  ARGO-YBJ, located at the YangBaJing Cosmic Ray Observatory (4300 m a.s.l.,
Tibet, China), is a full coverage air shower array, with an energy threshold of
300 GeV for gamma-ray astronomy. Most of the recorded events are single front
showers, satisfying the trigger requirement of at least 20 particles detected
in a given time window. However, in 13% of the events, two randomly arriving
showers may be recorded in the same time window, and the second one, in
generally smaller, does not need to satisfy the trigger condition. These events
are called double front shower events. By using these small showers, well under
the trigger threshold, the detector primary energy threshold can be lowered to
a few tens of GeV. In this paper, the angular resolution that can be achieved
with these events is evaluated by a full Monte Carlo simulation. The ARGO-YBJ
sensitivity in detecting gamma-ray bursts (GRBs) by using double front shower
events is also studied for various cutoff energies, time durations, and zenith
angles of GRBs in the field view of ARGO.
