Coronal activity from AB DOR and RST 137B.
Abstract
Two 12-h synthesis observations of the active star AB Dor (HD36705) made with the Molonglo Observatory Synthesis Telescope (MOST) as part of a 1990 international campaign of observations are presented. A weak variable source was detected near the stellar position during both sessions. The derived brightness temperatures are consistent with a gyrosynchrotron emission model. The complete sample of MOST observations of AB Dor made since 1985 reveals a quiescent level of radio emission with flare-like increases, and a discrepancy of ∼5 arcsec between the 843-MHz source and the optical position. An analysis of the variations in position of the radio source with flux density suggests that this discrepancy may be the result of confusion with the nearby, active dMe star RST 137B. Recent Australia Telescope observations have resolved both AB Dor and RST 137B as radio sources at 5 GHz, supporting this explanation. The unusually high levels of activity seen from both stars lead us to examine critically the currently accepted pre-main-sequence model for AB Dor and RST 137B. We propose a post-main-sequence FK Comae evolutionary model for AB Dor, and conclude by suggesting a number of observations that could support this conjecture.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 1993
- DOI:
- 10.1093/mnras/264.3.570
- Bibcode:
- 1993MNRAS.264..570B
- Keywords:
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- stars: activity - stars: evolution - stars: flare - stars: individual: AB Dor - stars: individual: RST 137B - radio continuum: stars