A photometric study of the Algol system Y Piscium

From the discussion of 417 photoelectric observations of this semi-detached Algol system, obtained in B and V during 82 nights in 1965–1971, the existence of a gas stream may be inferred for the following reasons: The scatter of the single observations is dependent on the orbital phase; the largest scatter occurs at the phases following both eclipses. The conventional photometric solution which is based on the long region rectification and neglects the photometric influences of the gas stream, gives for the two colours different geometric parameters of the system. However, the short region rectification allows a consistent photometric solution. According to this solution a short total phase exists, and the luminous regions caused by the impact of particles of the gas stream are hidden during the central part of the primary eclipse. Outside of eclipses, the additional light is seen during about half of the orbital period. From the variation of the visibility of the additional light during the primary eclipse it may be concluded that during about the first half of the observing time the luminous regions were situated at the high latitudes of the bright component, indicating the existence of magnetic fields on this component at this epoch, whilst later on the additional light came from an equatorial region on the following side of the massive component.Originally presented at the IAU Colloquium No. 16 held at the Univ. of Pennsylvenia, Philadelphia Pa., U.S.A. September 8–11, 1971.