Determining stellar macroturbulence using asteroseismic rotational velocities from Kepler
By A. Doyle, G. Davies, B. Smalley, W. Chaplin, Y. Elsworth. 2014
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The Rossiter-McLaughlin effect observed for transiting exoplanets often requires prior knowledge of the stellar projected equatorial rotational velocity (v sini). This is usually provided by measuring the broadening of spectral lines, however this method has uncertainties as lines are also broadened by velocity fields in the stellar photosphere known as macroturbulence (vmac). We have estimated accurate v sini values from asteroseismic analyses of main sequence stars observed by Kepler. The rotational frequency splittings of the detected solar-like oscillations of these stars are determined largely by the near-surface rotation. These estimates have been used to infer the vmac values for 28 Kepler stars. Out of this sample, 26 stars were used along with the Sun to obtain a new calibration between vmac, effective temperature and surface gravity. The new calibration is valid for the temperature range 5200 to 6400 K and the gravity range 4.0 to 4.6 dex. A comparison is also provided with previous vmac calibrations. As a result of this work, vmac, and thus v sini, can now be determined with confidence for stars that do not have asteroseismic data available. We present new spectroscopic v sini values for the WASP planet host stars, using high resolution HARPS spectra.
Subfields: Astronomy and Astrophysics, Instrumentation
View Paper: https://www.semanticscholar.org/paper/fb62d8d76e9532d7dfa8d4a5717f3688f8ad1d65
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Citations in the corpus
- WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, methodology): “A macroturbulent velocity (vmac) of 6.0 ± 0.6 km s−1 was assumed using the asteroseismic-based calibration of Doyle et al. (2014) and an instrumental resolution of 55,000.”