Multimessenger detections of binary neutron star mergers and their inclination angle distributions. (arXiv:1905.00314v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Saleem_M/0/1/0/all/0/1">M. Saleem</a>
For binary neutron star (BNS) mergers detectable from the nearby Universe,
the distribution of orbital inclination angles ($iota$), as measured from
gravitational wave (GW) observations follows Schutz distribution
citep{Schutz2011}. If the BNSs produce short GRBs which are independently
detected, they can trigger BNS detections and then the resulting inclination
angle distribution would also depend on the jet structure of the SGRBs and
hence deviate from the Schutz distribution. We demonstrate this by obtaining
the inclination angle distribution by assuming all the BNS mergers to have SGRB
counterparts with structured jets of Gaussian-like profiles, with the half
opening angle of the jet core $theta_c=5^circ$ and the total $gamma-$ray
energy in the rest frame $E_{gamma}=10^{50}$ erg, consistent with what was
inferred for GRB170817A. With the new distribution, we find that the detection
probability of low inclination angle events significantly increases depending
on the GW network configuration/sensitivity. Assuming a 50% duty cycle for GW
detectors and a 60% sky coverage for Fermi GBM, we find that almost 52% of
the total BNS detections in O3 with LHV network will have coincident prompt
$gamma$-ray detections. With the five-detector network LHVKI with designed
sensitivity and with Aplus sensitivity, the total BNS detections increases,
however, the coincident detection fraction decreases as 28% and as 19%.
For binary neutron star (BNS) mergers detectable from the nearby Universe,
the distribution of orbital inclination angles ($iota$), as measured from
gravitational wave (GW) observations follows Schutz distribution
citep{Schutz2011}. If the BNSs produce short GRBs which are independently
detected, they can trigger BNS detections and then the resulting inclination
angle distribution would also depend on the jet structure of the SGRBs and
hence deviate from the Schutz distribution. We demonstrate this by obtaining
the inclination angle distribution by assuming all the BNS mergers to have SGRB
counterparts with structured jets of Gaussian-like profiles, with the half
opening angle of the jet core $theta_c=5^circ$ and the total $gamma-$ray
energy in the rest frame $E_{gamma}=10^{50}$ erg, consistent with what was
inferred for GRB170817A. With the new distribution, we find that the detection
probability of low inclination angle events significantly increases depending
on the GW network configuration/sensitivity. Assuming a 50% duty cycle for GW
detectors and a 60% sky coverage for Fermi GBM, we find that almost 52% of
the total BNS detections in O3 with LHV network will have coincident prompt
$gamma$-ray detections. With the five-detector network LHVKI with designed
sensitivity and with Aplus sensitivity, the total BNS detections increases,
however, the coincident detection fraction decreases as 28% and as 19%.
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