Properties and nature of shell stars. 4. 88 Herculis: the 87-day period confirmed.

Summary. Radial-velocity variations of 88 Her as measured on the Haute Provence coude' spectrograms of 1963-1972 by Doazan (1973) seem to confirm the periodic character of the changes reported by us (see Papers 1 and 2). Combining her measurements with our original values and with the velocities of eighteen new Ondrejov coude' spectrograms of 1972-1973 we were able to determine a much more precise value of the period: 86.59+0.06 days. The long-term variations of the envelope of the star disclosed by Doazan are confirmed on our spectrograms. The obvious stability of the periodic radial-velocity changes with respect to these variations speaks in favour of their binary origin. Thus, the star is considered to be a spectroscopic binary and an improved set of orbital elements is given. The new elements coincide with older ones (presented in Paper 2) within the limits of errors computed for the older elements though they are based on measurements covering the time interval about ten times longer than those of the original set. Key words: shell star - spectroscopic binary - radial velocity of bydrogen lines - spectral variations - case B of mass exchange