A revisit to the region of Collinder 132 using Carte du Ciel and Astrographic Catalogue plates
^*

¹ Facultad de Ciencias Astronómicas y Geofisicas, UNLP, Paseo del Bosque s/n, 1900 La Plata, Argentina and Instituto de Astrofisica de La Plata - CONICET, UNLP, CCT La Plata, Argentina e-mail: [rorellan;debiasi]@fcaglp.unlp.edu.ar
² Observatorio Astronómico, Laprida 854, 5000 Córdoba, Argentina e-mail: [ivanbf;calderon]@mail.oac.uncor.edu

Received: 25 November 2009
Accepted: 27 May 2010

Abstract

Aims. Based on stellar positions and proper motions, we aim to re-analyse the region of the controversial open cluster Collinder 132.

Methods. We have developed a model which analyses the proper motion distribution and the stellar density to find moving groups. The astrometric data were obtained from four Carte du Ciel (CdC) and one Astrogaphic Catalogue (AC) plates of the Córdoba Astronomical Observatory collection (Argentina).

Results. We detected an open cluster from the field stars and calculated the mean proper motion and the membership probabilities of the region's stars. We report new coordinates of its centre α_c = 108347, δ_c = -31011, the components of mean proper motion μ_αcosδ = -2.62±0.44 mas/yr, μ_δ = 4.79±0.88 mas/yr. Thirteen stars are astrometric members giving a value of 20' for the cluster angular diameter. Six stars fulfil the astrometric and photometric criteria for being cluster members and locate the cluster at 360 pc from the Sun. We propose a simple model for the analysis of the proper motion distribution of an association. We report the components of the association mean proper motion μ_αcosδ = -1.38±0.14 mas/yr, μ_δ = 2.26±0.16 mas/yr. We found 149 astrometric members, 11 of which have reliable photometric data that locate them betweeen 417 and 660 pc from the Sun.