The On/Off nature of star-planet interactions in the HD 179949 and And systems

Evgenya Shkolnik, David A. Bohlender, Gordon A.H. Walker, Andrew Collier Cameron

Research output: Contribution to journalArticlepeer-review


Evidence suggesting an observable magnetic interaction between a star and its hot Jupiter (Porb < 7 days, a < 0.1 AU, Mpsini > 0.2 MJ) appears as a cyclic variation of stellar activity synchronized to the planet's orbit. HD 179949 has been observed almost every year since 2001. Synchronicity of the Ca II H & K emission with the orbit is clearly seen in four out of six epochs, while rotational modulation with Prot=7 days is apparent in the other two seasons. We observe a similar phenomenon on And, which displays rotational modulation (Prot=12 days) in September 2005, while in 2002 and 2003 variations appear to correlate with the planet's orbital period. This on/off nature of star-planet interaction (SPI) in the two systems is likely a function of the changing stellar magnetic field structure throughout its activity cycle. The tentative correlation between this activity in the 13 stars we have observed to date and the ratio of Mpsini to the planet's rotation period, a quantity proportional to the hot Jupiter's magnetic moment, first presented in Shkolnik et al. (2005) remains viable. This work furthers the characterization of SPI, improving its potential as a probe of extrasolar planetary magnetic fields.

Original languageEnglish (US)
Pages (from-to)151-158
Number of pages8
JournalProceedings of the International Astronomical Union
Issue numberS249
StatePublished - Oct 2007
Externally publishedYes


  • Chromospheric activity
  • HD 179949
  • Late-type stars
  • Planetary systems
  • ν And

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science


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