Epsilon Aurigae: An improved spectroscopic orbital solution

Abstract

A rare eclipse of the mysterious object Epsilon Aurigae will occur in 2009-2011. We report an updated single-lined spectroscopic solution for the orbit of the primary star based on 20 years of monitoring at the CfA, combined with historical velocity observations dating back to 1897. There are 518 new CfA observations obtained between 1989 and 2009. Two solutions are presented. One uses the velocities outside the eclipse phases together with mid-times of previous eclipses, from photometry dating back to 1842, which provide the strongest constraint on the ephemeris. This yields a period of 9896.0 +/- 1.6 days (27.0938 +/- 0.0044 years) with a velocity semi-amplitude of 13.84 +/- 0.23 km/s and an eccentricity of 0.227 +/- 0.011. The middle of the current on-going eclipse predicted by this combined fit is JD 2,455,413.8 +/- 4.8, corresponding to 2010 August 5. If we use only the radial velocities, we find that the predicted middle of the current eclipse is nine months earlier. This would imply that the gravitating companion is not the same as the eclipsing object. Alternatively, the purely spectroscopic solution may be biased by perturbations in the velocities due to the short-period oscillations of the supergiant.

20 pages, including 4 tables and 6 figures. To appear in The Astronomical Journal, March 2010. Machine-readable versions of Tables 1 and 3 will be available in the electronic edition of the Journal

References in corpus (1)

• RVSAO 2.0: Digital Redshifts and Radial Velocities

Cited by in corpus (17)

• In the Shadow of the Transiting Disk: Imaging epsilon Aurigae in Eclipse
• Spectral and photometric analysis of the eclipsing binary epsilon Aurigae prior to and during the 2009-2011 eclipse
• Interferometry of $\epsilon$ Aurigae: Characterization of the asymmetric eclipsing disk
• OGLE-BLG182.1.162852: An Eclipsing Binary with a Circumstellar Disk
• The Invisible Monster Has Two Faces: Observations of Epsilon Aurigae with the Herschel Space Observatory
• Effects of dust on light-curves of εAur type stars
• Occultations from an active accretion disk in a 72 day detached post-Algol system detected by K2
• BRITE photometry and STELLA spectroscopy of bright stars in Auriga: Rotation, pulsation, orbits, and eclipses
• MESA Models of the Evolutionary State of the Interacting Binary epsilon Aurigae
• 2D Monte-Carlo Radiative transfer modeling of the disk shaped secondary of Epsilon Aurigae
• Eta Geminorum: An Eclipsing Semiregular Variable Star Orbited by a Companion Surrounded by an Extended Disc
• K I 7699 Å and related shell lines during the recent eclipse of $\epsilon$ Aurigae
• Painting a Family Portrait of the Yellow Super- and Hypergiants in the Milky Way I. Constraining the Distances and Luminosities
• Structure in the Disk of epsilon Aurigae: Analysis of the ARCES and TripleSpec data obtained during the 2010 eclipse
• Epsilon Aurigae in Total Eclipse, 2010 - Mid-eclipse report
• Synthetic Spectra and Light Curves of Interacting Binaries and Exoplanets with Circumstellar Material: SHELLSPEC
• Modeling the Variable Polarization of epsilon Aurigae In and Out of Eclipse