A Population Study on the Radio Emission of Fast Blue Optical Transients

TL;DR

This study explores the radio emission characteristics of Fast Blue Optical Transients (FBOTs) by analyzing their population properties and assessing their detectability with current and future radio telescopes, providing insights into their progenitors and circumstellar environments.

Contribution

It offers the first statistical analysis of FBOT radio emission based on population parameters and evaluates detection prospects with upcoming telescopes.

Findings

Peak radio emission occurs around 100 days post-explosion.

Detection probability with current telescopes is approximately 8.7%.

Future telescopes could increase detection chances to about 23.9%.

Abstract

Despite the fact that the progenitor of fast blue optical transients (FBOTs) is still up for debate, FBOTs are sometimes suggested to originate from the core-collapse of ultra-stripped stars and be powered by a spinning-down neutron star. Following this consideration, it is expected that the late-time evolution of the progenitor stars can leave important imprints in the circumstellar material (CSM) of the FBOTs, due to the strong mass loss of the stars. The interaction of the FBOT ejecta with the CSM can drive a long-lasting shock to generate radio emission, which thus enables us to probe the CSM properties through radio observation although such observations are still rare. Within the framework of the magnetar-powered model, Liu et al.(2022) fitted the multi-band optical light curves of 40 FBOTs and, hence, the statistical distributions of the FBOT magnetar and ejecta parameters were obtained. Based on these FBOT population results, we investigate the dependence of the radio emission on the mass-loss rate of the progenitors and evaluate the detectability of radio emission from FBOTs with current and future telescopes. It is found that the distribution of the peak time and peak luminosity of the emission at 8.4 GHz are primarily in the regions of $t_{\rm{peak},\nu}=10^{2.12\pm0.63}$ days and $L_{\rm{peak},\nu}=10^{28.73\pm0.83}$ erg s$^{-1}$ Hz$^{-1}$, respectively. A joint detection of the Zwicky Transient Facility and Very Large Array could achieve success in about 8.7% FBOTs of $z\leq1$. Furthermore, if considering a joint observation of the Chinese Space Station Telescope and Square Kilometer Array, this fraction can be increased to about 23.9%.