Theoretical exploration of S-factors for nuclear reactions of astrophysical importance

Singh, Vinay; Lahiri, Joydev; Basu, Debabrata

doi:10.1016/j.nuclphysa.2019.05.005

Cited by 5 publications

(5 citation statements)

References 31 publications

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“…At P ≈ 1.0 × 10 30 dyn cm −2 , 34 Ne captures neutrons to become 38 Ne, whose typical pycnonuclear fusion time, τpyc, is approximately ten times shorter than for 34 Ne due to a larger nucleus size, which reduces the Coulomb barrier and simplifies tunneling. This is clearly seen in the astrophysical factors, differing by several orders of magnitude for various isotopes (see, e.g., Beard et al 2010;Afanasjev et al 2012;Singh et al 2019). Within our simplified reaction network all 34 Ne nuclei are converted into 38 Ne in one and the same crustal layer, where µn reaches the threshold for this reaction.…”

Section: Composition Profiles For Accreted Inner Crustmentioning

confidence: 84%

Accreting neutron stars: heating of the upper layers of the inner crust

Shchechilin

Gusakov

Chugunov

2022

Monthly Notices of the Royal Astronomical Society: Letters

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Neutron stars in low-mass X-ray binaries are thought to be heated up by accretion-induced exothermic nuclear reactions in the crust. The energy release and the location of the heating sources are important ingredients of the thermal evolution models. Here we present thermodynamically consistent calculations of the energy release in three zones of the stellar crust: at the outer-inner crust interface, in the upper layers of the inner crust (up to the density ρ ≤ 2 × 1012 g cm−3), and in the underlying crustal layers. We consider three representative models of thermonuclear ashes (Superburst, Extreme rp, and Kepler ashes). The energy release in each zone is parameterized by the pressure at the outer-inner crust interface, Poi, which encodes all uncertainties related to the physics of the deepest inner-crust layers. Our calculations allow us to set new theoretical lower limits on the net energy release (per accreted baryon): Q ≳ 0.28 MeV for Extreme rp ashes and Q ≳ 0.43 − 0.51 MeV for Superburst and Kepler ashes. Our results can be directly incorporated into numerical codes and provide an opportunity to constrain Poi by comparing thermal evolution models of accreting neutron stars with observations.

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Section: Composition Profiles For Accreted Inner Crustmentioning

confidence: 84%

Accreting neutron stars: heating of the upper layers of the inner crust

Shchechilin

Gusakov

Chugunov

2022

Monthly Notices of the Royal Astronomical Society: Letters

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“…У тій роботі було знайдено феноменологічні вирази для швидкості реакцій, що містять кілька підгоночних параметрів, які є ефективними для швидких обчислень. У [7] астрофізичні S-фактори було розраховано для 946 реакцій злиття, які включають стабільні та нейтрон-надлишкові ізотопи вуглецю, кисню, неону та магнію для енергій центра мас, що знаходяться у межах від 2 до ~ 18 -30 МеВ [8]. Великий масив астрофізичних S-факторів та їхній компактний вигляд було представлено у [9] для ізотопів берилію, бора, вуглецю, азоту, кисню, фтору, неону, натрію, магнію та кремнію (було створено масив даних S-факторів для близько 5000 нерезонансних реакцій злиття).…”

Section: вступunclassified

“…У роботі [14] було розпочато дослідження питань, вказаних вище, на прикладі реакції 12 C + 12 C. Така реакція часто використовується при аналізі властивостей та еволюції білих карликів. Іншою реакцією, що також часто використовується у таких дослідженнях, є 16 O + 16 O [8]. Тому у даній роботі ми продовжуємо такі дослідження, де в якості реакції обрали 16 O + 16 O.…”

unclassified

“…У розділі 2 представлене нове удосконалення формалізму багаторазових внутрішніх відбиттів (БВВ) з орієнтиром на опис пiкноядерних реакцій. У розділах 3 і 4 проаналізовано квантові властивості реакцій 16 O + 16 O [8], виконано розрахунки проникностей бар'єрів, перевірки оцінки ймовірностей утворення складеного ядра, енергій та інших квантових характеристик квазізв'язаних станів, швидкостей реакцій тощо. Висновки підсумовано у розділі 5.…”

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Quantum design in the study of pycnonuclear reactions in compact stars and new quasibound states

A.¹,

Maydanyuk²

2023

Nucl. Phys. At. Energy

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Quantum effects in pycnonuclear reactions in compact stars at zero temperatures are studied with high precision. The reaction 16O + 16O was analyzed using the method of multiple internal reflections. The study of such reactions requires full consideration of quantum fluxes in the internal nuclear region. This reduces the rate and number of pycnonuclear reactions up to 1.8 times. This leads to the appearance of new states (which we call quasibound states) where the compound nuclear system is formed with maximal probability. As shown, the minimal energy of such a state is slightly higher than the energy of zero-mode oscillations in the lattice nodes in the pycnonuclear reaction, however, the probability of the formation of a compound system in a quasibound state is significantly greater than the corresponding probability in a state of zero-mode oscillations. It is reasonable to say that the frequency of reactions in quasi-bound states is more likely than in states of zero-mode oscillations. This can lead to significant changes in estimates of reaction rates in stars.

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“…[8] the astrophysical S-factors were estimated for 946 fusion reactions involving stable and neutron-rich isotopes of C, O, Ne, and Mg for center-of-mass energies varying from 2 to ≈ 18-30 MeV (see also Ref. [9]). Large collection of astrophysical S factors and their compact representation was presented in Ref.…”

Section: Introductionmentioning

confidence: 99%

Quantum design in study of pycnonuclear reactions in compact stars and new quasibound states

Maydanyuk¹,

A.²

2022

Preprint

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Pycnonuclear reactions in the compact stars at zero temperatures are studied on quantum mechanical basis in the paper. Formalism of multiple internal reflections is generalized for analysis, that was developed for nuclear decays and captures by nuclei with high precision and tests. For the chosen reaction 12 C + 12 C = 24 Mg we find the following. A quantum study of the pycnonuclear reaction requires a complete analysis of quantum fluxes in the internal nuclear region. This reduces rate and number of pycnonuclear reactions by 1.8 times. This leads to the appearance of new states (called as quasibound states) where the compound nuclear system is formed with maximal probability. As shown, minimal energy of such a state is a little higher than energy of zero-point vibrations in lattice sites in pycnonuclear reaction, however probability of formation of compound system at the quasibound state is essentially larger than the corresponding probability at state of zero-point vibrations. Hence, there is a sense to tell about reaction rates in such quasibound states as more probable, rather than states of zero-point vibrations. This can lead to the essential changes in estimation of the rates of nuclear reactions in stars.

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Theoretical exploration of S-factors for nuclear reactions of astrophysical importance

Cited by 5 publications

References 31 publications

Accreting neutron stars: heating of the upper layers of the inner crust

Accreting neutron stars: heating of the upper layers of the inner crust

Quantum design in the study of pycnonuclear reactions in compact stars and new quasibound states

Quantum design in study of pycnonuclear reactions in compact stars and new quasibound states

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