The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars
Abstract
With an adaptive optics imaging survey of 148 B6-A7 stars, we have tested the hypothesis that unresolved lower mass companions are the source of the unexpected X-ray detections of stars in this spectral type range. The sample is composed of 63 stars detected in X-rays within the ROSAT All Sky Survey and 85 stars that form a control sample; both subsets have the same restricted distribution of spectral type, age, X-ray sensitivity and separation coverage. A total of 68 companion candidates are resolved with separations ranging from 0.3 to 26.2 arcsec, with 23 new detections. The multiple star frequency of the X-ray sample based on companions resolved within the ROSAT error ellipse is found to be 43+6-6 per cent. The corresponding control sample multiple star frequency is three times lower at 12+4-3 per cent - a difference of 31 ± 7 per cent. These results are presented in the first of a series of papers based on our Volume-limited A-Star (VAST) survey - a comprehensive study of the multiplicity of A-type stars.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2011
- DOI:
- 10.1111/j.1365-2966.2011.18765.x
- arXiv:
- arXiv:1103.4363
- Bibcode:
- 2011MNRAS.415..854D
- Keywords:
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- techniques: high angular resolution;
- binaries: general;
- stars: early-type;
- stars: imaging;
- X-rays: stars;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in Monthly Notices of the Royal Astronomical Society