Prospects of calibrating afterglow modeling of short GRBs with gravitational wave inclination angle measurements and resolving the Hubble tension with a GW-GRB association event

Abstract

In the past decades, an external forward shock model has been successfully developed to explain the main features of the afterglow emission of gamma-ray bursts (GRBs). In the numerical modeling of the GRB afterglow, some approximations have been made for simplicity, and different groups developed their codes. A robust test of these models/approaches is challenging because of the lack of directly measured physical parameters. Fortunately, the viewing angle inferred from the afterglow modeling is widely anticipated to be the same as the inclination angle of the binary neutron star (BNS) mergers that can be evaluated with the gravitational wave (GW) data. Therefore, in the future, it is possible to calibrate the afterglow modeling with the GW inclination angle measurements. We take three methods, including both analytical estimations and direct simulations, to project the uncertainties of the inclination angle measurements. For some BNS mergers accompanied with electromagnetic counterparts detected in the O4/O5 runs of LIGO/Virgo/KAGRA/LIGO-India detectors, we show that the inclination angle can be determined within an uncertainty of $\ensuremath{\le}0.1\text{ }\text{ }\mathrm{rad}$, supposing that the Hubble constant is known with an accuracy of $\ensuremath{\le}3%$ and the uncertainty of Hubble flow velocity is within $\ensuremath{\sim}1%$. The off-axis GRB outflow will give rise to afterglow emission, and the most energetic ones may be detectable at the distance of $\ensuremath{\sim}100--200\text{ }\text{ }\mathrm{Mpc}$ even for a viewing angle of $\ensuremath{\ge}0.3\text{ }\text{ }\mathrm{rad}$. Such events can thus serve as a robust test of the afterglow modeling approach. We have also evaluated the prospect of resolving the so-called Hubble tension with a single GW/GRB association event. We find out that a $\ensuremath{\sim}3%$ precision Hubble constant is obtainable if the uncertainty of the viewing angle can be constrained to be within $\ensuremath{\sim}0.1\text{ }\text{ }\mathrm{rad}$, which is expected to be the case for some nearby ($\ensuremath{\le}250\text{ }\text{ }\mathrm{Mpc}$) bright/on-axis GRBs with a well-behaved afterglow light curve displaying a clear achromatic break at early times.