Detection of 2$-$4 GHz Continuum Emission from $ϵ$ Eridani

The nearby star $ϵ\mathrm{E}\mathrm{r}\mathrm{i}\mathrm{d}\mathrm{a}\mathrm{n}\mathrm{i}$ has been a frequent target of radio surveys for stellar emission and extraterrestial intelligence. Using deep $\rm 2-4 \ GHz$observationswiththeVeryLargeArray,wehaveuncovereda$29
\mu {\rm Jy}$compact,steadycontinuumradiosourcecoincidentwith$\rm \epsilon \ Eridani$towithin0.06arcseconds($\lesssim 2\sigma$; 0.2 au at the distance of the star). Combining our data with previous high frequency continuum detections of $ϵ\mathrm{E}\mathrm{r}\mathrm{i}\mathrm{d}\mathrm{a}\mathrm{n}\mathrm{i}$, our observations reveal a spectral turnover at $6\mathrm{G}\mathrm{H}\mathrm{z}$. We ascribe the $2-6\mathrm{G}\mathrm{H}\mathrm{z}$ emission to optically thick, thermal gyroresonance radiation from the stellar corona, with thermal free-free opacity likely becoming relevant at frequencies below $\rm 1 \ GHz$\mathrm{.}Thesteepspectralindex($\alpha \simeq 2$)ofthe$\rm 2-6 \ GHz$ spectrum strongly disfavors its interpretation as stellar wind-associated thermal bremsstrahlung ($\alpha \simeq 0.6$). Attributing the entire observed $2-4\mathrm{G}\mathrm{H}\mathrm{z}$ flux density to thermal free-free wind emission, we thus, derive a stringent upper limit of $3 \times 10^{-11} \ M_{\odot} \ {\rm yr}^{-1}$onthemasslossratefrom$\rm \epsilon \ Eridani$. Finally, we report the non-detection of flares in our data above a $5\sigma$ threshold of $95\mu \mathrm{J}\mathrm{y}$. Together with the optical non-detection of the most recent stellar maximum expected in 2019, our observations postulate a likely evolution of the internal dynamo of $ϵ\mathrm{E}\mathrm{r}\mathrm{i}\mathrm{d}\mathrm{a}\mathrm{n}\mathrm{i}$.