Gl. Israel et al., BeppoSAX and Chandra observations of SAX J0103.2-7209=2E 0101.5-7225: A new persistent 345 second X-ray pulsar in the small magellanic cloud, ASTROPHYS J, 531(2), 2000, pp. L131-L134
We report the results of a 1998 July BeppoSAX observation of a field in the
Small Magellanic Cloud which led to the discovery of similar to 345 s puls
ations in the X-ray flux of SAX J0103.2-7209. The BeppoSAX X-ray spectrum i
s well fitted by an absorbed power law with a photon index of similar to 1.
0 plus a blackbody component with kT = 0.11 keV. The unabsorbed luminosity
in the 2-10 keV energy range is similar to 1.2 x 10(36) ergs s(-1). In a ve
ry recent Chandra observation, the 345 s pulsations are also detected. The
available period measurements provide a constant period derivative of -1.7
s yr(-1) over the last 3 years, making SAX J0103.2-7209 one of the most rap
idly spinning up X-ray pulsars known. The BeppoSAX position (30 " uncertain
ty radius) is consistent with that of the Einstein source 2E 0101.5-7225 an
d the ROSAT source RX J0103.2-7209. This source was detected at a luminosit
y level of a few times 10(35)-10(36) ergs s(-1) in all data sets of past X-
ray missions since 1979. The ROSAT HRI and Chandra positions are consistent
with that of a m(v) = 14.8 Be spectral-type star already proposed as the l
ikely optical counterpart of 2E 0101.5-7225. We briefly report and discuss
photometric and spectroscopic data carried out at the ESO telescopes 2 days
before the BeppoSAX observation. We conclude that SAX J0103.2-7209 and 2E
0101.5-7225 are the same source: a relatively young and persistent X-ray pu
lsar in the SMC.