Cyclotron emission, absorption, and the two faces of X-ray pulsar A 0535+262

Tsygankov, Sergey S.; Doroshenko, V.; Mushtukov, Alexander A.; Suleimanov, V.; Lutovinov, A.; Poutanen, Juri

doi:10.1093/mnrasl/slz079

Cited by 46 publications

(41 citation statements)

References 43 publications

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“…In the case of such high magnetic fields, collisional excitations in the atmosphere are barely possible. We therefore conclude that models that explain the high-energy component mainly by collisional excitations followed by cyclotron photon emission (Tsygankov et al 2019b;Mushtukov et al 2021) require an unreasonably high contribution of this process for the Coulomb braking regime, which is not supported by the detailed studies on collisional stopping in magnetized atmospheres.…”

Section: Collisional Excitationmentioning

confidence: 72%

“…The soft energy component peaks at around 5 keV followed by a dip at ∼10-20 keV and a subsequent hump, peaking at around 30-40 keV. The analysis of the spectrum of A 0535+262 by Tsygankov et al (2019b) also showed a possible cyclotron line at 47.7 keV. The persistent low-luminosity HMXB X Persei and the transient HMXB GRO J1008−57, which has recently been observed at ∼10 35 erg s −1 (Lutovinov et al 2021), are the other examples of a similar peculiar two-component continuum.…”

Section: Introductionmentioning

confidence: 99%

“…Motivated by recent NuSTAR observations of the transient X-ray pulsars GX 304−1 (Tsygankov et al 2019a) and A 0535+262 (Tsygankov et al 2019b), which allow the direct study of the broadband X-ray spectrum emitted by highly magnetized neutron stars at lowṀ, in this paper we consider the spectral formation in the atmosphere of a neutron star. Specifically, the NuSTAR observations were performed at luminosities of ∼10 34 erg s −1 for GX 304−1 and ∼7 × 10 34 erg s −1 for A 0535+262.…”

Section: Introductionmentioning

confidence: 99%

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X-ray emission from magnetized neutron star atmospheres at low mass-accretion rates. I. Phase-averaged spectrum

Sokolova-Lapa

Gornostaev²,

Wilms³

et al. 2021

A&A

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Recent observations of X-ray pulsars at low luminosities allow, for the first time, the comparison of theoretical models of the emission from highly magnetized neutron star atmospheres at low mass-accretion rates (Ṁ ≲ 1015 g s−1) with the broadband X-ray data. The purpose of this paper is to investigate spectral formation in the neutron star atmosphere at low Ṁ and to conduct a parameter study of the physical properties of the emitting region. We obtain the structure of the static atmosphere, assuming that Coulomb collisions are the dominant deceleration process. The upper part of the atmosphere is strongly heated by the braking plasma, reaching temperatures of 30–40 keV, while its denser isothermal interior is much cooler (∼2 keV). We numerically solve the polarized radiative transfer in the atmosphere with magnetic Compton scattering, free–free processes, and nonthermal cyclotron emission due to possible collisional excitations of electrons. The strongly polarized emitted spectrum has a double-hump shape that is observed in low-luminosity X-ray pulsars. A low-energy “thermal” component is dominated by extraordinary photons that can leave the atmosphere from deeper layers because of their long mean free path at soft energies. We find that a high-energy component is formed because of resonant Comptonization in the heated nonisothermal part of the atmosphere even in the absence of collisional excitations. However, these latter, if present, affect the ratio of the two components. A strong cyclotron line originates from the optically thin, uppermost zone. A fit of the model to NuSTAR and Swift/XRT observations of GX 304−1 provides an accurate description of the data with reasonable parameters. The model can thus reproduce the characteristic double-hump spectrum observed in low-luminosity X-ray pulsars and provides insights into spectral formation.

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Section: Collisional Excitationmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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X-ray emission from magnetized neutron star atmospheres at low mass-accretion rates. I. Phase-averaged spectrum

Sokolova-Lapa

Gornostaev²,

Wilms³

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…Nevertheless, for a quantitative comparison, we have chosen objects which are as similar as possible to the considered magnetars in terms of phenomenology and the quality of the existing observations. As a reference accreting pulsar, we have selected 1A 0535+262 observed with NuSTAR in quiescence in Tsygankov et al (2019a). In this observation, the source was found at a luminosity comparable with that of AXPs and it exhibited a two-component energy spectrum similar to that of X Persei and 4U 0142+61 (Tsygankov et al 2019a).…”

Section: Introductionmentioning

confidence: 99%

An observational argument against accretion in magnetars

Doroshenko

Santangelo

Suleimanov

et al. 2020

A&A

Self Cite

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The phenomenology of anomalous X-ray pulsars is usually interpreted within the paradigm of very highly magnetized neutron stars, also known as magnetars. According to this paradigm, the persistent emission of anomalous X-ray pulsars (AXPs) is powered by the decay of the magnetic field. However, an alternative scenario in which the persistent emission is explained through accretion is also discussed in literature. In particular, AXP 4U 0142+61 has been suggested to be either an accreting neutron star or a white dwarf. Here, we rule out this scenario based on the observed X-ray variability properties of the source. We directly compare the observed power spectra of 4U 0142+61 and of two other magnetars, 1RXS J170849.0−400910 and 1E 1841−045 with that of the X-ray pulsar 1A 0535+262, and of the intermediate polar GK Persei. In addition, we include a bright young radio pulsar PSR B1509-58 for comparison. We show that, unlike accreting sources, no aperiodic variability within the expected frequency range is observed in the power density spectrum of the magnetars and the radio pulsar. Considering that strong variability is an established feature of all accreting systems from young stellar objects to super-massive black holes and the absence of the variability reports from other magnetars, we conclude that our results also indicate that magnetars, in general, are not powered by accretion.

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“…In this case, a complicated picture of relation of the line energy on X-ray luminosity can be observed, e.g., in V0332+53, the energy changes linearly with the source luminosity being accompanied by changes in pulse profile [150]. Oppositely, in A 0535+262 it is excluded that there is a positive correlation of the cyclotron line energy with the accretion rate [151]. We show in Figure 4 the so-called Corbet diagram [152] for Be/X-ray binaries with measured orbital and spin periods in the Milky Way, and Small and Large Magellanic Clouds, based on the catalogue by [153].…”

Section: High-mass X-ray Binariesmentioning

confidence: 99%

Evolution of Neutron Star Magnetic Fields

2021

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Neutron stars are natural physical laboratories allowing us to study a plethora of phenomena in extreme conditions. In particular, these compact objects can have very strong magnetic fields with non-trivial origin and evolution. In many respects, its magnetic field determines the appearance of a neutron star. Thus, understanding the field properties is important for the interpretation of observational data. Complementing this, observations of diverse kinds of neutron stars enable us to probe parameters of electro-dynamical processes at scales unavailable in terrestrial laboratories. In this review, we first briefly describe theoretical models of the formation and evolution of the magnetic field of neutron stars, paying special attention to field decay processes. Then, we present important observational results related to the field properties of different types of compact objects: magnetars, cooling neutron stars, radio pulsars, and sources in binary systems. After that, we discuss which observations can shed light on the obscure characteristics of neutron star magnetic fields and their behaviour. We end the review with a subjective list of open problems.

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Cyclotron emission, absorption, and the two faces of X-ray pulsar A 0535+262

Cited by 46 publications

References 43 publications

X-ray emission from magnetized neutron star atmospheres at low mass-accretion rates. I. Phase-averaged spectrum

X-ray emission from magnetized neutron star atmospheres at low mass-accretion rates. I. Phase-averaged spectrum

An observational argument against accretion in magnetars

Evolution of Neutron Star Magnetic Fields

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