High-Resolution X-ray and Radio Observations of SGR 1900+14 in the Immediate Aftermath of a Giant Flare

Abstract

We present the results of Chandra, RXTE, and VLA observations of SGR 1900+14 in the immediate aftermath of its 2001 April 18 giant flare event. In the X-ray band we find the source in a pulsating and bursting state, with time-averaged 2--10 keV flux initially elevated by 20% above the source's previous quiescent periods. In the radio we establish upper limits on the strength of any persistent post-flare emission of 0.7 and 0.1 mJy at 1.4 GHz and 8.0 GHz, respectively. The position of the X-ray source is consistent, to approximately 1 arcsec precision, with the August 1998 VLA determination, and the one-dimensional X-ray profile is consistent with that of a point source. The X-ray spectrum is best-fit by a two component power-law plus blackbody model, with fitted blackbody temperature kT_{BB} ~ 0.5 keV and radius R_{BB} ~ 1.5 km for an assumed distance of 5 kpc. The spectral parameters of this thermal component are consistent with those reported for the source in quiescence, and the variations in the source flux we observe may be explained as variations in the power-law component alone, providing support for magnetar models of SGR 1900+14.