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Title: HERCULES X-1: USING ECLIPSE TO MEASURE THE X-RAY CORONA

Abstract

Observations of HZ Her/Her X-1 by the Rossi X-ray Timing Explorer during High State X-ray eclipses are analyzed. After a sharp ingress caused by the neutron star receding behind the companion star HZ Her, X-ray flux smoothly declines to a minimum at mid-eclipse. It then increases smoothly until egress. The mid-eclipse flux implies an extended emission region around the neutron star that is larger than that of HZ Her. The constancy of the X-ray softness ratio is consistent with electron scattering by an ionized corona. The corona is modeled as spherically symmetric with a power-law density profile. We find a best fit of ∝r {sup –1.25} with a normalization of ≅ 10{sup 12} cm{sup –3} at r = 2 × 10{sup 10} cm. The corona could either be in hydrostatic equilibrium, with heating by Compton scattering, a fast outflow, with a high mass-loss rate of ∼10{sup 18} gm s{sup –1}, or a hybrid, with an inner hydrostatic region and outer slow flow with a low mass-loss rate. A brightening at orbital phase 0.94 is suggested to be caused by the impact of the accretion stream with the accretion disk.

Authors:
 [1]
  1. Department of Physics, University of Calgary, Calgary, Alberta T2N 1N4 (Canada)
Publication Date:
OSTI Identifier:
22364249
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 800; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; COMPTON EFFECT; ECLIPSE; ELECTRONS; EQUILIBRIUM; MASS TRANSFER; NEUTRON STARS; PHOTON EMISSION; STELLAR WINDS; SYMMETRY; X RADIATION

Citation Formats

Leahy, D. A. HERCULES X-1: USING ECLIPSE TO MEASURE THE X-RAY CORONA. United States: N. p., 2015. Web. doi:10.1088/0004-637X/800/1/32.
Leahy, D. A. HERCULES X-1: USING ECLIPSE TO MEASURE THE X-RAY CORONA. United States. doi:10.1088/0004-637X/800/1/32.
Leahy, D. A. Tue . "HERCULES X-1: USING ECLIPSE TO MEASURE THE X-RAY CORONA". United States. doi:10.1088/0004-637X/800/1/32.
@article{osti_22364249,
title = {HERCULES X-1: USING ECLIPSE TO MEASURE THE X-RAY CORONA},
author = {Leahy, D. A.},
abstractNote = {Observations of HZ Her/Her X-1 by the Rossi X-ray Timing Explorer during High State X-ray eclipses are analyzed. After a sharp ingress caused by the neutron star receding behind the companion star HZ Her, X-ray flux smoothly declines to a minimum at mid-eclipse. It then increases smoothly until egress. The mid-eclipse flux implies an extended emission region around the neutron star that is larger than that of HZ Her. The constancy of the X-ray softness ratio is consistent with electron scattering by an ionized corona. The corona is modeled as spherically symmetric with a power-law density profile. We find a best fit of ∝r {sup –1.25} with a normalization of ≅ 10{sup 12} cm{sup –3} at r = 2 × 10{sup 10} cm. The corona could either be in hydrostatic equilibrium, with heating by Compton scattering, a fast outflow, with a high mass-loss rate of ∼10{sup 18} gm s{sup –1}, or a hybrid, with an inner hydrostatic region and outer slow flow with a low mass-loss rate. A brightening at orbital phase 0.94 is suggested to be caused by the impact of the accretion stream with the accretion disk.},
doi = {10.1088/0004-637X/800/1/32},
journal = {Astrophysical Journal},
number = 1,
volume = 800,
place = {United States},
year = {Tue Feb 10 00:00:00 EST 2015},
month = {Tue Feb 10 00:00:00 EST 2015}
}