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A photometric study of the open cluster NGC 7419 Thibault, Daniel


A set of UBV plates of the heavily-extinguished open cluster NGC 7419, obtained at the Observatoire Astronomique du Mont Megantic by Anthony F. J. Moffat, were digitized by the Dominion Astrophysical Observatory PDS (Photometric Data Systems, Perkin-Elmer Corporation) machine. The data was subsequently processed by Greg Fahlman and Chris Pritchett's TOODEE Command Language, and later John Nicol's SUPERTOODEE Command Language. The resulting set of intensity indices were calibrated in the UBV system using Handschel and Sandage's magnitudes into a set of observed magnitudes. These were then de-reddened and de-extinguished with the help of an updated variation of Serkowski's (1956) method. Handschel's claim of differential reddening across the face of the cluster was examined and found valid. Using our own Zero-Age main sequence culled from several sources, the distance modulus was estimated at 13.9 ± 0.1 mag. Comparison of our color-magnitude diagram with those of other young clusters as well as with theoretical isochrones leads us to estimate the cluster as being as young as, or younger than, 10 million years, although serious problems with the photometry preclude any further analysis. Low-resolution Reticon spectra were obtained with the Dominion Astrophysical Observatory's 180 cm telescope of some of the cluster's stars in the hope of measuring radial velocities. The spectra were processed with Stephenson Yang's RETICENT Command Language. These were used to attempt to resolve the question of the possible membership of the fringe-dwelling carbon star. The low-weight determinations obtained for the carbon star and another possible cluster member are inconclusive and stress the need for a more careful study of the problem. In conclusion, the cluster's color-magnitude turnoff was observed, and its age and distance evaluated as 5 ± 5 Ma and 6.0 ± 0.3 kpc respectively. Average extinction was found to be A[sub v] = 5.85, and reddening E(B-V) = 1.77.

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