Abundance Analysis of the J4 Equatorial Knot of the Born-again Planetary Nebula A30

TL;DR

This study analyzes the chemical composition of the J4 equatorial knot in the born-again planetary nebula A30, revealing differences from polar knots and providing insights into their distinct origins.

Contribution

It offers the first detailed abundance analysis of the J4 equatorial knot, confirming chemical segregation and lower ADF compared to polar knots in A30.

Findings

Lower ADF for O$^{2+}$ in the equatorial knot compared to polar knots.

Chemical segregation supports different formation events for equatorial and polar knots.

Spectroscopic data reinforce the distinct origins of the nebula's features.

Abstract

A30 belongs to a class of planetary nebulae identified as "born-again", containing dense, hydrogen-poor ejecta with extreme abundance discrepancy factors (ADFs), likely associated with a central binary system. We present intermediate-dispersion spectroscopy of one such feature-the J4 equatorial knot. We confirm the apparent physical and chemical segregation of the polar and equatorial knots observed in previous studies, and place an upper limit on the ADF for O$^{2+}$ of 35, significantly lower than that of the polar knots. These findings further reinforce the theory that the equatorial and polar knots originate from different events.