Production of p Nuclei from r -Process Seeds: The νr Process

We present a nucleosynthesis process that may take place on neutron-rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>r</a:mi></a:math> process, a sequence of neutron captures and beta decays with, however, charged-current neutrino absorption reactions on nuclei operating much faster than beta decays. Once neutron-capture reactions freeze out the produced <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>r</c:mi></c:math> process, neutron-rich nuclei undergo a fast conversion of neutrons into protons and are pushed even beyond the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>β</e:mi></e:math> stability line, producing the neutron-deficient <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>p</g:mi></g:math> nuclei. This scenario, which we denote as the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>ν</i:mi><i:mi>r</i:mi></i:math> process, provides an alternative channel for the production of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>p</k:mi></k:math> nuclei and the short-lived nucleus <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:mmultiscripts><m:mrow><m:mi>Nb</m:mi></m:mrow><m:mprescripts/><m:none/><m:mrow><m:mn>92</m:mn></m:mrow></m:mmultiscripts></m:mrow></m:math>. We discuss the necessary conditions posed on the astrophysical site for the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>ν</o:mi><o:mi>r</o:mi></o:math> process to be realized in nature. While these conditions are not fulfilled by current neutrino-hydrodynamic models of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mi>r</q:mi></q:math>-process sites, future models, including more complex physics and a larger variety of outflow conditions, may achieve the necessary conditions in some regions of the ejecta. Published by the American Physical Society 2024