The highly spotted photosphere of the young rapid rotator Speedy Mic

J R Barnes

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

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 languageEnglish
Pages (from-to)137-145
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume364
DOIs
Publication statusPublished - 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

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