New 60 millisecond X-ray pulsar and its massive early-type companion

Einstein Observatory IPC and HRI observations of a serendipitous, variable, X-ray source in the galactic plane in Carina are presented. Timing analysis shows the source to have a periodicity P about 60 ms. The optical identification with the 12.7 mag Wack 2134 star, suggested by the positional coincidence, is confirmed by spectroscopic observations done at ESO La Silla. The star appears to be probably of O5 type. The X-ray and optical data suggest the discovery of a new binary system where a hot massive star loses mass to a spinning neutron star, which would then be the fastest X-ray binary pulsar to date. 15 refs