The luminous type IIn supernova SN 2017hcc: Infrared bright, X-ray, and radio faint

Abstract

We present multiwavelength observations of supernova (SN) 2017hcc with the Chandra X-ray telescope and the X-ray telescope onboard Swift (Swift-XRT) in X-ray bands, with the Spitzer and the TripleSpec spectrometer in near-infrared (IR) and mid-IR bands and with the Karl G. Jansky Very Large Array (VLA) for radio bands. The X-ray observations cover a period of 29 to 1310 d, with the first X-ray detection on day 727 with the Chandra. The SN was subsequently detected in the VLA radio bands from day 1000 onwards. While the radio data are sparse, synchrotron-self absorption is clearly ruled out as the radio absorption mechanism. The near- and the mid-IR observations showed that late time IR emission dominates the spectral energy distribution. The early properties of SN 2017hcc are consistent with shock breakout into a dense mass-loss region, with M˙∼0.1 M⊙ yr−1 for a decade. At few 100 d, the mass-loss rate declined to ∼0.02 M⊙ yr−1, as determined from the dominant IR luminosity. In addition, radio data also allowed us to calculate a mass-loss rate at around day 1000, which is two orders of magnitude smaller than the mass-loss rate estimates around the bolometric peak. These values indicate that the SN progenitor underwent an enhanced mass-loss event a decade before the explosion. The high ratio of IR to X-ray luminosity is not expected in simple models and is possible evidence for an asymmetric circumstellar region.