The subdwarf-O pulsator SDSS J160043.6+074802.9: comments on atmospheric parameters and pulsation amplitude variations

SDSS J160043.6+074802.9 appears to be a binary consisting of a subwarf-O (sdO) star and a late-type Main Sequence companion; the sdO is the only known pulsator in this class of stars and some modes have pulsation amplitude and frequency variations. Surface gravity and helium abundance determinations in the literature do not agree within quoted error limits; these appear to have unidentified systematic errors which, once accounted for, should show that surface gravity and helium abundance determinations to date are not as discordant as is currently supposed. Non-linear pulsation effects are proposed as a possible interpretation of pulsation amplitude and frequency variations observed in some modes.