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Title: A COORDINATED X-RAY AND OPTICAL CAMPAIGN OF THE NEAREST MASSIVE ECLIPSING BINARY, δ ORIONIS Aa. I. OVERVIEW OF THE X-RAY SPECTRUM

Abstract

We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of δ Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, δ Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, δ Ori Aa2, has a much lower X-ray luminosity than the brighter primary (δ Ori Aa1), δ Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around δ Ori Aa1 via occultation by the photosphere of, and wind cavity around, the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ks and covering nearly the entire binary orbit. The companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities obtained simultaneously with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectra. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution frommore » the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about 0.3−0.5 times the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of Fe xvii and Ne x are inconsistent with model predictions, which may be an effect of resonance scattering.« less

Authors:
;  [1];  [2]; ; ;  [3]; ; ;  [4];  [5];  [6];  [7];  [8];  [9];  [10];
  1. CRESST and X-ray Astrophysics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 34, Cambridge, MA 02138 (United States)
  3. Département de physique and Centre de Recherche en Astrophysique du Québec (CRAQ), Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec, H3C 3J7 (Canada)
  4. Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam (Germany)
  5. European Space Agency, XMM-Newton Science Operations Centre, European Space Astronomy Centre, Apartado 78, E-28691 Villanueva de la Cañada (Spain)
  6. Eureka Scientific, Inc., 2452 Delmer St., Oakland, CA 94602 (United States)
  7. NASA-GSFC, Code 662, Goddard Space Flight Center, Greenbelt, MD, 20771 (United States)
  8. Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
  9. Groupe d’Astrophysique des Hautes Energies, Institut d’Astrophysique et de Géophysique, Université de Liége, 17, Allée du 6 Août, B5c, B-4000 Sart Tilman (Belgium)
  10. Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614 (United States)
Publication Date:
OSTI Identifier:
22525555
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 809; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ECLIPSE; EXCITATION; IRON IONS; LINE WIDTHS; LUMINOSITY; MASS TRANSFER; ORBITS; PHOTOMETRY; PHOTOSPHERE; RADIAL VELOCITY; SPACE; SPATIAL DISTRIBUTION; STARS; STELLAR WINDS; TEMPERATURE DISTRIBUTION; ULTRAVIOLET SPECTRA; X RADIATION; X-RAY SPECTRA

Citation Formats

Corcoran, M. F., Hamaguchi, K., Nichols, J. S., Pablo, H., Moffat, A. F. J., Richardson, N. D., Shenar, T., Oskinova, L., Hamann, W.-R., Pollock, A. M. T., Waldron, W. L., Russell, C. M. P., Huenemoerder, D. P., Nazé, Y., Ignace, R., and and others. A COORDINATED X-RAY AND OPTICAL CAMPAIGN OF THE NEAREST MASSIVE ECLIPSING BINARY, δ ORIONIS Aa. I. OVERVIEW OF THE X-RAY SPECTRUM. United States: N. p., 2015. Web. doi:10.1088/0004-637X/809/2/132.
Corcoran, M. F., Hamaguchi, K., Nichols, J. S., Pablo, H., Moffat, A. F. J., Richardson, N. D., Shenar, T., Oskinova, L., Hamann, W.-R., Pollock, A. M. T., Waldron, W. L., Russell, C. M. P., Huenemoerder, D. P., Nazé, Y., Ignace, R., & and others. A COORDINATED X-RAY AND OPTICAL CAMPAIGN OF THE NEAREST MASSIVE ECLIPSING BINARY, δ ORIONIS Aa. I. OVERVIEW OF THE X-RAY SPECTRUM. United States. doi:10.1088/0004-637X/809/2/132.
Corcoran, M. F., Hamaguchi, K., Nichols, J. S., Pablo, H., Moffat, A. F. J., Richardson, N. D., Shenar, T., Oskinova, L., Hamann, W.-R., Pollock, A. M. T., Waldron, W. L., Russell, C. M. P., Huenemoerder, D. P., Nazé, Y., Ignace, R., and and others. Thu . "A COORDINATED X-RAY AND OPTICAL CAMPAIGN OF THE NEAREST MASSIVE ECLIPSING BINARY, δ ORIONIS Aa. I. OVERVIEW OF THE X-RAY SPECTRUM". United States. doi:10.1088/0004-637X/809/2/132.
@article{osti_22525555,
title = {A COORDINATED X-RAY AND OPTICAL CAMPAIGN OF THE NEAREST MASSIVE ECLIPSING BINARY, δ ORIONIS Aa. I. OVERVIEW OF THE X-RAY SPECTRUM},
author = {Corcoran, M. F. and Hamaguchi, K. and Nichols, J. S. and Pablo, H. and Moffat, A. F. J. and Richardson, N. D. and Shenar, T. and Oskinova, L. and Hamann, W.-R. and Pollock, A. M. T. and Waldron, W. L. and Russell, C. M. P. and Huenemoerder, D. P. and Nazé, Y. and Ignace, R. and and others},
abstractNote = {We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of δ Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, δ Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, δ Ori Aa2, has a much lower X-ray luminosity than the brighter primary (δ Ori Aa1), δ Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around δ Ori Aa1 via occultation by the photosphere of, and wind cavity around, the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ks and covering nearly the entire binary orbit. The companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities obtained simultaneously with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectra. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about 0.3−0.5 times the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of Fe xvii and Ne x are inconsistent with model predictions, which may be an effect of resonance scattering.},
doi = {10.1088/0004-637X/809/2/132},
journal = {Astrophysical Journal},
number = 2,
volume = 809,
place = {United States},
year = {Thu Aug 20 00:00:00 EDT 2015},
month = {Thu Aug 20 00:00:00 EDT 2015}
}