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A Coordinated X-Ray and Optical Campaign of the Nearest Massive Eclipsing Binary, Delta Orionis Aa. I. Overview of the X-Ray Spectrum We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary (Delta Ori Aa1), Delta Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around Delta 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.
Document ID
20150023334
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Corcoran, M. F.
(Universities Space Research Association Columbia, MD, United States)
Nicholas, J. S.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Pablo, H.
(Montreal Univ. Quebec, Canada)
Shenar, T.
(Potsdam Univ. Potsdam, Germany)
Pollock, A. M. T.
(European Space Astronomy Centre (ESAC) Madrid, Spain)
Waldron, W. L.
(Eureka Scientific, Inc. Oakland, CA, United States)
Moffat, A. F. J.
(Montreal Univ. Quebec, Canada)
Richardson, N. D.
(Montreal Univ. Quebec, Canada)
Russell, C. M. P.
(Oak Ridge Associated Universities Greenbelt, MD, United States)
Hamaguchi, K.
(Maryland Univ. Baltimore, MD, United States)
Leutenegger, M.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Gull, T. R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Iping, R. C.
(Maryland Univ. College Park, MD, United States)
Date Acquired
December 18, 2015
Publication Date
August 18, 2015
Publication Information
Publication: The Astrophysical Journal
Publisher: The American Astronomical Society
Volume: 809
Issue: 2
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN27991
Funding Number(s)
CONTRACT_GRANT: NNH06CC03B
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Other
Keywords
Chandra HETGS
Ori Aa2
eclipsing spectroscopic binary

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