  We present the discovery of NGTS-19b, a high mass transiting brown dwarf
discovered by the Next Generation Transit Survey (NGTS). We investigate the
system using follow up photometry from the South African Astronomical
Observatory, as well as sector 11 TESS data, in combination with radial
velocity measurements from the CORALIE spectrograph to precisely characterise
the system. We find that NGTS-19b is a brown dwarf companion to a K-star, with
a mass of $69.5 ^{+5.7}_{-5.4}$ M$_{Jup}$ and radius of $1.034
^{+0.055}_{-0.053}$ R$_{Jup}$. The system has a reasonably long period of 17.84
days, and a high degree of eccentricity of $0.3767 ^{+0.0061}_{-0.0061}$. The
mass and radius of the brown dwarf imply an age of $0.46 ^{+0.26}_{-0.15}$ Gyr,
however this is inconsistent with the age determined from the host star SED,
suggesting that the brown dwarf may be inflated. This is unusual given that its
large mass and relatively low levels of irradiation would make it much harder
to inflate. NGTS-19b adds to the small, but growing number of brown dwarfs
transiting main sequence stars, and is a valuable addition as we begin to
populate the so called brown dwarf desert.
