SMC X-3 Identified with RXTE 7.78s Pulsar from Archive Chandra Data.
ATel #225; W. R.T. Edge & M. J. Coe (Southampton University), R. H.D. Corbet (GSFC and USRA), C. B. Markwardt (GSFC and University of Maryland), S. Laycock (CfA)
on 30 Jan 2004; 07:45 UT
Credential Certification: W R T Edge (wrte@astro.soton.ac.uk)
Subjects: X-ray, Binary, Transient, Pulsar
SMC X-3 (Clark et al. 1978, ApJ, 221, L37) has been identified with a previously detected 7.78s RXTE pulsar by using archive Chandra Data. An examination of Chandra Observation ID 2947, which took place between 2002-07-20 23:03:50 and 2002-07-21 01:46:41 (Zezas et al. astro-ph/0310562, 2003), shows SMC X-3 at R.A. = 00h52m05.7s Decl. = -72d26m05s (equinox 2000) with a 90% confidence radial uncertainty of 0.6 arcsec. This is consistent with the position of the optical counterpart proposed for SMC-X-3 by Crampton et al. (1978, ApJ, 223, L79). The ACIS-I count rate implies a luminosity of about 2.2x10^36 erg/s assuming a distance of 65 kpc. Timing analysis shows the Chandra object to have a pulse period of 7.781s +/- 0.002s with a confidence of >98%. An X-ray pulsar with a pulse period of 7.781s +/- 0.002s was detected by RXTE in early 2002 and on eight subsequent occasions, giving a probable binary period of 45.1 +/- 0.4 days (Corbet et al. 2003, AAS HEAD, 35, 1730C). The position of the RXTE source was tentatively determined to be within 15 arcmins of the known position of SMC X-3. An examination of the RXTE data shows that an outburst was detected in an observation which took place on MJD 52478, three days after the Chandra observation on MJD 52475. It is concluded that all these observations are of the same object, namely SMC X-3.
