Nucleosynthesis in Classical Novae: CO versus ONe White Dwarfs

Abstract

Detailed nucleosynthesis in the ejecta of classical novae has been determined for a grid of hydrodynamic nova models. The reported 14 evolutionary sequences, followed from the onset of accretion up to the explosion and ejection stages, span a range of CO and ONe white dwarf masses (0.8-1.35 M ⊙ ) and mixing levels between the accreted envelope and the underlying white dwarf core (25-75%). The synthesis of each isotope, from 1 H to 40 Ca, is discussed along with its sensitivity to model parameters. Special emphasis is given to isotopes such as 13 C, 15 N, and 17 O, which may account for a significant fraction of their Galactic content. Production of the radioactive isotopes 7 Be, 22 Na, and 26 Al is also analyzed, since they may provide a direct test of the thermonuclear runaway model through their γ-ray emission. The resulting elemental yields reproduce fairly well the spectroscopic abundance determinations of several well studied classical novae.

Absolute determination of theNa22(p,γ)Sallaska1, Wrede2, Garcı́a3 et al. 2011Phys. Rev. C255340View full textAdd to dashboardCite

“…R central is the 50% quantile of the distribution of rates at a given temperature, and Rupper and R lower are the 16% and 84% quantiles, respectively. [3]. The total mass ejected is given for each case, along with the mass fractions of 22 Na obtained using the central value of the previous [24,25] and both present 22 Na(p, γ) 23 Mg reaction rates compiled in Table V.…”

“…[3], for details). Results have been compared with those obtained in three additional hydrodynamic simulations, for the same white dwarf masses described above and same input physics except for the 22 Na(p, γ) rate, which was derived from Refs.…”

“…Such novae are ideal sites for the study of explosive nucleosynthesis because the observational [1], theoretical [2,3], and nuclear-experimental [4,5] aspects of their study are each fairly advanced. In particular, due to the relatively low peak temperatures in nova outbursts (0.1 < T < 0.4 GK), most of the nuclear reactions involved are not too far from the valley of beta stability to be studied in the laboratory, and the corresponding thermonuclear reaction rates are mostly based on experimental information [4].…”

Explosive Nucleosynthesis

“…CO novae produce mainly 7 Be, whereas ONe produce 22 Na and 26 Al. Other radioactivities with shorter lifetimes, such as 13 N and 18 F (τ = 862s and 158min, respectively) are produced in similar amounts in CO and ONe novae (see José and Hernanz, 1998 The two short-lived isotopes 13 N and 18 F are crucial for the prompt gamma-ray emission of novae, which is the most intense emission (10 −3 phot cm −2 s −1 ), but of very short duration (a few days) and appearing before optical detection. The medium-lived isotopes ( 7 Be and 22 Na) produce fluxes of around 10 −6 and 10 −5 phot cm −2 s −1 , for distances of 1 kpc.…”

“…However, the large metallicities and neon abundances observed in some novae are not well reproduced. Another approach is based on 1D models with an initial (parametrized) enrichment, such that the general properties of observed novae (mainly abundances) are well modeled (see for instance Starrfield et al 1998, José andHernanz 1998).…”