Atmospheres and radiating surfaces of neutron stars with strong magnetic fields

Potekhin, A. Y.; Ho, Wynn C. G.; Chabrier, G.

doi:10.22323/1.262.0016

Cited by 3 publications

(5 citation statements)

References 147 publications

(230 reference statements)

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“…The surface of a neutron star can be covered by a gaseous atmosphere, where radiative processes alter the emergent spectrum. Model atmospheres of highly magnetized neutron stars were computed by many authors, following the pioneering work of Shibanov et al (1992) (see, e.g., Potekhin et al 2016 for a review and references therein). Here we use the approach of Suleimanov et al (2009) and corresponding code to compute a grid of model atmospheres in the required ranges of surface effective temperature T eff and surface magnetic field.…”

Section: Magnetized Hydrogen Atmospherementioning

confidence: 99%

Thermal Emission and Magnetic Beaming in the Radio and X-Ray Mode-switching PSR B0943+10

Rigoselli

Mereghetti

Turolla

et al. 2019

ApJ

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PSR B0943+10 is a mode-switching radio pulsar characterized by two emission modes with different radio and X-ray properties. Previous studies, based on simple combinations of blackbody and power law models, showed that its X-ray flux can be decomposed in a pulsed thermal plus an unpulsed non-thermal components. However, if PSR B0943+10 is a nearly aligned rotator seen pole-on, as suggested by the radio data, it is difficult to reproduce the high observed pulsed fraction unless magnetic beaming is included. In this work we reanalyze all the available X-ray observations of PSR B0943+10 with simultaneous radio coverage, modeling its thermal emission with polar caps covered by a magnetized hydrogen atmosphere or with a condensed iron surface. The condensed surface model provides good fits to the spectra of both pulsar modes, but, similarly to the blackbody, it can not reproduce the observed pulse profiles, unless an additional power law with an ad hoc modulation is added. Instead, the pulse profiles and phase-resolved spectra are well described using the hydrogen atmosphere model to describe the polar cap emission, plus an unpulsed power law. For the X-ray brighter state (Q-mode) we obtain a best fit with a temperature kT ∼ 0.09 keV, an emitting radius R ∼ 260 m, a magnetic field consistent with the value of the dipole field of 4 × 10 12 G inferred from the timing parameters, and a small angle between the magnetic and spin axis, ξ = 5 • . The corresponding parameters for the X-ray fainter state (B-mode) are kT ∼ 0.08 keV and R ∼ 170 m.

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Section: Magnetized Hydrogen Atmospherementioning

confidence: 99%

Thermal Emission and Magnetic Beaming in the Radio and X-Ray Mode-switching PSR B0943+10

Rigoselli

Mereghetti

Turolla

et al. 2019

ApJ

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“…As argued by [e.g. [36][37][38][39][40], this thermal emission is expected to be nearly fully polarized as it is emitted. We have used the phase-resolved spectral fits of [35] to simulate the polarized spectra in XIMPOL [41] for a 10.0-ks observation with eXTP.…”

Section: Resultsmentioning

confidence: 90%

“…The magnetar 4U 0142+61 exhibits a X-ray spectrum from 2-8 keV (the range of sensitivity of IXPE and eXTP) that is dominated by thermal emission [35]. As argued by (e.g., [36][37][38][39][40]), this thermal emission is expected to be nearly fully polarized as it is emitted. We have used the phase-resolved spectral fits of [35] to simulate the polarized spectra in XIMPOL [41] for a 10.0-ks observation with eXTP.…”

Section: Resultsmentioning

confidence: 95%

Strongly Magnetized Sources: QED and X-ray Polarization

Caiazzo

2018

Galaxies

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Radiative corrections of quantum electrodynamics cause a vacuum threaded by a magnetic field to be birefringent. This means that radiation of different polarizations travels at different speeds. Even in the strong magnetic fields of astrophysical sources, the difference in speed is small. However, it has profound consequences for the extent of polarization expected from strongly magnetized sources. We demonstrate how the birefringence arises from first principles, show how birefringence affects the polarization state of radiation and present recent calculations for the expected polarization from magnetars and X-ray pulsars.

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“…In our fiducial analyses we assume that the 0-2 keV NS spectra are blackbody in order to verify that its extrapolation does not produce the observed 2-8 keV excesses. However, at least some of the M7 likely have a thin (∼1 cm) atmosphere, leading to a modified spectrum (for a comprehensive review, see [24] or [25]). The surface composition is unknown, although due to the high surface gravity a hydrogen atmosphere is expected if hydrogen is present on the surface, usually due to accretion at formation.…”

Section: B Ns Surface Modelingmentioning

confidence: 99%

“…Figure25. Systematic variations on the analysis procedure on the reconstructed fluxes and limits at each energy bin for RX J0420.0-5022.…”

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confidence: 99%

Hard X-Ray Excess from the Magnificent Seven Neutron Stars

Dessert

Foster

2020

ApJ

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We report significant hard X-ray excesses in the energy range 2–8 keV for two nearby isolated neutron stars: RX J1856.6−3754 and RX J0420.0−5022. These neutron stars have previously been observed in soft X-rays to have nearly thermal spectra at temperatures ∼100 eV, which are thought to arise from the warm neutron star surfaces. We find nontrivial hard X-ray spectra well above the thermal surface predictions with archival data from the XMM-Newton and Chandra X-ray telescopes. We analyze possible systematic effects that could generate such spurious signals, such as nearby X-ray point sources and pileup of soft X-rays, but we find that the hard X-ray excesses are robust to these systematics to the extent that is possible to test. We also investigate possible sources of hard X-ray emission from the neutron stars and find no satisfactory explanation with known mechanisms, suggesting that a novel source of X-ray emission is at play. We do not find high-significance hard X-ray excesses from the other five Magnificent Seven isolated neutron stars.

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Atmospheres and radiating surfaces of neutron stars with strong magnetic fields

Cited by 3 publications

References 147 publications

Thermal Emission and Magnetic Beaming in the Radio and X-Ray Mode-switching PSR B0943+10

Thermal Emission and Magnetic Beaming in the Radio and X-Ray Mode-switching PSR B0943+10

Strongly Magnetized Sources: QED and X-ray Polarization

Hard X-Ray Excess from the Magnificent Seven Neutron Stars

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