A Broadband X-Ray View of the Precessing Accretion Disk and Pre-eclipse Dip in the Pulsar Her X-1 with NuSTAR and XMM-Newton

Brumback, McKinley C.; Hickox, Ryan C.; Fürst, Felix; Pottschmidt, K.; Tomsick, John A.; Wilms, J.; Staubert, R.; Vrtilek, S. D.

doi:10.3847/1538-4357/abe122

Cited by 18 publications

(15 citation statements)

References 62 publications

(124 reference statements)

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“…The precession of an accretion disk around NS provides another explanation ★ E-mail: kolesnikovkda@gmail.com to the 35-day cycle (e.g., Katz 1973;Roberts 1974;Petterson 1975, and subsequent papers). Presently, a rich phenomenology, both in the X-ray and optical, supports the presence of a tilted, retrograde, precessing accretion disk in Her X-1 (e.g., Boynton et al 1973;Leahy 2003;Klochkov et al 2006;Brumback et al 2021). In the middle of the Main-on and Short-on states, the disk is maximum open to the observer's view, while during the low states, the outer parts of the tilted disk block the X-ray source.…”

Section: Introductionmentioning

confidence: 93%

Evidence for neutron star triaxial free precession in Her X-1 from Fermi/GBM pulse period measurements

Kolesnikov,

Shakura,

Postnov

2022

Preprint

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Her X-1/HZ Her is one of the best studied accreting X-ray pulsars. In addition to the pulsating and orbital periods, the X-ray and optical light curves of the source exhibit an almost periodic 35-day variability caused by a precessing accretion disk. The nature of the observed long-term stability of the 35-day cycle has been debatable. The X-ray pulse frequency of Her X-1 measured by the Fermi/GBM demonstrates periodical variations with X-ray flux at the Main-on state of the source. We explain the observed periodic sub-microsecond pulse frequency changes by the free precession of a triaxial neutron star with parameters previously inferred from an independent analysis of the X-ray pulse evolution over the 35-day cycle. In the Fermi/GBM data, we identified several time intervals with a duration of half a year or longer where the neutron star precession period describing the pulse frequency variations does not change. We found that the NS precession period varies within one per cent in different intervals. Such variations in the free precession period on a year time scale can be explained by 1% changes in the fractional difference between the triaxial neutron star's moments of inertia due to the accreted mass readjustment or variable internal coupling of the neutron star crust with the core.

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Section: Introductionmentioning

confidence: 93%

Evidence for neutron star triaxial free precession in Her X-1 from Fermi/GBM pulse period measurements

Kolesnikov,

Shakura,

Postnov

2022

Preprint

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“…There are also cases of significant variations in observed profiles of transient sources during an outburst, where the pulse profiles can dramatically change their looks and behaviour (see e.g. Brumback et al 2021;Camero Arranz et al 2007;Cappallo et al 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Studying this energy dependence contains information about the physical processes inside the accretion column, like Comptonization, Bremsstrahlung and cyclotron radiation (Becker & Wolff 2005Wolff et al 2016). For disk-fed pulsars there will also be reprocessing of soft X-rays in the large accretion disk (Hickox et al 2004;Hickox & Vrtilek 2005;Brumback et al 2020Brumback et al , 2021. In addition, emission lines of heavy elements such as iron, produced by fluorescence stimulated in the accretion disk or in the circumstellar material, can produce significant effects at the corresponding line energies in the spectra and pulse profiles.…”

Section: Introductionmentioning

confidence: 99%

Common patterns in pulse profiles of high-mass X-ray binaries

Alonso-Hernández

Fürst

Kretschmar

et al. 2022

A&A

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Context. X-ray pulsars are binary systems which consist of a neutron star in orbit with a mass donor (companion). In these systems the neutron accretes matter from the companion star, which creates accretion columns or hot spots on the neutron star surface and gives rise to pulsations in the X-ray light curve. The pulse profiles carry information about the accretion and magnetic field geometry.Here we present a study and classification of energy-resolved pulse profiles of a sample of X-ray pulsars, focusing on high-mass X-ray binaries. Aims. Our goal is to perform a classification of X-ray pulsars based on their observed pulse profiles and look for correlations between this classification and their principle physical observables. The analysis pipeline is available online. Methods. We analysed the pulse profiles of a sample of X-ray pulsars using data obtained with the X-ray Multi-Mirror Mission (XMM-Newton) and the Nuclear Spectroscopic Telescope Array (NuSTAR ). We fitted the energy-resolved pulse profiles with a Fourier series of up to five harmonics. We then used the energy evolution of the different Fourier components to classify the pulse profiles into groups. We investigated relationships between the pulse profile properties and other observables of the systems (e.g. orbital period, magnetic field strength, and luminosity) to study the extreme physics of these systems.Results. The sources were divided into three groups using a classification based on the shape, the dominance of the fitted Fourier harmonics, and their respective evolution with energy. We do not find a conclusive correlation between the pulse profile shapes or groups and other parameters of the systems. However, a weak trend was found when comparing our classification to the sources' locations in the spin period-orbital period diagram. Further studies are required to confirm this trend. Conclusions. Despite the large variety of pulse profiles of the X-ray pulsars, we found that with our approach clear categories emerge which we use to classify their behaviour as a function of energy. As we do not find a clear relationship between our classification scheme and other parameters, like the luminosity, the magnetic field strength, or the orbital and spin periods, we conclude that X-ray pulse profiles are influenced by other hidden variables.

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“…9 in Kretschmar et al 2021). But there are also cases of significant variations in observed profiles of transient sources during an outburst, where the pulse profiles can dramatically change their looks and behavior (see, e.g., Brumback et al 2021;Camero Arranz et al 2007;Cappallo et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Common patterns in pulse profiles of High Mass X-ray Binaries

Alonso-Hernandez,

Fuerst,

Kretschmar

et al. 2022

Preprint

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Context. X-ray pulsars are binary systems which consist of a neutron star in orbit with a mass donor (companion). In these systems the neutron star accretes matter from the companion star, which creates accretion columns or hot spots on the neutron star surface and gives rise to pulsations in the X-ray light-curve. The pulse profiles carry information about the accretion and magnetic field geometry.Here we present a study and classification of energy resolved pulse profiles of a sample of X-ray pulsars, focusing on high-mass X-ray binaries. Aims. Our goal is to perform a classification of X-ray pulsars based on their observed pulse profiles and look for correlations between this classification and their principle physical observables. The analysis pipeline is available online. Methods. We analysed the pulse profiles of a sample of X-ray pulsars using data obtained with the X-ray Multi-Mirror Mission (XMM-Newton) and the Nuclear Spectroscopic Telescope Array (NuSTAR ). We fit the energy resolved pulse profiles with a Fourier series of up to five harmonics. We then use the energy evolution of the different Fourier components to classify the pulse profiles into groups. We investigate relationships between the pulse profile properties and other observables of the systems (e.g., orbital period, magnetic field strength, and luminosity) to study the extreme physics of these systems.Results. The sources were divided into three groups by a classification based on the shape, the dominance of the fitted Fourier harmonics and their respective evolution with energy. We do not find a conclusive correlation between the pulse profile shapes or groups and other parameters of the systems. However, a weak trend was found when comparing our classification to the sources' location in the spin period-orbital period diagram. Further studies are required to confirm this trend. Conclusions. Despite the large variety of pulse profiles of the X-ray pulsars, we found that with our approach clear categories emerge which we use to classify their behavior as function of energy. As we do not find a clear relationship between our classification scheme and other parameters, like the luminosity, the magnetic field strength, or the orbital and spin periods, we conclude that X-ray pulse profiles are influenced by other hidden variables.

show abstract

A Broadband X-Ray View of the Precessing Accretion Disk and Pre-eclipse Dip in the Pulsar Her X-1 with NuSTAR and XMM-Newton

Cited by 18 publications

References 62 publications

Evidence for neutron star triaxial free precession in Her X-1 from Fermi/GBM pulse period measurements

Evidence for neutron star triaxial free precession in Her X-1 from Fermi/GBM pulse period measurements

Common patterns in pulse profiles of high-mass X-ray binaries

Common patterns in pulse profiles of High Mass X-ray Binaries

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