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We report individual dynamical masses of $66.92 \pm 0.36 \; M_{Jup}$ and$53.25 \pm 0.29 \; M_{Jup}$ for the binary brown dwarfs $\varepsilon$ Indi Baand Bb, measured from long term ($\approx 10$ yr) relative orbit monitoring andabsolute astrometry monitoring data on the VLT. Relative astrometry with NACOfully constrains the Keplerian orbit of the binary pair, while absoluteastrometry with FORS2 measures the system's parallax and mass ratio. We find aparallax consistent with the Hipparcos and Gaia values for $\varepsilon$ IndiA, and a mass ratio for $\varepsilon$ Indi Ba to Bb precise to better than$0.2\%$. $\varepsilon$ Indi Ba and Bb have spectral types T1-1.5 and T6,respectively. With an age of $3.5^{+0.8}_{-1.0}$ Gyr from $\varepsilon$ IndiA's activity, these brown dwarfs provide some of the most precise benchmarksfor substellar cooling models. Assuming coevality, the very differentluminosities of the two brown dwarfs and our moderate mass ratio imply a steepmass-luminosity relationship $L \propto M^{5.37 \pm 0.08}$ that can beexplained by a slowed cooling rate in the L/T transition, as previouslyobserved for other L/T binaries. Finally, we present a periodogram analysis ofthe near-infrared photometric data, but find no definitive evidence of periodicsignals with a coherent phase.

Precise Dynamical Masses of Epsilon Indi Ba and Bb: Evidence of Slowed Cooling at the L/T Transition