2021MNRAS.505.1153S

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 L_R<(1.0-2.4)×_10²⁵ erg s^–1 Hz^–1 at a frequency of 7.5 GHz and a X-ray luminosity L_X<1.4×_10³⁸ erg s^–1 (0.3-10 keV) at ∼38-48 d 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(γe)∝γe^–p with p = 3. Our analysis constrains the progenitor system mass-loss rate to be {dot}M< 5.0 ×10^–6 M_☉ yr^–1 at distances r≲10¹⁶ cm for an assumed wind velocity v_w=100_km s^–1, and a fraction of post-shock energy into magnetic fields and relativistic electrons of ε_B = 0.01 and ε_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.