6 research outputs found
The open cluster NGC 6520 and the nearby dark molecular cloud Barnard 86
Wide field BVI photometry and CO(10) observations are presen ted
in the region of the open cluster NGC 6520 and the dark molecular cloud
Barnard~86. From the analysis of the optical data we find that the cluster is
rather compact, with a radius of 1.00.5 arcmin, smaller than previous
estimates. The cluster age is 15050 Myr and the reddening
E=0.420.10. The distance from the Sun is estimated to be
1900100 pc, and it is larger than previous estimates. We finally derive
basic properties of the dark nebula Barnard 86 on the assumption that it lies
at the same distance of the cluster.Comment: 21 pages, 8 eps figures (a few degraded in resolution), accepted for
publication in the Astronomical Journa
In Search of Possible Associations between Planetary Nebulae and Open Clusters
We consider the possibility of cluster membership for 13 planetary nebulae
that are located in close proximity to open clusters lying in their lines of
sight. The short lifetimes and low sample size of intermediate-mass planetary
nebulae with respect to nearby open clusters conspire to reduce the probability
of observing a true association. Not surprisingly, line of sight coincidences
almost certainly exist for 7 of the 13 cases considered. Additional studies are
advocated, however, for 6 planetary nebula/open cluster coincidences in which a
physical association is not excluded by the available evidence, namely M
1-80/Berkeley 57, NGC 2438/NGC 2437, NGC 2452/NGC 2453, VBRC 2 & NGC 2899/IC
2488, and HeFa 1/NGC 6067. A number of additional potential associations
between planetary nebulae and open clusters is tabulated for reference
purposes. It is noteworthy that the strongest cases involve planetary nebulae
lying in cluster coronae, a feature also found for short-period cluster
Cepheids, which are themselves potential progenitors of planetary nebulae.Comment: Accepted for publication in PASP (December 2007