Chemical abundances in Sgr A East: evidence for a Type Iax supernova remnant

Abstract

Recent observations have shown a remarkable diversity of the observational behaviors and explosion mechanisms in thermonuclear supernovae (SNe). An emerging class of peculiar type Ia SNe, called type Iax, show distinct photometric and spectroscopic behaviors. Their origin remains highly controversial, but pure turbulent deflagration of white dwarfs (WDs) has been regarded as the leading formation theory. The large population of type Iax indicates the existence of unidentified Galactic type Iax supernova remnants (SNRs). We report evidence that SNR Sgr A East in the Galactic center resulted from a pure turbulent deflagration of a Chandrasekhar-mass carbon-oxygen WD, an explosion mechanism used for type Iax SNe. Our X-ray spectroscopic study of Sgr A East using 3 Ms Chandra data shows a low ratio of intermediate-mass elements to Fe, and large Mn/Fe and Ni/Fe ratios. This abundance pattern does not accord with the core-collapse or normal type Ia models. Sgr A East is thus the first Galactic SNR for which a likely type Iax origin has been proposed, and the nearest target to study this peculiar class. We compared Sgr A East with the Fe-rich SNRs 3C 397 and W49B, which also have high Mn and Cr abundances and were claimed to result from deflagration-to-detonation explosions of Chandrasekhar-mass WDs (although with disputes). Our study shows that they have distinct abundance patterns. The X-ray spectroscopic studies of thermonuclear SNRs provide observational evidence for the theories that there are diverse explosion channels and various metal outputs for Chandrasekhar-mass WDs.

Exploration of Aspherical Ejecta Properties in Type Ia Supernova: Progenitor Dependence and Applications to Progenitor Classification

“…57 Ni/ 56 Ni, 55 Fe/ 56 Ni, 44 Ti/ 56 Fe) and element abundance ratios (e.g., Mn/Fe and Ni/Fe; see Mori et al 2018). These techniques had been applied to a few well-observed SNe Ia including SNe 2011fe, 2012cg, 2014J, 2015F and supernova remnants (SNR) 3C 397 (see recent works in for example Yamaguchi et al (2015); Leung & Nomoto (2017a); Dave et al (2017); Shen et al (2018); ; Zhou et al (2020)). The progenitor mass and metallicity are constrained by this method, which allows further identification of isotopic mass fractions of radioactive Ni isotopes in SN 2012cg (Graur et al 2016) and SN 2014J (Yang et al 2018), and stable Ni by the nebular IR spec-tra (see Dhawan et al 2018, for the application to SN 2014J).…”

A Grid of Core-Collapse Supernova Remnant Models I: The Effect of Wind-Driven Mass-Loss

“…Sgr-A East seems to be over-ionized compared to our models, which also seems to agree with the literature. We do note though that it is possible Sgr-A East is not a CC SNR, but instead the product of a Type Iax SN, which might explain the high line ratio (Zhou et al 2020).…”

X-rays observations of a super-Chandrasekhar object reveal an ONeMg and a CO white dwarf merger product embedded in a putative SN Iax remnant

“…The warm dust co-existing with the hot plasma is often observed in the supernova remnants (SNR) (Zhou et al 2020). The X-ray nebula is brightest in the medium X-ray band (0.7-1.2 keV).…”