Afterglow constraints on the viewing angle of binary neutron star mergers and determination of the Hubble constant

Understand

One of the key properties of any binary is its viewing angle (i.e., inclination), $\theta_{\rm obs}$.

• In binary neutron star (BNS) mergers it is of special importance due to the role that it plays in the measurement of the Hubble constant, $H_0$.
• The opening angle of the jet that these mergers launch, $\theta_j$, is also of special interest.
• Following the detection of the first BNS merger, GW170817, there were numerous attempts to estimate these angles using the afterglow light curve, finding a wide range of values.