The Orbit of the Binary Star Delta Scorpii

Although delta Scorpii is a bright and well-studied star, the details of its multiplicity have remained unclear. Here we present the first diffraction-limited image of this 0.12 arcsec binary star, made using optical interferometry, and resolve the confusion that has existed in the literature over its multiplicity. Examining published speckle measurements, together with the present result, reveals a periodicity of 10.5 yr and allows calculation of the orbital parameters. The orbit has a high eccentricity (e=0.82) and large inclination (i=70 degrees), making it a favourable target for radial velocity measurements during the next periastron (in 2000).Comment: (LaTex 8 pages. Send email to '[email protected]' for 4 postscript figures). To appear in the Astronomical Journal, August, 1993. ESO-TR

Observations of solar-like oscillations

There has been tremendous progress in observing oscillations in solar-type stars. In a few short years we have moved from ambiguous detections to firm measurements. We briefly review the recent results, most of which have come from high-precision Doppler measurements. We also review briefly the results on giant and supergiant stars and the prospects for the future.Comment: Invited review talk at the "Vienna Workshop on the Future of Asteroseismology", 20-22 September 2006, to appear in Communications in Asteroseismolog

Scaled oscillation frequencies and echelle diagrams as a tool for comparative asteroseismology

We describe a method for comparing the frequency spectra of oscillating stars. We focus on solar-like oscillations, in which mode frequencies generally follow a regular pattern. On the basis that oscillation frequencies of similar stars scale homologously, we show how to display two stars on a single echelle diagram. The result can be used to infer the ratio of their mean densities very precisely, without reference to theoretical models. In addition, data from the star with the better signal-to-noise ratio can be used to confirm weaker modes and reject sidelobes in data from the second star. Finally, we show that scaled echelle diagrams provide a solution to the problem of ridge identification in F-type stars, such as those observed by the CoRoT space mission.Comment: accepted for publication in Communications in Asteroseismolog