XTE J1829-098: a New 7.8 s Period Pulsar

ATel #317; C. B. Markwardt (U. Maryland & NASA/GSFC); J. H. Swank (NASA/GSFC); E. A. Smith (NASA/GSFC)
on 10 Aug 2004; 02:02 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)

Tweet

Within the past three months, RXTE PCA monitoring observations of the galactic center region have been enlarged to include portions of the galactic plane on either side of the galactic bulge. The scans extend to about +/- 25 degrees in galactic longitude and +/- 4 degrees in galactic latitude.

Scans on July 30.9 (UTC) detected a new source with intensity ~7 mCrab. In follow-up pointed PCA observations on August 5.3, the source was detected as an X-ray pulsar. The pulse period is 7.82 +/- 0.05 s. Preceding the July 30.9 observation, there were five PCA scans between May 22 and June 10, where the source was not detected, with upper limit ~2 mCrab.

A dedicated PCA scan for position was performed on August 8.5. The scans were fit to a model which included components from the galactic ridge (~2 mCrab) and the nearby supernova remnant G21.5-0.9 (~5 mCrab). The best fit pulsar position is R.A. = 18h29m35s, Decl. = -09d51' (J2000). The 99% confidence region is approximately elliptical with semimajor axes of 3.8' (R.A.) and 3' (Decl.). We designate this source XTE J1829-098.

After accounting for the galactic ridge emission, which contaminates the field of view, the spectrum of XTE J1829-098 is consistent with an absorbed power law with high energy cut-off. The N_H value was 10^{23} cm^{-1}, the power law photon index 1.0, and the cut-off energy was 9.8 keV. The 2-10 keV flux was 1.0 x 10^{-10} erg cm^{-2} s^{-1}.

Although the pulse period is close to those of Anomalous X-Ray Pulsars, the spectrum is as hard as spectra of high mass binaries. 4U 1626-67 also has a similar period and a hard spectrum. The closest cataloged X-ray source appears to be 1WGA J1830.1-0954, which is nominally 9' away, and thus outside of our quoted 99% error contour. In 1994 the ROSAT flux of that source was 1.650 x 10^{-13} ergs s^{-1} cm^{-2}. SIMBAD reports no bright stars within the error contour, but there are many with V>16 mag.