We investigate the effects of thermonuclear reaction rate variations on 26Al production in massive stars. The dominant production sites in such events were recently investigated by using stellar ...model calculations: explosive neon-carbon burning, convective shell carbon burning, and convective core hydrogen burning. Post-processing nucleosynthesis calculations are performed for each of these sites by adopting temperature-density-time profiles from recent stellar evolution models. For each profile, we individually multiplied the rates of all relevant reactions by factors of 10, ,0.5, and 0.1, and analyzed the resulting abundance changes of 26Al. In total, we performed 900 nuclear reaction network calculations. Our simulations are based on a next-generation nuclear physics library, called STARLIB, which contains a recent evaluation of Monte Carlo reaction rates. Particular attention is paid to quantifying the rate uncertainties of those reactions that most sensitively influence 26Al production. For stellar modelers our results indicate to what degree predictions of 26Al nucleosynthesis depend on currently uncertain nuclear physics input, while for nuclear experimentalists our results represent a guide for future measurements. We also investigate equilibration effects of 26Al. In all previous massive star investigations, either a single species or two species of 26Al were taken into account, depending on whether thermal equilibrium was achieved or not. These are two extreme assumptions, and in a hot stellar plasma the ground and isomeric states may communicate via Delta *g-ray transitions involving higher-lying 26Al levels. We tabulate the results of our reaction rate sensitivity study for each of the three distinct massive star sites referred to above. It is found that several current reaction rate uncertainties influence the production of 26Al. Particularly important reactions are 26Al(n,p)26Mg, 25Mg( Delta *a,n)28Si, 24Mg(n, Delta *g)25Mg, and 23Na( Delta *a,p)26Mg. These reactions should be prime targets for future measurements. Overall, we estimate that the nuclear physics uncertainty of the 26Al yield predicted by the massive star models explored here amounts to about a factor of three. We also find that taking the equilibration of 26Al levels explicitly into account in any of the massive star sites investigated here has only minor effects on the predicted 26Al yields. Furthermore, we provide for the interested reader detailed comments regarding the current status of certain reactions, including 12C(12C,n)23Mg, 23Na( Delta *a,p)26Mg, 25Mg( Delta *a,n)28Si, 26Al m (p, Delta *g)27Si, 26Al(n,p)26Mg, and 26Al(n, Delta *a)23Na.
We present the evolution and the explosion of two massive stars, 15 and 25 M\(_{\odot}\), spanning a wide range of initial rotation velocities (from 0 to 800 km/s) and three initial metallicities: ...Z=0 (Fe/H=\(-\infty\)), \(3.236\times10^{-7}\) (Fe/H=-5), and \(3.236\times10^{-6}\) (Fe/H=-4). A very large nuclear network of 524 nuclear species extending up to Bi has been adopted. Our main findings may be summarized as follows: a) rotating models above Z=0 are able to produce nuclei up to the neutron closure shell at N=50, and in a few cases up to N=82; b) rotation drastically inhibits the penetration of the He convective shell in the H rich mantle, phenomenon often found in zero metallicity non rotating massive stars; c) vice versa rotation favors the penetration of the O convective shell in the C rich layers with the consequence of altering significantly the yields of the products of the C, Ne, and O burning; d) none of the models that reach the critical velocity while in H burning, loses more the 1 M\(_{\odot}\) in this phase; e) conversely, almost all models able to reach their Hayashi track exceed the Eddington luminosity and lose dynamically almost all their H rich mantle. These models suggest that rotating massive stars may have contributed significantly to the synthesis of the heavy nuclei in the first phase of enrichment of the interstellar medium, i.e., at early times.
We present an extension of the set of models published in Limongi & Chieffi, 2018, ApJS, 237, 13, at metallicity two times solar, i.e. Fe/H=0.3. The key physical properties of these models at the ...onset of the core collapse are mainly due to the higher mass loss triggered by the higher metallicity: the super solar metallicity (SSM) models reach the core collapse with smaller He- and CO-core masses, while the amount of 12C left by the central He burning is higher. These results are valid for all the rotation velocities. The yields of the neutron capture nuclei expressed per unit mass of Oxygen (i.e. the X/O) are higher in the SSM models than in the SM ones in the non rotating case while the opposite occurs in the rotating models. The trend shown by the non rotating models is the expected one, given the secondary nature of the n-capture nucleosynthesis. Vice versa, the counter intuitive trend obtained in the rotating models is the consequence of the higher mass loss present in the SSM models that removes the H rich envelope faster than in the SM ones while the stars are still in central He burning, dumping out the entanglement (activated by the rotation instabilities) and therefore a conspicuous primary n-capture nucleosynthesis.
We present a new and homogeneous set of explosive yields for masses 13, 15, 20, 25, 30, and 35 M sub(o) and metallicities Z = 0, 10 super(-6), 10 super(-4), 10 super(-3), 6 x 10 super(-3), and 2 x 10 ...super(-2). A wide network extending up to Mo has been used in all computations. We show that at low metallicities (Z < 10 super(- 4)), the final yields do not depend significantly on the initial chemical composition of the models, so a scaled solar distribution may be safely assumed at all metallicities. Moreover, no elements above Zn are produced by any mass in the grid up to a metallicity approx10 super(-3). These yields are available for any choice of the mass cut on request.
We present the last version of {\scshape{Hyperion}} (HYdrodynamic Ppm Explosion with Radiation diffusION), a hydrodynamic code designed to calculate the explosive nucleosynthesis, remnant mass and ...light curve associated to the explosion of a massive star. By means of this code we compute the explosion of a subset of red supergiant models, taken from the database published by \cite{lc18}, for various explosion energies in the range \(\rm \sim 0.20-2.00~10^{51}~erg\). The main outcomes of these simulations, i.e., remnant mass, \(\rm ^{56}Ni\) synthesized, luminosity and length of the plateau of the bolometric light curve, are analyzed as a function of the initial parameters of the star (mass and metallicity) and of the explosion energy. As a first application of {\scshape{Hyperion}} we estimated the mass and the metallicity of the progenitor star of SN 1999em, a well studied SN IIP, by means of the light curve fitting. In particular, if the adopted distance to the host galaxy NGC 1637 is \(\rm 7.83~Mpc\), the properties of the light curve point toward a progenitor with an initial mass of \(\rm 13~M_\odot\) and a metallicity Fe/H=-1. If, on the contrary, the adopted distance modulus is \(\rm 11.7~Mpc\), all the models with initial mass \(13\leq M/M_\odot\leq 15\) and metallicities \(\rm -1\leq Fe/H \leq 0\) are compatible with the progenitor of SN 1999em.
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