Eta Carinae: going naked again in a couple of orbits

Data: 
15/08/2018 - 14:00 - 15:00
Local: 
Auditório 1

Eta Carinae: going naked again in a couple of orbits

Augusto Damineli

IAG/USP

 

Analysis of the light curve of the massive colliding wind binary eta Carinae,  using all the available photometric data from the ground and the space during more than half century revealed unexpected features. We confirm previous suggestions that the central source is brightening more quickly than the nebula due to a coronograph placed in our line-of-sight to the central star, which will dissipate in a timescale of ~10 years, leaving the central star with a brightness similar to what it were before the Great Eruption and a radically different light curve. The coronograph also explains the paradox of  “a red star inside a blue reflecting nebula”, and the fact that the blueing of the star colours is changing faster than those of the Homunculus. The detrended stellar light curve displays three features connected with the orbital period (P=5.538yr), the one with largest amplitude (V=0.6), the Orbital Modulation, is probably produced by a "light-house" effect as the wind-wind collision (WWC) cavity sweeps around the primary star. In past works, this oscillation was attributed to instabilities in the central star, but we found no evidence for significant instabilities, specially of the S Doradus type. In addition, our analysis shows no evidence of dust production in the WWC at present time and does not support shell ejections at periastron. Most of the variability has circumstellar origin, what calls for attention when interpreting variability of eta Car analogues in the post eruption quiescent state.