On the Nature of the Eclipses of ζ Aurigae.

Abstract

view Abstract Citations (9) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Nature of the Eclipses of ζ Aurigae. Kopal, Zdenek Abstract An analysis of the light-changes observed photoelectrically during the ingress of the 1939 minimum of the eclipsing system of ~ Aurigae leads to the following conclusions: 1. The ratio of racffi le of its B and K components can be determined with considerable accuracy from the fractional loss of light during totality. The ensemble of photoelectric observations made at different effective wave lengths leads to k = 0.0145 ± 0.0003, which renders the K supergiant sixty-nine nine times as large as its companion. This ratio appears to be relatively the most dependable character- istic of the system that can so far be inferred from its light-changes. 2. The observed duration of the disappearance of the B star, coupled with the foregoing value of k, excludes the possibility of the orbital inclination ~ being less than 78°, this latter value corresponding to an eclipse of two sharp-edged disks. The actual light-curve at the respective phases bears, however, little resemblance to any theoretical light-curve of a bodily eclipse, whatever the limb darkening on the ap- parent disk of the B star may be. 3. If 1> 78°, the apparent distance by which the B star gets displaced by orbital motion between the first and the second contact of the eclipse exceeds the diameter of the B star, which suggests that this eclipse may have been partly due to the extinction of the B light in a semitransparent envelope surround- ing the K supergiant. In order to analyze the situation, a theory of eclipses of stellar disks of finite rela- tive dimensions by semitra~nsparent outer layers of their mates has been developed, and equations are set up which relate the observed loss of light with variable absorption coefficient of these layers. The practical problem has been reduced to the solution of a pair of integral equations, one of which admits of a formal inversion, while the other must be solved by numerical means. 4. An application of this type of analysis to the light-changes of ~ Aurigae exhibited during the gradual disappearance of the B component shows that the orbital inclination must be very close to 900 in order to make a solution possible. A detailed interpretation of the light-changes leads us to conclude that, at the beginning of the eclipse, the B star must have been obscured, first, by an almost completely opaque cloud of a width equal roughly to O.5TB, followed by a nearly transparent region O.6rB wide, before disappearing ultimately behind the limb of the K star, which, as far as we can tell, may have been quite sharp. Assuming that the depth of the cloud along the line of sight was equal to its width and that its continuous absorption was due to metallic ions, we find the density nece~sary to produce the observed effects to be of the order of 10" ions per cubic centimeter-i.e., a quantity of the same order of magnitude as the density of solar prominences. 5. The absolute radii of the K and B components of ~ Aurigae should be approximately 200 and 2.8 0; and their masses, 22 and 10 0, respectively. The observational errors of quantities from which these elements were derived make these radii and masses uncertain by about 10 per cent Publication: The Astrophysical Journal Pub Date: May 1946 DOI: 10.1086/144813 Bibcode: 1946ApJ...103..310K full text sources ADS |