Viability of Novae as Sources of Galactic Lithium

Kemp, Alex J. and Karakas, Amanda I. and Casey, Andrew R. and Coté, Benoit and Izzard, Robert G. (2022) Viability of Novae as Sources of Galactic Lithium. ASTROPHYSICAL JOURNAL LETTERS, 933 (2). ISSN 2041-8205

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Abstract

Of all the light elements, the evolution of lithium (Li) in the Milky Way is perhaps the most difficult to explain. Li is difficult to synthesize and is easily destroyed, making most stellar sites unsuitable for producing Li in sufficient quantities to account for the protosolar abundance. For decades, novae have been proposed as a potential explanation for this "Galactic Li problem," and the recent detection of Be-7 in the ejecta of multiple nova eruptions has breathed new life into this theory. In this work, we assess the viability of novae as dominant producers of Li in the Milky Way. We present the most comprehensive treatment of novae in a galactic chemical evolution code to date, testing theoretically and observationally derived nova Li yields by integrating metallicity-dependent nova ejecta profiles computed using the binary population synthesis code binary_c with the galactic chemical evolution code OMEGA+. We find that our galactic chemical evolution models which use observationally derived Li yields account for the protosolar Li abundance very well, while models relying on theoretical nova yields cannot reproduce the protosolar observation. A brief exploration of physical uncertainties including single-stellar yields, the metallicity resolution of our nova treatment, common-envelope physics, and nova accretion efficiencies indicates that this result is robust to physical assumptions. Scatter within the observationally derived Li yields in novae is identified as the primary source of uncertainty, motivating further observations of Be-7 in nova ejecta.

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