✦ LIBER ✦

LMC X-4: 13.5 s pulsations and an X-ray flare observed by EXOSAT

✍ Scribed by W. Pietsch; M. Pakull; W. Voges; R. Staubert

Publisher: Springer Netherlands
Year: 1985
Tongue: English
Weight: 340 KB
Volume: 40
Category: Article
ISSN: 0038-6308
DOI: 10.1007/bf00179843

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✦ Synopsis

EXOSAT observed LMC X-4 on November 17/19, 1983 for one 1.4 day binary period during the high state of the 30.5 day cycle. An eclipse with sharp ingress and slow egress was detected with an eclipse angle of 27.1+1.0 dgr. In the medium energy experiment the source showed 'a hard power law spectrum. Outside eclipse the source was remarkably constant and only one flare was detected on November 17 at 19 UT lasting for about 1 h. The energy spectrum of the source softens considerably during that time and shows an emission line of cold iron. 13.5 sec pulsations are strongly present during the flare and have also been detected during the quiescent period and during several 1 rain flares in another EXOSAT LMC X-4 observation on November 22, 1983. A pulse delay time analysis results in the determination of the pulse period (13.5019+0.0002) s and of the semimajor axis os the orbit of the X-ray star (26.0+0T6) It-see. These results, together with other available information on LMC X-4, allowed to improve0tb4esbinary parameters. The mass os the neutron star is found to be 1.34_2_0~4 4 M o (95% confidence errors).

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