Details

Autor(en) / Beteiligte

• Staab, D
• Haswell, C. A
• Smith, Gareth D
• Fossati, L
• Barnes, J. R
• Busuttil, R
• Jenkins, J. S

Titel

SALT observations of the chromospheric activity of transiting planet hosts: mass-loss and star–planet interactions

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2017-04, Vol.466 (1), p.738-748

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2017

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Abstract We measured the chromospheric activity of the four hot Jupiter hosts WASP-43, WASP-51/HAT-P-30, WASP-72 and WASP-103 to search for anomalous values caused by the close-in companions. The Mount Wilson Ca ii H & K S-index was calculated for each star using observations taken with the Robert Stobie Spectrograph at the Southern African Large Telescope. The activity level of WASP-43 is anomalously high relative to its age and falls among the highest values of all known main-sequence stars. We found marginal evidence that the activity of WASP-103 is also higher than expected from the system age. We suggest that for WASP-43 and WASP-103 star–planet interactions (SPI) may enhance the Ca ii H & K core emission. The activity levels of WASP-51/HAT-P-30 and WASP-72 are anomalously low, with the latter falling below the basal envelope for both main-sequence and evolved stars. This can be attributed to circumstellar absorption due to planetary mass-loss, though absorption in the interstellar medium may contribute. A quarter of known short-period planet hosts exhibit anomalously low activity levels, including systems with hot Jupiters and low-mass companions. Since SPI can elevate and absorption can suppress the observed chromospheric activity of stars with close-in planets, their Ca ii H & K activity levels are an unreliable age indicator. Systems where the activity is depressed by absorption from planetary mass-loss are key targets for examining planet compositions through transmission spectroscopy.