Affiliation:
1. Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, PL-00-716 Warszawa, Poland
Abstract
ABSTRACT
We analyse photometry of ∼2000 Galactic Cepheids available in the OGLE Collection of Variable Stars. We analyse both Galactic disc and Galactic bulge fields; stars classified both as single- and multiperiodic. Our goal was to search for additional low-amplitude variability. We extend the sample of multimode radial pulsators by identifying 10 new candidates for double mode and 6 new candidates for triple-mode pulsation. In the first overtone OGLE sample, we found 12 Cepheids with additional periodicity having period ratio $P_{\rm x}/P_{\rm 1O}\in (0.60,\, 0.65)$. These periodicities do not correspond to any other radial mode. While such variables are abundant in the Magellanic Clouds, only one Cepheid of this class was known in the Galaxy before our analysis. Comparing our sample with the Magellanic Cloud Cepheids, we note a systematic shift towards longer pulsation periods for more metal rich Galactic stars. Moreover, in 11 stars we find one more type of additional variability, with characteristic frequencies close to half of that reported in the group with (0.60, 0.65) period ratios. Two out of the above inventory show simultaneous presence of both signals. Most likely, origin of these signals is connected to excitation of non-radial pulsation modes. We report three Cepheids with low-amplitude periodic modulation of pulsation: two stars are single-mode fundamental and first overtone Cepheids and one is a double-mode Cepheid pulsating simultaneously in fundamental and in first overtone modes. Only the former mode is modulated. It is a first detection of periodic modulation of pulsation in this type of double-mode Cepheids.
Funder
Ministry of Science and Higher Education
Foundation for Polish Science
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
6 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献