Discovery of nine runaway stars with strange rotation rates

20 Feb

Screen Shot 2015-02-20 at 1.07.24 PMEvans et al. investigated the nearly 300  B-type stars in the Tarantula nebula measuring their velocities toward and away from us using the Doppler effect.  Nine stars have extreme velocities and are candidate runaway stars. 

They appear to have strange rotation rates: either they spin very very fast or very slow.  The most extreme case is star VFTS 358, which is moving at 100 km/s. It is a very rapid rotator and shows peculiar surface chemistry.  This is very suggestive of the so-called “binary ejection scenario”.  Likely, the star was member of a close binary where it was enriched and spun up by its companion star. When the companion died (in a supernova explosion), star VFTS 358 was ejected, now flying through space all by it self.

The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars, C. J. Evans, et al. A&A, 574, A13, 2015…574A..13E