[Joe Keller]

Six of the seven "disappearing dots" I've found (on online archive sky survey plate scans) with magnitudes about +18.8 or brighter, fit a mildly elliptical two-body mutual orbit with major axis at least 1.95 AU. The eccentricity is between 0.19 (absolute lower bound) and about 0.38 (better than 67% confidence upper bound). The mutual orbital plane is inclined about 10.7deg to Barbarossa's orbital plane. The mass ratio of these two, Barbarossa and Frey, is 5:1. The period is 42 yr. The implied mass of Barbarossa is between 0.0051 solar mass for 0.19 eccentricity and 0.0080 solar mass for 0.38 eccentricity. The orbital period of the center-of-mass about the sun is 2850 yr, assuming a circular orbit.

The magnitudes of Barbarossa are about +17.3, 17.9 & 18.0; of Frey, +17.6, 18.3 & 18.8. The dimmest Frey magnitude occurs, near maximum elongation, but much nearer to a point at which Frey's orbit intersects that plane (through the center of mass of Barbarossa & Frey) which is parallel to the principal plane of the solar system.

There might be a dust belt there. Neither Frey nor Barbarossa could be found on the March 1986 plate. Then, the line through Barbarossa & Frey, as seen from Earth, was theoretically only 1.8deg from the plane which contained the center of mass and was parallel to the principal plane of the solar system. Now, 21 yrs = 0.50 orbit later, the same situation holds.

In this model, the geocentric coordinates for April 5 (for the next few days the usual minus 1s RA & +6" Decl per day correction applies) are:

Barbarossa: RA 11 26 07.5 Decl -8 59 53.5

Frey: RA 11 27 35.5 Decl -9 10 47.5