Non-evolutionary effects on period change in Magellanic Cepheids I. New binary systems revealed from Light Travel Time Effect

Abstract

Period change studies give a window to probe into the evolution and dynamics of Cepheids. While evolutionary period changes have been well studied both observationally and theoretically, non-evolutionary period changes lack a systematic and quantitative description. The overall objective is to have a quantitative understanding of the full picture of non-evolutionary period changes in Cepheids, to develop a formalism to disentangle it from the secular evolutionary period change. In the first part of the series of works, we aim to conduct a systematic search for non-evolutionary period changes to search for Cepheids in likely binary configuration and quantify their incidence rates in the Magellanic Clouds. We collect more than decade-long time-series photometry from the publically available survey, Optical Gravitational Lensing Experiment (OGLE), with more than 7200 Cepheids collectively from the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). Our sample contains both fundamental-mode and first overtone-mode Cepheids. Then we calculate observed minus calculated ($O-C$) diagrams to reveal the light-travel time effect (LTTE). In our search, out of an overall sample of more than 7200 Cepheids, we found 52 candidate Cepheid binary systems in the LMC (30 fundamental and 22 first overtone-mode) and 145 in the SMC (85 fundamental and 60 first overtone-mode). The majority of the sample is characterized by orbital periods of 2000-4000\,d and eccentricities of 0.2-0.5. Moreover, we report two candidates in each galaxy with the Cepheid likely existing with a giant companion. The incidence rate ratio for SMC to LMC calculated from our sample is in agreement with binary Cepheid population synthesis predictions.

version2: 17 pages, 10 figures, Appendix

References in corpus (23)

• Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with LambdaCDM
• Direct Detection of the Close Companion of Polaris with the Hubble Space Telescope
• A red giant orbiting a black hole
• Cepheids in external galaxies. I. The maser-host galaxy NGC 4258 and the metallicity dependence of P-L and P-W relations
• Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2 - I. Binarity from proper motion anomaly
• Cepheid Mass-loss and the Pulsation -- Evolutionary Mass Discrepancy
• Frequency analysis of Cepheids in the Large Magellanic Cloud. New types of classical Cepheid pulsators
• New RR Lyrae variables in binary systems
• Observations of Cepheids with the MOST satellite: Contrast between Pulsation Modes
• TESS observations of Cepheid stars: first light results
• The occurrence of classical Cepheids in binary systems
• Cepheids with giant companions. I. Revealing a numerous population of double-lined binary Cepheids
• Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution
• Period Change Rates in Large Magellanic Cloud Cepheids Revisited
• Frequency analysis of OGLE-IV photometry for classical Cepheids in Galactic fields: non-radial modes and modulations
• Binarity among Cepheids in the Magellanic Clouds
• Discovery of the spectroscopic binary nature of six southern Cepheids
• On the dynamical evolution of Cepheids in star clusters
• Discovery of a binary-origin classical Cepheid in a binary system with a 59-day orbital period
• Synthetic population of binary Cepheids. I. The effect of metallicity and initial parameter distribution on characteristics of Cepheids' companions
• First Overtone Cepheids of the OGLE Magellanic Cloud Collection -- beyond radial modes
• Spectral energy distributions of classical cepheids in the Magellanic Clouds
• Synthetic Population of Binary Cepheids. II. The effect of companion light on the extragalactic distance scale