2023ApJ...951....3S

Magnetars are believed to be neutron stars (NSs) with strong magnetic fields. X-ray flares and fast radio bursts (FRBs) have been observed from the magnetar (soft gamma-ray repeater, SGR J1935+2154). We propose that the phase transition of the NS can power the FRBs and SGRs. Based on the equation of state provided by the MIT bag model and the mean field approximation, we solve the Tolman-Oppenheimer-Volkoff equations to get the NS structure. With the spin-down of the NS, the hadronic shell gradually transfers to the quark shell. The gravitational potential energy released by one time of the phase transition can be achieved. The released energy, time interval between two successive phase transitions, and glitch are all consistent with the observations of the FRBs and the X-ray flares from SGR J1935 + 2154. We conclude that the phase transition of an NS is a plausible mechanism to power the SGRs as well as the repeating FRBs.