EXPLAINING THE EARLY EXIT OF ETA CARINAE FROM ITS 2009 X-RAY MINIMUM WITH THE ACCRETION MODEL

Abstract

We use the accretion model to explain the early exit of η Car from its 2009 X-ray minimum. In the accretion model, the secondary star accretes mass from the primary wind near periastron passage, a process that suppresses the secondary wind. As the shocked secondary wind is responsible for most of the X-ray emission, the accretion process accounts for the X-ray minimum. The early exit from the 2009 X-ray minimum after four weeks, instead of 10 weeks as in the two previous minima, is attributed to the primary wind that during the last minimum was somewhat faster and of lower mass-loss rate than during the two previous X-ray minima. This results in a much lower mass accretion rate during the X-ray minimum. We show that using fluctuations in these quantities that are within the range deduced from fluctuations in the X-ray flux outside the minimum, can account for the short duration of the last X-ray minimum. The shorter X-ray minimum may have further implications on the recovery of the system from the spectroscopic event.