The Effects of Starspots and Faculae on the G-band, Ca I, and Hγ Photospheric Indices

The observation and analysis of solar-type stars has been a rich area of research. Determining what the Sun was like when life was first taking hold on Earth, and what the Sun will be like as it ages with the potential impacts on the future Earth, provides the motivation for a number of monitoring campaigns to photometrically and spectroscopically measure collections of solar-like stars (solar analogs). One such campaign, The Young Solar Analogs (YSA) Project, has been monitoring 30 stars in the range of ages 300 million to 1.5 billion years old, and spectral classes F8 - K2 [10]. The focus of this thesis is the creation and implementation of a computational model for the photospheres of the YSA program stars. I analyze the links between the photospheric features on a model star and the rotational modulation of photometric flux in the Johnson-Cousins B, V, and R bands, as well as spectroscopic indices derived from the G Band, Hγ, and Ca I photospheric features. This project constructs a computer model of stellar photospheres built on ATLAS9 models and the SPECTRUM spectral synthesis code that models rotational modulation of stars due to stellar spots. This paper presents preliminary results that show that the variations in the photospheric indices found by Gray et al. cannot be explained solely by faculae and star spots.