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A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. I. Overview of thr 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 theWe 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.show moreshow less

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Author:Michael F. Corcoran, Joy S. Nichols, Herbert Pablo, Tomer ShenarORCiDGND, Andy M. T. Pollock, Wayne L. Waldron, Anthony F. J. Moffat, Noel D. Richardson, Christopher M. P. Russell, Kenji Hamaguchi, David P. Huenemoerder, Lida Oskinova, Wolf-Rainer HamannORCiDGND, Yael Naze, Richard Ignace, Nancy Remage Evans, Jamie R. Lomax, Jennifer L. Hoffman, Kenneth Gayley, Stanley P. Owocki, Maurice Leutenegger, Theodore R. Gull, Karen Tabetha Hole, Jennifer Lauer, Rosina C. Iping
DOI:https://doi.org/10.1088/0004-637X/809/2/132
ISSN:0004-637X (print)
ISSN:1538-4357 (online)
Parent Title (English):The astrophysical journal : an international review of spectroscopy and astronomical physics
Publisher:IOP Publ. Ltd.
Place of publication:Bristol
Document Type:Article
Language:English
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
Tag:X-rays: stars; binaries: close; binaries: eclipsing; stars: early-type; stars: individual (Delta Ori); stars: mass-loss
Volume:809
Issue:2
Pagenumber:15
Funder:National Aeronautics and Space Administration [GO3-14015A, GO3-14015E]; National Aeronautics Space Administration [NAS8-03060]; NASA [NNG06EO90A, NNX13AF40G]; Chandra X-ray Center NASA [NAS8-03060]; NASA Postdoctoral Program at the Goddard Space Flight Center; Leibniz Graduate School for Quantitative Spectroscopy in Astrophysics; Leibniz Institute for Astrophysics Potsdam (AIP); institute of Physics and Astronomy of the University of Potsdam; Fonds National de la Recherche Scientifique (Belgium); Communaute Francaise de Belgique; PRODEX XMM and Integral contracts; "Action de Recherche Concertee" (CFWB-Academie Wallonie Europe); CRAQ (Centre de Recherche en Astrophysique du Quebec) fellowship; NSERC (Canada); FRQNT (Quebec); NSF [AST-0807477]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert