Cyclotron line evolution revealed with pulse-to-pulse analysis in the 2020 outburst of 1A 0535+262

Abstract

We present a detailed analysis of the X-ray luminosity (Lx) dependence of the cyclotron absorption line energy (Ecyc) for the X-ray binary pulsar 1A 0535+262 during its 2020 giant outburst based on pulse-to-pulse analysis. By applying this technique to high cadence observations of Insight-HXMT, we reveal the most comprehensive Ecyc-Lx correlation across a broad luminosity range of ~(0.03-1.3)*10^38 erg/s. Apart from the positive and negative correlations between cyclotron line energy and luminosity at Lx~(1-3)*10^37 erg/s and ~(7-13)*10^37 erg/s, which are expected from the typical subcritical and supercritical accretion regimes, respectively, a plateau in the correlation is also detected at ~(3-7)*10^37 erg/s^-1. Moreover, at the lowest luminosity level (Lx<10^37 erg/s), the positive Ecyc-Lx correlation seems to be broken, and the pulse profile also occurs a significant transition. These discoveries provide the first complete view on the correlation between luminosity and the centriod energy of the cyclotron line, and therefore are relevant for understanding how accretion onto magnetized neutron stars depends on luminosity.

Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

References in corpus (23)

• The critical accretion luminosity for magnetized neutron stars
• Discovery of a flux-related change of the cyclotron line energy in Her X-1
• Patterns of variability in Be/X-ray pulsars during giant outbursts
• 4U 0115+63 from RXTE and INTEGRAL Data: Pulse Profile and Cyclotron Line Energy
• Luminosity dependence of the cyclotron line and evidence for the accretion regime transition in V 0332+53
• A 0535+26 in the August/September 2005 outburst observed by RXTE and INTEGRAL
• Luminosity-dependent changes of the cyclotron line energy and spectral hardness in Cep X-4
• Cyclotron emission, absorption, and the two faces of X-ray pulsar A 0535+262
• Transient X-ray pulsar V0332+53: pulse phase-resolved spectroscopy and the reflection model
• Discovery and Modeling of a Flattening of the Positive Cyclotron Line/Luminosity Relation in GX 304-1 with RXTE
• X-ray emission from magnetized neutron star atmospheres at low mass accretion rates. I. Phase-averaged spectrum
• The Swift-BAT monitoring reveals a long term decay of the cyclotron line energy in Vela X-1
• Insight-HXMT observations of Swift J0243.6+6124 during its 2017-2018 outburst
• MHD instabilities in accretion mounds - 1: 2D axisymmetric simulations
• Looking at A 0535+26 at low luminosities with NuSTAR
• Relation of cyclotron resonant energy and luminosity in a strongly magnetized neutron star GRO J1008-57 observed by Insight-HXMT
• Insight-HXMT firm detection of the highest energy fundamental cyclotron resonance scattering feature in the spectrum of GRO J1008-57
• Timing properties of the X-ray accreting pulsar 1A 0535+262 studied with Insight-HXMT
• Beam pattern evolution of accreting X-ray pulsar 1A 0535+262 during its 2020 giant outburst
• High energy Millihertz quasi-periodic oscillations in 1A 0535+262 with Insight-HXMT challenge current models
• Phase dependent evolution within large luminosity range of 1A 0535+262 observed by Insight-HXMT during 2020 giant outburst
• X-ray spectral-timing variability of 1A 0535+262 during the 2020 giant outburst
• Deep search for gamma-ray emission from the accreting X-ray pulsar 1A 0535+262

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