RXTE Observations of Renewed Burst Activity from SGR 1627-41

ATel #1549; P. M. Woods (Dynetics/NSSTC), C. Kouveliotou (MSFC/NSSTC), E. Gogus (Sabanci Univ.), K. Hurley (UC-Berkeley), and J. Tomsick (UC-Berkeley)
on 29 May 2008; 12:31 UT
Credential Certification: Peter Woods (Peter.Woods@nsstc.nasa.gov)

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Following the Swift detection of the reactivation of SGR 1627-41 (Palmer et al. ATEL 1548 and GCN 7777), we searched serendipitous RXTE observations of the region targeting the black-hole transient 4U 1630-47. The 1 degree field-of-view of the PCA includes 4U 1630-47 and SGR 1627-41. We found no evidence for burst activity in 3 observations of the region between 2008 May 25 and 2008 May 27. During an RXTE observation of the region on 2008 May 28 (93702-01-14-01), we detect at least 8 bursts in a 1600 s exposure. The temporal and spectral properties of these bursts resemble those of SGR 1627-41. In particular, the bursts show rise times of ~10-100 ms and significantly slower fall times with total durations of 0.2-0.5 s. Some of the time histories exhibit double-peaked morphologies commonly seen from SGRs. The energy spectra are well characterized by a 4 keV blackbody in the PCA band (2-20 keV) where we have assumed a column density of 9x10^22 cm^-2 based upon modeling of the persistent emission (Kouveliotou et al. 2003). The peak luminosities of the eight bursts were on average 10^39 ergs/s for a distance of 11 kpc (Corbel et al. 1999). The brightest burst at 30103.9 SOD UT saturated the PCA having a peak luminosity of at least 10^40 ergs/s. We note that the spin period of this SGR has not yet been positively identified. Due to the poor signal-to-noise ratio during this observation, the limit on coherent pulsations from SGR 1627-41 for these data is not constraining. Follow-up ToO observations with RXTE and Chandra are planned for the next week. Daily observations of 4U 1630-47 with RXTE will also continue.