COMMUNICATIONS / MITTEILUNGEN
Photoelectric UBV Photometry of Northern Cepheids I
No. 70
Budapest, 1977
Abstract
New UBV photoelectric observational data on 38 northern cepheids with periods
of less than 5 days are presented. The period changes of the observed cepheids
are investigated. Four variables (SU Cyg, DT Cyg, V532 Cyg, SZ Tau) show a
period jump and a subsequent "rejump" to the earlier value of the period,
which results in the overall constancy of the period. DT Cyg pulsates
with the same period for at least the fourth time which is in keeping
with the recent hypothesis on the evolution of cepheids along the lines of
constant period in the HRD. AU peg, a Population II variable, shows extremely
strong period changes.
In three cases, secular light curve variation was discovered. The
amplitude of the light variation as AS Per is decreasing; the other
type of light curve variation is the variation in the steepness of the rising
branch (SU Cyg, FF Aql). The effect of the orbital motion on the O-C diagram
is also investigated for FF Aql.
Finally, the instability of the period for different types of cepheids
is discussed.
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