Expanded calculations of proton–neutron quasi-particle random phase approximation (pn-QRPA) electron capture rates on ⁵⁵Co for presupernova and supernova physics

Abstract

Because of its abundance and its relatively high capture rates, 55 Co is one of the key nuclide that can control the dynamics of core collapse of a massive star. Previously we introduced our microscopic calculations of capture rates on 55 Co using the proton-neutron quasi-particle random phase approximation (pn-QRPA) theory. Here, we present for the first time an expanded calculation of the electron capture rates on 55 Co on an extensive temperature-density scale. This type of scale is appropriate for interpolation purposes and of greater utility for simulation codes. PACS Nos.: 26.50.+x, 21.60.Jz, 27.40.+z Résumé : À cause de son abondance et de ses taux de capture relativement élevés, le 55 Co est l'un des noyaux clés susceptibles de contrôler la dynamique de l'effondrement du coeur d'une étoile massive. Nous introduisons d'abord nos calculs microscopiques des taux de captures du 55 Co qui utilisent la théorie RPA à quasi-particule proton-neutron (pn-QRPA). Nous présentons ici pour la première fois un calcul étendu des taux de capture électronique du 55 Co sur une large échelle de température-densité. Ces types d'échelle sont appropriés pour les interpolations et de plus grande utilité pour les programmes de simulation.[Traduit par la Rédaction] ). collapse of the core of massive stars triggering a supernova explosion. The capture of electrons also plays a key role in the neutronization of the core material, and also effects the formation of heavy elements beyond iron (including the so-called cosmochronometers, which provide information about the age of the Galaxy and of the Universe) via the r-process at the final stage of a supernova explosion.The electron capture rates also determine the initial dynamics of the collapse and also, via (1), the size of the collapsing core and in turn the fate of the shock wave. The electron neutrinos, produced as a result of capture reactions, escape and in turn contribute to the cooling of the iron core. This lowers the entropy of the stellar core and consequently favors the collapse of the core. Bethe et al. [2,3] pointed out that stellar collapse is very sensitive to the entropy of the core and lepton-to-baryon ratio. Fuller, Fowler, and Newman (FFN) [4] performed the first-ever extensive calculation of stellar weak rates including the capture rates, neutrino energy loss rates, and decay rates for a wide density and temperature domain. They made these detailed calculations for 226 nuclei in the mass range 21 ≤ A ≤ 60. They also stressed the importance of the Gamow-Teller (GT) giant resonance strength in the capture of the electron and estimated the GT centroids using the zeroth-order (0 ω ) shell model.At the final evolution of the massive star, the electron capture is dominated by Fermi and GT transitions. The treatment of the Fermi transitions, which are important in beta decays, are straightforward while a correct description of GT transitions poses a challenging problem in nuclear structure. Later, Aufderheide et al. [5] extended the FFN work for heavier nuclei with...

Ground and excited states Gamow-Teller strength distributions of iron isotopes and associated capture rates for core-collapse simulations

“…These included the weak interaction rates for nuclei with A = 40 to 44 (not yet calculated by shell model). Since then these calculations were further refined with use of more efficient algorithms, computing power, incorporation of latest data from mass compilations and experimental values, and finetuning of model parameters Rahman 2005, 2007;Nabi et al , 2008, 2008a, 2008bNabi 2009Nabi , 2010aNabi , 2010b. There is a considerable amount of uncertainty involved in all types of calculations of stellar weak interactions.…”

Stellar β±-decay rates of iron isotopes and its implications in astrophysics

“…Nevertheless, the β-decay rates for these isotopes of iron are also argued to be relevant during the presupernova evolution of massive stars in literature. Because of their astrophysical importance 55,56 Fe were included in the list of key β-decay nuclei that have a significant impact on the presupernova evolution of massive stars after core silicon burning for 0.47 ≤ Y e ≤ 0.49 compiled by Aufderheide and collaborators (see Tables 19,20 and 26 of Ref. (5)).…”

Neutrino energy loss rates and positron capture rates onCo55for presupernova and supernova physics

“…Earlier, Nabi and Sajjad [19] The GT strength distribution (GT ± ) from ground state and first two excited states of 55 Co was presented earlier [21]. We calculated the position of our GT − (in this direction a neutron is changed into a proton) centroid around Recently, we presented the extensive calculation of electron capture rates on 55 Co on a fine temperature-density scale where we also discussed our results in detail [23]. Here we would like to present a similar calculation for the positron capture and the associated (anti)neutrino energy loss rates due to weak-interaction mediated reactions in the core of massive stars.…”

“…However there was a need to perform a fine calculation of these important capture rates on a detailed temperature-density grid suitable for collapse simulation codes (see, for example, Ref. [18,23]). …”