The Chemical Abundances of Tycho G in Supernova Remnant 1572

Creators: González Hernández, Jonay I.; Ruiz-Lapuente, Pilar; Filippenko, Alexei V.; Foley, Ryan J.; Gal-Yam, Avishay; Simon, Joshua D.

Abstract

We present an analysis of the chemical abundances of the star Tycho G in the direction of the remnant of supernova (SN) 1572, based on Keck high-resolution optical spectra. The stellar parameters of this star are found to be those of a G-type subgiant with T eff = 5900 ± 100 K, log(g/cms2) = 3.85 ± 0.30 dex, and [Fe/H] = –0.05 ± 0.09. This determination agrees with the stellar parameters derived for the star in a previous survey for the possible companion star of SN 1572 (Ruiz-Lapuente et al.). The chemical abundances follow the Galactic trends, except for Ni, which is overabundant relative to Fe, [Ni/Fe] = 0.16 ± 0.04. Co is slightly overabundant (at a low significance level). These enhancements in Fe-peak elements could have originated from pollution by the SN ejecta. We find a surprisingly high Li abundance for a star that has evolved away from the main sequence. We discuss these findings in the context of companion stars of SNe.

Additional Information

© 2009. The American Astronomical Society. Received 2008 June 24; accepted 2008 September 3; published 2009 January 7. Print publication: Issue 1 (2009 January 20). J.I.G.H. is supported by EU contract MEXT-CT-2004-014265 (CIFIST). P.R.-L. acknowledges support from AYA2006-05639. A.V.F. is funded by NSF grant AST-0607485, as well as by NASA/HST grant GO-11114 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. We are grateful to Tom Marsh for the use of the MOLLY analysis package, and to Ryan Chornock for very helpful discussions on a number of issues. P.R.-L. is grateful to Eduardo Martín and Rafa Rebolo for useful exchanges on the Li topic. A.G. acknowledges support by the Benoziyo Center for Astrophysics and the William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute. This study is based primarily on data from the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; it was made possible by the generous financial support of the W.M. Keck Foundation. We thank the Keck staff for their assistance with the observations. This work has utilized IRAF facilities and the 2MASS catalog.

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