1996A&A...315..526L

The abundances characterizing chemically peculiar (CP) stars modify the atmosphere structure with respect to normal stars of equal effective temperature and gravity. Being classical methods to infer the effective temperature and gravity of stars calibrated for and from solar composition stars, they cannot be used for CP stars. Thus, the effective temperature and gravity of a CP star have to be determined simultaneously with the anomalous abundances. We have obtained time-resolved high-resolution spectra in the 482-513 nm region of the silicon stars HD 9484, HD 12767, HD 22920 and HD 171247. For each of them, we have adopted the effective temperature and gravity of the ATLAS9 (Kurucz 1993, ASP Conf. Ser. Vol. 44, p.98) atmosphere model which, matching the observed H_β line, has been computed with a metal opacity scale consistent with the abundances. The H_β lines have been computed with SYNTHE (Kurucz & Avrett 1981, SAO Special Rep. 391) and the abundances with WIDTH9 (Kurucz & Avrett 1981, SAO Special Rep. 391). The microturbulent velocity has been inferred from the unblended iron lines. All unblended lines have been used to determine the rotational and radial velocity.