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A deep proper-motion survey of the nearby open cluster Blanco 1

Platais, I. ; Girard, T. M. ; Vieira, K. ; López, C. E. ; Loomis, C. ; McLean, B. J. ; Pourbaix, D. ; Moraux, E. ; Mermilliod, J.-C ; James, D. J. ; Cargile, P. A. ; Barnes, S. A. ; Castillo, D. J.

In: Monthly Notices of the Royal Astronomical Society, 2011, vol. 413, no. 2, p. 1024-1035

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    Title
    • A deep proper-motion survey of the nearby open cluster Blanco 1
    Author
    • Platais, I.. Department of Physics & Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA
    • Girard, T. M.. Astronomy Department, Yale University, PO Box 208101, New Haven, CT 06520, USA
    • Vieira, K.. Centro de Investigaciones de Astronomia, Apartado Postal 264, Mérida 5101-A, Venezuela
    • López, C. E.. Yale Southern Observatory, Universidad Nacional de San Juan, Av. Benavídez 8175 Oeste, San Juan, Argentina
    • Loomis, C.. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
    • McLean, B. J.. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
    • Pourbaix, D.. Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
    • Moraux, E.. Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
    • Mermilliod, J.-C. Laboratoire d'Astrophysique de l'École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Versoix, Switzerland
    • James, D. J.. Physics & Astronomy Department, University of Hawaii at Hilo, Hilo, HI 96720, USA
    • Cargile, P. A.. Department of Physics & Astronomy, Vanderbilt University, Box 1807 Station B, Nashville, TN 37235, USA
    • Barnes, S. A.. Lowell Observatory, Flagstaff, AZ 86001, USA
    • Castillo, D. J.. Department of Science Operations, KM 121 CH 23, San Pedro de Atacama, II Region-ALMA, Chile
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:291988
    Summary
    We provide two comprehensive catalogues of positions and proper motions in the area of open cluster Blanco 1. The main catalogue, CtlgM, contains 6271 objects down to V∼ 18.5 and covers a circular ∼11 deg2 area. The accuracy of CtlgM proper motions, at about 0.3-0.5 mas yr−1 for well-measured stars, permits an excellent segregation between the cluster and field stars. The vector-point diagram of proper motions indicates an estimated total of ∼165 cluster members among the stars in our sample, while 314 stars with σμ < 2.5 mas yr−1 have membership probabilities Pμ≥ 1 per cent. We also explored the astrometric potential of the Catalogue of Objects and Measured Parameters from All Sky Surveys (COMPASS) data base in order to obtain additional proper motions for fainter stars in the area of Blanco 1. This effort produced the second catalogue of proper motions, CtlgD, containing 11 598 objects down to V∼ 21. A total of 4273 objects are common between the two catalogues. The accuracy of proper motions in CtlgD ranges from 1.0 to 6 mas yr−1. A combination of both proper-motion catalogues was instrumental in confirming that Blanco 1 contains a large population of M dwarfs (∼150 down to M5 V - the limit of our survey). In many respects, Blanco 1 is a scaled down ‘twin' of the Pleiades. The noted discrepancy between the distance from a new Hipparcos parallax of Blanco 1 and the cluster's photometric distance, at least partially, might be due to the apparent correlation between parallax and proper motion in right ascension for the ensemble of cluster members