The first radio view of a type Ibn supernova in SN 2023fyq: Understanding the mass-loss history in the last decade before the explosion

Abstract

Supernovae that interact with hydrogen-poor, helium-rich circumstellar material (CSM), known as Type Ibn supernovae (SNe Ibn), present a unique opportunity to probe mass-loss processes in massive stars. In this work, we report the first radio detection of a SN Ibn, SN 2023fyq, and characterize the mass-loss history of its stellar progenitor using the radio and X-ray observations obtained over 18 months post-explosion. We find that the radio emission from 58--185 days is best modeled by synchrotron radiation attenuated by free-free absorption from a CSM of density $\sim$ $10^{-18}$ g/$\mathrm{c}{\mathrm{m}}^3$ ($\sim 10^6\ddot{\mathrm{I}}{}_{\mathrm{ISM}}$) at a radius of $10^{16}$ cm, corresponding to a mass-loss rate of $\sim$ $4\times 10^{-3}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ (for a wind velocity of 1700 km/s from optical spectroscopy) from 0.7 to 3 years before the explosion. This timescale is consistent with the time frame over which pre-explosion optical outbursts were observed. However, our late-time observations at 525 days post-explosion yield non-detections, and the 3$\ddot{I}ƒ$ upper limits (along with an X-ray non-detection) allow us to infer lower-density CSM at $2\times 10^{16}$ cm with $\dot{\mathrm{M}}$ $<2.5\times 10^{-3}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$. These results suggest a shell-like CSM from at most $4\times 10^{15}$ to $2\times 10^{16}$ cm ($\sim 10^5{R}_{\odot }$) with an elevated CSM density (0.004 ${\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$) that is roughly consistent with predictions from a merger model for this object. Future radio observations of a larger sample of SNe Ibn will provide key details on the extent and density of their helium-rich CSM.

Updating for full consistency with ApJ published version