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RXTE PCA and Swift BAT detects the Millisecond Pulsar Swift J1756.9-2508 in Outburst

ATEL # 2130; A. Patruno (U.Amsterdam),C. B. Markwardt (U. Maryland and NASA/GSFC), , T. E. Strohmayer (NASA/GSFC), J. H. Swank (NASA/GSFC), S.E. Smith (WIS/NASA/GSFC),D. Pereira (Wyle IS and NASA/GSFC)
on 14 Jul 2009; 20:16 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Alessandro Patruno (

Subjects: X-ray, Request for Observations, Binaries, Neutron Stars, Pulsars, Transients

We report a detection of increased activity of the accreting millisecond X-ray pulsar Swift J1756.9-2508 observed with the RXTE-PCA monitoring on July 8, 9hr UTC. Increased flux is detected simultaneously on the Swift-BAT camera. RXTE-PCA follow up observations starting on July 13, 23hr UTC, detected the source in the 2-16 keV band at a flux level of approximately 19 mCrab, rising to 22 mCrab on July 14, 2hr UTC. Swift J1756.9-2508 was previously observed in outburst in June 2007 (Atel #1107), suggesting a recurrence time of approximately 2 years. Barycentered data at the Swift-XRT position (Krimm et al. 2007) show a peak in the power density spectrum which is entirely consistent with the 182.0658 Hz reported by Krimm et al. (2007). More PCA observations are planned. Follow-up observations at other wavelengths are encouraged.

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