New Transient X-ray Pulsars in the SMC (XTE J0103-728, XTE SMC144s)

ATel #163; R. H.D. Corbet (GSFC and USRA) C. B. Markwardt (GSFC & University of Maryland) F. E. Marshall (GSFC), M. J. Coe and W. R.T. Edge (Southampton University) and S. Laycock (CfA)
on 4 Jun 2003; 21:47 UT
Credential Certification: Robin Corbet (corbet@gsfc.nasa.gov)

Tweet

We have detected two new transient X-ray pulsars in the direction of the Small Magellanic Cloud with the RXTE Proportional Counter Array. The sources were detected within the 2 degree FWZI field of view of the PCA while pointed at R.A. = 00h53m53s, Decl. = -72o26m42s (equinox 2000.0).

A source with a period of 6.8482 +/- 0.0007 s was seen in observations made on 2003 Apr. 29, May 7, May 15 and May 19 but not detected in observations made on Apr. 24 and May 28. Other pulsars were also detected during these observations. Pulsations with periods near 152s from CXOU J005750.3-720756 (Macomb et al. 2003, ApJ, 584, L79) were seen on Apr 29 and May 7. Pulsations wither periods near 59s from XTE J0055-724 (Marshall et al. 1998, IAUC # 6818 ) were seen on May 15 and May 19. Pulsations from another previously unknown source with a period of 144.1 +/- 0.3 s were also seen on May 19.

Slews were made across this field in both R.A. and declination for all observations. From the observations made on April 19, May 7, May 15, and May 19 we find for the 6.8s pulsar count rates of 7.6 +/- 0.4 (3.8 mCrab), 6.9 +/- 0.4 (3.5 mCrab), 4.5 +/- 0.3 (2.3 mCrab) and 5.8 +/- 0.4 (2.9 mCrab) counts/s/Proportional Counter Unit (2 - 30 keV) respectively. From a combined fit to all slews a position of R.A. = 15.36, Decl. = -72.72 (equinox 2000.0) was obtained. The error box is ellipsoidal with maximum extent 2 sigma statistical errors of approximately +/- 0.14 degrees in R.A. and 0.06 degrees in declination. Systematic errors on the source position are unknown but may well be significant as the region contains a complex superposition of active sources. The statistical error box is available at http://lheawww.gsfc.nasa.gov/users/corbet/pulsars/xtej0103_ebox.ps. We designate this source XTE J0103-728.

The coordinates of the 144.1s source could not be constrained due to the number of sources active in the single observation during which this source was detected. We hence use the "timing" name of XTE SMC144s for this source.

A list of known X-ray pulsars in the SMC is provided at: http://lheawww.gsfc.nasa.gov/users/corbet/pulsars

X-ray Pulsars in the SMC