Open AccessThe highly spotted photosphere of the young rapid rotator Speedy Mic
Author(s) -
Barnes J. R.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09544.x
Subject(s) - physics , differential rotation , astrophysics , longitude , photosphere , equator , polar , rotation (mathematics) , latitude , binary number , astronomy , radial velocity , stars , geometry , mathematics , arithmetic , spectral line
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.