HERMES, a high-resolution fiber-fed spectrograph for theMercator Telescope

摘要

HERMES, a fiber-fed , high-resolution echelle spectrograph is currently in its integration phase at the 1.2-meter Mercator Telescope at the Roque de Los Muchachos Observatory on La Palma (Spain). The design of HERMES, optimized for high efficiency and high instrumental stability, is based on a large R2.7 echelle grating. It is operating in quasi-Littrow white-pupil configuration, with a double-prism as cross-disperser. It records the complete spectrum from 377 to 900 nm on one 2048×4608 pixel CCD in a single exposure. HERMES offers 1) a high-resolution and high-efficiency observation mode through a 80-μm optical fiber (2.5 arcsec sky aperture) equipped with a two-slice image slicer, resulting in a spectral resolution of R=85000 and a peak-efficiency above 25%; and 2) a high-stability mode through a 60-μm fiber (2.15 arcsec sky aperture, R=55000) equipped with a double fiber scrambler for improved spectrograph illumination stability. This mode is intended for high-precision radial velocity measurements and it offers the possibility of recording simultaneously the spectrum of a wavelength calibration lamp interlaced with the science spectrum. This allows for precise tracking of instrumental drifts during integration. To increase instrumental stability further, the spectrograph will be housed in a temperature and pressure controlled chamber. This spectrograph mounted on a flexible-scheduling telescope has a wide astronomical scope, going from asteroseismology to binary star research and chemical studies of stars and circumstellar material. In this contribution we present the final design of HERMES and we report on the project status.