Variability of the post-AGB star HR 4049 : dust obscuration in a binary system.
Waters, L. B. F. M.; Ferlet, R.; Vidal-Madjar, A.; Lamers, H. J. G. L. M.; Trams, N. R.; Waelkens, C.; Le Bertre, T.; Rufener, F.
Belgium, Netherlands, Switzerland
Abstract
Results obtained from a large number of coordinated photometric and spectroscopic observations lead to the conclusion that HR 4049 is a binary with an orbital period near 434 days and a companion of similar mass which either is a white dwarf or a main-sequence star, more likely the second. The H-alpha line is in emission with either a P Cygni profile or a shell profile. The data suggest a smooth transition from P Cygni to shell and back, correlated with the photometric and radial-velocity variations. The mass flow from HR 4049 is thus altered by the presence of a companion. The photometric variability is best explained by variable extinction of the star by circumstellar matter surrounding the system. The infrared variability can only be explained if the extinction variations reflect a change in the characteristics of dust rather than purely geometric changes.