X-ray spectra from protons illuminating a neutron star

Deufel, B.; Dullemond, C. P.; Spruit, H. C.

doi:10.1051/0004-6361:20011129

Cited by 41 publications

(64 citation statements)

References 20 publications

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“…Sunyaev and Shakura 1986;Inogamov and Sunyaev 1999;Deufel et al 2001;Popham and Sunyaev 2001;Grebenev et al 2002;Suleimanov and Poutanen 2006). Such a layer is formed because the gas must decelerate from the near-Keplerian velocities in the inner accretion disk (≈ 0.2c-0.4c for typical inner disk radii; see below) to the slower rotational motion of the NS (typically a few hundred Hz; see , for the most recent overview of spin rates measured for NS LMXBs).…”

Section: Accretion Disks and X-ray Spectral Statesmentioning

confidence: 99%

Accretion Disks and Coronae in the X-Ray Flashlight

et al. 2017

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Plasma accreted onto the surface of a neutron star can ignite due to unstable thermonuclear burning and produce a bright flash of X-ray emission called a Type-I X-ray burst. Such events are very common; thousands have been observed to date from over a hundred accreting neutron stars. The intense, often Eddington-limited, radiation generated in these thermonuclear explosions can have a discernible effect on the surrounding accretion flow that consists of an accretion disk and a hot electron corona. Type-I X-ray bursts can there- fore serve as direct, repeating probes of the internal dynamics of the accretion process. In this work we review and interpret the observational evidence for the impact that Type-I X-ray bursts have on accretion disks and coronae. We also provide an outlook of how to make further progress in this research field with prospective experiments and analysis techniques, and by exploiting the technical capabilities of the new and concept X-ray missions ASTROSAT, NICER, Insight-HXMT, eXTP, and STROBE-X.

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Section: Accretion Disks and X-ray Spectral Statesmentioning

confidence: 99%

Accretion Disks and Coronae in the X-Ray Flashlight

et al. 2017

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“…Its quiescent spectrum consists of a soft, thermal component (dominating at energies 3 keV) and a harder component that can be described by a simple power law (e.g., Verbunt et al 1994;Rutledge et al 2002a;Campana & Stella 2003;Cackett et al 2011a;Campana et al 2014). The thermal emission component is thought to be coming from the neutron star surface, and is either due to it being heated by continued low-level accretion (e.g., van Paradijs et al 1987;Zampieri et al 1995;Campana et al 1997;Deufel et al 2001), or due to radiation of heat deposited in its interior during accretion episodes (e.g., Brown et al 1998;Rutledge et al 1999;Campana et al 2000).…”

Section: Aql X-1mentioning

confidence: 99%

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Waterhouse

Degenaar

Wijnands

et al. 2016

Mon. Not. R. Astron. Soc.

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Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as well as the short and faint 2015 outburst, to investigate the hypothesis that cooling of the accretion-heated neutron star crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that the X-ray light curves and measured neutron star surface temperatures are consistent with the expectations of the crust cooling paradigm. By using a thermal evolution code, we find that ≃1.2 − 3.2 MeV nucleon −1 of shallow heat release describes the observational data well, depending on the assumed mass-accretion rate and temperature of the stellar core. We find no evidence for varying strengths of this shallow heating after different outbursts, but this could be due to limitations of the data. We argue that monitoring Aql X-1 for up to ≃1 year after future outbursts can be a powerful tool to break model degeneracies and solve open questions about the magnitude, depth and origin of shallow heating in neutron star crusts.

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“…The overlap region is a source of hard X-rays (Deufel et al 2001. The ISAF itself, however, may actually be the main X-ray producing region, and its oscillations are expected to have direct implications on the shape of the emitted spectrum.…”

Section: Spectral Evolution During the Oscillationmentioning

confidence: 99%

Excitation of low-frequency QPOs in black hole accretion

Giannios

Spruit²

2004

A&A

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Abstract. We study possible mechanisms of excitation of quasiperiodic oscillations in the accretion flow of black hole accreters in their hard spectral states, in the context of the "truncated disk" model. Quasi-spherical oscillations of the inner ion-supported accretion flow (ISAF) can be excited by the interaction of this hot flow with the cool disk extending outward from it. The fundamental mode of (p-mode) oscillation is most easily excited, and has a frequency near the Kepler frequency at the inner edge of the cool disk. The strongest excitation mechanism is a feedback loop involving cooling of the ISAF by soft photons from the cool disk and heating of the cool disk by the ISAF, while synchrotron emission can be a relatively strong damping effect. Growth times are computed by detailed Comptonization calculations of the interaction of an idealized ISAF with a cool disk. Typical growth times as short as a few dynamical times are found, while amplitudes can be as large as 10%.

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X-ray spectra from protons illuminating a neutron star

Cited by 41 publications

References 20 publications

Accretion Disks and Coronae in the X-Ray Flashlight

Accretion Disks and Coronae in the X-Ray Flashlight

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Excitation of low-frequency QPOs in black hole accretion

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