Abell 41: shaping of a planetary nebula by a binary central star?

TL;DR

This study provides the first detailed spatio-kinematical analysis of Abell 41, demonstrating that its bipolar shape is aligned with the binary star system at its center, supporting theories of binary influence on nebula shaping.

Contribution

It offers the first observational confirmation that the nebula's symmetry axis is perpendicular to the binary star plane, validating key predictions of planetary nebula evolution theories.

Findings

Abell 41 has a waisted, bipolar structure with ~40 km/s expansion velocity.

The nebula's symmetry axis is within 5° of perpendicular to the binary plane.

This is only the second nebula with confirmed binary-shaping alignment.

Abstract

We present the first detailed spatio-kinematical analysis and modelling of the planetary nebula Abell 41, which is known to contain the well-studied close-binary system MT Ser. This object represents an important test case in the study of the evolution of planetary nebulae with binary central stars as current evolutionary theories predict that the binary plane should be aligned perpendicular to the symmetry axis of the nebula. Deep narrowband imaging in the light of [NII], [OIII] and [SII], obtained using ACAM on the William Herschel Telescope, has been used to investigate the ionisation structure of Abell 41. Longslit observations of the H-alpha and [NII] emission were obtained using the Manchester Echelle Spectrometer on the 2.1-m San Pedro M\'artir Telescope. These spectra, combined with the narrowband imagery, were used to develop a spatio-kinematical model of [NII] emission from Abell 41. The best fitting model reveals Abell 41 to have a waisted, bipolar structure with an expansion velocity of ~40km\s at the waist. The symmetry axis of the model nebula is within 5$\degr$ of perpendicular to the orbital plane of the central binary system. This provides strong evidence that the close-binary system, MT Ser, has directly affected the shaping of its nebula, Abell 41. Although the theoretical link between bipolar planetary nebulae and binary central stars is long established, this nebula is only the second to have this link, between nebular symmetry axis and binary plane, proved observationally.