Origin of doublet-burst behavior

Determine whether the short-recurrence-time doublet bursts observed in neutron-star low-mass X-ray binaries share a common physical origin with double-peaked bursts or constitute a separate class of phenomena.

Background

The paper reports a rare doublet thermonuclear burst from the neutron-star low-mass X-ray binary 4U 1323-619, with approximately 20 minutes separating the primary and secondary peaks. Such short recurrence times challenge standard ignition models because insufficient fresh fuel should have accumulated between the two events.

The authors note that the secondary burst may result from residual fuel left unburned during the primary burst and subsequently transported to deeper layers. However, they explicitly leave unresolved whether this mechanism is related to the origin of double-peaked bursts or whether doublet bursts represent a distinct phenomenological class.