The Mass and Other Characteristics of the Magnetic Star HD 98088

This system is a double-lined spectroscopic binary involving an Ap primary and having an orbital period of 5d905, which is also the period of the magnetic variation and rotation. The system is not an eclipsing one, but it is sufficiently inclined that the minimum mass of the Ap star is 9J~ sin3 I = 1.70 9Qo. The Ap star has hydrogen lines as in an A3 V star. From line ratios, it is concluded that the secondary is 1.2 mag fainter, or an A8 V star. Assuming a normal mass for the latter, we find an inclination of 67° and a primary mass of 2.2 9J1o. Such a mass is identical with that of a normal star at that location on the main sequence. This strongly suggests that the Ap star is on the main sequence for the first time. The spectrum variation is described and shows two maxima for some elements, with a phasing that is consist- ent with the characteristics of the eccentric orbit. The problem of synchronism between rotation and orbital motion for an eccentric orbit is discussed