Investigating potential planetary nebula/cluster pairs

Abstract

Context. Fundamental parameters characterizing the end-state of intermediate-mass stars may be constrained by discovering planetary nebulae (PNe) in open clusters (OCs). Cluster membership may be exploited to establish the distance, luminosity, age, and physical size for PNe, and the intrinsic luminosity and mass of its central star. Aims. Four potential PN-OC associations were investigated to assess the cluster membership for the PNe. Methods. Radial velocities were measured from intermediate-resolution optical spectra, complemented with previous estimates in the literature.When the radial velocity study supported the PN/OC association, we analyzed whether other parameters (e.g., age, distance, reddening, central star brightness) were consistent with this conclusion. Results. Our measurements imply that the PNe VBe 3 and HeFa 1 are not members of the OCs NGC5999 and NGC6067, respectively, and that they very likely belong to the background bulge population. Conversely, consistent radial velocities indicate that NGC2452/NGC 2453 could be associated, but our results are not conclusive so additional observations are warranted. Finally, we demonstrate that all the available information point to He 2-86 being a young, highly internally obscured PN member of NGC4463. New near-infrared photometry acquired via the Vista Variables in the Via Lactea ESO public survey was used in tandem with existing UBV photometry to measure the distance, reddening, and age of NGC4463, finding d = 1.55 ± 0.10 kpc, E(B − V) = 0.41 ± 0.02, and τ = 65 ± 10 Myr, respectively. The same values should be adopted for the PN if the proposed cluster membership is confirmed.