Magnetic field, differential rotation and activity of the hot-Jupiter-hosting star HD 179949
Abstract
HD 179949 is an F8V star, orbited by a giant planet at ∼8 R★ every 3.092 514 d. The system was reported to undergo episodes of stellar activity enhancement modulated by the orbital period, interpreted as caused by star-planet interactions (SPIs). One possible cause of SPIs is the large-scale magnetic field of the host star in which the close-in giant planet orbits.
In this paper we present spectropolarimetric observations of HD 179949 during two observing campaigns (2009 September and 2007 June). We detect a weak large-scale magnetic field of a few gauss at the surface of the star. The field configuration is mainly poloidal at both observing epochs. The star is found to rotate differentially, with a surface rotation shear of dΩ= 0.216 ± 0.061 rad d-1, corresponding to equatorial and polar rotation periods of 7.62 ± 0.07 and 10.3 ± 0.8 d, respectively. The coronal field estimated by extrapolating the surface maps resembles a dipole tilted at ∼70°. We also find that the chromospheric activity of HD 179949 is mainly modulated by the rotation of the star, with two clear maxima per rotation period as expected from a highly tilted magnetosphere. In 2009 September, we find that the activity of HD 179949 shows hints of low-amplitude fluctuations with a period close to the beat period of the system.- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2012
- DOI:
- 10.1111/j.1365-2966.2012.20780.x
- arXiv:
- arXiv:1202.4472
- Bibcode:
- 2012MNRAS.423.1006F
- Keywords:
-
- planet-star interactions;
- stars: activity;
- stars: individual: HD 179949;
- stars: magnetic fields;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in Monthly Notices of The Royal Astronomical Society