Constraints on the Sub-pc Environment of the Nearby Type Iax SN 2014dt from Deep X-ray and Radio Observations

TL;DR

This study uses deep X-ray and radio observations of SN 2014dt to place constraints on its environment and progenitor system, ruling out certain companion star scenarios and highlighting the need for more sensitive future observations.

Contribution

First constraints on the environment of SN 2014dt using deep X-ray and radio data, informing progenitor models for Type Iax supernovae.

Findings

Progenitor mass-loss rate < 5E-6 solar masses/year.

Radio luminosity < (1.0-2.4)E25 erg/s/Hz at 7.5 GHz.

X-ray luminosity < 1.4E38 erg/s at 38-48 days post-explosion.

Abstract

We present X-ray and radio observations of what may be the closest type Iax supernova (SN) to date, SN 2014dt (d=12.3-19.3 Mpc) and provide tight constraints on the radio and X-ray emission. We infer a specific radio luminosity of < (1.0-2.4)E25 erg/s/Hz at a frequency of 7.5 GHz and a X-ray luminosity < 1.4E38 erg/s (0.3-10 keV) at ~38-48 days post-explosion. We interpret these limits in the context of Inverse Compton (IC) emission and synchrotron emission from a population of electrons accelerated at the forward shock of the explosion in a power-law distribution $N_e(\gamma_e)\propto \gamma_e^{-p}$ with p=3. Our analysis constrains the progenitor system mass-loss rate to be smaller than 5E-6 solar masses per year at distances where r <= 1E16 cm for an assumed wind velocity v=100 km/s, and a fraction of post-shock energy into magnetic fields and relativistic electrons of epsilon_B=0.01 and epsilon_e=0.1, respectively. This result rules out some of the parameter space of symbiotic giant star companions, and it is consistent with the low mass-loss rates expected from He-star companions. Our calculations also show that the improved sensitivity of the next generation Very Large Array (ngVLA) is needed to probe the very low-density media characteristic of He stars that are the leading model for binary stellar companions of white dwarfs giving origin to type Iax SNe.