Absolute radius of an M giant.

We determine the absolute radius of an M2.4 III giant to be 75 solar radii, and we discuss and estimate the expected error. This value is found from the 1991 eclipse of the symbiotic binary EG And, observed in the UV. This system consists of a hot prewhite dwarf and an M giant. From two observed eclipses, separated by 6 orbital periods, we derive an ephemeris with a period of 482.2 d. The inclination of the system is sin i = 0.99 + 0.01. We also estimate the masses of the hot component and of the red giant, and we determine a bolometric distance of 400 pc for the EG And system. This is the first bolometric distance determination of a symbiotic system, and it therefore provides a check to the commonly used spectroscopic parallaxes of the red giants.