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  • CAFE2: an upgrade to the CA...
    Lillo-Box, J; Aceituno, J; Pedraz, S; Bergond, G; Galadí-Enríquez, D; Azzaro, M; Arroyo-Torres, B; Fernández-Martín, A; Guijarro, A; Hedrosa, R P; Hermelo, I; Hoyo, F; Martín-Fernández, P

    Monthly notices of the Royal Astronomical Society, 01/2020, Letnik: 491, Številka: 3
    Journal Article

    ABSTRACT CAFE is a high-resolution spectrograph with high-precision radial velocity capabilities mounted at the 2.2 m telescope of Calar Alto Observatory. It suffered from strong degradation after 4 yr of operations and it has now been upgraded. The upgrades of the instrument (now named CAFE2) aimed at recovering the throughput and improving the stability due to the installation of a new grating, an active temperature control in the isolated coudé room, and a new scrambling system. In this paper, we present the results of the new commissioning of the instrument and a new pipeline (CAFExtractor) that provides the user with fully reduced data including radial velocity measurements of FGK dwarf stars. The commissioning results show a clear improvement in the instrument performance. The room temperature is now stabilized down to 5 mK during one night and below 50 mK over two months. CAFE2 now provides 3 m s−1 precision on the reference ThAr frames and the on-sky tests provide a radial velocity precision of 8 m s−1 during one night (for S/N > 50). The throughput of the instrument is now back to nominal values with an efficiency of around 15 per cent at 550 nm. The limiting magnitude of the instrument for a 1 h exposure and S/N = 20 is V = 15. With all these properties, CAFE enters into the small family of high-resolution spectrographs at 2–4 m telescopes capable of reaching radial velocity precisions below 10 m s−1.