The Long Stare at Hercules X-1. I. Emission Lines from the Outer Disk, the Magnetosphere Boundary, and the Accretion Curtain
| Autor: | P. Kosec, E. Kara, A. C. Fabian, F. Fürst, C. Pinto, I. Psaradaki, C. S. Reynolds, D. Rogantini, D. J. Walton, R. Ballhausen, C. Canizares, S. Dyda, R. Staubert, J. Wilms |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | The Astrophysical Journal. 936:185 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.3847/1538-4357/ac897e |
| Popis: | Hercules X-1 is a nearly edge-on accreting X-ray pulsar with a warped accretion disk, precessing with a period of about 35 days. The disk precession allows for unique and changing sightlines towards the X-ray source. To investigate the accretion flow at a variety of sightlines, we obtained a large observational campaign on Her X-1 with XMM-Newton (380 ks exposure) and Chandra (50 ks exposure) for a significant fraction of a single disk precession cycle, resulting in one of the best datasets taken to date on a neutron star X-ray binary. Here we present the spectral analysis of the High State high-resolution grating and CCD datasets, including the extensive archival data available for this famous system. The observations reveal a complex Fe K region structure, with three emission line components of different velocity widths. Similarly, the high-resolution soft X-ray spectra reveal a number of emission lines of various widths. We correct for the uncertain gain of the EPIC-pn Timing mode spectra, and track the evolution of these spectral components with Her X-1 precession phase and observed luminosity. We find evidence for three groups of emission lines: one originates in the outer accretion disk (10^5 RG from the neutron star). The second line group plausibly originates at the boundary between the inner disk and the pulsar magnetosphere (10^3 RG). The last group is too broad to arise in the magnetically-truncated disk and instead must originate very close to the neutron star surface, likely from X-ray reflection from the accretion curtain (~10^2 RG). Comment: Accepted for publication in ApJ. 26 pages, 17 figures, 4 tables |
| Databáze: | OpenAIRE |
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