The Discovery of 8.9 Second Pulsations from the Variable X-Ray Source 2E 0050.1-7247 in the Small Magellanic Cloud

摘要

During a systematic search for periodic signals in a sample of ROSAT PSPC light curves, we discovered ～8.9 s X-ray pulsations in 2E 0050.1-7247, a variable X-ray source in the Small Magellanic Cloud. The source was detected several times between 1979 and 1993 at luminosity levels ranging from ～5 * 10~34 ergs s~-1 up to 1.4 * 10~36 ergs s~-1 with both the Einstein IPC and ROSAT PSPC. The X-ray energy spectrum is consistent with a power-law spectrum that steepens as the source luminosity decreases. We revealed a pronounced Hα activity from at least two B stars in the X-ray error circles. These results strongly suggest that the X-ray pulsar 2E 0050.1-7247 is in a Be-type massive binary.