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

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 LR < (1.0 − 2.4) × 1025 erg s−1 Hz−1 at a frequency of 7.5 GHz and a X-ray luminosity LX < 1.4 × 1038 erg s−1 (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 Ne (γe) ∝ γ−p e with p = 3. Our analysis constrains the progenitor system mass-loss rate to be ¤ M < 5.0 × 10−6M yr−1 at distances r . 1016 cm for an assumed wind velocity vw = 100 km s−1, and a fraction of post-shock energy into magnetic fields and relativistic electrons of εB = 0.01 and εe = 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.