Tomography of the unique on-going jet in the planetary nebula NGC 2392

TL;DR

This study uses high-resolution spectroscopic tomography to reveal the detailed morphology and kinematics of the jet in planetary nebula NGC 2392, showing it is currently being collimated and launched, with implications for binary central star systems.

Contribution

First detailed tomographic imaging of the jet in NGC 2392, demonstrating ongoing collimation and launching, and suggesting a binary system with accretion processes.

Findings

Jet emanates from the central star and extends outside the nebula.

Jet exhibits an S-shaped morphology indicative of precession.

Supports the presence of a double-degenerate system with accretion.

Abstract

Jets (fast collimated outflows) are claimed to be the main shaping agent of the most asymmetric planetary nebula (PNe) as they impinge on the circumstellar material at late stages of the asymptotic giant branch (AGB) phase. The first jet detected in a PN was that of NGC 2392, yet there is no available image because its low surface brightness contrast with the bright nebular emission. Here we take advantage from the tomographic capabilities of GTC MEGARA high-dispersion integral field spectroscopic observations of the jet in NGC 2392 to gain unprecedented details of its morphology and kinematics. The jet of NGC 2392 is found to emanate from the central star, break through the walls of the inner shell of this iconic PN and extend outside the nebula's outermost regions with an S-shaped morphology suggestive of precession. At odds with the fossil jets found in mature PNe, the jet in NGC 2392 is currently being collimated and launched. The high nebular excitation of NGC 2392, which implies a He$^{++}$/He ionization fraction too high to be attributed to the known effective temperature of the star, has been proposed in the past to hint at the presence of a hot white dwarf companion. In conjunction with the hard X-ray emission from the central star, the present-day jet collimation would support the presence of such a double-degenerate system where one component undergoes accretion from a remnant circumbinary disk of the common envelope phase.