

GRB 090306B, detected in Swift/BAT slew data (Copete et al. GCN 8944), 
has been independently detected by the SPI Anti-Coincidence
System (ACS) on-board INTEGRAL. The SPI-ACS light curve shows the peak 
of the burst at 2009-03-06T23:07:21.9 with a maximum count-rate of ~390 
counts/50msec. The duration of the GRB is about 14 seconds.

The SPI-ACS light curves are available (both as images and data files)
at http://isdc.unige.ch/Soft/ibas/ibas_acs_web.cgi

The light curves, binned at 50 ms, are derived from 91 independent
detectors with different lower energy thresholds (mainly between 50 keV
and 150 keV) and an upper threshold at about 100 MeV. The ACS response
varies as a function of the GRB incident angle. For these reasons we
caution that the count rates cannot be easily translated into physical
flux units.