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Astron. Astrophys. 334, L65-L68 (1998)

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Letter to the Editor

ROSAT archival observations of 1SAX J0054.9-7226 = 2E 0053.2-7242, a newly discovered X-ray pulsar in the SMC

G.L. Israel * 1, S. Campana [FORMULA] 2, G. Cusumano 3, F. Frontera 4, M. Orlandini 4, A. Santangelo 3 and L. Stella *, 1

1 Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone (Roma), Italy
2 Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Lecco), Italy
3 Istituto di Fisica Cosmica e Applicazioni all'Informatica, C.N.R., Via La Malfa 153, I-90146 Palermo, Italy
4 Istituto Tecnologie e Studio Radiazioni Extraterrestri, C.N.R., Via Gobetti 101, I-40129 Bologna, Italy

Received 1 April 1998 / Accepted 17 April 1998


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 luminosity level ranging from [FORMULA] 8 [FORMULA] 1034 - 4 [FORMULA] 1035 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 R XTE and Beppo SAX yields a period derivative of P_= - 0.016 s yr-1. A much more accurate source position ([FORMULA] uncertainty) was obtained through the ROSAT HRI detection on 1996 April restricting to three [FORMULA] [FORMULA] 15.5 stars the likely counterpart of 1SAX J0054.9-7226 = 2E 0053.2-7242.

Key words: binaries: general – stars: neutron – pulsars: individual (1SAX J0054.9 – 7226; 2E 0053.2 – 7242) – galaxies: Magellanic Clouds – X-rays: stars

* Affiliated to I.C.R.A.

Send offprint requests to: G.L. Israel (e-mail: gianluca@coma.mporzio.astro.it)

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998