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

Abstract

We present an overview of four phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system which includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object which 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 A 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 ksec and covering nearly the entire binary orbit. Companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities simultaneous with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectrum. 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 \ion{Fe}{17} and \ion{Ne}{10} are inconsistent with model predictions, which may be an effect of resonance scattering

accepted by ApJ; revised according to ApJ proof

References in corpus (13)

• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• A coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, $\delta$ Orionis Aa: IV. A multiwavelength, non-LTE spectroscopic analysis
• Speckle interferometry at SOAR in 2012 and 2013
• The Effect of Porosity on X-ray Emission Line Profiles from Hot-Star Winds
• An Exact Integration Scheme for Radiative Cooling in Hydrodynamical Simulations
• High resolution X-ray spectroscopy of bright O type stars
• An Extensive Collection of Stellar Wind X-ray Source Region Emission Line Parameters,Temperatures, Velocities, and Their Radial Distributions as Obtained from Chandra Observations of 17 OB Stars
• Modeling the RXTE light curve of $\eta$ Carinae from a 3-D SPH simulation of its binary wind collision
• Young stars and brown dwarfs surrounding Alnilam (eps Ori) and Mintaka (del Ori)
• A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, delta Orionis Aa: III. Analysis of Optical Photometric MOST and Spectroscopic (Ground Based) Variations
• The Correlation between X-Ray Line Ionization and Optical Spectral Types of the OB Stars
• A Coordinated X-ray and Optical Campaign of the Nearby Massive Binary $\delta$ Orionis Aa: II. X-ray Variability
• The X-ray spectrum of delta Orionis observed by LETGS aboard Chandra

Cited by in corpus (8)

• A coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, $\delta$ Orionis Aa: IV. A multiwavelength, non-LTE spectroscopic analysis
• Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
• A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, delta Orionis Aa: III. Analysis of Optical Photometric MOST and Spectroscopic (Ground Based) Variations
• X-ray diagnostics of massive star winds
• A Coordinated X-ray and Optical Campaign of the Nearby Massive Binary $\delta$ Orionis Aa: II. X-ray Variability
• Spectrum of the secondary component and new orbital elements of the massive triple star Delta Ori A
• An X-ray Study of Two B+B Binaries: AH Cep and CW Cep
• VLTI observations of the Orion Belt stars: I. eps Orionis