In this paper we study some van den Bergh open clusters combining photometry and astrometry. A model which analyses the proper motion distribution and the stellar density is applied to find the kinematic parameters and stellar membership in the region of the open clusters vdB92, vdB146 (NGC 7129) and vdB150. The astrometric data are obtained from UCAC4 catalogue. The centre coordinates, the components of mean proper motion, the angular diameter and the astrometric members are reported, taking the following values: for vdB92: α=105.97281°±0.13113°, δ=−11.57814°±0.10575°,？μαcosδ=−3.46±0.19mas/yr,μδ=1.27±0.19mas/yr, 34', 60 members; for vdB146: α=325.78423°±0.15297°, δ=66.13575°±0.02907°, μαcosδ=−2.71±0.25mas/yr, μδ=−3.32±0.25mas/yr, 9', 5 members; and for vdB150: α=332.22519°±0.06074°, δ=73.40232°±0.0.07789°, μαcosδ=3.07±0.90mas/yr, μδ=4.65±0.90mas/yr, 15', 7 members. The incidence of the proper motion errors in the determination of the cluster parameters and of the stellar membership is analysed and it is found that they do not significantly change. We finally compare the astrometric members with the photometric ones given in the literature.
References
[1]
Corti, M.A. and Orellana, R.B. (2013) Members of Centaurus OB1 and NGC 4755: New Spectroscopic and Astrometric Studies. Astronomy and Astrophysics, 553, Article ID: A108. https://doi.org/10.1051/0004-6361/201220743
[2]
Orellana, R.B., De Biasi, M.S. , Paz, L.G., Bustos Fierro, I.H. and Calderón, J.H. (2015) A Revisit to the Regions of Some van den Bergh Open Clusters Using Photometric and Astrometric Parameters. New Astronomy, 36, 70-79. https://doi.org/10.1016/j.newast.2014.10.005
[3]
Bonatto, C. and Bica, E. (2010) The Fate of the Pre-Main Sequence-Rich Clusters Collinder 197 and vdB 92: Dissolution? Astronomy and Astrophysics, 516, Article ID: A81. https://doi.org/10.1051/0004-6361/201014146
[4]
van den Bergh, S. (1966) A Study of Reflection Nebulae. Astronomical Journal, 71, 990-998. https://doi.org/10.1086/109995
[5]
Racine, R. (1968) Stars in Reflection Nebulae. Astronomical Journal, 73, 233-245. https://doi.org/10.1086/110624
[6]
Soares, J.B. and Bica, E. (2003) The Embedded Star Clusters in the Nebulae vdB-RN 92 and Gy 3-7 in Canis Majoris R1. Astronomy and Astrophysics, 404, 217-222. https://doi.org/10.1051/0004-6361:20030485
[7]
Froebrich, D., Scholz, A. and Raftery, C.L. (2007) A Systematic Survey for Infrared Star Clusters with b < 20° Using 2MASS. Monthly Notices of the Royal Astronomical Society, 374, 399-408. https://doi.org/10.1111/j.1365-2966.2006.11148.x
[8]
Dias, W.S., Monteiro, H., Caetano, T.C., Lépine, J.R.D., Assafin, M. and Oliveira, A.F. (2014) Proper Motions of the Optically Visible Open Clusters Based on the UCAC4 Catalog. Astronomy and Astrophysics, 564, A79. https://doi.org/10.1051/0004-6361/201323226
[9]
Dias, W.S., Alessi, B.S., Moitinho, A. and Lépine, J.R.D. (2002) New Catalogue of Optically Visible Open Clusters and Candidates. Astronomy and Astrophysics, 389, 871-873. https://doi.org/10.1051/0004-6361:20020668
[10]
Aveni, A.F. and Hunter, J.H. (1972) Observational Studies Relating to Star Formation, III. Astronomical Journal, 77, 17-23. https://doi.org/10.1086/111239
[11]
Straizys, V., Maskoliūnas, M., Boyle, R.P., Prada Moroni, P.G., Tognelli, E., Zdanavicius, K., Zdanavicius, J., Laugalys, V. and Kazlauskas, A. (2004) The Distance to the Young Cluster NGC 7129 and Its Age. Monthly Notices of the Royal Astronomical Society, 438, 1848-1855. https://doi.org/10.1093/mnras/stt2334
[12]
Zacharias, N., Finch, C.T., Girard, T.M., Henden, A., Bartlett, J.L., Monet, D.G. and Zacharias, M.I. (2013) The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). The Astronomical Journal, 145, 44. https://doi.org/10.1088/0004-6256/145/2/44
[13]
Stock, J. and Abad, C. (1988) The Unification of Astrometric Catalogues. Revista Mexicana de Astronoma y Astrofsica, 16, 63.
[14]
Vasilevskis, S., Klemola, A. and Preston, G. (1958) Relative Proper Motions of Stars in the Region of the Open Cluster NGC 6633. Astronomical Journal, 63, 387-395. https://doi.org/10.1086/107787
[15]
Sanders, W.L. (1971) An Improved Method for Computing Membership Probabilities in Open Clusters. Astronomy and Astrophysics, 14, 226-232.
[16]
Jones, B.F. and Walker, M.F. (1988) An Improved Method for Computing Membership Probabilities in Open Clusters. Astronomical Journal, 95, 1755-1782. https://doi.org/10.1086/114773
[17]
Chen, B., Asiain, R., Figueras, F. and Torra, J. (1997) Identification of Moving Groups from a Sample of B, A and F Type Stars. Astronomy and Astrophysics, 318, 29-36.
