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Astrosat SXT X-ray Spectrum Changes over the 35-Day Cycle in Hercules X-1
Version 1
: Received: 6 June 2024 / Approved: 6 June 2024 / Online: 7 June 2024 (08:00:20 CEST)
A peer-reviewed article of this Preprint also exists.
Leahy , D.; Sharma , R. Soft X-ray Spectrum Changes over the 35-Day Cycle in Hercules X-1 Observed with AstroSat SXT. Universe 2024, 10, 298. Leahy , D.; Sharma , R. Soft X-ray Spectrum Changes over the 35-Day Cycle in Hercules X-1 Observed with AstroSat SXT. Universe 2024, 10, 298.
Abstract
Observations of the X-ray binary system Her X-1 by the AstroSat Soft X-ray Telescope 1 (SXT) were carried out in 2020 through 2023 with the goals of measuring X-ray spectrum changes with the 35-day disk rotation phase and measuring eclipses at different 35-day phases. The four multi-day long observations were scheduled during: turn-on to Main High (MH) and MH rise; MH state; Short High (SH) state; and Low State (LS). 35-day phase was determined using monitoring observations with the Swift Burst Alert Telescope (BAT). Nine eclipses were observed at a range of 35-day phases, with at least one eclipse during each observation. Data with dips were separated from data without dips. The variation of X-ray spectral parameters vs. 35-day phase shows the following: eclipse parameters are nearly constant, showing that the scattering corona does not change with 35-day phase; dips show an increase in covering fraction but not column density compared to non-dip data; the 1 keV line normalization indicates an origin in a small region near the continuum emission region, likely the magnetospheric accretion flow from the inner disk onto the neutron star; and the change in blackbody normalization (area) shows that the emission region is much larger than the 1 keV emission region, and consistent with the inner edge of the accretion disk.
Keywords
binaries; eclipsing — star; neutron— stars; individual (HZ Her/ Her X-1)
Subject
Physical Sciences, Astronomy and Astrophysics
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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