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Session 19 - Hot Stars.
Display session, Monday, January 15
North Banquet Hall, Convention Center
Classification spectra (1-3 A resolution) of early B stars give an impression that the CII 4267 line is unreliable as a classification criterion. Its erratic behaviour is quite unlike OII or NII lines which are relatively well behaved and vary predictably with temperature and log g. In fact, even other lines of CII such as 6578 and 6582 are much more predictable than 4267. Models (e.g. Lennon, et al., 1983; Eber and Butler, 1988) indicate that non-LTE effects may be the cause of the erratic behavior. We have confirmed and quantified this impression using a large database of 788 photographic spectra of 512 well-classified stars, as well as multiple high-resolution CCD spectra of 13 stars. No variability greater than 5spectra over timescales of hours, days, weeks, or months, and no major changes were observed in the photographic spectra over years. While there is some vague correlation with temperature and log g, it is not possible to account for the large scatter observed without invoking something like non-LTE.
