2017MNRAS.466.2151M

We present narrow-band, broad-band and Wide-field Infrared Survey Explorer (WISE) archive images, and high- and intermediate-resolution long-slit spectra of K4-37, a planetary nebula that has never been analysed in detail. Although K4-37 appears bipolar, the morphokinematical analysis discloses the existence of three distinct axes and additional particular directions in the object, indicating that K4-37 is a multi-axis planetary nebula that has probably been shaped by several bipolar outflows at different directions. A 4-6 M_☉ main-sequence progenitor is estimated from the derived high nebular He and N abundances, and very high N/O abundance ratio (∼2.32). The general properties are compatible with K4-37 being a highly evolved planetary nebula located at ∼14 kpc. The WISE image at 22 µm reveals K4-37 to be surrounded by a large (∼13 x 8 pc²) elliptical detached shell probably related to material ejected from the asymptotic giant branch (AGB) progenitor. The observed elliptical morphology suggests deformation of an originally spherical AGB shell by the interstellar medium magnetic field or by the influence of a companion. We compare K4-37 and NGC 6309 and found remarkable similarities in their physical structure but noticeably different chemical abundances that indicate very different progenitor mass. This strongly suggests that, irrespective of the initial mass, their (presumably binary) central stars have shared a very similar mass ejection history.