IAU Colloquium 170 - Precise Radial Velocities

The art of measuring radial accelerations with an error of only a few m/s/year has become a highly respected skill in observational astronomy. It complements recent spectacular improvements in astrometric precision from satellites such as Hipparcos and interferometry from the ground. The regular announcements of candidate planets, of which several were made at this meeting, have generated a huge amount of scientific and public interest and given NASA copious free publicity for its Origins program. The mapping of stellar surfaces and the probing of interior structure from nonradial pulsations must be among the most exquisite measurements in science. All of these achievements were celebrated at a quite excellent colloquium held in the idyllic setting of Dunsmuir Lodge 20 km north of Victoria in the week of 21 June 1998.

There were some 80 participants, many of them major players in the PRV field, and the local organisers arranged for superb summer weather. One day was given over to tours and whale watching with Marimba music in the evening, with Dave Latham running regular wine-tasting sessions each evening

Russll Robb (University of Victoria) relaxing between sessions with Dan Popper (UCLA), one of the liveliest participants at the meeting.
Two groups provided the most convincing evidence yet for Solar-type oscillations of Procyon. The whole question of the meaning of radial velocity and particularly the variety of surface motions affecting line profiles and measured velocity were discussed. Velocities and astrometry have reduced the errors in many orbital parallaxes below 1% giving sufficiently accurate masses and absolute magnitudes to critically test evolutionary theories and answer questions about core convection. We saw some remarkable results for several roAp stars which oscillate in high radial overtones with a series of closely spaced periods of a few minutes. The velocity amplitude is strongly wavelength and line dependent with some lines showing spectacular velocity excursions while others show none. The mapping of stellar surfaces continues to progress. Using a large number of lines extends the technique to fainter stars and a high level of surface resolution is now possible for magnetically active late-type stars.

A 2.1 Jupiter-mass candidate companion at 0.2 AU from Gliese 876 was announced, to date, the closest system to the Sun (4.7 pc). The predominance of short-period planetary systems seems real with the chance of detecting a transit by one of the short period systems considered to be high. The candidate primaries have significantly enhanced metallicity.

The exciting science would have been impossible without the exceptional quality f the associated spectroscopic and interferometic equipment coupled with the ingenuity and dedication the builders. There were several presentations on existing and planned equipment including an intriguing suggestion from André Baranne of a split pupil arrangement to increase throughput. In some cases auxiliary instruments appear to have quite outgrown their telescopes!

Slavek Rucinski (CFHT) and John Lester (University of Toronto) review the finer points of measuring accurate line profiles.

The members of the University of Victoria Physics & Astronomy Department and John Hearnshaw from University of Canterbury, New Zealand can be warmly congratulated for organising such a great meeting. The proceedings will be published in the PASP series.


Previous HIA Recent Events   Next New Perspectives on the Interstellar Medium   Table of contents Tables of Contents