We report pulsations in the X-ray flux of RX J0101.3 $ - $ 7211 in the Small Magellanic Cloud ( SMC ) with a period of ( 455 \pm 2 ) s in XMM-Newton EPIC-PN data .
The X-ray spectrum can be described by a power-law with a photon index of 0.6 \pm 0.1 .
Timing analysis of ROSAT PSPC and HRI archival data confirms the pulsations and indicates a period increase of \sim 5 s since 1993 . RX J0101.3 $ - $ 7211 varied in brightness during the ROSAT observations with timescales of years with a maximum unabsorbed flux of 6 \times 10 ^ { -13 } erg cm ^ { -2 } s ^ { -1 } ( 0.1 – 2.4 keV ) .
The flux during the XMM-Newton observation in the ROSAT band was lower than during the faintest ROSAT detection .
The unabsorbed luminosity derived from the EPIC-PN spectrum is 2 \times 10 ^ { 35 } erg s ^ { -1 } ( 0.2 – 10.0 keV ) assuming a distance of 60 kpc .
Optical spectra of the proposed counterpart taken at the 2.3 m telescope of MSSSO in Australia in August 2000 show strong H \alpha emission and indicate a Be star .
The X-ray and optical data confirm RX J0101.3 $ - $ 7211 as a Be/X-ray binary pulsar in the SMC .