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| Paper: |
Precision versus Accuracy: Some Astrophysical and Operational Limitations |
| Volume: |
185, Precise Stellar Radial Velocities, IAU Colloquium 170 |
| Page: |
52 |
| Authors: |
Griffin, R. E. M. |
| Abstract: |
The measurement of accurate radial velocities for A or B dwarfs is dogged by particular problems: the small numbers of suitable lines, the wide wavelength range over which such lines are distributed, thermal broadening, rotational broadening, line distortions caused by rotating spots, spectrum variations due to obvious duplicity, and low-level velocity variations due to undetected companion spectra. Moreover, the fact that A and B-type spectra fall into very distinct groups, each with its own sub-set of the above problems, means that it may be both difficult and unsatisfactory to specify velocity standards, since intrinsic uncertainties caused by differences in spectral type may mask the measuring errors. I have investigated the nature and magnitude of some of these inherent errors by employing wide spans of high-resolution, high-dispersion spectra of Sirius and Vega as `natural' templates. I pay particular attention to systematic errors which are generated whenever a spectrum or a cross-correlation dip is measured in the unavoidable presence of another such spectrum or dip. |
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