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A Coordinated X-Ray and Optical Campaign of the Nearest Massive Eclipsing Binary, Delta Orionis Aa. II. X-Ray VariabilityWe present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral data set of the delta Ori Aa binary system. The four observations, obtained with Chandra ACIS (Advanced CCD Imaging Spectrometer) HETGS (High Energy Transmission Grating), have a total exposure time approximately equal to 479 kiloseconds and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range of 5-25 angstroms is confirmed, with a maximum amplitude of about plus or minus15 percent within a single approximately equal to125 kiloseconds observation. Periods of 4.76 and 2.04 days are found in the total X-ray flux, as well as an apparent overall increase in the flux level throughout the nine-day observational campaign. Using 40 kiloseconds contiguous spectra derived from the original observations, we investigate the variability of emission line parameters and ratios. Several emission lines are shown to be variable, including S (sub XV), Si (sub XIII), and Ne (sub IX). For the first time, variations of the X-ray emission line widths as a function of the binary phase are found in a binary system, with the smallest widths at phi = 0.0 when the secondary delta Ori Aa2 is at the inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds, we relate the emission line width variability to the presence of a wind cavity created by a wind-wind collision, which is effectively void of embedded wind shocks and is carved out of the X-ray-producing primary wind, thus producing phase-locked X-ray variability.
Document ID
20150023308
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Nichols, J.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Huenemoerder, D. P.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Corcoran, M. F.
(Universities Space Research Association Greenbelt, MD, United States)
Waldron, W.
(Universities Space Research Association Columbia, MD, United States)
Naze, Y.
(Eureka Scientific, Inc. Oakland, CA, United States)
Pollock, A. M. T.
(Liege Univ. Belgium)
Moffat, A. F. J.
(European Space Agency Cologne, Germany)
Lauer, J.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Shenar, T.
(Montreal Univ. Quebec, Canada)
Russell, C. M. P.
(Oklahoma Univ. Norman, OK, United States)
Hamaguchi, K.
(Universities Space Research Association Greenbelt, MD, United States)
Gull, T.
(Maryland Univ. Baltimore County Baltimore, 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
Astronomy
Report/Patent Number
GSFC-E-DAA-TN27985
Funding Number(s)
CONTRACT_GRANT: NNG06EO90A
CONTRACT_GRANT: NNH06CC03B
Distribution Limits
Public
Copyright
Other
Keywords
X-ray flux
Ori Aa binary system
Chandra ACIS HETGS

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