NASA | MSFC | SAO | Chandra X-ray Observatory | 2015 Nov 12
[img3="Credit: X-ray: NASA/CXC/GSFC/M. Corcoran et al.; Optical: Eckhard Slawik"]http://chandra.si.edu/photo/2015/dori/dori_525.jpg[/img3][hr][/hr]One of the most recognizable constellations in the sky is Orion, the Hunter. Among Orion's best-known features is the "belt," consisting of three bright stars in a line, each of which can be seen without a telescope.
The westernmost star in Orion's belt is known officially as Delta Orionis. (Since it has been observed for centuries by sky-watchers around the world, it also goes by many other names in various cultures, like "Mintaka".) Modern astronomers know that Delta Orionis is not simply one single star, but rather it is a complex multiple star system.
Delta Orionis is a small stellar group with three components and five stars in total: Delta Ori A, Delta Ori B, and Delta Ori C. Both Delta Ori B and Delta Ori C are single stars and may give off small amounts of X-rays. Delta Ori A, on the other hand, has been detected as a strong X-ray source and is itself a triple star system as shown in the artist's illustration.
In Delta Ori A, two closely separated stars orbit around each other every 5.7 days, while a third star orbits this pair with a period of over 400 years. The more massive, or primary, star in the closely-separated stellar pair weighs about 25 times the mass of the Sun, whereas the less massive, or secondary star, weighs about ten times the mass of the Sun.
The chance alignment of this pair of stars allows one star to pass in front of the other during every orbit from the vantage point of Earth. This special class of star system is known as an "eclipsing binary," and it gives astronomers a direct way to measure the mass and size of the stars. ...
A Coordinated X-ray and Optical Campaign of the Nearby Massive Binary δ Orionis Aa:
- I. Overview of the X-ray Spectrum - M. F. Corcoran et al
- arXiv.org > astro-ph > arXiv:1507.05101 > 17 Jul 2015 (v1), 22 Jul 2015 (v2)
- II. X-ray Variability - J. S. Nichols et al
- arXiv.org > astro-ph > arXiv:1507.04972 > 17 Jul 2015
- III. Analysis of Optical Photometric MOST and Spectroscopic (Ground Based) Variations - Herbert Pablo et al
- arXiv.org > astro-ph > arXiv:1504.08002 > 29 Apr 2015
- IV. A multiwavelength, non-LTE spectroscopic analysis - T. Shenar et al
- arXiv.org > astro-ph > arXiv:1503.03476 > 11 Mar 2015