Populations in the Kepler field

Farmer, Robert (2014). Populations in the Kepler field. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000fae5

Abstract

Using a population synthesis model I have created a synthetic catalogue of stars in the Kepler field of view. This model has then been subjected to the same biases and selection effects inherent in the selection of stars for the Kepler transit survey mission. This produced a synthetic Kepler Input Catalogue (KIC) which was subjected to the Kepler Stellar Classification Program (SCP) method for determining stellar parameters. I achieve a satisfactory match between the synthetic KIC and the real KIC in the logg vs log Teff diagram. I find a median difference of ΔTeff = +500 K and ~ Δlogg = -0.2 dex for main sequence stars, although there is a large variation across parameter space. I find no significant difference between ΔTeff and Δlogg for single stars and the primary star in a binary system. I also re-created the Kepler target selection method and found that the binary fraction is unchanged by the target selection. The fraction of main sequence stars in the sample increases from 75% to 80%, and the giant star fraction decreases from 25% to 20%. I have then used the synthetic KIC to build a of synthetic sample of eclipsing binaries (EBs) in the Kepler field. Comparing the synthetic catalogue to the Kepler EB catalogue I find that the Kepler EB pipeline introduces significant biases into the derived temperature ratio and fractional radii. I then tested the effect of different initial mass ratio distributions (IMRDs) and initial binary fraction distributions (IBFDs). At this time, all distributions fail to match the data, such that their parameters can not be constrained. Modelling the population of asteroseismic binaries, where both stars have a detectable asteroseismic signal, have shown a way to constrain the IMRD for equal mass systems. This method is independent of the binary period and orbital orientation. The number of detectable asteroseismic binaries increases from 87 for the IMR parameter s = -0.5 to 256 for s = 1.0. The number of detectable asteroseismic EBs increases from 34.0 ± 6.0 (s = -0.5) to 59.0 ± 6.0 (s = 1.0). This number shows disagreement with the number of actual systems detected (2 for Porb < 40 days), which can not be explained by incompleteness alone.

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