The spectroscopic orbit of HD 90707.

lID 90707 (Bi III) is an eclipsing binary and a probable member of the open cluster IC 2581 in Carina. The spectroscopic orbit has been determined from 29 observations of the radial velocity of the primary. Weak lines arising in the secondary yield = I 09, a value which suggests that mass transfer has occurred. The brighter star nearly fills its Roche lobe. The light curve has nearly equal minima and shows variations between eclipses. The assumption that sin i = I leads to masses of I and m0 for the two components, larger than expected from an earlier comparison of the colour-magnitude diagram with theoretical evolutionary tracks. The uncertainty introduced by the reflection effect on the determination of the velocity amplitude and hence the mass function may vitiate this conclusion.