2005A&A...433..629G -
Astronomy and Astrophysics, volume 433, 629-634 (2005/4-2)
BS Indi: An enigmatic object in the Tucana association.
GUENTHER E.W., COVINO E., ALCALA J.M., ESPOSITO M. and MUNDT R.
Abstract (from CDS):
BS Ind (=HD 202947) is a young K0V star in the Tucana association. Photometric observations with the Hipparcos satellite show an eclipse-like light-curve with primary and secondary eclipse. The eclipsing binary has a period of 0.435338-days and a circular orbit. Our spectroscopic observations however show that the K0V primary is a single-line spectroscopic binary with a period of 3.3-years. The minimum mass of the invisible component is about 0.9M☉ which means that the mass of the companion is about the same as that of the primary. The first inspection of our FEROS spectra with a resolution of 48000, as well as a CES spectrum with a resolution of 220000 shows no obvious companion. However, when the FEROS spectra are cross-correlated with an M-star, a secondary becomes visible as a broad peak in the cross-correlation function. The width and the position of this broad peak is variable on a short time. When phased to a period of 0.435338-days, the radial velocity variations of the broad peak show the characteristic sine-wave of a spectroscopic binary in a circular orbit. The best interpretation of this data is that the broad peak in the cross-correlation function is caused by an eclipsing binary consisting of two late-K, or early-M stars with an orbital period of 0.435338-days. This is the eclipsing system. These two stars then orbit the K0V-primary with a period of 3.3-years. The assumption that BS Ind is a triple system consisting of a K0V star and two late-K, or early-M stars also explains the unusual brightness of the object and the near infrared excess. Thus, BS Ind is unique, as it contains by far the shortest-period young binary star, and these stars are eclipsing.
Abstract Copyright:
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Journal keyword(s):
stars: individual: BS Ind - binaries: eclipsing - binaries: spectroscopic - stars: formation - stars: evolution
Simbad objects:
8
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