Phase dependent evolution within large luminosity range of 1A 0535+262 observed by Insight-HXMT during 2020 giant outburst

Abstract

We have performed phase-resolved spectral analysis of the accreting pulsar 1A~0535+262 based on observations of Insight-HXMT during the 2020 Type-II outburst of the source. We focus on the two-dimensional dependence of the cyclotron resonance scattering features (CRSFs) along the outburst time and at different phases. The fundamental CRSF line (f-CRSF) shows different time- and phase-dependent behaviors. At higher luminosity, the phase profile of the f-CRSF energy changes from a single peak to double peaks, with the transition occurring at MJD 59185. On the contrary, the first harmonic CRSF (1-st CRSF) at $\sim$ 100 keV is only detected within a narrow phase range (0.8$-$1.0) accompanied by a shallow f-CRSF line. Based on these results, we speculate that when the source enters the supercritical regime, the higher accretion column can significantly enhance the harmonic line at a narrow phase through an "anti-pencil" beam at a higher energy band. At the same time, it will also affect the behavior of the fundamental line.

References in corpus (32)

• On the Absorption of X-rays in the Interstellar Medium
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• TEMPO2, a new pulsar timing package. I: Overview
• Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite
• Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
• Cyclotron lines in highly magnetized neutron stars
• The critical accretion luminosity for magnetized neutron stars
• The Medium Energy (ME) X-ray telescope onboard the Insight-HXMT astronomy satellite
• A model for cyclotron resonance scattering features
• A reflection model for the cyclotron lines in the spectra of X-ray pulsars
• Luminosity dependence of the cyclotron line and evidence for the accretion regime transition in V 0332+53
• Confirmation of Two Cyclotron Lines in Vela X-1
• Pulse-amplitude-resolved spectroscopy of bright accreting pulsars: indication of two accretion regimes
• The distances to the X-ray binaries LSI +61 303 and A0535+262
• A 0535+26 in the August/September 2005 outburst observed by RXTE and INTEGRAL
• On the radiation beaming of bright X-ray pulsars and constraints on neutron star mass-radius relation
• Spectral Formation in X-Ray Pulsars: Bulk Comptonization in the Accretion Shock
• Giant outburst of EXO 2030+375: pulse-phase resolved analysis of INTEGRAL data
• Transient X-ray pulsar V0332+53: pulse phase-resolved spectroscopy and the reflection model
• BeppoSAX observations of the X-ray pulsar MAXI J1409-619 in low state: discovery of cyclotron resonance features
• The pre-outburst flare of the A 0535+26 August/September 2005 outburst
• Discovery of a pulse-phase-transient cyclotron line in the X-ray pulsar GROJ2058+42
• Analyzing X-ray pulsar profiles: geometry and beam pattern of A 0535+26
• The appearance of magnetospheric instability in flaring activity at the onset of X-ray outbursts in A0535+26
• Changes in the cyclotron line energy on short and long timescales in V 0332+53
• Cyclotron lines: from magnetic field strength estimators to geometry tracers in neutron stars
• Study of timing and spectral properties of the X-ray pulsar 1A 0535+262 during the giant outburst in 2020 November-December
• Analyzing X-Ray Pulsar Profiles: Geometry and Beam Pattern of EXO 2030+375
• The Background Model of the Medium Energy X-ray telescope of Insight-HXMT
• Background Model for the Low-Energy Telescope of Insight-HXMT
• Background Model for the High-Energy Telescope of Insight-HXMT
• Luminosity dependence of the cyclotron line energy in 1A 0535+262 observed by Insight-HXMT during 2020 giant outburst

Cited by in corpus (4)

• Cyclotron line evolution revealed with pulse-to-pulse analysis in the 2020 outburst of 1A 0535+262
• X-ray Polarimetry of the accreting pulsar 1A~0535+262 in the supercritical state with PolarLight
• Deep search for gamma-ray emission from the accreting X-ray pulsar 1A 0535+262
• Timing and spectral studies of the Be/X-ray binary EXO 2030+375 using Insight-HXMT observations