# Imprints of neutrino-pair flavor conversions on nucleosynthesis in ejecta from neutron-star merger remnants

**Authors:** Meng-Ru Wu, Irene Tamborra, Oliver Just, Hans-Thomas Janka  
**arXiv:** [1711.00477](https://arxiv.org/abs/1711.00477)  
**Date:** 2017-11-01  
**Summary page:** https://www.summarizepaper.com/en/paper/1711.00477v1/

## Key points

- Wu et al. study the impact of neutrino-pair flavor conversions on nucleosynthesis in neutron-star merger remnants
- Analysis based on data from a hydrodynamical simulation of a binary neutron star merger remnant with specific characteristics
- Initial observation: local number density of electron antineutrinos surpasses that of electron neutrinos above the remnant
- Shift in neutrino distribution as accretion torus approaches equilibrium, leading to abundance exceeding antineutrinos in a funnel-shaped area around the polar region
- Reduction in region for fast pairwise flavor conversions over time due to this change
- Rapid flavor conversions significantly influence most ejecta driven by neutrinos
- Notable enhancement in nuclei with mass numbers greater than 130 assumed after fast flavor conversions result in equilibration
- Substantial alteration observed in lanthanide mass fraction by more than a thousandfold
- Implications suggest crucial role of neutrino flavor oscillations in predicting kilonova (macronova) light curves and warrant further investigation

## Summary

In their study, Wu et al. explore the impact of neutrino-pair flavor conversions on nucleosynthesis in the ejecta from remnants of neutron-star mergers. They base their analysis on data from a hydrodynamical simulation of a binary neutron star merger remnant containing a central black hole with a mass of $3\ M_\odot$, a dimensionless spin parameter of 0.8, and an accretion torus weighing 0.3$M_\odot$. Initially, they observe that the local number density of electron antineutrinos ($\bar{\nu}_e$) surpasses that of electron neutrinos ($\nu_e$) across the entire region above the remnant. As the accretion torus approaches self-regulated equilibrium, there is a shift in the distribution of neutrinos. Their abundance exceeds that of antineutrinos specifically in a funnel-shaped area around the polar region. This change leads to a reduction in the region where fast pairwise flavor conversions can take place as time progresses. Nevertheless, Wu et al. find that these rapid flavor conversions significantly influence most of the ejecta driven by neutrinos. Assuming that fast flavor conversions ultimately result in flavor equilibration, the researchers identify a notable enhancement in nuclei with mass numbers greater than 130. Additionally, they observe a substantial alteration in the lanthanide mass fraction by more than a thousandfold. These findings suggest that neutrino flavor oscillations may play a crucial role in predicting kilonova (macronova) light curves and warrant further investigation in this direction. The study conducted by Wu and colleagues sheds light on how neutrino-pair flavor conversions can impact nucleosynthesis processes within remnants of neutron-star mergers, providing valuable insights into understanding these astrophysical phenomena more comprehensively.