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Swift-BAT discovery of a transient pulsar SWIFT J1626.6-5156

ATel #678; D. Palmer (LANL), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), J. Kennea (PSU), H. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), J. Tueller (GSFC) on behalf of the Swift-BAT team
on 20 Dec 2005; 20:42 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

Referred to by ATel #: 679, 687, 688, 713, 739, 2036, 3300, 14454, 14457

Swift-BAT detected a new pulsar at RA, Dec 246.632,-51.945 {16h 26m 31.8s,-51d 56' 41.6"} (J2000) with an uncertainty of 2.5 arcmin (radius, 90%, stat+sys). We designate this new source SWIFT J1626.6-5156 (Krimm, et al., GCN 4361; Barthelmy et al, GCN 4362). No obvious counterparts were found in a search of Simbad, or the ROSAT all-sky survey.

This source has been detected multiple times by BAT, with the earliest detection at 2005 Dec 18 04:21 (UTC) and the most recent at 2005 Dec 20 06:28 (as of 2005 Dec 20 15:00).

The period is 15 +/- 1 sec with flares of pulsations lasting several minutes long. The most notable flare seen by BAT so far is around 2005-12-19 00:06, with a pulsation amplitude greater than 1500 mCrab.

Using data from the Dec 18, 2005 initial detection (a 90 second interval starting at 19:06 UT), the spectrum is consistent with a power law with photon index 3.2 +/- 0.6. The fluxes in the 15-25, 25-50, and 50-100 keV bands were 3.1, 2.1 and 0.9 in units of 1E-9 erg/cmE2/s. However, as noted above, there appears to be significant variability in the flux.

The source is within 33 degrees of the Sun. Swift pointed observations can be done when it emerges from constraint on 09 Jan 2005. We encourage other follow-up observations.