66) of an unseen stellar companion definitely piqued my curiosity, since I seemed to recall that there was already a suspected
main-sequence star companion near the central star of this nebula.
Among the topics are circum-binary components of contact binaries, extremely short-period contact binaries, the first spectroscopic solutions of two southern eclipsing binaries: HO Tel and QY Tel, effective temperatures of selected
main-sequence stars with the most accurate parameters, heating of the upper atmosphere of a hot Jupiter for various spectral energy distributions of the host star, and plants and brown dwarfs orbiting evolved binaries.
The fainter one is a
main-sequence star similar to our Sun but shining blue because it's much hotter.
Where the accretor is always a white dwarf, the donor star can be either a (helium or hybrid) white dwarf, a low-mass helium star or an evolved
main-sequence star.
Among the topics are the origin and evolution of helium-rich hot subdwarfs, the high-resolution spectropolarimetric observations of hot subdwarfs, the discovery of a stripped red-giant core in a bright eclipsing binary star, statistical tests for changes inpulsation mode properties, and EO Ceti as an example of a pulsating hot subdwarf with a
main-sequence companion.
But, over the period May to December of the years 2006 and 2007, the WASP telescope at Sutherland has made 8235 photometric observations of the star HD10069, known as WASP-18, a relatively young
main-sequence object of type F6.
This would make Beta Pictoris far too young to qualify as a
main-sequence star, burning hydrogen at its core.
Over billions of years, enough of this material could accumulate in a
main-sequence star to leave a core of strange matter when the star dies.
The analysis, reported in two papers in the August 1st Astrophysical Journal, shows that the host star is a K5
main-sequence star (still fusing hydrogen in its core, as the Sun does), with a mass about two-thirds that of our star.
For nearly a decade, Beta Pictoris has reigned as the only mature,
main-sequence star with an encircling disk of dust - perhaps much like the disk from which our solar system evolved 4.6 billion years ago - that astronomers have clearly imaged.
Optical pictures of the cluster, taken by ground-based telescopes, detect mainly red giant stars and yellow
main-sequence stars, whereas the ultraviolet image primarily spotlights hotter, less common stars that evolved from red giants by ejecting their outer atmosphere.
The resulting plot draws a "
main-sequence wedge," reminiscent of the Hertzsprung-Russel!