[CSC][ITAL]BeppoSAX[/ITAL][/CSC] Observations of SGR 1900+14 in Quiescence and during an Active Period

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Abstract
We present results from two BeppoSAX Narrow-Field Instrument observations of SGR 1900+14 made during a quiescent and an active period of the source. We detect pulsations in the 1997 May 12-13 observation (quiescence) at 5.157190(7) s and the 1998 September 15-16 observation (active period) at 5.160261(12) s. Using results recently reported by Hurley et al., we establish a long-term spin-down rate during quiescence of 5.82(2) × 10-11 s s-1, which implies a dipole magnetic field of ~5.5 × 1014 G. We confirm deviations from a constant spin-down rate during the active period. We also find spectral similarities between SGR 1900+14 in quiescence and anomalous X-ray pulsars.