The Impact of Axion-Like Particles on Late Stellar Evolution From Intermediate-Mass Stars to core-collapse Supernova Progenitors

TL;DR

This study investigates how axion-like particles (ALPs) affect the late evolution of intermediate-mass stars (3–11 $M_\odot$) by introducing ALP energy losses through photon and electron couplings and computing a grid of solar-metallicity models with the FuNS code. The authors find that ALP cooling raises the thresholds for off-center carbon and neon ignition, shifts the minimum and maximum initial masses separating white-dwarf and core-collapse outcomes, and shortens He-burning lifetimes by up to about 25%, leading to somewhat more massive CO white dwarfs and heavier CCSN progenitors. These shifts have implications for WD populations, CCSN progenitor demographics, and the interpretation of observational constraints, while current bounds from astrophysics do not exclude ALP production; however, reconciling CCSN progenitor ages with star-formation histories may require modest extra mixing during the main sequence. The work emphasizes the potential of combining stellar evolution with ALP physics to constrain beyond-Standard-Model particles using astrophysical data and future experiments like BabyIAXO/IAXO.

Abstract

Context. Stars with masses ranging from 3 to 11 M_\odot exhibit multiple evolutionary paths. Less massive stars in this range conclude their evolution as carbon-oxygen (CO) white dwarfs. However, those that achieve carbon ignition before the pressure by degenerate electron halts the core contraction may either form massive CONe/ONe white dwarfs, or undergo an electron-capture supernova, or photo-disintegrate neon and proceed with further thermonuclear burning, ultimately leading to the formation of a gravitationally unstable iron core. Aims. An evaluation of the impact of the energy loss caused by the production of axion-like-particles (ALPs) on evolution and final destiny of these stars is the main objective of this paper. Methods. We compute various sets of stellar models, all with solar initial composition, varying the strengths of the ALP coupling with photons and electrons. Results. As a consequence of an ALP thermal production, the critical masses for off-center C and Ne ignitions are both shifted upward. When the current bounds for the ALP coupling strengths are assumed, the maximum mass for CO WD progenitors is about 1.1 M_\odot heavier than that obtained without the ALP energy loss, while the minimum mass for a core collapse supernova (CCSN) progenitor is 0.7 M_\odot higher. Conclusions. Current constraints from observed Type II-P supernova light curves and pre-explosive luminosity do not exclude an ALP production within the current bounds. However, the maximum age of CCSN progenitors, as deduced from the star formation rate of the parent stellar population, would require a smaller minimum mass. This discrepancy can be explained by assuming a moderate extra mixing (as due to core overshooting or rotational induced mixing) above the fully convective core that develops during the main sequence.

Figures (9)

• Figure 1: Left panel: evolution of the ALP and neutrino luminosities through the late portion of the He-burning phase and the subsequent early-AGB. Right panel: evolution of the contributions to the ALP luminosity of the different production processes. The plots refers to the 7 M$_\odot$ model with $g_{10}=0.6$ and $g_{13}=1.5$.
• Figure 2: Energy-loss rates due to ALPs production within the core of a 7 M$_\odot$ with $g_{10}=0.6$ and $g_{13}=1.5$. The left and the right panels refer to the two blue points in Fig. \ref{['fig_2dup_7M']}, as taken before and after the SDU, respectively. The solid-black line is the total ALP energy-loss rate, while the blue, the red and the magenta lines represent the contributions of the Primakoff, Compton and Bremsstrahlung processes, respectively. For comparison, the neutrino energy-loss rate is also reported (black-dashed line).
• Figure 3: ALP impact on the SDU. Black lines (top to botton): inner border of the convective envelope, location of the H-burning shell and location of the He-burning shell, for a 7 M$_\odot$ (no ALPs), during the early-AGB phase; red lines (top to bottom): same as the black lines, but with $g_{10}=0.6$ and $g_{13}=1.5$. The filled circles represent the He-shell locations for the two models in Fig. \ref{['fig_rates_7M']}
• Figure 4: Top to bottom: density, temperature and chemical profiles within the core of a 7.7 M$_\odot$ model at the onset of the super-AGB phase. In the bottom panel, lines represent the mass fractions of $^{4}$He (green), $^{12}$C (black), $^{16}$O (red), $^{20}$Ne (blue) and $^{24}$Mg (magenta). No ALP production has been included in this model. Note that only above 0.85 M$_\odot$ the C burning has been active. This model represents an example of hybrid WD progenitors.
• Figure 5: Kippenhahn diagram of the degenerate C burning in the 9 M$_\odot$ stellar model. The red region represents the convective envelope, while the violet regions are convective C-burning episodes. The t=0 point is arbitrary. Note that the SDU occurs after the first C flash.