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

Kong, Ling-Da; Zhang, Shu; Ji, Long; Doroshenko, Victor; Santangelo, Andrea; Orlandini, Mauro; Frontera, Filippo; Li, Jian; Chen, Yu-Peng; Wang, Peng-Ju; Chang, Zhi; Qu, Jin-Lu; Zhang, Shuang-Nan

doi:10.48550/arxiv.2204.11222

Cited by 2 publications

(4 citation statements)

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“…A CRSF is discovered with high statistical significance at energies around 120-146 keV, in a period when the source stayed at a luminosity around 2 × 10 39 erg s −1 , far beyond the supercritical luminosity of the accretion column and the Eddington luminosity of the accreting NS. The energy of this newly detected CRSF is much higher than both the ∼90 keV fundamental CRSF of GRO J1008-57 (Ge et al 2020) and the ∼100 keV first-harmonic CRSF of 1A 0526+261 (Kong et al 2021(Kong et al , 2022; both were the previous high-energy records of CRSF detection, whose existence was firmly established for the first time by Insight-HXMT with a significance much higher than 5σ. We note that a marginal detection (absorption depth unconstrained) of the possible third CRSF harmonic at ∼128 keV was reported in the spectrum of MAXI J1409-619 (Orlandini et al 2012).…”

Section: Discussionmentioning

confidence: 51%

“…Fortunately, the launch of Insight-HXMT in 2017 (Zhang et al 2014;Zhang et al 2020), which has a broad energy coverage and a large detection area at energies above 100 keV, changed the situation. The two previous records of the highest energy detection of CRSFs with higher than 5σ significance were also both set by Insight-HXMT-the ∼90 keV fundamental CRSF from GRO J1008-57 (Ge et al 2020) and the ∼100 keV first harmonic of a CRSF from 1A 0535+262 (Kong et al 2021;Kong et al 2022)-proving that Insight-HXMT has a strong advantage in detecting high-energy CRSFs.…”

Section: Introductionmentioning

confidence: 76%

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Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

Kong

Zhang

et al. 2022

ApJL

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The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity of ∼2 × 1039 erg s−1, the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin-phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF because no spectral feature exists at 60–70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field of ∼1.6 × 1013 G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest-energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario.

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Section: Discussionmentioning

confidence: 51%

Section: Introductionmentioning

confidence: 76%

Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

Kong

Zhang

et al. 2022

ApJL

View full text Add to dashboard Cite

show abstract

“…A CRSF is discovered with high statistical significance at energies around 120 − 146 keV, in a period when the source stayed at a luminosity around 2 × 10 39 erg s −1 , far beyond the super-critical luminosity of the accretion column and the Eddington luminosity of the accreting NS. The energy of this newly detected CRSF is much higher than both the ∼ 90 keV fundamental CRSF of GRO J1008-57 (Ge et al 2020) and the ∼ 100 keV first harmonic CRSF of 1A 0526+261 (Kong et al 2021(Kong et al , 2022; both were the previous high energy records of CRSF detection, whose existence was firmly established for the first time by Insight-HXMT with a significance much higher than 5 σ. We note that a marginal detection (absorption depth unconstrained) of the possible third CRSF harmonic at ∼128 keV was reported in the spectrum of MAXI J1409-619 (Orlandini et al 2012).…”

Section: Discussionmentioning

confidence: 54%

“…Fortunately, the launch of Insight-HXMT in 2017 (Zhang et al 2014;Zhang et al 2020), which has a broad energy coverage and a large detection area at energies above 100 keV changed the situation. The two previous records of the highest energy detection of CRSFs with higher than 5 σ significance were also both set by Insight-HXMT: the ∼90 keV fundamental CRSF from GRO J1008-57 (Ge et al 2020) and the ∼100 keV first harmonic of a CRSF from 1A 0535+262 (Kong et al 2021;Kong et al 2022) proving that Insight-HXMT has a strong advantage in detecting high-energy CRSFs.…”

mentioning

confidence: 83%

Insight-HXMT discovery of the highest energy CRSF from the first Galactic ultra-luminous X-ray pulsar Swift J0243.6+6124

Kong,

Zhang,

Zhang

et al. 2022

Preprint

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The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity ∼ 2 × 10 39 erg s −1 , the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF, since no spectral feature exists at 60 − 70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field ∼ 1.6 × 10 13 G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario.

show abstract

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

Cited by 2 publications

References 45 publications

Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

Insight-HXMT discovery of the highest energy CRSF from the first Galactic ultra-luminous X-ray pulsar Swift J0243.6+6124

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