The 3″ pair of B9 stars , HD 28867 , is one of the brightest X-ray sources in the Taurus-Auriga star forming region .
In this multi-wavelength study , we attempt to deduce the source of the X-ray emission .
We show that the East component is the X-ray source .
The East component has a near-IR excess and displays narrow absorption lines in the optical , both of which are consistent with a cool stellar companion .
This companion is one of the brightest low mass pre-main sequence stars in Tau-Aur ; at 2 \mu m it and the B9 star are equally bright .
We see evidence for radial velocity variability in the cool component of > 34 km s ^ { -1 } .
It is not visible in K band speckle imaging , which constrains the companion to lie within 14 AU of the B star .

We also report on a possible fourth member of the group , an M1 star 18″ south of HD 28867 .