THE EFFECTS OF THEpepNUCLEAR REACTION AND OTHER IMPROVEMENTS IN THE NUCLEAR REACTION RATE LIBRARY ON SIMULATIONS OF THE CLASSICAL NOVA OUTBURST

Abstract

Nova explosions occur on the white dwarf (WD) component of a Cataclysmic Variable binary stellar system which is accreting matter lost by its companion. When sufficient material has been accreted by the WD, a thermonuclear runaway (TNR) occurs and ejects material in what is observed as a Classical Nova explosion. We have continued our studies of TNRs on 1.25M ⊙ and 1.35M ⊙ WDs (ONeMg composition) under conditions which produce mass ejection and a rapid increase in the emitted light, by examining the effects of changes in the nuclear reaction rates on both the observable features and the nucleosynthesis during the outburst. In order to improve our calculations over previous work, we have incorporated a modern nuclear reaction network into our one-dimensional, fully implicit, hydrodynamic computer code. We find that the updates in the nuclear reaction rate libraries change the amount of ejected mass, peak luminosity, and the resulting nucleosynthesis. Because the evolutionary sequences on the 1.35M ⊙ WD reach higher temperatures, the effects of library changes are more important for this mass. In addition, as a result of our improvements, we discovered that the pep reaction (p + e − + p → d + ν) was not included in our previous studies of CN explosions (or to the best of our knowledge those of other investigators).

Presolar Grains From Novae: Evidence From Neon and Helium Isotopes in Comet Dust Collections

“…The actual maximum is therefore lower. Although orders of magnitude higher than the theoretical-and unmeasurable-prediction of <10 −8 in a neon nova outburst (Starrfield et al 2009), the <10 −4 upper limit is still below the 3 He/ 4 He range in solar system matter, from 1.66 × 10 −4 in Jupiter's atmosphere (Mahaffy et al 1998) to an average of 4.49 × 10 −4 in the SW (Mabry et al 2007;Heber et al 2009; Table 4). …”

“…Of the combination of theoretical hydrodynamic calculations and nuclear reaction networks describing element synthesis in stellar environments, only those for total ejecta compositions in neon nova outbursts specifically predict the combination of negligible 3 He, low 4 He/ 20 Ne, high 20 Ne/ 21 Ne, and 20 Ne/ 22 Ne ratios in and above the range of ∼25 to ∼150 (Figure 3) measured in these particles (Starrfield et al 2009;José et al 2004).…”

“…Each nova outburst ejects material with unique abundances because of the large range in parameters affecting the properties of the explosion. These include WD mass and composition, initial WD luminosity, the mass accretion rate, and the nuclear reactions in the TNR itself (José et al 2004;Starrfield et al 2008Starrfield et al , 2009). Once propelled from the WD, the expanding shell of ejected gas can be observed spectroscopically to determine its chemical composition (Gehrz et al 1998).…”

“…Velocity broadening prevents assignment of observed Ne emission lines to a particular isotope, but the composition of the dredged-up ONe WD core material predicts that Ne initially in the ejecta is essentially all 20 Ne. Detailed calculations (José et al 2004;Starrfield et al 2008Starrfield et al , 2009 show that repeated proton captures on 20 Ne will fuse some of the neon to 22 Na. Pre-existing 3 He and 22 Ne are virtually annihilated in the TNR by fusion to heavier species; 3 He/ 4 He is driven to <10 −8 and 20 Ne/ 22 Ne to >10 6 (Starrfield et al 2009).…”

Post common envelope binaries from SDSS

“…In addition, the amount of ejected mass predicted by the models is very sensitive on the nuclear-reaction rates used in the model calculations, and also on the specific nuclear reactions that are taken into account (see e.g. Starrfield et al 2009). Finally, one key point to keep in mind is that the observed classical novae are not at all representative of the entire A42, page 13 of 16 A&A 536, A42 (2011) CV population, because the nova recurrence time is decreasing with increasing mass-transfer rate and increasing WD mass, and therefore the classical novae are strongly biased towards highmass WDs in novalike variables with high mass-transfer rates.…”