Mon. Not. R. Astron. Soc., 466, 738-748 (2017/March-3)
SALT observations of the chromospheric activity of transiting planet hosts: mass-loss and star-planet interactions.
STAAB D., HASWELL C.A., SMITH G.D., FOSSATI L., BARNES J.R., BUSUTTIL R. and JENKINS J.S.
Abstract (from CDS):
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.
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: activity - circumstellar matter - stars: individual: (WASP-43, WASP-51, WASP-72, WASP-103) - stars: individual: (WASP-43, WASP-51, WASP-72, WASP-103)
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