SWIFT J1756.9-2508 is a 182 Hz Millisecond X-ray Pulsar
ATel #1108; C. B. Markwardt (CRESST/U. Md./GSFC), H. A. Krimm (CRESST/USRA/GSFC), J. H. Swank (NASA/GSFC)
on 14 Jun 2007; 06:34 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)
Subjects: X-ray, Gamma Ray, Request for Observations, Binary, Neutron Star, Transient, Pulsar
We report that the new transient SWIFT J1756.9-2508 (ATEL #1105)
is the eighth known millisecond X-ray pulsar.
RXTE PCA observed the sources
starting on 13 June 2007 (19:00 UTC) for about 1700 seconds. X-ray
pulsations were detected at a (barycentered) frequency of 182.06 Hz, with
an r.m.s. pulsed amplitude of a few percent. In a crude analysis,
small changes in the pulse frequency are seen (of order mHz), which might
be suggestive of orbital period modulation. However the current data span is
far too short to capture a full orbital cycle, if such a cycle exists.
RXTE observations will continue for at least the next few days. Observations
at other wavelengths are encouraged.
