Fabry-Pérot etalons for high precision radial velocity calibration

von Sebastian Schäfer
Dissertation
Datum der mündl. Prüfung:2014-04-23
Erschienen:2014-06-24
Betreuer:Prof. Dr. Ansgar Reiners
Gutachter:Prof. Dr. Ansgar Reiners
Gutachter:Prof. Dr. Stefan Dreizler
Zum Verlinken/Zitieren: http://dx.doi.org/10.53846/goediss-4574

 

 

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Englisch

The current generation of astronomical spectrographs can measure radial velocity signals of exoplanets down to a few m/s, in ideal cases even 60 cm/s can be achieved. This led to the discovery of rocky planets with masses of only a few times the mass of the Earth, orbiting their host stars within days or weeks. However, Earth only produces a radial velocity shift of about 9 cm/s during its one year orbit around the Sun. Thus, the radial velocity precision of astronomical spectrographs has to be improved by at least one magnitude in order to find these planets, even though the radial velocity signal of Earth-like planets in the habitable zone of low mass stars would be larger. Currently, a large fraction of the radial velocity uncertainty of astronomical spectrographs is due to the wavelength calibration. The established methods, e.g. using Hollow Cathode emission lamps as a wavelength reference, do not provide the precision needed for finding a second Earth. They also do not work particularly well in certain wavelength regions which could otherwise be used to find planets, for example the near infrared. One of the candidates for an improved wavelength calibration at the sub m/s level, especially in the near infrared, are Fabry-P érot etalons. This thesis explains how a Fabry-P érot unit was developed for the upcoming CARMENES spectrograph and how it will be able to achieve a radial velocity stability of 10 cm/s. Simulations of the impact of temperature, pressure and mechanical stability on the resulting radial velocity performance have been made. The results con firm the feasibility of using a Fabry-P érot unit for the wavelength calibration of an astronomical spectrograph with a radial velocity precision of the order of 10 cm/s and provide first requirements for the unit. Additionally, the eff ect of fi bers in combination with Fabry-P érots has been investigated. A close relation between certain fiber properties and the resulting spectrum has been found which impacts the radial velocity precision of Fabry-Pérot units in general. The final setup of the Fabry-P érot unit for CARMENES was designed and developed accordingly. The setup and the components used are explained and fi rst light measurements are shown.
Keywords: wavelength calibration; radial velocity; CARMENES; fibers; Fabry-Pérot
 
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