0053 . 2 – 7242 , a newly discovered X – ray pulsar in the SMC

ASTRONOMY AND ASTROPHYSICS ROSAT archival observations of 1SAX J0054.9–7226 = 2E 0053.2–7242, a newly discovered X–ray pulsar in the SMC Abstract. We analysed 13 archival ROSAT PSPC and HRI observations which included the position of a newly discovered 59 s X–ray pulsar in the Small Magellanic Cloud, 1SAX J0054.9–7226 = 2E 0053.2–7242. The source was detected three times between 1991 and 1996 at a lumi-nosity level ranging from ∼8×10 34-4× 10 35 erg s −1 (0.1– 2.4 keV). Highly significant pulsations at 59.072 s were detected during the 1991 October 8–9 observation. The ROSAT period, together with those measured by RXTE and BeppoSAX yields a period derivative of ˙ P= – 0.016 s yr −1. A much more accurate source position (10 ′′ uncertainty) was obtained through the ROSAT HRI detection on 1996 April restricting to three m V > 15.5 stars the likely counterpart of 1SAX J0054.9–7226 = 2E 0053.2– 7242.