Abstract
We present a photometric and astrometric analysis of the NGC 2158 cluster using Gaia DR2 and 2MASS data. The cluster age, color excess, intrinsic distance modulus and distance are calculated to be t = 2.240 ± 0.260 Gyr, E(B - V) = 0.420 ± 0.050 mag, (m - M)⊙ = 12.540 ± 0.130 mag and d⊙ = 3224 ± 200 pc respectively. The photometric analysis and light curve modelling of the proposed eclipsing binary member [NBN2015]78 is performed using the latest version of the Wilson-Devinney (W-D) code. The solutions show that the system is an over-contact binary with a secondary component filling its Roche lobe, with a mass ratio q = 0.262. The primary and the secondary components of the system consist of two late spectral types K1 and K2 respectively. The membership of [NBN2015]78 is discussed using two independent methods, and we find that [NBN2015]78 is an interloper and not a member of NGC 2158.
