COMMUNICATIONS / MITTEILUNGEN

S.M. Kung

The Zero Point of the Period-Luminosity Relation of Cepheids and the Absolute Magnitude of the RR Lyrae Variables

No. 47
Budapest, 1960

Abstract

33 results including 3 results of this paper in connection with the zero point of the period-luminosity relation since Wilson's result of 1939 are tabulated. They are collected in 6 tables according both the nature of the results and the methods used. A comment for each result is made. 11 results are rejected for various reasons stated in section II. The absolute magnitude of cepheids fainter more than 1m in Wilson's result, according which the original zero point of Shapley's P-L relation was fixed is fully explained. The expression for the correction due to the spread both of the apparent and absolute magnitudes of the stars is derived in section III. With the correction thus derived the correct formula for the product of the mean distance and the mean parallax, r*pi, is obtained. Finally, in section IV all the useful results are collected separately to get 3 weighted means, one for the difference between the observed magnitude and the calculated magnitude, based on the assumed absolute magnitude of the RR Lyrae variables and the Shapley's P-L relation, one for the correction to the zero point of the P-L relation, and one for the absolute magnitude of the RR Lyrae variables. With the double weight for the first one, we obtain from all the 3 kinds of data taken together the correction to the zero point of the Shapley's P-L relation to be -1.28m and the absolute magnitude of the RR Lyrae variables to lie +0.34m.

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