Defined Orbital Elements and Solution Parameters for Binary Star System ET Tau Open Access

Evavold, Charles Lee (2013)

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ET Tau is a semi-detached variable star system of combined visual magnitude of 8.8 with a period of around 5.996 days. The Wilson-Devinney program was used to solve the Emory University and Fernbank Science Center BV light curves simultaneously with single-line radial velocity measurements of the secondary star. The system has the secondary component filling its Roche Lobe. The resulting masses are M1=16.43 Msun and M2=7.17 Msun with mean radii R1=5.77 Rsun and R2=12.32 Rsun. Light curve parameters, radial velocity parameters, orbital elements, and absolute dimensions are presented in the paper. Observations were taken in the UBV filter sets for the Fernbank Science Center data from January 1983 - April 1986. Observations were taken in BVR filter sets for the Emory University Observatory data during Spring 2013. After varying all parameters, our data and theoretical solution suggests that period has remained constant between the Fernbank and Emory data over the course of 27 years.

Table of Contents

Table of Contents

Chapter 1: Introduction to Eclipsing Binaries and Astronomical Quantities

1.1 Eclipsing Binary Star Systems...1

1.2 Parameters of the System...2

1.3 Naming Conventions and Classification...5

1.4 How Do We Measure Brightness...8

1.5 Astronomical Timing and Heliocentric Julian Date Correction...9

1.6 Stellar Spectra...11

1.7 Radial Velocity Curves...13

1.8 Telescope Configuration and CCD Cameras...15

1.9 Differential Photometry...19

Chapter 2: Light Curve Data, Fitting, and Stellar Modeling

2.1 Overview of Modeling...21

2.2 Times of Minima...22

2.3 O-C Diagram...22

2.4 Solutions of Varied Parameters...23

2.5 Wilson-Devinney Code...24

Chapter 3: ET Tau Observations and Analysis

3.1 Background Information...25

3.2 Observations...26

3.3 Light Curves and Model...27

3.4 Results...27

3.5 Discussion...36


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