This paper presents a photometric and spectroscopic study of the bright blue
eclipsing binary LMC-SC1-105, selected from the OGLE catalog as a candidate
host of very massive stars (>=30Mo). The system is found to be a double-lined
spectroscopic binary, which indeed contains massive stars. The masses and radii
of the components are M1= 30.9+/-1.0 Mo, M2= 13.0+/-0.7 Mo, and R1= 15.1+/-0.2
Ro, R2= 11.9+/-0.2 Ro, respectively. The less massive star is found to be
filling its Roche lobe, indicating the system has undergone mass-transfer. The
spectra of LMC-SC1-105 display the Struve-Sahade effect, with the HeI lines of
the secondary appearing stronger when it is receding and causing the spectral
types to change with phase (O8+O8 to O7+O8.5). This effect could be related to
the mass-transfer in this system. To date, accurate (<=10%) fundamental
parameters have only been measured for 15 stars with masses greater than 30 Mo,
with the reported measurements contributing valuable data on the fundamental
parameters of very massive stars at low metallicity. The results of this work
demonstrate that the strategy of targeting the brightest blue stars in
eclipsing binaries is an effective way of studying very massive stars.Comment: 32 pages, 13 figures, 5 tables; accepted for publication in The
Astrophysical Journa
