Spectroscopic binary orbits from photoelectric radial velocities. Paper 171: HD 152028 and HDE 284195 (GK Dra and V1094 Tau)

The two stars that form the subject of this paper are both short-period double- lined eclipsing binaries having non-circular orbits despite their short periods. Although the HD type of HD 152028 is G0, the integrated spectral type of the system must actually be much earlier: the B-V colour index is only about 0.37 mag and the parallax indicates an integrated absolute magnitude as bright as +1.4 mag. A published photometric investigation suggests that the primary star exhibits delta Scuti pulsations, with a period of 0.1138 days. That period is not present in the radial velocities, but we have identified a comparable periodicity in the initially excessive residuals (sigma of the order of 2 km/s) in the radial velocities of the primary star: there is an asymmetrical pulsational velocity curve with a semi-amplitude of about 3 km/s and a period of 0.1178 days. HDE 284195 was not observed by Hipparcos, but its HDE type of G0 is in reasonable agreement with its colour and the nature of its radial-velocity traces. The rotations of both stars appear to be pseudo-synchronized to the orbit. The orbital inclinations are not formally determined but they must be very high,however and there is specific evidence that the inclination of HD 152028 is very close to 90 degrees,so it is permissible to assume that the masses are scarcely above the minimum values, which in the case of HD 152028 are 1.78 and 1.42 solar mass and in that of HDE 284195 are 1.10 and 1.01 solar mass, with uncertainties below 1%.(ABRIDGED)