The ZeroPoint of the PeriodLuminosityRelation of Cepheids
Abstract
The zeropoint of the periodluminosityrelation has been redetermined by applying the method of secular parallaxes. The determination presented here is based on proper motions, radial velocities and photometric data of about a hundred Cepheids of Population I. This approach was encouraged by the availabfflty of improved proper motions and photometric data. All proper motions were reduced to the system of FK4, and, for purposes of comparison, to the N30 system. The effects of galactic rotation, of incorrect precession, and of a motion of the equinox were taken into account. The radial velocities were discussed with respect to solar motion, differential galactic rotation and Kterm. Adopting the slope of Kraft's periodluminosityrelation, the zeropoint is found to be  1' 88 + O 45 (m.e.). Kraft's value was 1' 67. With the slope of Fernie's periodluminosityrelation the zeropoint is found to be 2 .05 + 0rn.45 (m.e.). Fernie obtained the value  1rn.99.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 1970
 Bibcode:
 1970A&A.....5..116G