Early and Extensive Ultraviolet Through Near Infrared Observations of the Intermediate-Luminosity Type Iax Supernovae 2024pxl

TL;DR

This paper presents comprehensive UV to NIR observations of the intermediate-luminosity Type Iax supernova 2024pxl, revealing unique spectral features, color homogeneity, and potential correlations between spectral velocities and luminosity, advancing understanding of SN Iax characteristics.

Contribution

It provides the earliest NIR spectrum of a SN Iax, detailed photometric and spectroscopic data, and identifies possible velocity-luminosity correlations, offering new insights into SN Iax explosion mechanisms.

Findings

SN 2024pxl's rising light curve follows a single power law.

$J-H$ colors of SNe Iax are more homogeneous than normal SNe Ia.

Tentative correlation between H-band Co II velocity and luminosity.

Abstract

We present ultraviolet (UV) through near-infrared (NIR) photometric and spectroscopic observations of the nearby SN 2024pxl, the third Type Ia supernova (SN Ia) in NGC 6384. SN 2024pxl is a Type Iax supernova (SN Iax) with an intermediate luminosity ($M_r = -16.99\pm0.32$ mag) and an average SN Iax light curve decline rate. SN 2024pxl was discovered $\sim$3 days after first light, and the rising light curve follows a single power law that is inconsistent with significant interaction with a companion star or circumstellar material. Our extensive NIR photometric coverage is comparable to that of the well-observed SNe Iax 2005hk and 2012Z, and we demonstrate that the $J-H$ colors of SNe Iax differ from normal SNe Ia and appear to be more homogeneous as a class. Spectroscopically, we report the earliest-ever NIR spectrum of a SN Iax as measured from maximum light ($t\approx-9$ days): a featureless continuum with similarities to a $\sim$9,000 K blackbody, and the line velocities are consistent with a mixed-ejecta structure, with C, Si, and Fe having similar velocities and velocity evolutions. We find a tentative correlation between the $H$-band break Co II velocity $\sim$20 days post-peak and absolute magnitude, with more luminous SNe Iax showing faster Co II velocities. Our observations suggest that SN 2024pxl resulted from the thermonuclear disruption of a CO white dwarf star that undergoes deflagration burning.