Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

The Origin of the Mg-rich Supernova Remnant J0550-6823 and the Frequency of Similar Events in the Large Magellanic Cloud

Yui Kuboike, Toshiki Sato, Hiromasa Suzuki, Kai Matsunaga, Hiroyuki Uchida, John P. Hughes, Paul P. Plucinsky

TL;DR

The paper investigates Mg-rich SNRs in the Large Magellanic Cloud as signatures of late-stage shell burning in massive stars, focusing on J0550--6823. It reanalyzes Chandra X-ray data with improved background modeling and finds $Ne/Mg$ mass ratios near unity and Mg abundances above solar, supporting an Mg-rich ejecta origin. By comparing observed $Ne/Mg$ and $Si/Mg$ to 1D pre-SN models, it concludes that shell-merger or Ne-shell intrusion scenarios are required to reproduce the Mg-rich pattern, placing J0550--6823 within this late-stage shell-burning regime via the $M_r(\mathrm{Si}=0.05)$ diagnostic. The study estimates the Mg-rich SNR fraction in the LMC to be at least a few percent and possibly up to ~40%, implying a non-negligible role for shell mergers in galactic chemical evolution and odd-Z element production, and highlighting the need for deeper X-ray spectroscopy and multidimensional progenitor models.

Abstract

Shell burning and internal mixing in massive stars play an important role in setting the initial conditions for core-collapse supernova explosions. In the late stages of stellar evolution, intense shell burning can cause distinct convective regions to merge, fundamentally restructuring the stellar interior. Although such phenomena are difficult to observe directly, the observation of ``Mg-rich'' supernova remnants (SNRs) has recently emerged as a potential signature of these events. In this study, we reanalyze X-ray observations of J0550--6823, a SNR in the Large Magellanic Cloud (LMC) and a new candidate Mg-rich SNR. Our spectral analysis confirms a low Ne/Mg mass ratio of $\approx$1, and its classification as Mg-rich. By comparing the observational results with pre-supernova models, we suggest that the progenitor of J0550-6823 likely had an extended convective shell that reduces the Ne/Mg ratio prior to its explosion. Furthermore, we observe that $\sim$2--3 Mg-rich SNRs exist in the LMC, suggesting that $\lesssim$10--40\% of massive stars in the LMC may have had an extended convective shell, similar to what we observed in J0550-6823. This fraction would be important for understanding the final stages of the evolution of massive stars and galactic chemical evolution.

The Origin of the Mg-rich Supernova Remnant J0550-6823 and the Frequency of Similar Events in the Large Magellanic Cloud

TL;DR

The paper investigates Mg-rich SNRs in the Large Magellanic Cloud as signatures of late-stage shell burning in massive stars, focusing on J0550--6823. It reanalyzes Chandra X-ray data with improved background modeling and finds mass ratios near unity and Mg abundances above solar, supporting an Mg-rich ejecta origin. By comparing observed and to 1D pre-SN models, it concludes that shell-merger or Ne-shell intrusion scenarios are required to reproduce the Mg-rich pattern, placing J0550--6823 within this late-stage shell-burning regime via the diagnostic. The study estimates the Mg-rich SNR fraction in the LMC to be at least a few percent and possibly up to ~40%, implying a non-negligible role for shell mergers in galactic chemical evolution and odd-Z element production, and highlighting the need for deeper X-ray spectroscopy and multidimensional progenitor models.

Abstract

Shell burning and internal mixing in massive stars play an important role in setting the initial conditions for core-collapse supernova explosions. In the late stages of stellar evolution, intense shell burning can cause distinct convective regions to merge, fundamentally restructuring the stellar interior. Although such phenomena are difficult to observe directly, the observation of ``Mg-rich'' supernova remnants (SNRs) has recently emerged as a potential signature of these events. In this study, we reanalyze X-ray observations of J0550--6823, a SNR in the Large Magellanic Cloud (LMC) and a new candidate Mg-rich SNR. Our spectral analysis confirms a low Ne/Mg mass ratio of 1, and its classification as Mg-rich. By comparing the observational results with pre-supernova models, we suggest that the progenitor of J0550-6823 likely had an extended convective shell that reduces the Ne/Mg ratio prior to its explosion. Furthermore, we observe that 2--3 Mg-rich SNRs exist in the LMC, suggesting that 10--40\% of massive stars in the LMC may have had an extended convective shell, similar to what we observed in J0550-6823. This fraction would be important for understanding the final stages of the evolution of massive stars and galactic chemical evolution.

Paper Structure

This paper contains 6 sections, 5 figures, 1 table.

Table of Contents

  1. introduction
  2. Observation and spectrum fitting of J0550--6823
  3. discussion
  4. The origin of J0550--6823
  5. The rate of Mg-rich events in the LMC
  6. summary and conclusion

Figures (5)

  • Figure 1: (a) The internal structure of a star, which experiences an active shell burning process. (b) Mass fraction profile of the 15.05 $M_{\odot}$ model. The Si mass fraction that reaches 0.05 is shown by the dashed line. (c) Same as (b), but for the 15.06 $M_{\odot}$ model. The models are taken from 2018ApJ...860...93S.
  • Figure 2: Chandra X-ray image of J0550--6823. The red ellipse shows the outer shell, which was used as the extraction region for spectral analysis. The rectangle region is used for modeling sky background.
  • Figure 3: X-ray spectrum extracted from the rectangle region in Fig. \ref{['J0550region2']} to model the sky background. The orange line represents the plasma model for the foreground emission. The blue line represents the background spectrum generated by mkacispback. The red line represents the final result of the background model with photon absorption model, foreground emission model ($\rm phabs\times apec$), and the acispback model.
  • Figure 4: X-ray spectrum of the Mg-rich ejecta of J0550--6823 and the best-fit model with $\tau=1.0\times 10^{12} \rm ~s ~cm^{-3}$ (top panel). The red line represents the best-fit plasma model, which includes the effect of photon absorption ($\rm phabs\times vnei$). The black line represents the background spectrum generated by "mkacispback". The black dashed line represents the sky background model. The blue line represents the sum of all model components. The bottom panel represents the residuals of the fit.
  • Figure 5: Si/Mg-Ne/Mg mass ratios of pre-supernova models and those of J0550--6823 (green plot). The green diamond marker shows the result with $\tau =1.00 \times 10^{12}\,[\rm s\cdot cm^{-3}]$ that we use as the best-fit result (See Table \ref{['taubestfit_transpose']}). The colored data points are derived from 1D pre-supernova models, with different markers used to represent each progenitor mass range 2018ApJ...860...93S. The radius of the Si-rich layer in the progenitor, $M_r$(Si=0.05), is shown in color. Using BH-NS separation curve for the w18.0 calibration that do not explode are identified and shown as colored dots 2016ApJ...818..124E. The SNRs of the LMC for which previous studies have shown the composition of Si , Ne, and Mg abundances are also plotted on the figure; N63A is from mean abundance of 2003ApJ...583..260W, B0453-685 is from vpshock model of 2012AA...543A.154H, SN1987A is from vpshock W00 of 2008ApJ...676..361H, N49 is from 2015ApJ...808...77U, and N23 and N49B obtained values from 2016AA...585A.162M. The LMC average mass ratio is shown in blue marker 2016AJ....151..161S.