| Speaker: | Chris Belczynski (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences) |
|---|---|
| Title: | Binary neutron star formation and the origin of GW170817 |
| Date (JST): | Tue, Jan 15, 2019, 12:00 - 13:00 |
| Place: | Seminar Room A |
| Related File: | 2231.pdf |
| Abstract: |
The first neutron star-neutron star merger (NS-NS: GW170817) was detected in gravitational waves by LIGO/Virgo in a galaxy in which the majority of star formation was taking place a long time ago (~11 Gyr). Based on this single event, LIGO/Virgo estimated that local cosmic NS-NS merger rate is 110-3840 Gpc^-3 yr^-1. Only some extreme evolutionary models can generate NS-NS merger rates in old host galaxies consistent with the LIGO/Virgo estimate. However, we show that these models generate rates exceeding empirical Galactic NS-NS merger rates based on the large population of Milky Way NS-NS binaries. Typically, current evolutionary models produce NS-NS merger rates that are consistent with the Milky Way empirical rates (~10-200 Myr^-1). However, these models generate local (z=0) cosmic NS-NS merger rate in old host galaxies (1-70 Gpc^-3 yr^-1) that are below the LIGO/Virgo estimate. The reason behind this tension is the predicted delay time distribution between star formation and NS-NS mergers that favors short delays. This study highlights the tension between the current evolutionary predictions and the observation of the first NS-NS merger in an old host galaxy. It is crucial to understand that models need to explain not only the LIGO/Virgo rate estimate, but also the merger site. |
