Type-I X-ray burst evolution of the new millisecond pulsar MAXI J1816–195 revealed by Insight-HXMT

Abstract

We report a study of the type-I X-ray bursts and persistent spectrum of the 2022 outburst of the newly discovered accreting millisecond pulsar MAXI J1816–195 observed by Insight-HXMT. The spectra of MAXI J1816–195 are similar to other accreting millisecond pulsars, i.e., a Comptonization shape with an electron temperature of ∼10 keV. We find that the profiles of type-I X-ray bursts, as well as their spectra, evolve during the outburst. The evolutionary pattern becomes varied towards the end phase of outburst, suggesting a potential correlation with alterations in the burst fuel or the ignition region. Moreover, we find a giant burst, for the first time, with a peak luminosity twice than others and a shorter burst duration. The complete burst sample derived from this research provides more clues in probing the thermonuclear bursts during the outburst of the accreting millisecond pulsar system.