Majaess, Daniel J.; Turner, David Gerald, 1945-; Moni Bidin, Christian; Mauro, Francesco; Geisler, Douglas; Gieren, Wolfgang; Minniti, Dante; Chene, Andre-Nicolas; Lucas, Philip; Borissova, Jura
Abstract:
The putative association between the 10.d 8 classical Cepheid TW Nor and the open cluster Lyngå 6 has generated considerable debate in the literature. New JHKs photometry in tandem with existing radial velocities for Lyngå 6 stars implies cluster membership for TW Nor and establishes the variable as a high-weight calibrator for classical Cepheid relations. Fundamental mean parameters determined for Lyngå 6 are: d = 1.91 ± 0.10 kpc, E(J−H) = 0.38 ± 0.02, and log τ = 7.9 ± 0.1. The Benedict et al./Turner Galactic VIc Wesenheit function was revised using TW Nor's new parameters: WV I,0 = (−3.37 ± 0.08) log P0−2.48 ± 0.08. TW Nor/Lyngå 6 lie beyond the Sagittarius–Carina spiral arm and occupy the Centaurus arm, along with innumerable young Cepheids and clusters (e.g., VW Cen and VVV CL070).