emamajek on 13-Mar-2019 05:55:06 GMT about WASP-31B
2011A&A...531A..60A point out that 2MASS J11174477-1903521 is a likely physical companion star to WASP-31 at separation 35".
"WASP-31 is a visual double with a V∼15.8 star (2MASS 11174477-1903521) approximately 35" away. The 2MASS colours of the companion suggest that it is a mid-to-late K-type star. The proper motions for the two stars listed in thePPMXL (Roeser et al. 2010) and UCAC3 (Zacharias et al. 2010) catalogues suggest that this is a common proper motion pair (Table 1)."
Gaia DR2 data supports the interpretation that this is a physical binary.
WASP-31 = Gaia DR2 3545873945303316224
RA, Dec = 169.43886026146, -19.05477810599 (ICRS, epoch 2015.5)
plx = 2.5772 +- 0.0427 mas
pmRA, pmDec = -28.708, 0.990 (+-0.081, 0.054) mas/yr
companion = Gaia DR2 3545873567346193920
RA, Dec = 169.43639327726, -19.06447467031 (ICRS, epoch 2015.5; Gaia DR2)
plx = 2.5765 +- 0.0454 mas
pmRA, pmDec = -29.486, 2.025 (+-0.085, 0.050) mas/yr
separation = 35".90, PA = 193.52 deg
While WASP-31 has an entry in Washington Double Star catalog (WDS J11178-1903), the B component is an unrelated 20th magnitude star at 15.8" (Gaia DR2 3545873945303324672), not this object. WDS J11178-1903 B is a background object with negligible proper motion and parallax, clearly unrelated to WASP-31.
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