J1316+2614 at $z$=3.613 is the UV-brightest ($M_ UV = -24.7$) and strongest Lyman continuum-emitting ($f_ esc LyC $90<!PCT!>) star-forming galaxy known; it also shows signatures of inflowing gas from its blue-dominated Lyalpha profile. We present high-resolution imaging with the Hubble Space Telescope (HST) and the Very Large Telescope (VLT) of the LyC, Lyalpha , rest-UV, and optical emission of J1316+2614.
Detailed analysis of the LyC and UV light distributions reveals compact yet resolved profiles, with LyC and UV morphologies showing identical half-light radii of $r_ eff 220$\,pc. The continuum-subtracted Lyalpha emission, obtained with the HST ramp-filter FR551N, reveals an extended filamentary structure of $ 6.0$\,kpc oriented south to north with only residual flux within the stellar core, suggesting a Lyalpha `hole'. Our spectral energy distribution analysis shows that J1316+2614 is characterised by a young (5.7pm 1.0\,Myr), nearly un-obscured stellar population with a high star-formation rate ($ SFR = 898 odot $) and a stellar mass of $M_ star young M_ odot $. Additionally, the spectral energy distribution analysis supports the absence of an underlying old stellar population ($M_ star old M_ odot $, 3sigma ). J1316+2614 presents remarkably high SFR and stellar mass surface densities of log($ SFR M_ odot kpc^ 0.11$ and log($ star M_ odot 0.06$, respectively, which are among the highest observed in star-forming galaxies and are more typically observed in local young massive star clusters and globular clusters. Our findings indicate that J1316+2614 is a powerful, young, and compact starburst that is leaking a significant amount of LyC photons due to a lack of gas and dust within the starburst. We explored the conditions for gas expulsion using a simple energetic balance and find that, given the strong binding force in J1316+2614, a high star-formation efficiency ($ SF 0.7$) is necessary to explain the removal of gas and its exposed nature. Our results thus suggest a close link between high $ SF $ and high $f_ esc LyC $. This high efficiency can also naturally explain the remarkably high SFR, UV luminosity, and efficient mass growth of J1316+2614, which acquired at least 62<!PCT!> of its mass in the last 6\,Myr. J1316+2614 may exemplify an intense, feedback-free starburst with a high $ SF $, similar to those proposed for UV-bright galaxies at high redshifts.