Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997aj....114.2764t&link_type=abstract
Astronomical Journal v.114, p.2764
Astronomy and Astrophysics
Astronomy
38
Binaries: Eclipsing, Stars: Evolution
Scientific paper
We have redetermined the masses of the unevolved F-type eclipsing binary HS Hya (P = 1.57 days) from 70 observations with the CfA digital speedometers, combined with other observations from the literature. Analysis of our radial velocities determined with a two-dimensional cross-correlation technique shows the presence of a third star in the system, which we find to be most likely an MO dwarf with a mass of ˜0.5 M0 in a 190-day orbit of small eccentricity and apparently co-planar with the eclipsing system. We also reanalyze an earlier set of light curves in the uvby system, using modem analysis techniques and combining all available spectroscopic and photometric data in the analysis. The resulting masses for the eclipsing stars are MA 1.255±0.008 Msun and MB1.219 ± 0.007 Msun, ˜6% smaller and 6 times more accurate than previous values. The radii are RA = 1.275±0.007 Rsun and RB 1 216±0.007 Rsun, and the effective temperatures TA = 6500±50 K, TB = 6400±50 K further properties of the stars are given in Table 7. Current stellar evolution models for the observed metallicity (slightly below solar) match the observed properties of both stars in HS Hya very well for a single, but strongly model-dependent age of ˜1.0 Gyr. A precise spectroscopic determination of [Fe/H] for HS Hya is needed to further refine comparison with theoretical models.
Andersen Johannes
Clausen Jens Viggo
Latham David W.
Nordström Birgitta
Stefanik Robert P.
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