A Search for Neutron Star-Black Hole Binary Mergers in the Short Gamma-Ray Burst Population
Abstract
Short gamma-ray bursts (SGRBs) are now known to be the product of the merger of two compact objects. However, two possible formation channels exist: neutron star -- neutron star (NS -- NS) or NS -- black hole (BH). The landmark SGRB 170817A provided evidence for the NS -- NS channel, thanks to analysis of its gravitational wave signal. We investigate the complete population of SGRBs with an associated redshift (39 events), and search for any divisions that may indicate that a NS -- BH formation channel also contributes. Though no conclusive dichotomy is found, we find several lines of evidence that tentatively support the hypothesis that SGRBs with extended emission (EE; 7 events) constitute the missing merger population: they are unique in the large energy band-sensitivity of their durations, and have statistically distinct energies and host galaxy offsets when compared to regular (non-EE) SGRBs. If this is borne out via future gravitational wave detections it will conclusively disprove the magnetar model for SGRBs. Furthermore, we identify the first statistically significant anti-correlation between the offsets of SGRBs from their host galaxies and their prompt emission energies.
Keywords
Cite
@article{arxiv.2001.08706,
title = {A Search for Neutron Star-Black Hole Binary Mergers in the Short Gamma-Ray Burst Population},
author = {B. P. Gompertz and A. J. Levan and N. R. Tanvir},
journal= {arXiv preprint arXiv:2001.08706},
year = {2020}
}
Comments
23 pages, 9 figures, 2 tables. 1 appendix (2 pages, 1 table). Author's final accepted version, to be published in ApJ