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#

Directions of GRBs with the GRBM

Although the GRBM is an all-sky monitor without imaging capabilities,
and, therefore, it could not determine the arrival direction of a GRB,
nevertheless the ratios of the counts detected by each single detector
unit due to the same burst strongly depend on this direction;
thus, in priciple this relationship can be exploited to reconstruct the
arrival direction of a burst and to convert its counts into physical
units: the total counts into fluence (
), the peak count rate
into peak flux (
): in other words, a proper response matrix
can be obtained.
The GRBM response matrix, exploiting this property, is based on
a Monte Carlo model of the BeppoSAX payload and it has been initially
developed by [Rapisarda et al., 1997] and completed by [Calura et al., 2000]
(see also [Montanari et al., 2000]).
Below a brief description of the payload model and of the localization
technique are given. In the next chapters, the localizing capabilities
and the spectral reconstruction performances of the GRBM response
matrices derived from this model and finally tested with on-flight
data are widely discussed.
The importance of such matrices is obvious: as it will be shown,
thanks to them, it has been possible to estimate the incoming directions
of about two hundreds bursts among those that were detected only by
the GRBM with an accuracy of about 20-40.
Morevoer, in the hope of an automatic localization of
on-line detected bursts, this could help some of the current
robotic searches for optical flashes, like the
Robotic Optical Transient Search Experiment (ROTSE)
^{}([Akerlof et al., 2000], [Akerlof et al., 1999]), or the Burst Observer
and Optical Transient Exploring System (BOOTES)
^{}([Castro Ceron et al., 2001]).

**Subsections**

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** Up:** BeppoSAX and the Gamma
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Cristiano Guidorzi
2003-07-31