Surface Gravity as a Diagnostic of Stellar Youth
Date
2005
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Swarthmore College. Dept. of Physics & Astronomy
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Thesis (B.A.)
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en_US
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Full copyright to this work is retained by the student author. It may only be used for non-commercial, research, and educational purposes. All other uses are restricted.
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Abstract
Young stars, those less than 100 Myr old, provide much information about the formation
of planetary systems. The study of such objects is impossible without reliable indicators
of stellar youth. The most reliable age diagnostic, placing candidate stars on an HR
diagram, hinges on knowing the luminosity. We avoid the need to measure this quantity
by finding the star's surface gravity instead. Using computer-generated spectra, we compare
individual spectral lines in our data to models of known gravity. By minimizing the
chi-square of the difference between the fluxes of the data and the model, we arrive at a
best-fit value of log g, Te ff , and v sin i . The gravity value also fixes the star's position on
an HR diagram as either above the main-sequence, or on it. We find that this technique
is, by itself, insufficient to constrain log g well enough to determine the appoximate age
of stars.