Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.5912c&link_type=abstract
American Astronomical Society, AAS Meeting #211, #59.12; Bulletin of the American Astronomical Society, Vol. 39, p.843
Astronomy and Astrophysics
Astronomy
Scientific paper
This study measures, for the first time, titanium isotope ratios in low-mass stars and compares them to models of Galactic chemical evolution. The isotopes of titanium are tracers of the nucleosynthetic events in the galaxy. 46Ti and 47Ti are the products of oxygen burning, while 48Ti and 49Ti are the result of 48Cr and 49Cr decay. Formation of 50Ti occurs in more rare environments, resulting from electron capture. Because of these different formation sites, studying the isotopes provides a look into the nucleosynthetic environments in the history of the Galaxy. The ratios of the minor (46, 47, 49, 50) isotopes is measured from the isotopic features seen in the TiO spectra. Using the 2d coude' spectrograph at the 2.7 m telescope at McDonald Observatory, I observed 12 M dwarf spectra at a resolving power of 120,000. I selected stars from various Galactic kinematic population, observing an even mix of thin disk, thick disk and halo stars. Using spectrum synthesis, I measured the isotopic ratios from the isotopic features seen in the TiO gamma 0-0 band from 7054 to 7085 Angstroms. I measured these ratios, 46Ti/48Ti and 50Ti/48Ti, because these are predicted to increase significantly with metallicity. Comparisons among the minor isotopes are also valuable since these features are relatively the same strength. I also fit these ratios: 46Ti/47Ti, 50Ti/47Ti, 49Ti/50Ti. These stars, ranging in metallicity from -0.8 to 0.0 [Fe/H], seem to show little trend in the ratios with metallicity.
Chavez Joy M.
Lambert David L.
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