An object that defies stereotypes. X-ray observations of SBS 1150+599A -- the binary nucleus of PN G135.9+55.9

TL;DR

This paper reports X-ray observations of the binary nucleus of a very oxygen-poor planetary nebula in the Galactic halo, revealing a hot compact star and suggesting a potential future Type Ia supernova.

Contribution

It provides new X-ray data confirming the presence of an unseen hot component, reconstructing the binary's history, and identifying the nebula as a potential Type Ia supernova progenitor.

Findings

The unseen component is a very hot compact star.

The binary likely originated from a symbiotic supersoft X-ray source.

PN G135.9+55.9 may become a Type Ia supernova.

Abstract

We present X-ray observations of the close binary nucleus of the planetary nebula PN G135.9+55.9 obtained with the XMM satellite. The nebula is the most oxygen-poor PN known to date and is located in the Galactic halo. It is known to harbor a close binary nucleus of which only one component can be observed in optical-UV range. New X-ray observations show that the invisible component is a very hot compact star. This finding allows us to reconstruct the immediate past of the object and predict its future. The parameters of the binary components we determine strongly suggest that the precursor was a symbiotic supersoft X-ray source that finished its life by Roche lobe overflow. PN G135.9+55.9 is an excelent candidate for a future type Ia supernova.