Im Licht der Lagune

The Discovery of an Outburst and Pulsed X-Ray Flux from SMC X-2 Using the [ITAL]Rossi X-Ray Timing Explorer[/ITAL]

“…Note that in this paper we use an assumed distance of 65 kpc to the SMC for consistency with several recent publications (e.g. Kahabka & Pietsch 1996, Haberl & Sasaki 2000 which is somewhat smaller than the 71 kpc adopted by Clark et al (1978).…”

“…However, now that the transient X-ray pulsar population of the SMC is known to be so large this shift to higher luminosities is called into question (see e.g. Haberl & Sasaki 2000) as the earlier observations were only detecting the high-luminosity tip of the large SMC X-ray pulsar population. Extensive studies of these objects down to low flux levels are required to fully establish their overall properties as a class.…”

“…However, they have since exhibited little activity. SMC X-2 was not detected in an Einstein IPC survey (Seward & Mitchell 1980) and was seen in only one of two observations made with the ROSAT PSPC detector (Kahabka & Pietsch 1996, Haberl & Sasaki 2000 at a luminosity of 2.7 × 10 37 ergs s −1 (0.15 − 2.4 keV). SMC X-3 was also not detected by Seward & Mitchell (1980) but was seen in one ROSAT HRI observation (Haberl & Sasaki 2000).…”

“…SMC X-2 was not detected in an Einstein IPC survey (Seward & Mitchell 1980) and was seen in only one of two observations made with the ROSAT PSPC detector (Kahabka & Pietsch 1996, Haberl & Sasaki 2000 at a luminosity of 2.7 × 10 37 ergs s −1 (0.15 − 2.4 keV). SMC X-3 was also not detected by Seward & Mitchell (1980) but was seen in one ROSAT HRI observation (Haberl & Sasaki 2000). An optical counterpart for SMC X-2 was proposed by Crampton, Hutchings, & Cowley (1978) which was resolved into a pair of stars, "A" and "B", with the fainter object ("B"), a main-sequence Be star, identified as the likely -2counterpart by Murdin, Morton, & Thomas (1979).…”

“…Further RXTE, ASCA and SAX observations have now lead to the identification of over 20 X-ray pulsars in the SMC (e.g. Haberl & Sasaki 2000, and references therein) and their variability and several optical identifications suggests that at least the vast majority are transient Be star systems. The number of known Be star X-ray binaries in the SMC is thus now starting to rival the number known in the Galaxy (e.g.…”