WR140 = HD 193793 is a massive binary system containing a Wolf-Rayet star of the carbon sequence accompanied by a giant/supergiant O star in a highly elliptical 7.94-year orbit. With components WC7pd + O5.5fc it is a one of the 8 bright WR stars in Cygnus, with v = 7.0 mag. WR140 is referred to as the Rosetta stone of colliding wind binaries, producing copious quantities of carbon-based dust mainly around periastron passage. It was the main target of a pro-am study during 4 months centered at periastron at mid January 2009, when most of the wind-collision action takes place. The main results are published in Fahed et al. (2011, MNRAS, vol. 418, p.2).
The next periastron passage will be in late December 2016, at which time we are seeking amateur and other collaboration to carry out the following intensive monitoring from early October 2016 through late March 2017:
1. NIR spectroscopy of the very bright HeI 10830A line, which shows very clear wind-wind collision excess, but which was observed only occasionally during the last periastron passage. This line might be doable using optical CCDs at their extreme red limit.
2. Multiple optical broadband high-precision linear polarimetry (Stokes Q, U). The previous data were again incomplete, especially during the 2-month interval centered on periastron passage.
If you have the means to carry out either or both of these campaigns, please contact me in good time:
Tony Moffat,
moffat@astro.umontreal.ca
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