Napiwotzki et al. (1993) claim fitting errors of order 200 K in and 0.2 dex in surface gravity among the middle B to early F star. Hence the use of photometric relations for normal stars has appeared to work for the cooler mCP and HgMn stars as the errors are similar to those for the fitting errors. But the use of such relations for hotter class members is inappropriate without using corrections similar to those found in this paper. When these corrections are ignored, systematic errors occur for mCP and HgMn stars with about 10000 K and 12000 K, respectively. As the effective temperatures are too large, so will be many of the abundances. Some investigators have minimized these effects by deriving differential corrections similar to those of this paper and then applying them to stars with only photometrically determined effective temperatures and surface gravities.
There are still some mCP and HgMn stars with good quality spectrophotometry in the literature for which H profiles can be observed. Values derived from this data can help better define the relations shown in Figs. 4 and 5. In addition investigations using non-solar composition models should help. Although ultraviolet and infrared data can each play a role in defining such values, that the absolute calibration of fluxes in the optical region is so much better than those of these two regions means that the comparisons between theory and observations are best done here at present. Spectrophotometric fluxes with a resolution of at least 20 Å from 3300-9000 with nearly continuous coverage and errors not greater than 2% are required for establishing a more reliable temperature scale for these stars with non-solar photospheric compositions. To obtain such data will require a building a spectrophotometer with a CCD as a detector.
© European Southern Observatory (ESO) 2000
Online publication: March 17, 2000