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The extremely low-luminosity Type Iax SNe 2022ywf and 2023zgx

Barnabás Barna, Dominik Bánhidi, Tamás Szalai, Joseph P. Anderson, Teresa Boland, K. Azalee Bostroem, Ting-Wan Chen, Joseph Farah, Mariusz Gromadzki, Griffin Hosseinzadeh, D. Andrew Howell, Cosimo Inserra, Saurabh W. Jha, Lindsey A. Kwok, Colin Macrie, Curtis McCully, Erika Mochnács, Tomás E. Müller-Bravo, Megan Newsome, Estefania Padilla Gonzalez, Jeniveve Pearson, Tanja Petrushevska, David J. Sand, Manisha Shrestha, Nathan Smith, Shubham Srivastav, Giacomo Terreran, József Vinkó

Abstract

We present the optical follow-up of SNe 2022ywf and 2023zgx, two examples from the Iax subclass of thermonuclear supernova (SN) events. With peak absolute magnitudes of $M_\mathrm{V} = -13.7$ and $-14.4$ mag, respectively, both objects belong to the extremely low-luminosity (EL) population of the class. A common origin of SNe in the Iax subclass is still under debate since the distribution of certain observables may indicate that the extremely low-luminosity explosions form a distinct population. We aim to estimate the physical properties of the two EL objects, including mapping the ejecta structure. We perform spectral tomography on the spectral series of SNe 2022ywf and 2023zgx around their maxima to map the physical properties of the ejecta. Together with the analysis of BgVriz photometry, a wide range of observables can be studied to investigate their distribution against luminosity. The constrained chemical abundances of the ejecta are compared to the predictions of the hydrodynamic simulations with similar peak luminosities. Constant abundances provide a good match for the distribution of chemical elements for both SNe 2022ywf and 2023zgx. The discrepancies compared to the least luminous pure deflagration model N5def_hybrid are minor, especially at post-maximum epochs. The two SNe also share similar characteristics in their constrained density structures, as well as the evolution of the photosphere. The analysis supports the assumption that pure deflagration models can reproduce the main characteristics of SNe Iax, even for the EL population. The presented indirect observational evidence indicates that these objects show similar intrinsic properties to the relatively luminous Iax sample and fit into the velocity distribution of the subclass.

The extremely low-luminosity Type Iax SNe 2022ywf and 2023zgx

Abstract

We present the optical follow-up of SNe 2022ywf and 2023zgx, two examples from the Iax subclass of thermonuclear supernova (SN) events. With peak absolute magnitudes of and mag, respectively, both objects belong to the extremely low-luminosity (EL) population of the class. A common origin of SNe in the Iax subclass is still under debate since the distribution of certain observables may indicate that the extremely low-luminosity explosions form a distinct population. We aim to estimate the physical properties of the two EL objects, including mapping the ejecta structure. We perform spectral tomography on the spectral series of SNe 2022ywf and 2023zgx around their maxima to map the physical properties of the ejecta. Together with the analysis of BgVriz photometry, a wide range of observables can be studied to investigate their distribution against luminosity. The constrained chemical abundances of the ejecta are compared to the predictions of the hydrodynamic simulations with similar peak luminosities. Constant abundances provide a good match for the distribution of chemical elements for both SNe 2022ywf and 2023zgx. The discrepancies compared to the least luminous pure deflagration model N5def_hybrid are minor, especially at post-maximum epochs. The two SNe also share similar characteristics in their constrained density structures, as well as the evolution of the photosphere. The analysis supports the assumption that pure deflagration models can reproduce the main characteristics of SNe Iax, even for the EL population. The presented indirect observational evidence indicates that these objects show similar intrinsic properties to the relatively luminous Iax sample and fit into the velocity distribution of the subclass.
Paper Structure (11 sections, 2 equations, 11 figures, 2 tables)

This paper contains 11 sections, 2 equations, 11 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Observations
  3. SN 2022ywf
  4. SN 2023zgx
  5. Photometric analysis
  6. Spectral analysis
  7. SN 2022ywf
  8. SN 2023zgx
  9. Comparison with other extremely faint SNe Iax
  10. Conclusions
  11. Some extra material

Figures (11)

  • Figure 1: ATLAS photometry of SNe 2022ywf and 2023zgx. The observation dates of SN 2023zgx are shifted with 400 days earlier. The red dashed line show the fit of Eq. \ref{['eq:fireball']} on the pre-maximum $o$-band data of SN 2022ywf.
  • Figure 2: Ground-based photometry of SNe 2022ywf (filled circles) and 2023zgx (fainter diamonds). The horizontal axis represents the observational dates of SN 2022ywf in MJD. For SN 2023zgx, the data points are shifted with 400 days earlier for better comparison. The LC fits with fourth-order polynomial functions are also shown for SN 2022ywf (solid lines).
  • Figure 3: Optical spectra of SN 2022ywf. The epochs show the days with respect to r-maximum. The observation log of spectra can be found in Tab. \ref{['tab:22ywf_spectra']}. The first three spectra of SN 2023zgx (blue) close in phase to those of SN 2022ywf (grey) are also shown as comparison.
  • Figure 4: Optical spectra of SN 2023zgx. The epochs show the days with respect to r-maximum. The observation log of spectra can be found in Tab. \ref{['tab:23zgx_spectra']}.
  • Figure 5: Five spectral epochs of SN 2022ywf (grey) fitted with the TARDIS synthetic spectra (red) produced in the abundance tomography analysis.
  • ...and 6 more figures