Eclipsing binary system SZ PISCIUM

Abstract

Results are reported for photoelectric photometry and radial-velocity determinations of SZ Psc, a double-line spectroscopic binary in which the K1 subgiant is more massive than the main-sequence companion. The period is found to undergo a linear rate of decrease; an expression is derived which provides a good representation of observed minima between 1927 and 1974. The photoelectric observations are plotted as a light curve, and reasonably accurate values are determined for the radii, masses, and absolute bolometric luminosities of both stars. It is shown that the K star nearly fills its Roche lobe and that mass transfer is most likely taking place. A mass-transfer rate of about one-millionth of a solar mass per year is estimated, indicating that the initial phase of mass transfer will be completed on a time scale of the order of a million years. It is concluded that SZ Psc appears to be a close binary system that has just entered its first phase of interactive eovlution.