Late-time Kilonova Light Curves and Implications to GW170817
Abstract
We discuss the late-time (tens of days) emission from the radioactive ejecta of mergers involving neutron stars, when the ionization energy loss time of beta-decay electrons and positrons exceeds the expansion time. We show that if the e± are confined to the plasma (by magnetic fields), then the time dependence of the plasma heating rate, {\dot{\varepsilon }}d, and hence of the bolometric luminosity L={\dot{\varepsilon }}d, are given by d{log}L/d{log}t≃ -2.8, nearly independent of the composition and of the instantaneous radioactive energy release rate, \dot{\varepsilon }. This universality of the late-time behavior is due to the weak dependence of the ionization loss rate on composition and on e± energy. The late-time IR and optical measurements of GW170817 are consistent with this expected behavior provided that the ionization loss time exceeds the expansion time at t > t ɛ ≈ 7 days, as predicted based on the early (few day) electromagnetic emission.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2019
- DOI:
- 10.3847/1538-4357/ab1f71
- arXiv:
- arXiv:1902.01197
- Bibcode:
- 2019ApJ...878...93W
- Keywords:
-
- gravitational waves;
- nuclear reactions;
- nucleosynthesis;
- abundances;
- stars: neutron;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Improved treatment of synchrotron subtraction