Abstract
We present high-resolution images of the young rapidly rotating K3 dwarf Speedy Mic (BO Mic, HD 197890). The photospheric spot maps reveal a heavily and uniformly spotted surface from equatorial to high-latitude regions. Contrary to many images of similar objects, Speedy Mic does not possess a uniform filling at high latitudes, but exhibits structure in the polar regions showing greatest concentration in a particular longitude range. The asymmetric rotation profile of Speedy Mic indicates the presence of a companion or nearby star which shows radial velocity shifts over a time-scale of several years. Using a simple dynamical argument, we show that Speedy Mic is unlikely to be a binary system, and conclude that the feature must be the result of a chance alignment with a background binary. Complete phase coverage on two consecutive nights in addition to 60 per cent phase coverage after a three-night gap has enabled us to track the evolution of spots with time. By incorporating a solar-like differential rotation model into the image reconstruction process, we find that the equator laps the polar regions once every 191 +/- 17 d. This finding is in close agreement with measurements for other late-type rapid rotators.
Original language | English |
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Pages (from-to) | 137-145 |
Number of pages | 9 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 364 |
DOIs | |
Publication status | Published - 21 Nov 2005 |
Keywords
- line : profiles
- methods : data analysis
- stars : activity
- stars : atmospheres
- stars : individual : Speedy Mic (HD 197890)
- stars : late-type
- DUAL-SITE OBSERVATIONS
- MAIN-SEQUENCE STARS
- CLEAN-LIKE APPROACH
- DIFFERENTIAL ROTATION
- DOPPLER IMAGES
- ACTIVE STARS
- AB-DORADUS
- G DWARFS
- LO PEG
- EVOLUTION