The Evolutionary Status of GK Subgiants
Abstract
Snowden & Young suggested that the reason why there are GK subgiants is because they are members of binaries, which would bring them above the main sequence in an Hertzsprung-Russell (HR) diagram. They studied a sample of 30 G0-K1 IV stars and were disappointed to find only two to be spectroscopic binaries. With more accurate radial velocities I found seven binaries in their samples of subgiants and control stars; orbital elements are given for those seven. Using Hipparcos parallaxes and SIMBAD data, I found that nearly all of the G0-K1 IV stars fall on the evolutionary tracks by Garardi et al. for Population I stars with masses of 0.9-1.9 M ⊙ and ages of up to 1010 yr, which are normal parameters for nearby field stars. Therefore there is no problem regarding the existence of GK subgiants.
- Publication:
-
The Astronomical Journal
- Pub Date:
- May 2019
- DOI:
- 10.3847/1538-3881/ab11c6
- Bibcode:
- 2019AJ....157..177A
- Keywords:
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- binaries: spectroscopic;
- stars: evolution;
- stars: late-type