Line-profile tomography of exoplanet transits I: The Doppler shadow of HD 189733b - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




Line-profile tomography of exoplanet transits I: The Doppler shadow of HD 189733b - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present a direct method for isolating the component of the starlightblocked by a planet as it transits its host star, and apply it to spectra ofthe bright transiting planet HD 189733b. We model the global shape of thestellar cross-correlation function as the convolution of a limb-darkenedrotation profile and a gaussian representing the Doppler core of the averagephotospheric line profile. The light blocked by the planet during the transitis a gaussian of the same intrinsic width, whose trajectory across the lineprofile yields a precise measure of the misalignment angle and an independentmeasure of v sin I. We show that even when v sin I is less than the width ofthe intrinsic line profile, the travelling Doppler -shadow- cast by the planetcreates an identifiable distortion in the line profiles which is amenable todirect modelling. Direct measurement of the trajectory of the missing starlightyields self-consistent measures of the projected stellar rotation rate, theintrinsic width of the mean local photospheric line profile, the projectedspin-orbit misalignment angle, and the system-s centre-of-mass velocity.Combined with the photometric rotation period, the results give a geometricalmeasure of the stellar radius which agrees closely with values obtained fromhigh-precision transit photometry if a small amount of differential rotation ispresent in the stellar photosphere.



Author: A. Collier Cameron, V. A. Bruce, G. R. M. Miller, A. H. M. J. Triaud, D. Queloz

Source: https://arxiv.org/







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