Award Date

1-1-2002

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics

First Committee Member

Jeremy R. King

Number of Pages

59

Abstract

Parameters and relative abundances of Fe, Ni, Ti, Cr, Ca, Si, Al, and Mg have been derived for nine M34 G and K dwarfs from high-resolution, modest S/N, Keck/HIRES spectra. Effective temperatures have been derived spectroscopically and fall in the range 4750 ≤ Teff ≤ 6130 K. Despite modest scatter in Fe, Ti, Cr, Ca, Al, and Mg (none of which is found to be correlated with Li scatter in M34), our two coolest stars are slightly though consistently underabundant in these elements relative to the warmer stars. The two cool stars are slightly overabundant in Si, whose abundances are derived from higher excitation lines. This and our finding that Fe II-based abundances are significantly higher than Fe I-based values in the cool stars seems to point towards the action of NLTE effects (overionization and/or overexcitation), though additional analysis is required to exclude inadequacies in the model atmospheres. Final mean cluster abundances are based on five warm stars, which indicate [Fe/H] = +0.07 +/- 0.04, and are void of any statistically significant scatter. The other elements scale well with Fe, except for Ni, which appears to be slightly underabundant with respect to Fe. K abundances are derived and show a surprising marked trend with temperature, which further supports our suspicion of the presence of NLTE effects. Moreover, the expected similar spectroscopic behavior of the neutral alkali resonance lines we employ suggests the apparent Li and K underabundances in cool M34 dwarfs are partly related; thus, some portion of the well-known Li-Teff trend in cool M34 dwarfs may be illusory.

Keywords

Abundances; Cluster; Dwarfs; M34 Open; Solar; Spectroscopic; Type

Controlled Subject

Astronomy

File Format

pdf

File Size

1617.92 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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