Forward Modeling of Double Neutron Stars: Insights from Highly Offset Short Gamma-Ray Bursts
Abstract
We present a detailed analysis of two well-localized, highly offset short gamma-ray bursts—GRB 070809 and GRB 090515—investigating the kinematic evolution of their progenitors from compact object formation until merger. Calibrating to observations of their most probable host galaxies, we construct semi-analytic galactic models that account for star formation history and galaxy growth over time. We pair detailed kinematic evolution with compact binary population modeling to infer viable post-supernova velocities and inspiral times. By populating binary tracers according to the star formation history of the host and kinematically evolving their post-supernova trajectories through the time-dependent galactic potential, we find that systems matching the observed offsets of the bursts require post-supernova systemic velocities of hundreds of kilometers per second. Marginalizing over uncertainties in the stellar mass-halo mass relation, we find that the second-born neutron star in the GRB 070809 and GRB 090515 progenitor systems received a natal kick of $\gtrsim 200\,\mathrm{km}\,{{\rm{s}}}^{-1}$ at the $78 \% $ and $91 \% $ credible levels, respectively. Applying our analysis to the full catalog of localized short gamma-ray bursts will provide unique constraints on their progenitors and help unravel the selection effects inherent to observing transients that are highly offset with respect to their hosts.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2020
- DOI:
- 10.3847/1538-4357/abc266
- arXiv:
- arXiv:1910.03598
- Bibcode:
- 2020ApJ...904..190Z
- Keywords:
-
- Gamma-ray bursts;
- Supernova dynamics;
- Neutron stars;
- Compact binary stars;
- Stellar evolution;
- Galaxy evolution;
- 629;
- 1664;
- 1108;
- 283;
- 1599;
- 594;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 18 pages, 7 figures, 1 table. ApJ, in press