Astronomy and Astrophysics, volume 362, 585-594 (2000/10-2)
The planet search program at the ESO Coude Echelle spectrometer. I. Data modeling technique and radial velocity precision tests.
ENDL M., KUERSTER M. and ELS S.
Abstract (from CDS):
We present the modeling technique we apply to analyse data of the ESO Coude Echelle Spectrometer (CES) planet search program, in order to obtain high precision stellar radial velocity (RV) measurements. The detection of the Doppler reflex motion of a star due to an orbiting planet has so far been the most successful method to discover planetary companions to solar-type stars. The first extrasolar planet discovered by the CES program is the companion to the young (ZAMS) G0V star ι Hor (Kuerster et al., 2000A&A...353L..33K
). To achieve a high long-term RV measurement stability the CES spectra are self-calibrated by a superimposed iodine vapor (I2
) reference spectrum. In the modeling process a multi-parameter χ2
-optimization is employed to generate an accurate description of the observation. We largely follow the general modeling approach for I2
-calibrated data outlined by Butler et al. (1996PASP..108..500B
) and Valenti et al. (1995PASP..107..966V
). The sharp I2
reference lines allow the reconstruction of the spectrograph instrumental profile (IP) and the precise determination of the Doppler shift of the stellar absorption lines. We show examples of the application of the modeling technique to CES data obtained over a time span of five and a half years at ESO La Silla. The small spectral bandwidth of only 4.85nm for CES spectra makes this data challenging for high precision radial velocities. We demonstrate for the known RV-constant star τ Cet, for two stars with known extrasolar planets, 51 Peg and 70 Vir, and for α Men and GJ 570A, two stars from our survey that the achievable RV precision for CES data is 8-15m/s.
methods: data analysis - techniques: radial velocities - stars: planetary systems
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