Speaker
Dr
Gert Raskin
(KU Leuven)
Description
After nearly ten years of successful operations, HERMES, the fibre-fed high-resolution spectrograph of the Mercator telescope is currently being upgraded. We are equipping it with a new optical fibre link and a new wavelength calibration system is under development. Three measures will increase the radial-velocity (RV) performance of the fibre link. The use of octagonal instead of circular core fibres and imaging the stellar image instead of the telescope pupil on the fibre entrance, will both help to improve the illumination stability of the spectrograph. Furthermore, the new fibre link will also allow to observe, simultaneously with the high-resolution stellar spectrum, a wavelength reference source. This makes it possible to track any instrumental drift during the exposure. High-accuracy RV measurements require very precise wavelength calibration. To overcome the insufficiencies of the standard Thorium-argon emission lamps, we are developing a wavelength calibration system based on a Fabry-Perot etalon. Illuminated with a white-light source, the etalon provides a dense comb spectrum with very regular spacing and amplitude. Using laser spectroscopy to anchor the etalon spectrum to a precisely known hyperfine transition of Rubidium, delivers sub-m/s stability over time scales of years. Both developments will increase the RV accuracy of the HERMES spectrograph and could also be of great benefit for the future high-resolution spectrograph on the DOT@ARIES telescope.
Primary author
Dr
Gert Raskin
(KU Leuven)
Co-authors
Mr
Dmytro Rogozin
(KU Leuven)
Prof.
Hans Van Winckel
(KU Leuven)
