par Metzger, Brian D.;Bauswein, Andreas;Goriely, Stéphane 
;Kasen, Daniel
Référence Monthly notices of the Royal Astronomical Society, 446, page (1115)
Publication Publié, 2014-11-19
;Kasen, DanielRéférence Monthly notices of the Royal Astronomical Society, 446, page (1115)
Publication Publié, 2014-11-19
Article révisé par les pairs
| Résumé : | The merger of binary neutron stars (NSs) ejects a small quantity of neutron-rich matter, the radioactive decay of which powers a day to week long thermal transient known as a kilonova. Most of the ejecta remains sufficiently dense during its expansion that all neutrons are captured into nuclei during the r-process. However, recent general relativistic merger simulations by Bauswein and collaborators show that a small fraction of the ejected mass (a few per cent, or ~10-4 M⊙) expands sufficiently rapidly for most neutrons to avoid capture. This matter originates from the shocked-heated interface between the merging NSs. Here, we show that the β-decay of these free neutrons in the outermost ejecta powers a 'precursor' to the main kilonova emission, which peaks on a time-scale of ~ few hours following merger at U-band magnitude ~22 (for an assumed distance of 200 Mpc). The high luminosity and blue colours of the neutron precursor render it a potentially important counterpart to the gravitational wave source, that may encode valuable information on the properties of the merging binary (e.g. NS-NS versus NS-black hole) and the NS equation of state. Future work is necessary to assess the robustness of the fast-moving ejecta and the survival of free neutrons in the face of neutrino absorptions, although the precursor properties are robust to a moderate amount of leptonization. Our results provide additional motivation for short latency gravitational wave triggers and rapid follow-up searches with sensitive ground-based telescopes. |
