The impact of electroncapture supernovae on merging double neutron stars
Abstract
Natal kicks are one of the most debated issues about double neutron star (DNS) formation. Several observational and theoretical results suggest that some DNSs have formed with low natal kicks (≲ 50 km s^{1}), which might be attributed to electroncapture supernovae (ECSNe). We investigate the impact of ECSNe on the formation of DNSs by means of population synthesis simulations. In particular, we assume a Maxwellian velocity distribution for the natal kick induced by ECSNe with onedimensional root mean square σ_{ECSN} = 0, 7, 15, 26, 265 km s^{1}. The total number of DNSs scales inversely with σ_{ECSN} and the number of DNS mergers is higher for relatively low kicks. This effect is particularly strong if we assume low efficiency of commonenvelope ejection (described by the parameter α = 1), while it is only mild for high efficiency of commonenvelope ejection (α = 5). In most simulations, more than 50 per cent of the progenitors of merging DNSs undergo at least one ECSN and the ECSN is almost always the first SN occurring in the binary system. Finally, we have considered the extreme case in which all neutron stars receive a low natal kick (≲ 50 km s^{1}). In this case, the number of DNSs increases by a factor of 10 and the percentage of merging DNSs that went through an ECSN is significantly suppressed (<40 per cent).
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2019
 DOI:
 10.1093/mnras/sty2848
 arXiv:
 arXiv:1805.11100
 Bibcode:
 2019MNRAS.482.2234G
 Keywords:

 gravitational waves;
 methods: numerical;
 binaries: general;
 stars: neutron;
 Astrophysics  Solar and Stellar Astrophysics;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 11 pages, 7 figures, 1 tables, to appear in MNRAS