Recurrent X‐Ray Emission Variations of η Carinae and the Binary Hypothesis

Abstract

Recent studies by Damineli and coworkers suggest that the supermassive star η Carinae may have a massive stellar companion, although the dense ejecta surrounding the star make this claim hard to test using conventional methods. Settling this question is critical for determining the current evolutionary state and future evolution of the star. We address this problem by an unconventional method: If η Carinae is a binary, X-ray emission should be produced in shock waves generated by wind-wind collisions in the region between η Carinae and its companion. Detailed X-ray monitoring of η Carinae for more than 2 years shows that the observed emission generally resembles colliding-wind X-ray emission, but with some significant discrepancies. Briefly, the presence of enhanced absorbing material—such as a circumstellar disk—has been examined to explain the discrepancies. Furthermore, periodic X-ray "flaring" may provide an additional clue to determine the presence of a companion star and for atmospheric pulsation in η Carinae.