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Vanishing Behind a Red Dwarf Star

1 Jul 2015, 23:00 UTC
Vanishing Behind a Red Dwarf Star
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Derekas et al. (2015) present the discovery of a totally-eclipsing binary system identified as J0640+3856. This binary system consists of a hot subdwarf O (sdO) star and a red dwarf star. An sdO star is basically a very hot low mass star that is burning helium in its core and a thin envelope of hydrogen surrounds the star’s core. Such a star can be created when a red giant star sheds its outer layers. J0640+3856 has an orbital period of 4.5 hours and the orbital plane of the system is orientated edge-on such that the sdO star disappears entirely behind the red dwarf star every orbit.Light curve of J0640+3856. The large dip in relative flux occurs when the more luminous sdO star disappears behind the red dwarf star, while the smaller dip in relative flux occurs when the sdO star passes in front of the less luminous red dwarf star. Derekas et al. (2015).Spectroscopic and photometric observations of J0640+3856 show that the sdO star has 0.567 ± 0.138 times the Sun’s mass, 0.0955 ± 0.0077 times the Sun’s radius, 73.692 ± 11.819 times the Sun’s luminosity and a very hot surface temperature of 55,000 ± 3,000 K. As for the ...

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