No abstract

A new method of determining absolute visual magnitudes of early‐type stars, based on averaging Hipparcos parallaxes (ESA 1997) inside samples of the same spectrum and luminosity (Sp/L) classes, is proposed. The used sample consists of 6262 unreddened and reddened OB stars as well as 430 Be stars of luminosity classes Ia, Iab, Ib, II, III, IV and V. The colour excesses of the reddened stars have been calculated using the mean colour indices, according to the SIMBAD data base and the intrinsic (B−V) values calibrated for given Sp/L classes by Papaj, Wegner & Krełowski. The values of the total‐to‐selective extinction RV=AV/E(B−V) for all reddened stars were calculated from the published near‐infrared photometric measurements. The calculated visual magnitudes MV of OB and Be stars are compared to those published by Wegner in Paper I, and the earlier determinations of Schmidt‐Kaler. Generally, the new values of MV agree well with those given in Paper I, except those for O stars which are systematically brighter than the earlier estimates. The mean absolute magnitudes published by Schmidt‐Kaler are generally brighter (except OB stars of luminosity class V) than those determined in this paper.

Abstract. The paper presents an extensive list of the total to selective extinction ratios R calculated from the infrared magnitudes of 597 O and B stars using the extrapolation method. The IR magnitudes of these stars were taken from the literature. The IR colour excesses are determined with the aid of "artificial standards" -Wegner (1994). The individual and mean values of total to selective extinction ratios R differ in most cases from the average value R=3.10 ±0. 05 -Wegner (1993) in different OB associations. The relation between total to selective extinction ratios R determined in this paper and those calculated using the "method of variable extinction" and the Cardelli et al. (1989) formulae is discussed. The R values presented in this paper can be used to determine individual absolute magnitudes of reddened OB stars with known trigonometric parallaxes.

Absolute visual magnitudes of OB stars are determined from Hipparcos parallaxes using a sample of 1207 unreddened and 441 reddened stars of luminosity classes V–IV, III, Ia and Iab–Ib–II. The value of total‐to‐selective extinction R for reddened stars was calculated from near‐infrared photometry. The new MV calibration is compared with existing calibrations. The visual absolute magnitudes of Be stars were obtained from a sample of 90 unreddened and 25 reddened stars. Generally, Be stars are brighter than B stars of the corresponding spectral types, in agreement with earlier results.

The absolute visual magnitudes, MV, of A–M stars are based on calculated Hipparcos trigonometric parallaxes. The sample used consists of 30 986 unreddened and reddened A–M stars in luminosity classes Ia, Iab, Ib, II, III, IV and V. The colour excesses of the reddened stars were calculated using the mean colour indices, according to the SIMBAD data base and the intrinsic B−V values calibrated for the given spectral types and luminosity classes by Schmidt‐Kaler. The values of the total‐to‐selective extinction, RV=AV/E(B−V), for all the reddened stars were calculated from previously published near‐infrared photometric measurements. The calculated visual magnitudes, MV, of A–M stars compare with the earlier determinations of Schmidt‐Kaler. The mean absolute magnitudes published by Schmidt‐Kaler are generally brighter (except for the stars in luminosity classes V and IV) than those determined in this paper.