Strange star system may hold first evidence of an ultra-rare 'dark matter star'

Astronomers long thought that a peculiar star system observed by the European Space Agency's Gaia satellite was a simple case of a star orbiting a black hole. 
But now, two astronomers are challenging that claim, finding that the evidence suggests something far stranger: Possibly, a never-before-seen type of star made of invisible dark matter. Their research, which has yet to be peer-reviewed, was published April 18 on the preprint server arXiv.
The system itself consists of a sunlike star and, well, something else. The star weighs a little less than the sun (0.93 solar mass) and has roughly the same chemical abundance as the sun. Its mysterious companion is much more massive — around 11 solar masses. The objects orbit each other at a distance of 1.4 astronomical units, about the distance at which Mars orbits the sun, making a complete orbit every 188 days.
Strange star system may hold first evidence of an ultra-rare 'dark matter star'