Recently, Ph.D. GUO Yunlang, from Nanjing University, and Prof. WANG Bo, from Yunnan Observatories of the Chinese Academy of Sciences, investigated the formation of double neutron star through electron-capture supernovae (EC-SNe) in NS+He star systems. This work was published in Monthly Notices of the Royal Astronomical Society.
Double NS (DNS) systems are important potential gravitational wave sources, which can be formed in NS + He star systems after the He star companions undergo EC-SNe or iron core collapse supernovae. It seems that most DNS systems are produced by small NS kick velocities, indicating that the EC-SN channel may provide an important contribution to the formation of DNS binaries. However, there are still some uncertainties for the origin of EC-SNe, although they play a vital role in the formation of DNS binaries and the NS mass distribution in observations. The researchers explored the formation of the EC-SNe in NS + He star binaries, and the properties of DNSs originating from the EC-SN channel.
The researchers provided the initial parameter spaces for producing EC-SNe in the initial orbital period - initial He star mass (log Piorb - MiHe) diagram, and found that both and minimum for EC-SNe increase with metallicity. Then, by considering NS kicks added to the newborn NS, the researchers investigated the properties of the formed DNS systems after the He star companions collapse into NSs, such as the orbital periods, eccentricities, and spin periods of recycle pulsars (Pspin), etc. The results show that most of the observed DNS systems can be produced by NS kicks of < 50 km/s. In addition, we found that NSs could accrete more material if the residual H envelope on the He star companions is considered, which can form the mildly recycled pulsars (Pspin ～ 20 ms) in DNS systems.
This work provided the initial parameter spaces for producing DNSs through EC-SN channel, and investigated the properties of the formed DNS systems.
Contact:
GUO Yunlang, Nanjing University
yunlang@nju.edu.cn
