C, N, and O Abundances in VR 5-7 Compared to IRS 7

Ramírez, S. V.1, Sellgren, K.2, Blum, R. D.3, Terndrup, D. M.2

1 MS 105-24, Caltech, Pasadena, CA 91125 USA
2 Astronomy Dept., Ohio State University, 140 West 18th Av., Columbus, OH 43210 USA
3 Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile

E-mail contact: sellgren@astronomy.ohio-state.edu

We have previously published a differential analysis of the iron abundance, [Fe/H], in ten luminous M stars within 30 pc of the Galactic Center (GC), compared to 11 stars of similar temperature and luminosity in the solar neighborhood. We found that both samples of stars had a narrow distribution of [Fe/H], centered at the solar value. Carr et. al (2000) also studied [C/H], [N/H], and [O/H] in IRS 7 (M1 I), which lies at a projected distance of 0.2 pc from Sgr A*, in a differential analysis compared to Ori (M1 I), in the solar neighborhood. They found that dredge-up of CNO-processed material was present in both M supergiants, as expected theoretically, but that the amount of internal mixing was much stronger in IRS 7, stronger than predicted by current evolutionary models. Is this strong internal mixing due to the unusual conditions for star formation in the central 100 pc of the Galaxy, or is it due to some interaction between IRS 7 and the 2.6 x 106 black hole at the GC? To investigate these questions, we will present results on [C/H], [N/H], and [O/H] in the M supergiant VR 5-7, which lies in the Quintuplet cluster, 30 pc from the GC.