Timing Properties of the X-Ray Accreting Pulsar 1A 0535+262 Studied with Insight-HXMT

Wang, P. J.; Kong, L. D.; Zhang, S.; Doroshenko, V.; Santangelo, A.; Ji, Long; S., Yorgancioglu, E.; Chen, Y. P.; Zhang, S. N.; Qu, J. L.; Ge, M. Y.; Li, Jingjing; Chang, Zhi; Tao, Lian; Peng, Jing-Qiang; Shui, Qing-Cang

doi:10.3847/1538-4357/ac8230

Cited by 18 publications

(23 citation statements)

References 45 publications

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“…Apart from this transient feature, the pulse profiles do not show any appreciable luminosity dependence. This is contrary to several other sources (see, e.g., Klochkov et al 2008;Malacaria et al 2015;Epili et al 2017;Koliopanos & Vasilopoulos 2018;Wilson-Hodge et al 2018;Wang et al 2022), where a drastic change of the pulse profile is observed as a function of luminosity, and is interpreted as a change of the accretion column beaming pattern (Basko & Sunyaev 1976;Becker et al 2012;Mushtukov et al 2015b). Here, despite the probed outburst stages ranging from a bolometric luminosity of about 5 × 10 37 erg s −1 to a peak luminosity that is about 60% of the Eddington luminosity for a 1.4 M NS (see Fig.…”

Section: A Steady Pulse Profile and Pulsed Fractioncontrasting

confidence: 99%

The unaltered pulsar: GRO J1750-27, a supercritical X-ray neutron star that does not blink an eye

Malacaria

Ducci²,

Falanga³

et al. 2023

A&A

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When accreting X-ray pulsars (XRPs) undergo bright X-ray outbursts, their luminosity-dependent spectral and timing features can be analyzed in detail. The XRP GRO J1750-27 recently underwent one such episode, during which it was observed with NuSTAR and monitored with NICER. Such a data set is rarely available, as it samples the outburst over more than 1 month at a luminosity that is always exceeding ∼5 × 10 37 erg/s. This value is larger than the typical critical luminosity value, where a radiative shock is formed above the surface of the neutron star. Our data analysis of the joint spectra returns a highly (NH ∼ (5 − 8) × 10 22 cm −2 ) absorbed spectrum showing a Kα iron line, a soft blackbody component likely originating from the inner edge of the accretion disk, and confirms the discovery of one of the deepest cyclotron lines ever observed, at a centroid energy of ∼44 keV corresponding to a magnetic field strength of 4.7 × 10 12 G. This value is independently supported by the best-fit physical model for spectral formation in accreting XRPs which, in agreement with recent findings, favors a distance of 14 kpc and also reflects a bulk-Comptonizationdominated accretion flow. Contrary to theoretical expectations and observational evidence from other similar sources, the pulse profiles as observed by NICER remain remarkably steady through the outburst rise, peak and decay. The NICER spectrum, including the iron Kα line best-fit parameters, also remain almost unchanged at all probed outburst stages, similar to the pulsed fraction behavior. We argue that all these phenomena are linked and interpret them as resulting from a saturation effect of the emission from the accretion column, which occurs in the high-luminosity regime.

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Section: A Steady Pulse Profile and Pulsed Fractioncontrasting

confidence: 99%

The unaltered pulsar: GRO J1750-27, a supercritical X-ray neutron star that does not blink an eye

Malacaria

Ducci²,

Falanga³

et al. 2023

A&A

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“…b Adopted from Sartore et al (2015). c Derived from Insight-HXMT observations (Wang et al 2022; see text).…”

Section: Discussionmentioning

confidence: 99%

“…For the 2011 outburst, we used the timing solution reported in Sartore et al (2015) derived using INTEGRAL observations. For the recent 2020 outburst, thanks to the extensive coverage of Insight-HXMT observations (Wang et al 2022), we used the phase-connection technique (Deeter et al 1981) to determine the spin evolution accurately. In practice, for each 1000 s segment we folded background-subtracted light curves in the energy range of 25-80 keV, for which the pulse profile shape is relatively stable.…”

Section: Timing Solutionsmentioning

confidence: 99%

Deep Search for Gamma-Ray Emission from the Accreting X-Ray Pulsar 1A 0535+262

Hou

Zhang

Torres

et al. 2023

ApJ

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Binary systems are a well-established subclass of gamma-ray sources. The high mass X-ray binary pulsar 1A 0535+262 has been considered to be a possible gamma-ray emitter for a long time, although former gamma-ray searches using the Fermi Large Area Telescope (LAT) and VERITAS data resulted in upper limits only. We aim at a deep search for gamma-ray emission and pulsations from 1A 0535+262 using more than 13 yr of Fermi-LAT data. The analysis was performed for both the whole Fermi-LAT data set, as well as for the X-ray outbursts that 1A 0535+262 has experienced since the launch of Fermi. Various X‐ray observations have been used to generate the ephemeris for the pulsation search. We also investigate the long-term gamma-ray flux variability and perform orbital phase-resolved analysis for the outbursts. We did not detect any steady or pulsed gamma-ray emission from 1A 0535+262 during the whole Fermi-LAT mission span or its X-ray outbursts. We thus derived the deepest gamma-ray luminosity upper limits to date at the 95% confidence level to be around (2.3–4.7) × 1032 erg s−1 depending on different spectral indices assumed, which results in a ratio of L γ to L X (2–150 keV) being (1.9–3.9) × 10−6.

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“…Insight-HXMT (Zhang et al 2014(Zhang et al , 2020 performed a highcadence observational campaign and obtained unprecedented high-quality data of 1A 0535+026 during its giant outburst in 2020. In Figure 1 we show the observed evolution of the pulse profiles (adopted from Wang et al 2022), as a function of the bolometric luminosity of the source estimated using the broadband spectroscopy in the energy range of 2-150 keV and assuming a distance of 2 kpc. During the outburst, as reported by Wang et al (2022), the pulse profile shows a complex variation with energy and luminosity.…”

Section: Available Data and Data Selectionmentioning

confidence: 99%

“…Kong et al (2021) also reported significant differences in the observed broadband X-ray spectrum between the rising and fading phases of the outburst, suggesting a somewhat different emission region geometry even at the same accretion rate in two phases of the outburst. On the other hand, using Insight-HXMT observations, Wang et al (2022) reported the complex pulse profile evolution throughout the outburst, which exhibits a strong energy and luminosity dependence. Here we investigate observed variations of the pulse profile more quantitatively and apply the decomposition method by Kraus et al (1995) to Insight-HXMT data.…”

Section: Introductionmentioning

confidence: 99%

Beam Pattern Evolution of Accreting X-Ray Pulsar 1A 0535+262 during Its 2020 Giant Outburst

et al. 2023

ApJ

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We report on pulse profile decomposition analysis of bright transient X-ray pulsar 1A 0535+262 using broadband Insight-HXMT observations during a giant outburst of the source in 2020. We show that the observed pulse profile shape can be described in terms of a combination of two symmetric single-pole contributions for a wide range of energies and luminosities for a fixed geometry defining the basic geometry of the pulsar. This corresponds to a slightly distorted dipole magnetic field, i.e., one pole has to be offset by ∼12° from the antipodal position of the other pole. We reconstruct the intrinsic beam patterns of the pulsar assuming that the geometry is recovered from the decomposition analysis, and we find evidence for a transition between “pencil” and “fan” beams in energy ranges above the cyclotron line energy, which can be interpreted as a transition from sub- to supercritical accretion regimes associated with the onset of an accretion column. At lower energies, however, the beam pattern appears to be more complex and contains a substantial “fan” beam and an additional “pencil” beam component at all luminosities. The latter is not related to the accretion rate and is stronger in the fading phase of the outburst. We finally discuss the results in the context of other observational and theoretical findings earlier reported for the source in the literature.

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Timing Properties of the X-Ray Accreting Pulsar 1A 0535+262 Studied with Insight-HXMT

Cited by 18 publications

References 45 publications

The unaltered pulsar: GRO J1750-27, a supercritical X-ray neutron star that does not blink an eye

The unaltered pulsar: GRO J1750-27, a supercritical X-ray neutron star that does not blink an eye

Deep Search for Gamma-Ray Emission from the Accreting X-Ray Pulsar 1A 0535+262

Beam Pattern Evolution of Accreting X-Ray Pulsar 1A 0535+262 during Its 2020 Giant Outburst

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