Phosphorus Enrichment By ONe Novae In The Galaxy

By Keith Cowing
Status Report
May 16, 2024
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Phosphorus Enrichment By ONe Novae In The Galaxy
Distribution of the Galactic P-normal stars with [P/Fe]< 1 on the [Fe/H]−[P/Fe] plane and illustration of the predicted evolutionary path of the “ONe nova” scenario (wide gray line). Observational results for P-normal stars ([P/Fe]< 1) from (i) Roederer et al. (2014, 2016), (ii) Maas et al. (2022), and (iii) Caffau et al. (2016, 2019), M20, Maas et al. (2022), and Nandakumar et al. (2022) are plotted by filled circles, open circles, and crosses, respectively. The gray line just illustrates how [P/Fe] evolves with [Fe/H]: the exact details of the evolutionary paths (e.g., [Fe/H] at the maximum [P/Fe]) from the present chemical evolution model can be different from this line. Characteristic features of the models are explained with short phrases at appropriate places (e.g., “CCSN only” at [Fe/H]< −2.4). -- astro-ph.GA

Recent observations have shown that [P/Fe] in the Galactic stars decreases with increasing [Fe/H] for [Fe/H] > -1 whereas it is almost subsolar for [Fe/H]< -2. These [P/Fe] trends with [Fe/H] have not been well reproduced by previous theoretical models incorporating phosphorus (P) enrichment only by core collapse supernoave.

We here show, for the first time, that the trends can be naturally explained by our new models incorporating P enrichment by oxygen-neon (ONe) novae which occur at the surface of massive white dwarfs whose masses are larger than 1.25 M_sun with a metallicity-dependence rate. We also show that the observations can be better reproduced by the models by assuming that (i) the total mass of gaseous ejecta per ONe nov (M_ej) is as high as 4 * 10^{-5} M_sun and (ii) the number of such novae per unit mass (N_ONe) is as large as 0.01 at [Fe/H]~-3.

The assumed M_ej is consistent with observations, and the high N_ONe is expected from recent theoretical models for ONe nova fractions. We predict that (i) [P/Fe] increases with increasing [Fe/H] for -2 < [Fe/H] < -1 and (ii) [P/Fe] and [Cl/Fe] trends with [Fe/H] are very similar with each other due to very large yields of P and Cl from ONe nova. It is thus worthwhile for future observations to assess the validity of the proposed P enrichment by ONe novae by confirming or ruling out these two predictions.

Kenji Bekki, Takuji Tsujimoto

Comments: 5 pages, 5 figures, published in ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2405.06325 [astro-ph.GA] (or arXiv:2405.06325v1 [astro-ph.GA] for this version)
Submission history
From: Kenji Bekki Prof
[v1] Fri, 10 May 2024 08:54:00 UTC (144 KB)

Astrobiology, Astrochemistry,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻