Abstract
The long-period (P = 27.1 years) peculiar eclipsing binary epsilon Aur, which has recently completed its two year-long primary eclipse, has perplexed astronomers for over a century. The eclipse arises from the transit of a huge, cool and opaque, disk across the face of the F0 Iab star.
One of the principal problems with understanding this binary is that the very small parallax of p = (1.53 +/- 1.29) mas, implying a distance range of d similar to (0.4-4.0) kpc, returned by a revised reduction of the HIPPARCOS satellite observations, is so uncertain that it precludes a trustworthy estimate of the luminosities and masses of the binary components. A reliable distance determination would help solve the nature of this binary and distinguish between competing models.
A new approach is discussed here: we estimate the distance to epsilon Aur from the calibration of reddening and interstellar-medium gas absorption in the direction of the system. The distance to epsilon Aur is estimated from its measured E(B-V) and the strength of the diffuse interstellar band 6613.56 angstrom.
Spectroscopy and UBV photometry of several B- and A-type stars (<1 degrees of epsilon Aur) were carried out. The distances of the reference stars were estimated from either measured or spectroscopic parallaxes.