CCD Washington photometry of the moderately metal-poor open cluster NGC 2236

Abstract

CCD CT1 Washington photometry in the field of the open cluster NGC 2236 is presented, together with photoelectric CMT1T2 photometry of 13 red giant candidates. Based on the best fits of isochrones computed for Z = 0.008 to the (T1,C-T1) diagram, we derive reddening, distance and age. A metal abundance [Fe/H] = -0.3 ± 0.2 is estimated from five independent abundance indices. We also derive a cluster core radius of rc = 1.2 pc and an annular cluster corona of ∆rc = 2.2 pc. The properties of a sample of 20 known open clusters aligned along the line-of-sight to NGC 2236 are examined.

Presentamos fotometrıa de Washington CCD CT1 en el campo del cumulo abierto NGC 2236, juntamente con fotometrıa fotoelectrica CMT1T2 de 13 candidatas a gigantes rojas. En base a ajustes de isocronas teoricas al diagrama (T1,C-T1) para Z = 0.008, derivamos enrojecimiento, distancia y edad. La abundancia metalica que resulta a partir de cinco ındices de abundancia independientes es [Fe/H] = -0.3 ± 0.2. Se obtienen ademas valores de 1.2 pc y 2.2 pc para el radio del nucleo y de la corona del cumulo, respectivamente. Se examinan las propiedades de una muestra de 20 cumulos conocidos alineados en la direccion de NGC 2236.