Very massive star winds as sources of the short-lived radioactive isotope Al-26

• Main Authors: Martinet, Sebastien, Meynet, Georges, Nandal, Devesh, Ekstrom, Sylvia, Georgy, Cyril, Haemmerle, Lionel, Hirschi, Raphael, Yusof, Norhasliza, Gounelle, Matthieu, Dwarkadas, Vikram
• Format: Article
• Published: EDP Sciences S A 2022
• Subjects: QC Physics
• Online Access: http://eprints.um.edu.my/41335/
• Institution: Universiti Malaya

Context. The Al-26 short-lived radioactive nuclide is the source of the observed galactic diffuse gamma-ray emission at 1.8 MeV. While different sources of Al-26 have been explored, such as asymptotic giant branch stars, massive stellar winds, and supernovae, the contribution of very massive stars has not been studied so far. Aims. We study the contribution of the stellar wind of very massive stars, here, stars with initial masses between 150 and 300 M-circle dot, to the enrichment in Al-26 of the galactic interstellar medium. Methods. We studied the production of Al-26 by studying rotating and non-rotating very massive stellar models with initial masses between 150 and 300 M-circle dot for metallicities Z  = 0.006, 0.014, and 0.020. We compared this result to a simple Milky Way model and took the metallicity and the star formation rate gradients into account. Results. We obtain that very massive stars in the Z  = 0.006 - 0.020 metallicity range might be very significant contributors to the Al-26 enrichment of the interstellar medium. Typically, the contribution of the winds of massive stars to the total quantity of Al-26 in the Galaxy increases by 150% when very massive stars are considered. Conclusions. Despite their rarity, very massive stars might be important contributors to Al-26 and might overall be very important actors for nucleosynthesis in the Galaxy.