Determination of Cepheid parameters by light-curve template-fitting

Abstract

We describe techniques to characterise the light-curves of regular variable stars by applying principal component analysis (PCA) to a training set of high quality data, and to fit the resulting light-curve templates to sparse and noisy photometry to obtain parameters such as periods, mean magnitudes etc. The PCA approach allows us to efficiently represent the multi-band light-curve shapes of each variable, and hence quantitatively describe the average behaviour of the sample as a smoothly varying function of period, and also the range of variation around this average. In this paper we focus particularly on the utility of such methods for analysing HST Cepheid photometry, and present simulations which illustrate the advantages of our PCA template-fitting approach. These are: accurate parameter determination, including light-curve shape information; simultaneous fitting to multiple passbands; quantitative error analysis; objective rejection of variables with non Cepheid-like light-curves or those with potential period aliases. We also use PCA to confirm that Cepheid light-curve shapes are systematically different (at the same period) between the Milky Way (MW) and the Large and Small Magellanic Clouds (LMC, SMC), and consider whether light-curve shape might therefore be used to estimate the mean metallicities of Cepheid samples, thus allowing metallicity corrections to be applied to derived distance estimates.

MNRAS in press: revised in light of referees comments

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Cited by in corpus (18)

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• Comparison of Distances from RR Lyrae Stars, the Tip of the Red-Giant Branch and Classical Cepheids
• Light curve analysis of Variable stars using Fourier decomposition and Principal component analysis
• A Study of Cepheids in M81 with the Large Binocular Telescope (Efficiently Calibrated with HST)
• The Cepheid Distance to the Seyfert 1 Galaxy NGC 4151
• A Global Physical Model for Cepheids
• Search for high-amplitude Delta Scuti and RR Lyrae stars in Sloan Digital Sky Survey Stripe 82 using principal component analysis
• A Panoply of Cepheid Light Curve Templates
• A Comparative Study of Multiwavelength Theoretical and Observed Light Curves of Cepheid Variables
• A Data-driven Study of RR Lyrae Near-IR Light Curves: Principal Component Analysis, Robust Fits, and Metallicity Estimates
• Computation of the Fourier parameters of RR Lyrae stars by template fitting
• A Physically-Based Method for Scaling Cepheid Light Curves for Future Distance Determinations
• Period-color and amplitude-color relations in classical Cepheid variables V: The Small Magellanic Cloud Cepheid models
• The ACS Nearby Galaxy Survey Treasury III: Cepheids in the Outer Disk of M81
• On the Metallicity Dependence of Classical Cepheid Light Amplitudes
• GRAPE: Genetic Routine for Astronomical Period Estimation
• OGLE-IV Period-Luminosity relation of the LMC: an analysis using mean and median magnitudes
• Bayesian functional data analysis in astronomy