In this work we investigate the thermodynamics conditions at which neutrinos decouple from matter in neutron star merger remnants by post-processing results of merger simulations. We find that the matter density and the neutrino energies are the most relevant quantities in determining the decoupling surface location. For mean energy neutrinos (∼ 9, 15 and 24 MeV for νe, ν¯ e and νμ,τ, respectively) the transition between diffusion and free-streaming conditions occurs around 1011gcm-3 for all neutrino species. Weak and thermal equilibrium freeze-out occurs deeper (several 1012gcm-3) for heavy-flavor neutrinos than for ν¯ e and νe (≳1011gcm-3). Decoupling temperatures are broadly in agreement with the average neutrino energies, with softer equations of state characterized by ∼ 1 MeV larger decoupling temperatures. Neutrinos streaming at infinity with different energies come from different remnant parts. While low-energy neutrinos (∼3MeV) decouple at ρ∼1013gcm-3, T∼10MeV and Ye≲ 0.1 close to weak equilibrium, high-energy ones (∼50MeV) decouple from the disk at ρ∼109gcm-3, T∼2MeV and Ye≳ 0.25. The presence of a massive NS or a BH influences the neutrino thermalization. While in the former case decoupling surfaces are present for all relevant energies, the lower maximum density (≲1012gcm-3) in BH-torus systems does not allow softer neutrinos to thermalize and diffuse.

Thermodynamics conditions of matter in the neutrino decoupling region during neutron star mergers / Endrizzi, A.; Perego, A.; Fabbri, F. M.; Branca, L.; Radice, D.; Bernuzzi, S.; Giacomazzo, B.; Pederiva, F.; Lovato, A.. - In: THE EUROPEAN PHYSICAL JOURNAL. A, HADRONS AND NUCLEI. - ISSN 1434-6001. - 56:1(2020), pp. 15.1-15.21. [10.1140/epja/s10050-019-00018-6]

Thermodynamics conditions of matter in the neutrino decoupling region during neutron star mergers

Perego A.;Giacomazzo B.;Pederiva F.;
2020-01-01

Abstract

In this work we investigate the thermodynamics conditions at which neutrinos decouple from matter in neutron star merger remnants by post-processing results of merger simulations. We find that the matter density and the neutrino energies are the most relevant quantities in determining the decoupling surface location. For mean energy neutrinos (∼ 9, 15 and 24 MeV for νe, ν¯ e and νμ,τ, respectively) the transition between diffusion and free-streaming conditions occurs around 1011gcm-3 for all neutrino species. Weak and thermal equilibrium freeze-out occurs deeper (several 1012gcm-3) for heavy-flavor neutrinos than for ν¯ e and νe (≳1011gcm-3). Decoupling temperatures are broadly in agreement with the average neutrino energies, with softer equations of state characterized by ∼ 1 MeV larger decoupling temperatures. Neutrinos streaming at infinity with different energies come from different remnant parts. While low-energy neutrinos (∼3MeV) decouple at ρ∼1013gcm-3, T∼10MeV and Ye≲ 0.1 close to weak equilibrium, high-energy ones (∼50MeV) decouple from the disk at ρ∼109gcm-3, T∼2MeV and Ye≳ 0.25. The presence of a massive NS or a BH influences the neutrino thermalization. While in the former case decoupling surfaces are present for all relevant energies, the lower maximum density (≲1012gcm-3) in BH-torus systems does not allow softer neutrinos to thermalize and diffuse.
2020
1
Endrizzi, A.; Perego, A.; Fabbri, F. M.; Branca, L.; Radice, D.; Bernuzzi, S.; Giacomazzo, B.; Pederiva, F.; Lovato, A.
Thermodynamics conditions of matter in the neutrino decoupling region during neutron star mergers / Endrizzi, A.; Perego, A.; Fabbri, F. M.; Branca, L.; Radice, D.; Bernuzzi, S.; Giacomazzo, B.; Pederiva, F.; Lovato, A.. - In: THE EUROPEAN PHYSICAL JOURNAL. A, HADRONS AND NUCLEI. - ISSN 1434-6001. - 56:1(2020), pp. 15.1-15.21. [10.1140/epja/s10050-019-00018-6]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/255913
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