Constraining Type Iax Supernova Progenitor Systems with Stellar Population Aging

Abstract: Type Iax supernovae (SNe~Iax) are the most common class of peculiar SNe. While they are thought to be thermonuclear white-dwarf (WD) SNe, SNe~Iax are observationally similar to, but distinct from SNe~Ia. Unlike SNe~Ia, where roughly 30\% occur in early-type galaxies, only one SN~Iax has been discovered in an early-type galaxy, suggesting a relatively short delay time and a distinct progenitor system. Furthermore, one SN~Iax progenitor system has been detected in pre-explosion images with its properties consistent with either of two models: a short-lived (<100 Myr) progenitor system consisting of a WD primary and a He-star companion, or a singular Wolf-Rayet progenitor star. Using deep \textit{Hubble Space Telescope} images of nine nearby SN~Iax host galaxies, we measure the properties of stars within 200 pc of the SN position. The ages of local stars, some of which formed with the SN progenitor system, can constrain the time between star formation and SN, known as the delay time. We compare the local stellar properties to synthetic photometry of single-stellar populations, fitting to a range of possible delay times for each SN. With this sample, we uniquely constrain the delay-time distribution for SNe~Iax, with a median and $1-\sigma$ confidence interval delay time of $63_{- 15}^{+ 58} \times 10^{6}$ years. The measured delay-time distribution provides an excellent constraint on the progenitor system for the class, indicating a preference for a WD progenitor system over a Wolf-Rayet progenitor star.

• The paper estimates a median delay time of approximately 63 Myr for Type Iax supernova progenitors using HST-based stellar aging analysis.
• It employs synthetic photometry and Bayesian hierarchical modeling to robustly correlate local stellar populations with supernova events.
• The findings favor a progenitor system where a white dwarf accretes from a helium star, distinguishing it from other supernova progenitor scenarios.

Constraining Type Iax Supernova Progenitor Systems with Stellar Population Aging

The paper "Constraining Type Iax Supernova Progenitor Systems with Stellar Population Aging" by Takaro et al. explores the progenitor systems of Type Iax supernovae (SNe Iax), a peculiar and common class of supernovae that are distinct from the more widely studied Type Ia supernovae (SNe Ia). This investigation is conducted through an analysis of the stellar populations surrounding SNe Iax, employing a methodology that utilizes the ages of these local stellar populations to constrain the delay-time distribution (DTD) of the supernova progenitors.

Key Findings and Methodology

The study makes use of deep Hubble Space Telescope images of nine nearby host galaxies of SNe Iax to analyze the ages of stars located within 200 pc of the supernova sites. By fitting observed star properties to synthetic photometry derived from single-stellar population models, the authors were able to estimate the time interval between star formation and supernova event, known as the delay time. The paper's noteworthy result is the calculation of a median delay time of approximately 63 million years, with a 1-sigma confidence interval of $63_{- 15}^{+ 58} \times 10^{6}$ years.

The analysis indicates a preference for progenitor systems characterized by a white dwarf (WD) primary accreting matter from a helium star companion, rather than singular Wolf-Rayet stars. This conclusion is largely driven by the absence of observed SNe Iax in early-type galaxies and the relatively young ages of the surrounding stellar populations. This supports the notion of a prompt progenitor system, as opposed to a delayed one seen in typical core-collapse supernovae.

The statistical and methodological framework employed in this paper is robust, utilizing Bayesian hierarchical modeling to draw inferences from the available photometric data. The synthetic photometry approach allows for a detailed understanding of the stellar ages, aligning well with observational constraints. Furthermore, the study takes into account uncertainties in stellar distances and extinction through careful application of error modeling.

Implications and Future Directions

The paper's findings contribute valuable information that aids in distinguishing SNe Iax progenitors from those of SNe Ia. The differentiation between these two types of supernovae is crucial, as SNe Ia serve as standard candles for cosmological distance measurements, necessitating precise characterization of their progenitor systems.

The constraints proposed on the DTD of SNe Iax also have broader implications for our understanding of stellar evolution and binary interaction dynamics. By narrowing down likely progenitor models, researchers can better simulate these events to predict observable phenomena such as spectral characteristics and light curves, facilitating improved identification and classification of supernovae.

The paper identifies several avenues for future research, including deepening the exploration of the progenitor systems using upcoming larger datasets from observatories like the Large Synoptic Survey Telescope (LSST). Understanding possible variations within the Iax class itself, potentially due to differences in progenitor masses or binary evolution histories, remains a compelling future endeavor.

In summary, Takaro et al. deliver a significant contribution to the supernova field through rigorous analysis of SNe Iax progenitors, sharpening our understanding of these intriguing cosmic events. As further observational data becomes available, the methodologies demonstrated in this paper will be instrumental in refining the progenitor models of SNe Iax, shedding more light on this distinct class of supernovae.