Gamma-Ray Burst in a Binary System

Regardless of their different types progenitors and central engines, gamma-ray bursts (GRBs) were always assumed to be standalone systems after they formed. Little attention has been paid the possibility that a stellar companion can still accompany GRB itself. This paper investigates such GRB-involved binary system studies effects on observed emission when it is located inside jet opening angle. Assuming typical radius $\sim10^{15}\,$cm, we show blockage by star with $R_\mathrm{c}\sim67\,\mathrm{R_\odot}$ becomes non-negligible within angle (e.g., $\sim10$ degrees) beyond site. In case, an on-axis observer will see similar temporal behavior but 25% dimmer. On other hand, off-axis outside (hence missed original GRB) delayed "reflected" GRB, which much fainter in brightness, wider profile slightly softer energy. Our study naturally explain origin some low-luminosity GRBs. Moreover, also point out may shocked if site, give rise X-ray transient or followed bump top afterglows.