Progress toward a multiobject radial-velocity spectrometer

• Published in: The Astronomical journal 1987-12, Vol.94, p.1686-1693
• Main Authors: Lutz, Thomas E., Ingerson, Thomas, Weller, William G.
• Format: Article
• Language: English
• ISSN: 0004-6256
• DOI: 10.1086/114603

It is shown that it is possible to obtain stellar radial velocities of high accuracy using a fiber-fed echelle spectrograph with no cross disperser. Although the resulting spectrum contains many overlapping orders, the radial-velocity information is still present. Velocities may be obtained by cross correlation with reference data obtained with the same instrument. The accuracy is a function of the signal-to-noise ratio, and ranges from + or - 4 km/s to + or - 1 km/s. Velocities are obtained with exposure times just sufficient to obtain the barest trace of a spectrum using the same spectrograph and CCD detector with a cross disperser. Thus, it appears possible to obtain precision similar to that obtained with an order separator, but with considerably better sensitivity, due to a multiplexing gain. Moreover, the overlapping orders of the stellar spectrum only occupy a few rows of the CCD. Using a multiple-fiber-feed device, many such spectra could be fit on the CCD. This leads to the expectation of obtaining many radial velocities simultaneously using a multiobject spectrometer now under construction at Cerro Tololo. (Author)