Inhomogeneous Wind of the Wolf-Rayet Star V444 Cygni

All hot, massive stars drive fast, dense winds. To understand the evolution of a massive star is to understand how the mass is lost. Recently it has been found that all massive stars produce clumpy, highly inhomogeneous winds. The eclipsing binary V444 Cygni may be considered as a “Rosetta Stone” system for the population of star galactic binaries composed of Wolf-Rayet (WR) and OB-type stars. Indeed, more than 300 publications have been devoted to this system! However, there is a lingering question: Is the WR wind of V444 Cygni clumped? Solving this problem, we have processed the near infrared and optical images of V444 Cygni obtained almost simultaneously over twelve contiguous nights. We targeted the highest possible precision, finally achieving a standard deviation (σ) of 0.01 magnitudes (or ~1%) in the IR band. In the optical, we expected σ = 0.005 mag, but obtained σ = 0.01 mag. We find that the IR light curve is broader than the optical during the secondary eclipse, when the O star companion passes in front of WR star. This result supports the conclusion of a clumped WR wind