ABSTRACT. We report the recovery of a spectroscopic event in η Carinae in 1997/1998 after a prediction by Damineli in 1996. A true periodicity with P = 2020 ± 5 days (0.2% uncertainty) is obtained. The line intensities and the radial velocity curve display a phase-locked behavior, implying that the energy and dynamics of the event repeat from cycle to cycle. This rules out S Doradus oscillation or multiple shell ejection by an unstable star as the explanation of the spectroscopic events. A colliding-wind binary scenario is supported by our spectroscopic data and by X-ray observations. Although deviations from a simple case exist around periastron, intensive monitoring during the next event (mid-2003) will be crucial to our understanding of the system.

Subject headings: binaries: general; stars: emission-line, Be; stars: individual (η Carinae); stars: variables: other

Print publication: Issue 2 (2000 January 10)
Received 1999 October 7, accepted for publication 1999 November 10
Published 1999 December 8