TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1055 SUBJECT: BeppoSAX/NFI Follow-up Observation of SGR 1900+14 DATE: 01/04/27 16:26:03 GMT FROM: Marco Feroci at IAS/CNR Frascati BeppoSAX/NFI Follow-up Observation of SGR 1900+14 M. Feroci (IAS/CNR, Roma) and S. Mereghetti (IFC/CNR, Milano), on behalf of a larger SGR collaboration, and G. Gandolfi, L. Piro and E. Costa (IAS/CNR, Roma), on behalf of the BeppoSAX Team, report: "A ToO observation of SGR1900+14 was carried out with the BeppoSAX Narrow Field Instruments starting on April 18, 15:10 UT, less than 8 hours after the large flare reported in GCN #1041. Intense bursting activity is present during the 28 hr long observation. After removing the numerous short bursts, a significant flux decay is visible in the MECS and LECS light curves. By using our data and the Chandra 2-10 keV flux (GCN #1046) we find that the decay can be reasonably well described by a power law with index ~-0.6. There is also evidence for a spectral softening correlated with the intensity decrease. The average spectrum (after removal of the bursts) can be fit by a power law with photon index 2.6+/-0.1 and NH=(4.3 +/-0.3)x10^22 cm^-2. The average 2-10 keV flux during the whole BeppoSAX observation is 2.9x10^-11 erg/cm^2/s (unabsorbed). The bursts have a significantly harder spectrum (power law photon index ~0 in the 2-10 keV range). Pulsations, with a nearly sinusoidal light curve and a modulation of about 21%, are clearly detected at the barycentered period P=5.17277(1) s. When compared with the value measured with Chandra about 3 days later (GCN #1049), this yields a dP/dt ~ (4.1 +/- 1.9)x10^-10 s/s. An additional BeppoSAX/NFI observation will start on April 29, 20:30 UT." This message may be cited.