Evidence for gravitational-wave dominated emission in the central engine of short GRB 200219A

Understand

GRB 200219A is a short gamma-ray burst (GRB) with an extended emission (EE) lasting $\sim 90$s.

• By analyzing data observed with the {\em Swift}/BAT and {\em Fermi}/GBM, we find that a cutoff power-law model can adequately fit the spectra of the initial short pulse with $\rm E_{p}=1387^{+232}_{-134}$ keV.
• More interestingly, together with the EE component and early X-ray data, it exhibits plateau emission smoothly connected with a $\sim t^{-1}$ segment and followed by an extremely steep decay.
• The short GRB composed of those three segments is unique in the {\em Swift} era and is very difficult to explain with the standard internal/external shock model of a black hole central engine, but could be consistent with the prediction of a magnetar central engine from the merger of an NS binary.