Membership of the Planetary Nebula Abell 8 in the Open Cluster Bica 6 and Implications for the PN Distance Scale (Poster abstract)

Volume 40 number 1 (2012)

David G. Turner

Saint Mary’s University, Department of Astronomy and Physics, 923 Robie Street, Halifax, NS B3H 3C3, Canada; turner@ap.smu.ca

Joanne M. Rosvick

Thompson Rivers University, Department of Physics, 900 McGill Road, Kamloops, BC V2C 5N3, Canada; jrosvick@tru.ca

D. D. Balam

Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada

Arne A. Henden

AAVSO Headquarters, 49 Bay State Road, Cambridge, MA 02138; arne@aavso.org

Daniel J. Majaess

Saint Mary’s University, Department of Astronomy and Physics, 923 Robie Street, Halifax, NS B3H 3C3, Canada; dmajaess@ns.sympatico.ca; dlane@ap.smu.ca

David J. Lane

Saint Mary’s University, Department of Astronomy and Physics, 923 Robie Street, Halifax, NS B3H 3C3, Canada; dmajaess@ns.sympatico.ca; dlane@ap.smu.ca

Abstract

(Abstract only) The potential link between the newly discovered open cluster Bica 6 and the planetary nebula (PN) Abell 8 (PN G167.0-00.9) proposed by Bonatto et al. (2008) is confirmed on the basis of new UBVRI CCD photometry for the cluster and spectroscopic observations of its brightest stars, in conjunction with an analysis of 2MASS data for the cluster. The reddening, estimated distance, and radial velocity (+58 ± 6 km/s) of Abell 8 are a close match to the parameters derived for Bica 6: E(B–V)(B0) ≈ 0.40, d = 1.6 kpc, Vr = +57 ±4 km/s (11 stars). The radial velocity match is particularly interesting given that the velocities are more than 50 km/s larger than expected for Galactic orbital motion at l = 167°. The cluster age of 1 billion years implies a mass of –2.5–3 MÄ for the planetary nebula progenitor star, although the picture is complicated by a few blue stragglers as likely cluster members. The central star of the PN is an optical double in the 2MASS survey, with the companion indicated to be a cluster M dwarf. Abell 8 is a highly evolved PN containing a low luminosity central star (Mv ≈ +8), with a distance implied by cluster membership favoring the short PN distance scale.