Photometric Strömgren-HβQuantification for O and B Stars of Luminosity Class V

In any photometric system, the relationship between the spectral type and the intrinsic colors is fundamental for the photometric stellar classification and for a reliable derivation of stellar parameters. Such relationships are being constantly verified and improved based on larger and better samples. The capability of the Strömgren-H β photometry to provide reddening-free quantities allows the classification of reddened stars over the entire spectral sequence. However, a detailed consistent tabulation of the uvbyβ quantities for the O-B9 part of the main sequence is currently warranted. We combine spectral types and photometry from the literature to provide a new empirical tabulation of the intrinsic color b − y , color differences c 1 , m 1 , [ c 1 ] and [ m 1 ] and the H β index for main-sequence (luminosity class V) stars of spectral types O4.5 through B9.5 in terms of spectral sub-types. Our survey is based on more than 1400 stars. We use the established c 1 versus b − y intrinsic line and the accepted reddening slopes to obtain dereddened quantities and then calculate their median values as a function of the spectral sub-type. The classification ability of the system in this spectral range is reliable and the photometric quantities are not affected by the stellar rotation.