Thesis Abstract

Constraining the Period of LHA 118-S 18’s
Compact Companion

D.P. Scriven, L. Chomiuk, J. Strader

The star LHA-115S 18 is a supergiant B star in the SMC that doubles as an X-ray source. It’s an interesting system that expresses photometric and spectroscopic variability. In addition, the star has in few cases exhibited an extreme He II emission that has yet to be explained (Lepo). This star is of interest to us in particular because of its likelihood of companionship; the aptly named S18 is suspected to have a compact object companion which is yet to be verified. In the proceeding we examine spectra of S18 and attempt the first companion period determination by taking measurement of the star’s radial velocity semi-amplitude. Such a measurement would put a constraint on the nature of the CO, and determine whether or not it’s an NS or more favorably a WD. Both of these objects have interesting implications for such a B[e] system. Both of these objects have interesting implications for such a B[e] system. Should the companion be an NS several of it’s currently mysterious properties like it’s hot component and X-ray release. On the other hand, if the companion turns out to be a WD then this system has the possibility of evolving into an interesting NS-WD binary system.


  1. J. S. Clark, E. S. Bartlett, M. J. Coe, R. Dorda, F. Haberl, J. B. Lamb, I. Negueruela, A. Udalski. The supergiant B[e] star LHA 115-S 18 binary and/or luminous blue variable?. Astronomy & Astrophysics 560, A10 EDP Sciences, 2013. Link

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