New Insights into RU Cam (Abstract)

Volume 27 number 2 (1999)

John R. Percy

Jonathan Hale

Yvonne Tang

Abstract

(Abstract only) RU Cam is a peculiar Population II Cepheid which “stopped pulsating” in 1966. More precisely, it decreased its amplitude from 1 to 0.1 magnitude, but continued pulsating with a period of about 22 days. Using a compilation of photometry (1966–1982) and (O-C) values (1874–1982) from Szeidl et al. (1992, Comm. Konkoly Obs., No. 97), and AAVSO photoelectric photometry (1983–1997), we have reached the following conclusions: (1) the star has undergone random cycle-to-cycle fluctuations in period, both before and after 1966; (2) prior to 1966, the evolution of the star was visible in the (O-C) diagram but, after 1966, the fluctuations in period were large enough to mask the evolution; (3) the fluctuations in period, after 1966, seem to be coherent over about 10 cycles, rather than being random; (4) this, and the variations in the amplitude of the low-level pulsation on a time scale of about 10 cycles, suggest that the star may be sporadically multiperiodic. We acknowledge a research grant from NSERC Canada, and support from the Summer Career Placement Program, Canada. JH and YT were participants in the University of Toronto Mentorship Program, which enables outstanding senior high school students to work on research projects at the university.