Chemical Abundances and Dust in the Halo Planetary Nebula K648 in M15: Its Origin and Evolution based on an Analysis of Multiwavelength Data

TL;DR

This study analyzes the chemical composition, dust features, and evolutionary history of the metal-poor planetary nebula K648 in M15 using multiwavelength data, revealing insights into its progenitor star and dust chemistry.

Contribution

It provides detailed elemental abundances, dust characteristics, and evolutionary modeling of K648, linking its properties to a blue straggler progenitor and AGB nucleosynthesis.

Findings

Enhanced fluorine abundance similar to halo PN BoBn1

Detection of carbonaceous dust and PAHs in K648

Consistent chemical abundances with AGB nucleosynthesis models

Abstract

We report an investigation of the extremely metal-poor and C-rich planetary nebula (PN) K648 in the globular cluster M15 using the UV to far-IR data obtained using the Subaru, HST, FUSE, Spitzer, and Herschel. We determined the nebular abundances of ten elements. The enhancement of F ([F/H]=+0.96) is comparable to that of the halo PN BoBn1. The central stellar abundances of seven elements are determined. The stellar C/O ratio is similar to the nebular C/O ratios from recombination line and from collisionally excited line (CEL) within error, and the stellar Ne/O ratio is also close to the nebular CEL Ne/O ratio. We found evidence of carbonaceous dust grains and molecules including Class B 6-9 um and 11.3 um polycyclic aromatic hydrocarbons and the broad 11 um feature. The profiles of these bands are similar to those of the C-rich halo PNe H4-1 and BoBn1. Based on the theoretical model, we determined the physical conditions of the gas and dust and their masses, i.e., 0.048 Msun and 4.95x10^{-7} Msun, respectively. The observed chemical abundances and gas mass are in good agreement with an asymptotic giant branch nucleosynthesis model prediction for stars with an initial 1.25 Msun plus a 2.0x10^{-3} Msun partial mixing zone (PMZ) and stars with an initial mass of 1.5 Msun without a PMZ. The core-mass of the central star is approximately 0.61-0.63 Msun. K648 is therefore likely to have evolved from a progenitor that experienced coalescence or tidal disruption during the early stages of evolution, and became a ~1.25-1.5 Msun blue straggler.