Kinematics, structure and abundances of supernova remnant 0540-69.3

TL;DR

This study investigates the structure, elemental composition, and physical conditions of supernova remnant 0540-69.3 in the LMC using imaging and spectroscopy, revealing new spectral lines, elemental abundances, and insights into the remnant's dynamics and age.

Contribution

It provides detailed spectral analysis, elemental abundance estimates, and physical condition measurements of SNR 0540-69.3, including identification of new spectral lines and insights into explosion progenitors.

Findings

Elemental abundances suggest a 13-20 solar mass progenitor.

Estimated pulsar age of approximately 1,200 years.

Identification of new spectral lines and shock structures.

Abstract

The structure, elemental abundances, physical conditions of the LMC supernova remnant (SNR) 0540-69.3 and its surroundings were investigated using [O III] imaging and spectroscopy. Several new spectral lines are identified, both in central filaments and in interstellar clouds shocked by the supernova blast wave. The central lines are redshifted by $440\pm80$ km s$^{-1}$ with respect to the LMC, and the [O III] emission displays a symmetry axis of ring-like structures which could indicate that the pulsar shares the same general redshift as the central supernova ejecta. [O II], [S II], [Ar III] and H$\beta$ have more compact structures than [O III], and possibly [Ne III]. The average [O III] temperature is $23\,500 \pm 1\,800$ K, and the electron density from [S II] is typically $10^3$ cm$^{-3}$. By mass, the relative elemental abundances of the central shocked ejecta are ${\rm O:Ne:S:Ar} \approx 1:0.07:0.10:0.02$, consistent with explosion models of $13-20$ solar mass progenitors, and similar to that of SN 1987A, as is also the mixing of hydrogen and helium into the center. [O III] is also seen in freely coasting ejecta outside the pulsar-wind nebula out to well above $2\,000$ km s$^{-1}$. From this a pulsar age of $\approx 1\,200$ years is estimated. Four filaments of shocked interstellar medium with a wide range in degree of ionization of iron are identified. One was observed in X-rays, and another has a redshift of $85\pm30$ km~s$^{-1}$ relative to LMC. From this the electron density of the [O III]-emitting gas is estimated to be $10^3$ cm$^{-3}$. The line of the most highly ionized ion, [Fe XIV] $\lambda$5303, likely comes from an evaporation zone in connection with the radiatively cooled gas emitting, e.g., [O III].