Fallback Accretion onto a Newborn Magnetar: short GRBs with Extended Emission

Understand

There are a subset of short gamma-ray bursts (SGRBs) which exhibit a rebrightening in their high-energy light curves known as extended emission.

• These bursts have the potential to discern between various models proposed to describe SGRBs as any model needs to account for extended emission.
• In this paper, we combine fallback accretion into the magnetar propeller model and investigate the morphological changes fallback accretion has on model light curves and fit to the afterglows of 15 SGRBs exhibiting extended emission from the Swift archive.
• We have parameterised the fallback in terms of existing parameters within the propeller model and solved for the disc mass and angular frequency of the magnetar over time.