Intrinsic UBV colors of RR Lyrae stars
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Abstract
Photoelectric observations on the UB V system of more than one hundred Bailey type a, b RR Lyrae stars were obtained to investigate the color indices near minimum light. It is shown that for most purposes of galactic research B - V and U - B may be treated as constant in the phase interval 0 5 0 8. The U - B index during this interval is correlated with the metallic-line blanketing derived from high- dispersion spectrograms, and is used to find a line-free index, (B - V) A period versus (B - V) relation is found for those variables in the galactic caps and, combined with observations from stars at lower latitudes, is used to obtain a cosecant reddening law. A B - V excess at the poles of 0.03 mag is adopted. From this, intrinsic UB V colors and individual color excesses are derived for the RR Lyrne stars The probable error of an intrinsic color is only 0.01 mag. Applications to the determination of interstellar reddening and stellar populations are discussed.