ROSAT ARCHIVAL OBSERVATIONS OF 1SAX J0054.9-7226=2E-0053.2-7242, A NEWLY DISCOVERED X-RAY PULSAR IN THE SMC

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 Mag ellanic Cloud, 1SAX J0054.9-7226 = 2E 0053.2-7242. The source was dete cted three times between 1991 and 1996 at a luminosity level ranging f rom similar to 8 X 10(34) - 4 X 10(35) erg s(-1) (0.1-2.4 keV). Highly significant pulsations at 59.072 s were detected during the 1991 Octo ber 8-9 observation. The ROSAT period, together with those measured by RXTE and BeppoSAX yields a period derivative of (P) over dot= - 0.016 s yr(-1). A much more accurate source position (10 '' uncertainty) wa s obtained through the ROSAT HRI detection on 1996 April restricting t o three m(V) > 15.5 stars the likely counterpart of 1SAX J0054.9-7226 = 2E 0053.2-7242.