The study of thermonuclear X-ray bursts in accreting millisecond pulsar MAXI J1816-195 with NuSTAR and NICER

Abstract

The millisecond pulsar MAXI J1816-195 was recently discovered in an outburst by MAXI in 2022 May. We study different properties of the pulsar using data from NuSTAR and NICER observations. The unstable burning of accreted material on the surface of neutron stars induces thermonuclear (Type-I) bursts. Several such thermonuclear bursts have been detected by MAXI J1816-195 during its outburst. We investigate the evolution of the burst profile with flux and energy using NuSTAR and NICER observations. During the NuSTAR observation, a total of four bursts were detected from the source. The duration of each burst is around $\sim$ 30 s and the ratio of peak to persistent count rate is $\sim$ 26 as seen from the NuSTAR data. The burst profiles are modelled using a sharp linear rise and exponential decay function to determine the burst timing parameters. The burst profiles show a relatively long tail at lower energies. The broadband time-resolved spectra during the burst periods are successfully modelled with a combination of an absorbed blackbody along with a non-thermal component to account for the persistent emission. From our modelling results, we are able to estimate the maximum apparent emitting area of the blackbody of the neutron star to be $\sim$12.5 km during the peak of the outburst and the maximum distance to the object to be 8.7 kpc. Our findings for the mass accretion rate and the alpha factor indicate the stable burning of hydrogen via a hot CNO cycle during the bursts.

Accepted for publication in MNRAS

References in corpus (11)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• A catalogue of low-mass X-ray binaries in the Galaxy, LMC, and SMC (Fourth edition)
• An Empirical Background Model for the NICER X-ray Timing Instrument
• X-ray binaries
• The discovery of the 528.6 Hz accreting millisecond X-ray pulsar MAXI J1816-195
• Accretion rate and the occurrence of multi-peaked X-ray bursts
• The study of multi-peaked type-I X-ray bursts in the neutron-star low mass X-ray binary 4U 1636$-$536 with RXTE
• Thermonuclear X-ray bursts detected in Cyg X-2 using AstroSat/LAXPC
• Modelling Thermonuclear X-ray Bursts on Accreting Neutron Stars
• The prolific thermonuclear X-ray bursts from the outburst of the newly discovered millisecond pulsar MAXI~J1816--195 observed by Insight-HXMT and NICER
• Photospheric Radius Expansion and a double-peaked type-I X-ray burst from GRS 1741.9-2853

Cited by in corpus (3)

• Broadband X-ray timing and spectral characteristics of the accretion-powered millisecond X-ray pulsar MAXI J1816$-$195
• Detection of a strong ~2.5 Hz modulation in the Newly Discovered Millisecond Pulsar MAXI J1816-195
• Connecting the m-dots: accretion rates and thermonuclear burst recurrence times on neutron stars and white dwarfs