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@article{Haywood:2016:mnras/stw187,
author = {Haywood, RD and Cameron, AC and Unruh, YC and Lovis, C and Lanza, AF and Llama, J and Deleuil, M and Fares, R and Gillon, M and Moutou, C and Pepe, F and Pollacco, D and Queloz, D and Segransan, D},
doi = {mnras/stw187},
journal = {Monthly Notices of the Royal Astronomical Society},
pages = {3637--3651},
title = {The Sun as a planet-host star: proxies from SDO images for HARPS radial-velocity variations},
url = {http://dx.doi.org/10.1093/mnras/stw187},
volume = {457},
year = {2016}
}

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TY  - JOUR
AB  - The Sun is the only star whose surface can be directly resolved at high resolution, and therefore constitutes an excellent test case to explore the physical origin of stellar radial-velocity (RV) variability. We present HARPS observations of sunlight scattered off the bright asteroid 4/Vesta, from which we deduced the Sun's activity-driven RV variations. In parallel, the Helioseismic and Magnetic Imager instrument on board the Solar Dynamics Observatory provided us with simultaneous high spatial resolution magnetograms, Dopplergrams and continuum images of the Sun in the Fe I 6173 Å line. We determine the RV modulation arising from the suppression of granular blueshift in magnetized regions and the flux imbalance induced by dark spots and bright faculae. The rms velocity amplitudes of these contributions are 2.40 and 0.41 m s−1, respectively, which confirms that the inhibition of convection is the dominant source of activity-induced RV variations at play, in accordance with previous studies. We find the Doppler imbalances of spot and plage regions to be only weakly anticorrelated. Light curves can thus only give incomplete predictions of convective blueshift suppression. We must instead seek proxies that track the plage coverage on the visible stellar hemisphere directly. The chromospheric flux index R′HKRHK′ derived from the HARPS spectra performs poorly in this respect, possibly because of the differences in limb brightening/darkening in the chromosphere and photosphere. We also find that the activity-driven RV variations of the Sun are strongly correlated with its full-disc magnetic flux density, which may become a useful proxy for activity-related RV noise.
AU  - Haywood,RD
AU  - Cameron,AC
AU  - Unruh,YC
AU  - Lovis,C
AU  - Lanza,AF
AU  - Llama,J
AU  - Deleuil,M
AU  - Fares,R
AU  - Gillon,M
AU  - Moutou,C
AU  - Pepe,F
AU  - Pollacco,D
AU  - Queloz,D
AU  - Segransan,D
DO  - mnras/stw187
EP  - 3651
PY  - 2016///
SN  - 1365-2966
SP  - 3637
TI  - The Sun as a planet-host star: proxies from SDO images for HARPS radial-velocity variations
T2  - Monthly Notices of the Royal Astronomical Society
UR  - http://dx.doi.org/10.1093/mnras/stw187
UR  - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000373586000017&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR  - http://hdl.handle.net/10044/1/32614
VL  - 457
ER  -

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