Broad-band spectroscopy of Hercules X-1 with Suzaku

Asami, Fumi; Enoto, T.; Iwakiri, W.; Yamada, S.; Tamagawa, Toru; Mihara, T.; Nagase, F.

doi:10.1093/pasj/psu005

Cited by 13 publications

(15 citation statements)

References 27 publications

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“…We have shown that the X-ray spectrum of Her X-1 during the high state contains strong evidence of blueshifted wind absorption. The Fe K band of the spectrum by itself could be explained by an array of Fe emission lines (at 6.4, 6.7, 6.97 keV) rather than by absorption features (Asami et al 2014). However, the N vii, O viii and Ne x regions unambiguously show blueshifted absorption lines at the same systematic velocity, thus confirming that we are observing an ionised wind.…”

Section: Discussionmentioning

confidence: 96%

“…Such velocities are unlikely to occur in this system given that the accretion disc of Her X-1 is likely truncated by the magnetic field of the neutron star at ∼1000 R G . Asami et al (2014) consider different possible origins of the width of the line including line blending, comptonisation from an accretion disc corona or Doppler broadening but do not find a plausible explanation.…”

Section: Continuum Modellingmentioning

confidence: 96%

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An ionized accretion disc wind in Hercules X-1

Kosec

Fabian

Pinto

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Hercules X-1 is one of the best studied highly magnetised neutron star X-ray binaries with a wealth of archival data. We present the discovery of an ionised wind in its X-ray spectrum when the source is in the high state. The wind detection is statistically significant in most of the XMM-Newton observations, with velocities ranging from 200 to 1000 km/s. Observed features in the iron K band can be explained by both wind absorption or by a forest of iron emission lines. However, we also detect nitrogen, oxygen and neon absorption lines at the same systematic velocity in the high-resolution RGS grating spectra. The wind must be launched from the accretion disc, and could be the progenitor of the UV absorption features observed at comparable velocities, but the latter likely originate at significantly larger distances from the compact object. We find strong correlations between the ionisation level of the outflowing material and the ionising luminosity as well as the super-orbital phase. If the luminosity is driving the correlation, the wind could be launched by a combination of Compton heating and radiation pressure. If instead the super-orbital phase is the driver for the variations, the observations are likely scanning the wind at different heights above the warped accretion disc. If this is the case, we can estimate the wind mass outflow rate, corrected for the limited launching solid angle, to be roughly 70% of the mass accretion rate.

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Section: Discussionmentioning

confidence: 96%

Section: Continuum Modellingmentioning

confidence: 96%

An ionized accretion disc wind in Hercules X-1

Kosec

Fabian

Pinto

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Fürst et al fit a number of different continuum models and we compare our fit to their "HighE" cutoff power law model from their Table 3. For the "narrow" iron line, Fürst et al (2013) found an energy centroid of E(FeKα n ) = 6.601 +0.017 −0.016 keV and σ(FeKα n ) = 0.25 +0.04 Asami et al (2014) found in their analysis of Suzaku data alone from Her X-1 that their spectral fits required a broad line in the 4−9 keV energy range. They suggested a number of possible physical origins for this feature but their data was not sufficient to attribute the line emission to one unique mechanism.…”

Section: Iron Emissionmentioning

confidence: 97%

THE NuSTAR X-RAY SPECTRUM OF HERCULES X-1: A RADIATION-DOMINATED RADIATIVE SHOCK

Wolff

Becker

Gottlieb

et al. 2016

ApJ

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We report new spectral modeling of the accreting X-ray pulsar Hercules X-1. Our radiation-dominated radiative shock model is an implementation of the analytic work of Becker & Wolff on Comptonized accretion flows onto magnetic neutron stars. We obtain a good fit to the spin-phase averaged 4 to 78 keV X-ray spectrum observed by the Nuclear Spectroscopic Telescope Array during a mainon phase of the Her X-1 35-day accretion disk precession period. This model allows us to estimate the accretion rate, the Comptonizing temperature of the radiating plasma, the radius of the magnetic polar cap, and the average scattering opacity parameters in the accretion column. This is in contrast to previous phenomenological models that characterized the shape of the X-ray spectrum but could not determine the physical parameters of the accretion flow. We describe the spectral fitting details and discuss the interpretation of the accretion flow physical parameters.

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“…Further spectral observations with better instruments have improved the measurement of the spectrum and included partial covering absorption (e.g. [20]). That the precessing accretion disk produces both the 35-day light-curve and the 35-day cycle in pulse shape changes was confirmed by [21].…”

Section: New Results In the Past 10 Yearsmentioning

confidence: 99%

Hercules X-1 (Her X-1): New results from the past decade of observations

Leahy¹

2021

Proceedings of High Energy Astrophysics in Southern Africa 2021 — PoS(HEASA2021)

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Hercules X-1 is an accreting X-ray binary with well-determined properties based on measurements of light-curves and spectra since its discovery in 1972. Since discovery, it has been observed with most major X-ray astronomy instruments. Analyses of Her X-1 over the past decade include, among others, observations from RXTE/PCA and ASM, Suzaku, NuSTAR, AstroSat and Swift/BAT. These have added to the range of phenomena detected from this system. New aspects of the binary are reviewed. The data are being used to test models for the system, including the nature of the companion star (HZ Her), the accretion column on the neutron star, the shape of the accretion disk and its shadow, and the accretion stream.

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Broad-band spectroscopy of Hercules X-1 with Suzaku

Cited by 13 publications

References 27 publications

An ionized accretion disc wind in Hercules X-1

An ionized accretion disc wind in Hercules X-1

THE NuSTAR X-RAY SPECTRUM OF HERCULES X-1: A RADIATION-DOMINATED RADIATIVE SHOCK

Hercules X-1 (Her X-1): New results from the past decade of observations

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