GRB 070724b: First Gamma Ray Burst Localization by SuperAGILE onboard
M. Feroci, E. Costa, E. Del Monte, I. Donnarumma, Y. Evangelista,
I. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda, P. Soffitta,
A. Rubini, E. Morelli, M. Mastropietro, G. Di Persio, M. Frutti,
and S. Mereghetti, A. Pellizzoni, G. Di Cocco, C. Labanti, M. Trifoglio,
G. Barbiellini, P. Picozza, A. Argan and M. Tavani,
on behalf of the AGILE Team, P. Giommi, L.A. Antonelli,
C. Pittori (ASDC), and L. Salotti (ASI) report:
The SuperAGILE experiment onboard the AGILE mission, launched on April
23rd on an equatorial orbit, is currently performing the in-flight
check-out and performance verification. The experiment is not yet in its
optimal configuration and not all the functions are active. In
particular, the onboard triggering and imaging is not active yet
and the absolute position reconstruction is being calibrated by
using celestial X-ray sources.
During this testing phase SuperAGILE detected and imaged
GRB 070724b. The event starting time is approximately at
23:25:09 UT on July 24 and it was observed at 21 degrees off-axis.
The observed duration in the 20-60 keV energy range is about 55 seconds,
with a multi-peak time structure.
The burst position was reconstructed as (RA, Dec) (17.629 deg,
57.673 deg), which is:
RA(J2000) = 01h 10m 31.0s
Dec(J2000) = +57d 40' 23"
with an uncertainty of 20' radius. The given uncertainty is almost
entirely systematic and it is due to the very preliminary absolute
position calibration, carried out only on 3 X-ray sources. At this
preliminary stage the absolute positioning was obtained by the ground
calibrations, preliminarily checked with these sources. The error box
may be improved over the next hours/days.
An analysis of the AGILE Gamma Ray Imager (GRID) data is in progress.
A quick look analysis does not show any bright gamma-ray transient
in coincidence with the X-ray emission of GRB 070724b.