Timing analysis of 2S 1417-624 observed with NICER and Insight-HXMT

Abstract

We present a study of timing properties of the accreting pulsar 2S 1417-624 observed during its 2018 outburst, based on Swift/BAT, Fermi/GBM, Insight-HXMT and NICER observations. We report a dramatic change of the pulse profiles with luminosity. The morphology of the profile in the range 0.2-10.0keV switches from double to triple peaks at $\sim 2.5$ $\times 10^{37}{D}_{10}^2\mathrm{erg}{\mathrm{s}}^{-1}$ and from triple to quadruple peaks at $\sim 7$ $\times 10^{37}{D}_{10}^2\mathrm{erg}{\mathrm{s}}^{-1}$. The profile at high energies (25-100keV) shows significant evolutions as well. We explain this phenomenon according to existing theoretical models. We argue that the first change is related to the transition from the sub to the super-critical accretion regime, while the second to the transition of the accretion disc from the gas-dominated to the radiation pressure-dominated state. Considering the spin-up as well due to the accretion torque, this interpretation allows to estimate the magnetic field self-consistently at $\sim 7\times 10^{12}$G.

7 pages, 4 figures, 1 tables, accepted for publication in MNRAS

References in corpus (3)

• Thermal and Bulk Comptonization in Accretion-Powered X-Ray Pulsars
• The critical accretion luminosity for magnetized neutron stars
• Evidence for the radiation-pressure dominated accretion disk in bursting pulsar GRO J1744-28 using timing analysis

Cited by in corpus (10)

• The Ups & Downs of Accreting X-Ray Pulsars: Decade-long observations with the Fermi Gamma-Ray Burst Monitor
• Timing and spectral analysis of 2S 1417$-$624 during its 2018 outburst
• Insight-HXMT observations of Swift J0243.6+6124: the evolution of RMS pulse fractions at super-Eddington luminosity
• Timing analysis of EXO 2030+375 during its 2021 giant outburst observed with Insight-HXMT
• Switches between accretion structures during flares in 4U 1901+03
• GRMHD simulations of accreting neutron stars I: nonrotating dipoles
• Spectral & Timing analysis of Be/X-ray binary EXO 2030+375 during its giant 2021 outburst
• X-Ray Views of Galactic Accreting Pulsars in High-Mass X-Ray Binaries
• Timing and Spectral Studies of the X-ray Pulsar 2S 1417$-$624 During the Outburst in 2021
• Insight-HXMT insight into switch of the accretion mode: the case of the X-ray pulsar 4U 1901+03