Type IIP supernova SN2016X in radio frequencies

Abstract

Context. The study of radio emission from core-collapse supernovae (SNe) probes the interaction of the ejecta with the circumstellar medium (CSM) and reveals details of the mass-loss history of the progenitor. Aims. We report observations of the type IIP supernova SN 2016X during the plateau phase, at ages between 21 and 75 days, obtained with the Karl G. Jansky Very Large Array (VLA) radio observatory. Methods. We modelled the radio spectra as self-absorbed synchrotron emission, and we characterised the shockwave and the mass-loss rate of the progenitor. We also combined our results with previously reported X-ray observations to verify the energy equipartition assumption. Results. The properties of the shockwave are comparable to other type IIP supernovae. The shockwave expands according to a self-similar law R ∝ tm with m = 0.76 ± 0.08, which is notably different from a constant expansion. The corresponding shock velocities are approximately 10700–8000 km s−1 during the time of our observations. The constant mass-loss rate of the progenitor is Ṁ = (7.8 ± 0.9) × 10−7 α−8/19 (ϵB/0.1)−1 M⊙ yr−1, for an assumed wind velocity of 10 km s−1. We observe spectral steepening in the optically thin regime at the earlier epochs, and we demonstrate that it is caused by electron cooling via the inverse Compton effect. We show that the shockwave is characterised by a moderate deviation from energy equipartition by a factor of ϵe/ϵB ≈ 28, being the second type IIP supernova to show such a feature.

Modeling of Radio Supernovae: Including the Effects of Inhomogeneities and Radiative Cooling

“…Although Type Ib/c is the class of supernovae in which inverse Compton scattering is likely to be most dominant, there are indications of a substantial contribution to the X-ray emission also in other types of supernovae; for example, in the Type IIb supernova 2011dh (Krauss et al 2012;Soderberg et al 2012;Horesh et al 2013). Even in Type IIPs, in which the density of the circumstellar medium is thought to be much higher than in Type Ib/c, it has been argued that inverse Compton scattering gives an important contribution to the X-ray emission; for example, SN 2004dj (Chakraborti et al 2012;Nayana et al 2018) and SN 2016X (Ruiz-Carmona et al 2022).…”