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Modeling the Light Curve and Spectra of SN 2023aew

Rachid Ouyed

TL;DR

This study addresses SN 2023aew's unusual double-peaked light curve by proposing a delayed transition of a neutron star into quark matter or a hybrid star as a secondary energy source. The authors develop a two-channel engine: a quark-nova (QN) shock delivering roughly $2\times10^{49}$ erg over about 40 days after a delay of $\sim$105–109 days, or spin-down power from a highly magnetized HS, to re-energize the SN ejecta; the observed plateau and late bumps can arise from SN-CSM interaction or NS spin-down before conversion, with a two-stage NS-to-HS evolution providing a natural link to magnetar formation. They perform light-curve modeling and spectral synthesis (via a modified TARDIS) that favor a $M_{\rm ZAMS}\sim15$–$16\,M_\odot$ progenitor and ejecta of a few solar masses, matching the first peak with $^{56}$Ni decay and the second peak with delayed energy input, while highlighting modeling caveats such as LTE/nebular approximations and simplified ejecta geometry. The work connects SLSNe and LFBOTs under a common engine, offering tests via multi-messenger signals and providing potential constraints on the quark-matter equation of state and r-process nucleosynthesis.

Abstract

We propose that the delayed conversion of a neutron star (NS) into either a quark star (QS) or a hybrid star (HS), occurring approximately 105-109 days after the supernova (SN) explosion, injects ~ 2e49 erg of thermal energy into the expanded SN ejecta. This energy, delivered over ~ 40 days via a quark-nova (QN) shock or the spin-down power of the HS, can reproduce the photometric and spectral features observed in SN 2023aew. In this model, the first light curve peak corresponds to the 56Ni-powered SN resulting from a stripped-envelope progenitor with a zero-age main sequence mass of at least ~ (15-16)M_sun. The plateau between the two peaks may result from interaction between the SN ejecta and circumstellar material (CSM). Alternatively, it could be explained by the spin-down power of the NS prior to its conversion into a highly magnetized HS, which is responsible for powering the second bump. A scenario involving two phases of spin-down power - first from the NS and later from the HS - is compelling and supports the hypothesis that some magnetars are, in fact, HSs. These HSs acquire their ultra-strong magnetic fields through a quark matter phase capable of sustaining core fields on the order of ~ 1e18 G. In our model, the spin-down energy of the HS powers the QN ejecta - the outermost layers of the NS - before this energy is transferred to the expanded SN ejecta. This process produces luminous fast blue optical transients (LFBOTs). The model establishes a potential connection between superluminous SNe (SLSNe) and LFBOTs, with significant implications for high-energy astrophysics and the r-process nucleosynthesis of heavy elements. Potential consequences for Quantum Chromodynamics (QCD) are also discussed.

Modeling the Light Curve and Spectra of SN 2023aew

TL;DR

This study addresses SN 2023aew's unusual double-peaked light curve by proposing a delayed transition of a neutron star into quark matter or a hybrid star as a secondary energy source. The authors develop a two-channel engine: a quark-nova (QN) shock delivering roughly erg over about 40 days after a delay of 105–109 days, or spin-down power from a highly magnetized HS, to re-energize the SN ejecta; the observed plateau and late bumps can arise from SN-CSM interaction or NS spin-down before conversion, with a two-stage NS-to-HS evolution providing a natural link to magnetar formation. They perform light-curve modeling and spectral synthesis (via a modified TARDIS) that favor a – progenitor and ejecta of a few solar masses, matching the first peak with Ni decay and the second peak with delayed energy input, while highlighting modeling caveats such as LTE/nebular approximations and simplified ejecta geometry. The work connects SLSNe and LFBOTs under a common engine, offering tests via multi-messenger signals and providing potential constraints on the quark-matter equation of state and r-process nucleosynthesis.

Abstract

We propose that the delayed conversion of a neutron star (NS) into either a quark star (QS) or a hybrid star (HS), occurring approximately 105-109 days after the supernova (SN) explosion, injects ~ 2e49 erg of thermal energy into the expanded SN ejecta. This energy, delivered over ~ 40 days via a quark-nova (QN) shock or the spin-down power of the HS, can reproduce the photometric and spectral features observed in SN 2023aew. In this model, the first light curve peak corresponds to the 56Ni-powered SN resulting from a stripped-envelope progenitor with a zero-age main sequence mass of at least ~ (15-16)M_sun. The plateau between the two peaks may result from interaction between the SN ejecta and circumstellar material (CSM). Alternatively, it could be explained by the spin-down power of the NS prior to its conversion into a highly magnetized HS, which is responsible for powering the second bump. A scenario involving two phases of spin-down power - first from the NS and later from the HS - is compelling and supports the hypothesis that some magnetars are, in fact, HSs. These HSs acquire their ultra-strong magnetic fields through a quark matter phase capable of sustaining core fields on the order of ~ 1e18 G. In our model, the spin-down energy of the HS powers the QN ejecta - the outermost layers of the NS - before this energy is transferred to the expanded SN ejecta. This process produces luminous fast blue optical transients (LFBOTs). The model establishes a potential connection between superluminous SNe (SLSNe) and LFBOTs, with significant implications for high-energy astrophysics and the r-process nucleosynthesis of heavy elements. Potential consequences for Quantum Chromodynamics (QCD) are also discussed.
Paper Structure (6 sections, 5 figures, 5 tables)

This paper contains 6 sections, 5 figures, 5 tables.

Table of Contents

  1. Introduction
  2. The light curve
  3. The QN shock
  4. The HS spin-down (SpD) power
  5. The spectrum
  6. Discussion and conclusion

Figures (5)

  • Figure 1: Top panel: The pseudo-bolometric LC from our model. The first peak is powered by $^{56}$Ni, while the second peak arises from re-shocked SN ejecta due to delayed energy injection following the conversion of the NS (see § \ref{['sec:lc']}). The plot shows the re-brightening of the SN ejecta (second peak) for increasing time delays, $t_{\rm QN}$, between the SN and the QN. The pseudo-LC of SN 2023aew (without error bars) is shown for reference (sharma_2024kangas_2024). Bottom panel: Fit to the LC of SN 2023aew with $t_{\rm QN} = 105$. The plateau and the bumps beyond the second peak are due to the interaction between the SN ejecta and the CSM, starting at $t=0$ days for the first shell and at $t\sim 200$ days for the second shell (see Table \ref{['table:table1']} for relevant parameters).
  • Figure 2: Fit to the pseudo-bolometric luminosity of SN 2023aew using a combined $^{56}$Ni, SN-CSM interaction and HS spin-down power ($t_{\rm HS} = 109$ days). Top panel: Model includes hard emission leakage from the HS (see § \ref{['sec:lc']}). Bottom panel: Model includes hard emission leakage from a precessing HS. See Table \ref{['table:table2']} for parameter values.
  • Figure 3: Fit to the pseudo-bolometric luminosity of SN 2023aew using spin-down power and a precessing HS with $t_{\rm HS} = 109$ days. There is no CSM interaction or sweeping involved. The plateau is fit using NS spin-down power with $P_{\rm NS}= 22.3$ s ( top panel) and $P_{\rm NS}= 16.8$ s ( bottom panel). See Table \ref{['table:table2']} for parameter values.
  • Figure 4: Top panel: Light curves resulting from the spin-down powering of the ejected outermost layers of the NS ($\sim 0.05M_{\odot}$) following its conversion to a HS. The models explore different HS spin periods and magnetic field strengths. Shown for comparison are two LFBOTs: AT2018cow and Dougie (from nicholl_2023); see § \ref{['sec:HS-spindown']} and footnote 1. Bottom panel: The LFBOT luminosity undergoes re-processing by the expanded SN ejecta, with a subsequent late-time bump resulting from re-heating due to the collision between the QN and SN ejecta.
  • Figure 5: Comparison of the observed spectrum of SN 2023aew with the simulated spectrum (see § \ref{['sec:spectrum']}). Top panel: at the first peak (34 days after explosion). Middle panel: at the second peak (117 days after explosion). Bottom panel: at the second peak (136 days after explosion).