  We report on the confirmation and mass determination of Pi Men c, the first
transiting planet discovered by NASA's TESS space mission. Pi Men is a
naked-eye (V=5.65 mag), quiet G0 V star that was previously known to host a
sub-stellar companion (Pi Men b) on a long-period (Porb = 2091 days), eccentric
(e = 0.64) orbit. Using TESS time-series photometry, combined with Gaia data,
published UCLES@AAT Doppler measurements, and archival<EMAIL_ADDRESS>radial
velocities, we found that Pi Men c is a close-in planet with an orbital period
of Porb = 6.27 days, a mass of Mc = 4.52 +/- 0.81 MEarth, and a radius of Rc =
2.06 +/- 0.03 REarth. Based on the planet's orbital period and size, Pi Men c
is a super-Earth located at, or close to, the radius gap, while its mass and
bulk density suggest it may have held on to a significant atmosphere. Because
of the brightness of the host star, this system is highly suitable for a wide
range of further studies to characterize the planetary atmosphere and dynamical
properties. We also performed an asteroseismic analysis of the TESS data and
detected a hint of power excess consistent with the seismic values expected for
this star, although this result depends on the photometric aperture used to
extract the light curve. This marginal detection is expected from pre-launch
simulations hinting at the asteroseismic potential of the TESS mission for
longer, multi-sector observations and/or for more evolved bright stars.
