CAFE: Calar Alto Fiber-fed Échelle spectrograph

¹ Centro Astronómico Hispano Alemán, Calar Alto, (CSIC-MPG), C/Jesús Durbán Remón 2-2, 04004 Almería, Spain
e-mail: aceitun@caha.es
² Instituto de Astrofísica de Andalucía (CSIC), Camino Bajo de Huétor s/n, Aptdo. 3004, 18080 Granada, Spain .
e-mail: sanchez@iaa.es
³ Institut fur Astronomie und Astrophysik der Universitat Munchen, Scheinerstr. 1, 81679 Munchen, Germany
⁴ Departamento Astrofísica, Centro de Astrobiología (INTA-CSIC), ESAC campus, PO Box 78, 28691 Villanueva de la Cañada, Spain
⁵ Universidad Complutense de Madrid, Av. Complutense s/n, 28040 Madrid, Spain
⁶ University of Goettingen, Wilhelmsplatz 1, 37073 Goettingen, Germany

Received: 10 September 2012
Accepted: 4 January 2013

Abstract

We present here CAFE, the Calar Alto Fiber-fed Échelle spectrograph, a new instrument built at the Centro Astronomico Hispano Alemán (CAHA). CAFE is a single-fiber, high-resolution (R ~ 70   000) spectrograph, covering the wavelength range between 3650−9800 Å. It was built on the basis of the common design for Échelle spectrographs. Its main aim is to measure radial velocities of stellar objects up to V ~ 13−14 mag with a precision as good as a few tens of m s^-1. To achieve this goal the design was simplified at maximum, removing all possible movable components, the central wavelength is fixed, as is the wavelength coverage; there is no filter wheel, etc. Particular care was taken with the thermal and mechanical stability. The instrument is fully operational and publically accessible at the 2.2 m telescope of the Calar Alto Observatory. In this article we describe (i) the design, summarizing its manufacturing phase; (ii) characterize the main properties of the instrument; (iii) describe the reduction pipeline; and (iv) show the results from the first light and commissioning runs. The preliminar results indicate that the instrument fulfills the specifications and can achieve the planned goals. In particular, the results show that the instrument is more efficient than anticipated, reaching a signal-to-noise of  ~20 for a stellar object as faint as V ~ 14.5 mag in  ~2700 s integration time. The instrument is a wonderful machine for exoplanetary research (by studying large samples of possible systems cotaining massive planets), galactic dynamics (highly precise radial velocities in moving groups or stellar associations), or astrochemistry.