title: Infrared images of the transiting disk in the epsilon Aurigae system.
abstract: Epsilon Aurigae (epsilon Aur) is a visually bright, eclipsing binary star system with a period of 27.1 years. The cause of each 18-month-long eclipse has been a subject of controversy for nearly 190 years because the companion has hitherto been undetectable. The orbital elements imply that the opaque object has roughly the same mass as the visible component, which for much of the last century was thought to be an F-type supergiant star with a mass of approximately 15M[symbol:see text] (M[symbol:see text], mass of the Sun). The high mass-to-luminosity ratio of the hidden object was originally explained by supposing it to be a hyperextended infrared star or, later, a black hole with an accretion disk, although the preferred interpretation was as a disk of opaque material at a temperature of approximately 500 K, tilted to the line of sight and with a central opening. Recent work implies that the system consists of a low-mass (2.2M[symbol:see text]-3.3M[symbol:see text]) visible F-type star, with a disk at 550 K that enshrouds a single B5V-type star. Here we report interferometric images that show the eclipsing body moving in front of the F star. The body is an opaque disk and appears tilted as predicted. Adopting a mass of 5.9M[symbol:see text] for the B star, we derive a mass of approximately (3.6 +/- 0.7)M[symbol:see text] for the F star. The disk mass is dynamically negligible; we estimate it to contain approximately 0.07M[symbol:see text] (M[symbol:see text], mass of the Earth) if it consists purely of dust.
authors.affiliation: Department of Physics and Astronomy, University of Denver, 2112 East Wesley Avenue, Denver, Colorado 80208, USA. bkloppen@du.edu
authors.forename: Brian
authors.initials: B
authors.lastname: Kloppenborg
authors.forename: Robert
authors.initials: R
authors.lastname: Stencel
authors.forename: John D
authors.initials: JD
authors.lastname: Monnier
authors.forename: Gail
authors.initials: G
authors.lastname: Schaefer
authors.forename: Ming
authors.initials: M
authors.lastname: Zhao
authors.forename: Fabien
authors.initials: F
authors.lastname: Baron
authors.forename: Hal
authors.initials: H
authors.lastname: McAlister
authors.forename: Theo
authors.initials: T
authors.lastname: Ten Brummelaar
authors.forename: Xiao
authors.initials: X
authors.lastname: Che
authors.forename: Chris
authors.initials: C
authors.lastname: Farrington
authors.forename: Ettore
authors.initials: E
authors.lastname: Pedretti
authors.forename: P J
authors.initials: PJ
authors.lastname: Sallave-Goldfinger
authors.forename: Judit
authors.initials: J
authors.lastname: Sturmann
authors.forename: Laszlo
authors.initials: L
authors.lastname: Sturmann
authors.forename: Nathalie
authors.initials: N
authors.lastname: Thureau
authors.forename: Nils
authors.initials: N
authors.lastname: Turner
authors.forename: Sean M
authors.initials: SM
authors.lastname: Carroll