The central star of planetary nebula LT-5 - A triple system

IN Com, the central star of the planetary nebula LT-5, is concluded to be a triple system as a result of photometric and spectroscopic examination. Data from UBV photometric and high-dispersion spectroscopic studies conducted between 1984 and 1989 are analyzed by means of a light curve and radial velocity studies. The radial velocity studies show that a single-lined binary with a period of 1.7545 days comprises the inner system. Further analysis reveals that it is an evolved G-type star with an active chromosphere. The G star has a low-mass companion, and the third body is a hot subdwarf that excites the surrounding planetary nebula. A change in the observed systemic velocities with a period of approximately 2000 days points toward the existence of the third body. Photospheric and chromospheric disturbances on the surface of the G star account for the changeable period of light variance on the central star. The masses of all the components are calculated, and the rotational velocity of the primary component and the orbital inclination of the inner system are determined. The statistical relation between distance and apparent diameter for nebulae of this type suggests that the distance d = 100-170 pc is accurate. 26 refs