"I nearly fell out of my chair at the telescope when I saw one star change its speed by a staggering 750 miles per second in just a few minutes," said Smithsonian astronomer Warren Brown, lead author of the paper reporting the find."
The changing speed implies the orbit elliptical. When the pair gets close they whip past each other.
More info here:
"We have discovered a detached pair of white dwarfs (WDs) with a 12.75 min orbital period and a 1,315 km/s radial velocity amplitude. We measure the full orbital parameters of the system using its light curve, which shows ellipsoidal variations,..."
http://www.scientificamerican.com/podcast/episode.cfm?id=stars-do-dance-of-possible-death-11-07-13
Scientific paper here (pdf file):
http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.2389v1.pdf
I can see why! I mean, my God, an object with at least the mass of one hundred Jupiters is being yanked around like it's a rag doll... jaw hits floor.
Thanks for the links.