  The putative association between the 10.8 d classical Cepheid TW Nor and the
open cluster Lynga 6 has generated considerable debate in the literature. New
JHKs photometry in tandem with existing radial velocities for Lynga 6 stars
imply cluster membership for TW Nor, and establish the variable as a
high-weight calibrator for classical Cepheid relations. Fundamental mean
parameters determined for Lynga 6 are: d=1.91+-0.10 kpc, E(J-H)=0.38+-0.02, and
log(t)=7.9+-0.1. The Benedict et al.(2007)/Turner (2010) Galactic VIc Wesenheit
function was revised using TW Nor's new parameters:
W_VI,0=(-3.37+-0.08)log(P_0)-2.48+-0.08. TW Nor/Lynga 6 lie beyond the
Sagittarius-Carina spiral arm and occupy the Centaurus arm, along with
innumerable young Cepheids and clusters (e.g., VW Cen & VVV CL070).
