TheSOPHIE (Spectrographe pour l’Observation des Phénomènes des Intérieurs stellaires et des Exoplanètes, literally meaning "spectrograph for the observation of the phenomena of the stellar interiors and of the exoplanets")échelle spectrograph is a high-resolutionechelle spectrograph installed on the 1.93mreflector telescope at theHaute-Provence Observatory located in south-eastern France. The purpose of this instrument isasteroseismology[1] andextrasolar planet detection by theradial velocity method. It builds upon and replaces the olderELODIE spectrograph. This instrument was made available for use by the general astronomical community October 2006.[2]
Theelectromagnetic spectrumwavelength range is from 387.2 to 694.3 nanometers. The spectrograph is fed from theCassegrainfocus through either one of two separateoptical fiber sets, yielding two different spectral resolutions (HE and HR modes). The instrument is entirely computer-controlled. A standard data reduction pipeline automatically processes the data upon everyCCD readout cycle.
HR mode is the high resolution mode. This mode incorporates a 40 micrometre exit slit to achieve highspectral resolution of R = 75000.
HE mode is the high efficiency mode. This mode is used when a higher throughput is desired particularly in the case of faint objects spectral resolution is set to R = 40000.
The R2échellediffraction grating has 52.65 grooves per millimeter and was manufactured by Richardson Gratings. It isblazed at 65° and its size is 20.4 cm x 40.8 cm. It is mounted in a fixed configuration. Thespectrum is projected onto the E2V Technologies type 44-82CCD detector of 4096 x 2048pixels kept at a constant temperature of –100 °C. This grating yields 41spectral orders, of which 39 are currently extracted, to obtain wavelengths between 387.2 nm and 694.3 nm.[2]
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InHE mode, asignal-to-noise ratio (per pixel) of 27 was reached in 90 min for an object of magnitude 14.5 in theV band.
The stability of the instrument can be described by the lowest dispersion possible for radial velocity observations, in m/s. InHR mode the short term stability has been measured to be 1.3 m/s,[2] while it is 2 m/s for longer timescales.[3]
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