uGMRT Observations of a Fast and Blue Optical Transient—AT 2018cow

We present low-frequency radio observations of a fast-rising blue optical transient (FBOT), AT\,2018cow, with the upgraded Giant Metrewave Radio Telescope (uGMRT). Our span $t =$ 11 $-$ 570 days post-explosion and frequency range 250 1450 MHz. The uGMRT light curves are best modeled as synchrotron emission from an inhomogeneous radio-emitting region expanding into ionized medium. However, due to lack information on source covering factor, which is measure degree inhomogeneity, we derive various parameters assuming factor be unity. These parameters, hence, indicate limits actual values in model. lower limit shock radius $R \sim$ (6.1$-$14.4) $\times$ 10$^{16}$ cm at 138$-$257 post-explosion. find that fast-moving ejecta explosion moving velocity $v$ $>$ 0.2c up 257 upper mass-loss rate progenitor $\dot{M}$ $\sim$ (4.1$-$1.7) 10$^{-6}$ $M_{\odot}$\,yr$^{-1}$ (19.3$-$45.7) years before for wind $v_{\rm w}$ = 1000 km\,s$^{-1}$. 100 times smaller than previously reported 2.2 explosion, indicating enhanced phase event close end-of-life progenitor. results line speculation presence dense circumstellar shell vicinity AT\,2018cow previous radio, ultra-violet, observations.