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Swift/XRT non-detection of Millisecond X-ray Pulsar SWIFT J1756.9-2508

ATEL # 1117; S. Campana (INAF-OAB), P. Romano (Univ Bicocca&INAF-OAB), J. Kennea (PSU), C. Markwardt (GSFC/UMD), H. A. Krimm (GSFC/USRA), J. Tueller (GSFC)
on 22 Jun 2007; 10:14 UT
Password Certification: Sergio Campana (

Subjects: X-ray, Neutron Stars, Pulsars, Transients

During a ~1.9 ks pointed Swift/XRT observation performed on June 21, 2007 (03:27:38 to 06:53:56 UT), we did not detect SWIFT J1756.9-2508. We can set a 1-10 keV upper limit on the source unabsorbed flux of F(1-10)=3.2e-12 erg/cm2/s (assuming the spectral model that fits the longest XRT observation performed on 2007-06-15 for 9.1ks). This is more than a factor of 300 weaker than the X-ray flux observed with Swift/XRT on Jun 13 (ATEL #1111) and weaker by a factor of ~10 than the last Swift/XRT detection on June 19. We would like to thank the Swift-team for performing these XRT observations.

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R. E. Rutledge , Editor
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