PHOTOMETRIC AND SPECTROSCOPIC DISTANCES, FOR OB STARS - A COMPARISON

Reddenings, absolute magnitudes, and distances (D) based on both U bet a V beta photometry and MK-system spectral classifications are compute d and compared for 287 stars of spectral types 04-B2.5. While overall agreement is very good, (D-U beta V beta/D-MK)=1.06+/-0.39 (s.d.), sig nificant trends in photometric versus spectroscopic absolute magnitude s and distances as a function of both absolute magnitude and photometr ic versus spectroscopic luminosity classification are evident. Prescri ptions as to whether one is likely to overestimate or underestimate ph otometric as compared to spectroscopic distances in given circumstance s are developed. Almost all of the standard deviation in D-U beta V be ta/D-MK is attributable to differences in inferred absolute magnitudes .