Contributed paper on
ESPaDOnS: An Echelle SpectroPolarimetric Device for the Observation of Stars at CFHT

J.-F. Donati

presented at the Solar Polarization Workshop #3, eds: Trujillo Bueno J., Sanchez Almeida J. (2003). ASP Conf. Series (in press)

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We present in this paper the next generation cross-dispersed spectropolarimeter called ESPaDOnS in the final construction stage at Observatoire Midi-Pyrénées, to be mounted for general community use at the Canada-France-Hawaii Telescope (CFHT) in 2003, and cofunded by France, Canada, CFHT and the Research and Scientific Support Department of the European Space Agency (ESA/RSSD). This instrument is designed to obtain a complete optical spectrum (i.e. from 370 to 1,000 nm) in a single exposure, with a resolving power of about 70,000. In particular, ESPaDOnS is able to measure all polarisation components of the stellar light (both circular and linear) with the same resolving power. The spectrograph is bench-mounted and fed by a double optical fibre from a Cassegrain module containing all calibration facilities and the optional polarisation analyser, making it possible to have extremely good wavelength stability and minimal instrumental polarisation. When operational, ESPaDOnS will be the most powerful spectropolarimeter worldwide, and will be competitive with similar instruments on 8m class telescopes in non-polarimetric mode. With this facility, astronomers should be able to address a broad range of important issues in stellar physics with unprecedented detail, from studies of stellar interiors, to investigations of stellar atmospheres, stellar surfaces, stellar magnetic fields, and to observations of circumstellar environments.