Is Eta Carinae a long-period binary?

Abstract

Damineli et al. (1997)[NewA, 2, 107] have recently proposed a specific binary model for η Carinae. It is based on wavelength shifts in hydrogen and helium emission lines, and may explain a 5.5-year periodicity involving spectroscopic events. Here I amplify but also modify their discussion with the following points: (1) A more eccentric orbit gives a better fit to the velocities quoted by those authors. The higher eccentricity implies appreciably different behavior near periastron. (2) Intra-system eclipses may explain the 5.5-year spectroscopic events in a way that is different from the Damineli et al. scenario. (3) On the other hand, a 5.5-year binary model entails several implausibilities; a single-star model seems equally promising at this time. (4) Finally, I list a few specific, possibly decisive observations that can be made during the next critical “event”, which is expected to occur around the end of 1997. These and other observations of the event urgently merit detailed and intensive efforts.