Signatures of Supernovae in the Abundances of Metal-Rich Stars

Details Signatures of Supernovae in the Abundances of Metal-Rich Stars Signatures of Supernovae in the Abundances of Metal-Rich Stars

Dec 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.2307p&link_type=abstract

American Astronomical Society, 181st AAS Meeting, #23.07; Bulletin of the American Astronomical Society, Vol. 24, p.1159

Astronomy and Astrophysics

Astronomy

6

Scientific paper

Iron abundances and the abundance ratios of light elements with respect to iron have been determined for Arcturus, a bright metal-poor giant; two stars in the open cluster M67; and Mu Leo, the archetypical super metal rich star. Spectra calculated with R. Kurucz's program SYNTHE were compared with observations at a resolution exceeding 20,000. The calculations employ the new grid of Kurucz atomspheres and gf values, the latter revised to match the Sun, as described in a study of Arcturus by Peterson, Dalle Ore, and Kurucz (1993, ApJ, Feb. 10). The iron-to-hydrogen results are [Fe/H] = -0.5 for Arcturus, -0.1 for M67, and +0.2 for Mu Leo. Cyanogen is sufficiently strong in the M67 giant and in Mu Leo that spectral synthesis is required, even near 6300 Angstroms. There are distinct differences in the ratios of the light elements with respect to iron among the three groups of stars. Arcturus shows the pattern typical of the more metal-poor stars of the halo (see Wheeler, Sneden, and Truran, 1989, ARA& A, 27, 279), with oxygen and magnesium enhanced by 0.4 dex (a factor of three more abundant with respect to iron than in the solar mix), and silicon enhanced by 0.3 dex; the two M67 stars show O, Mg, and Si all enhanced by only 0.1 dex; while Mu Leo shows no enhancement at all for O and Mg, but Si enhanced by 0.3 dex. These differences could be due to the different types of supernovae (SN) responsible for element nucleosynthesis. In Arcturus, as for the halo stars, these were Type II SN. For M67, Type Ib SN undoubtedly were the primary contributors, since these produce primarily iron-peak elements. For Mu Leo, this work suggests that Type II SN again were primarily responsible, given the high Si/Fe ratio. However, the Type II progenitors were apparently more heavily weighted toward stars of 10 rather than 40 solar masses, since only the latter strongly overproduce O and Mg. The different weighting could arise either because of a change in the luminosity function itself or because of a more extended time period which allowed the impact of the evolution of lower-mass stars to be fully felt.

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