New Results for the Open Cluster Bica 6 and its Associated Planetary Nebula Abell 8

TL;DR

This study confirms the membership of the planetary nebula Abell 8 in the open cluster Bica 6 using spectroscopic and photometric data, providing new insights into the cluster's properties and its potential as a calibrator for distance measurements.

Contribution

The paper presents new observational evidence confirming the association of Abell 8 with Bica 6 and derives key parameters for both, enhancing the understanding of planetary nebulae in open clusters.

Findings

Confirmed membership of Abell 8 in Bica 6 through spectroscopic and photometric data.

Derived cluster parameters: E(B-V)=0.42, d=1.60 kpc, Vr=57 km/s, age ~1 Gyr.

Identified the planetary nebula's central star with specific reddening and luminosity.

Abstract

The likely membership of the planetary nebula Abell 8 (PN G167.0--00.9) in the open cluster Bica 6 is confirmed by CCD spectra, UBV(RI)c photometry, and radial velocities for luminous cluster stars. The reddening, estimated distance, and radial velocity of the planetary nebula agree with parameters derived for Bica 6 of E(B-V)=0.42, d=1.60+-0.11 kpc, and Vr=57+-1 km/s, with a cluster age of 1 Gyr, a diagnostic blue hook, and a few blue stragglers, including a peculiar B1 Vnn star (HDE 277593) that may be a post-AGB star. The results identify Bica 6 as a potential calibrator of the planetary nebula distance scale. The central star of the planetary nebula has a reddening of E(B-V)=0.49+-0.02, with a possible circumnebular excess, and an estimated luminosity of Mv=+7.44+-0.16. It is also an optical double in 2MASS images, with a likely progenitor according to evolutionary considerations being a late B-type dwarf of ~2.3 Msun.