Volume 535, November 2011
|Number of page(s)||12|
|Published online||26 October 2011|
Bisectors of the HARPS cross-correlation function⋆
The dependence on stellar atmospheric parameters
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
2 Ankara University, Astronomy & Space Sciences Research and Application Center, 06837 Ahlatlibel, Ankara, Turkey
3 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany
4 Ankara University, Faculty of Science, Department of Astronomy and Space Sciences, 06100 Tandogan-Ankara, Turkey
Received: 21 July 2011
Accepted: 20 September 2011
Context. Bisectors of the HARPS cross-correlation function (CCF) can discern between planetary radial-velocity (RV) signals and spurious RV signals from stellar magnetic activity variations. However, little is known about the effects of the stellar atmosphere on CCF bisectors or how these effects vary with spectral type and luminosity class.
Aims. Here we investigate the variations in the shapes of HARPS CCF bisectors across the HR diagram in order to relate these to the basic stellar parameters, surface gravity and temperature.
Methods. We use archive spectra of 67 well studied stars observed with HARPS and extract mean CCF bisectors. We derive previously defined bisector measures (BIS, vbot, cb) and we define and derive a new measure called the CCF bisector span (CBS) from the minimum radius of curvature on direct fits to the CCF bisector.
Results. We show that the bisector measures correlate differently, and non-linearly with log g and Teff. The resulting correlations allow for the estimation of log g and Teff from the bisector measures. We compare our results with 3D stellar atmosphere models and show that we can reproduce the shape of the CCF bisector for the Sun.
Key words: instrumentation: spectrographs / techniques: radial velocities / line: profiles / stars: atmospheres / stars: activity
© ESO, 2011
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