In sifting through the Kepler data taken so far, postdoctoral student Jason Rowe found a very curious light signature. When an object passed behind its central star, the light from the system dropped significantly. This means the object -- called KOI 74b -- must be glowing fiercely with its own light that was blocked out when the object was eclipsed.
In fact calculations show that the mystery object is hotter than the parent star. It is seething at 70,000 degrees Fahrenheit while the parent star is 17,000 degrees Fahrenheit. The strange object can’t be a star because the transit data show that it is no bigger than Jupiter. It is so close to the central star it completes an orbit in 23 days.
If that isn't weird enough, a super-hot Neptune-sized companion called KOI 81b was found orbiting another star with a 5.2-day orbital period.
Both parent stars are hot and short-lived A-class stars that bathe the companions in a torrent of ultraviolet light. What's more, gravitational tidal effects would heat the interiors of the companion objects. But that still probably doesn’t explain why the mystery objects are so unbelievably hot, even if they were newborn planets. (The hottest confirmed exoplanet to date in 3,700 degrees Fahrenheit.)
One idea is that a white dwarf migrated close to the primary star and was gravitationally stripped of some of its mass. With less mass and therefore lower gravity the dwarf would swell to the size of Jupiter.
more:
http://news.discovery.com/space/blazing-stellar-companion-defies-explanation.html