A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, δ Ori Aa: I. Overview of the X-ray Spectrum.

Creator(s)

Michael Corcoran, CRESST and X-ray Astrophysics Laboratory
Joy Nichols, Harvard-Smithsonian Center for Astrophysics
H. Pablo, Université de Montréal
Tomer Shenar, Universität Potsdam
Andy Pollock, European Space Agency
W. Waldron, Eureka Scientific, Inc.
A. Moffat, Université de Montréal
N. Richardson, Université de Montréal
C. Russell, Goddard Space Flight Center
K. Hamaguchi, University of Maryland
D. Huenemoerder, Massachusetts Institute of Technology
L. Oskinova, Universität Potsdam
W.-R. Hamann, Universität Potsdam
Y. Nazé, Institut d’Astrophysique et de Géophysique
Richard Ignace, East Tennessee State University
Nancy Evans, Harvard-Smithsonian Center for Astrophysics
Jamie Lomax, University of Oklahoma
J. Hoffman, University of Denver
K. Gayley, University of Iowa
S. Owocki, University of Delaware
M. Leutenegger, University of Maryland
T. Gull, Laboratory for Extraterrestrial Planets and Stellar Astrophysics
K. Hole, Weber State University
J. Lauer, Harvard-Smithsonian Center for Astrophysics
R. Iping, University of Maryland

Document Type

Article

Publication Date

8-18-2015

Description

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.

Copyright Statement

Copyright © 2015. The American Astronomical Society. All rights reserved.

Citation Information

M. F. Corcoran, J. S. Nichols, H. Pablo, T. Shenar, A. M. T. Pollock, W. L. Waldron, A. F. J. Moffat, N. D. Richardson, C. M. P. Russell, K. Hamaguchi, D. P. Huenemoerder, L. Oskinova, W.-R. Hamann, Y. Nazé, R. Ignace, N. R. Evans, J. R. Lomax, J. L. Hoffman, K. Gayley, S. P. Owocki, M. Leutenegger, T. R. Gull, K. T. Hole, J. Lauer, and R. C. Iping. "A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, δ Ori Aa: I. Overview of the X-ray Spectrum." The Astrophysical Journal 809 (2015): 132.
doi:10.1088/0004-637X/809/2/132
Available at: http://works.bepress.com/richard_ignace/37