ROSAT All-Sky Survey X-ray and EUV observations of YY Gem and AU Mic
Abstract
Simultaneous X-ray and extreme ultraviolet (EUV) (ROSAT XRT and WFC All-Sky Survey) observations of the highly active dMe flare stars YY Gem and AU Mic show that the two stars displayed an unusual type of flaring behaviour. We detect several X-ray and EUV flares superimposed on an enhanced and smoothly varying quiescent background. The two large impulsive-type X-ray flares on YY Gem reach peak X-ray luminosities of 1-1.6×1030ergs-1 and we estimate that they had similar integrated luminosities (~6-8×1033erg). AU Mic also produced several X-ray and EUV flares, with one very impulsive flare producing a 10-fold increase in XRT count rate. This flare was even larger than the YY Gem flares (peak LX of 2.4×1030ergs-1 and integrated LX of 1×1034erg). The LXLBol ratio for both stars is at the `saturation' limit found in rapidly rotating dwarfs and the most active RS CVn stars. We suggest that the gradually varying components are the result of a period of continuous, unresolved flaring activity. Alternatively, they may be the result of the emergence and subsequent decay of a new magnetic active region on the stellar surface of these stars.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2000
- DOI:
- 10.1046/j.1365-8711.2000.03905.x
- Bibcode:
- 2000MNRAS.319.1147T
- Keywords:
-
- STARS: ACTIVITY;
- STARS: FLARE;
- STARS: INDIVIDUAL: YY GEM;
- STARS: INDIVIDUAL: AU MIC;
- STARS: LATE-TYPE