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G.W. Hawkins (STScI), F. Favata (Astrophysics Division - Space Science Department of ESA, ESTEC)
We present results of a proper motion study of the open star cluster Blanco 1 (Blanco 1949, PASP 61, 183), using plate material and methods used to construct the second Guide Star Catalog. Blanco 1 is a southern cluster near the fourth magnitude star \zeta Sculptoris, with ~ 200 members spread over ~1.5\circ. It is young (50 - 90 Myr), relatively nearby at 250 pc, and has unusually high -79\circ galactic latitude. We processed a \rm 6\circ ~x ~6\circ region centered on the cluster, matching 30,000 galaxies and 38,000 stars down to magnitude 19 on four Schmidt plates. Plates were used from the POSS I (E and O, 1954), and southern SERC J (1976) and SES (1990) R band surveys. Our derived proper motion of \rm \mu\alpha ~= ~22 and \rm \mu\delta ~= ~5 ~milli arcsec ~yr-1 (\rm \sigma ~= ~5 ~mas ~yr-1) is the first published proper motion for this cluster derived from a large sample of stars. Many members claimed from previous studies based on photometry or spectroscopy do not have proper motions consistent with that of the cluster. We find many potential new members within 7.5 mas \rm yr-1 of the average cluster proper motion. We present a color-magnitude diagram and luminosity function for the cluster.
The author(s) of this abstract have provided an email address for comments about the abstract: hawkins@stsci.edu