Dust formation by the colliding wind WC5+O9 binary WR 19 at periastron passage

We present infrared photometry of the episodic dust-making Wolf-Rayet system WR 19 (LS 3), tracking its fading from a third observed dust formation episode in 2007 and strengthening the view that these episodes are periodic (P= 10.1 ± 0.1y) . Radial velocities (RVs) of the O9 component observed between 2001 and 2008 show RV variations consistent with WR 19 being a spectroscopic binary of high eccentricity (e= 0.8) , having periastron passage in 2007.14, shortly before the phase of dust formation. In this respect, WR 19 resembles the archetypical episodic dust-making colliding wind binary system WR 140.