U Sco 2010 outburst: observational evidence of an underlying ONeMg white dwarf

TL;DR

This study analyzes nebular spectra of U Sco's 2010 outburst, revealing strong neon lines that indicate an underlying ONeMg white dwarf, suggesting a different evolutionary outcome than typical CO white dwarf novae.

Contribution

It provides observational evidence of an ONeMg white dwarf in U Sco through spectral analysis, highlighting its potential to collapse into a neutron star instead of a supernova.

Findings

[Ne/O] abundance of 1.69 indicates ONeMg white dwarf

Spectral lines confirm the white dwarf's composition

U Sco unlikely to become a SN Ia

Abstract

This paper presents U Sco nebular spectra collected in the period March-May 2010 after the binary outburst on Jan 28, 2010. The spectra display strong [Ne V] and [Ne III] lines that can be used to compute the relative abundance of [Ne/O]. The value obtained ([Ne/O]=1.69) is higher than the typical [Ne/O] abundance found in classical novae from CO progenitors and suggests that U Sco has a ONeMg white-dwarf progenitor. It follows that U Sco will not explode as a SN Ia but rather collapse to become a neutron star or a millisecond pulsar.