The very reddened open clusters Pismis 23 (Lynga 10) and Stephenson 2

Abstract

Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic plane. We present VI and JH photometry for Pismis 23 and I and Gunn z for Stephenson 2. We derive a relatively old age of ~ 700 Myr for Pismis 23, with a reddening value of E(B−V) = 1:73 and a distance dʘ ≈ 2.6 kpc from the Sun. Stephenson 2 has a clump of red supergiants, indicating a young age of about 20 Myr, somewhat younger and more distant (dʘ ≈ 6 kpc) than recently reported in the literature. The age estimate for such a young object is crucial for the distance estimate. The high reddening of these two clusters relative to predictions from the di use interstellar medium at their distances is due to discrete intervening clouds.