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Description
We report the discovery of the massive hot Jupiter NGTS-13b by the Next Generation Transit Survey (NGTS). The V=12.7 host star is likely in the subgiant evolutionary phase with logg_*_=4.04+/-0.05, Teff=5819+/-73K, M_*_=1.30^+0.11^_-0.18_M_{sun}_, and R_*_=1.79+/-0.06R_{sun}_. NGTS detected a transiting planet with a period of P=4.12 days around the star, which was later validated with the Transiting Exoplanet Survey Satellite (TESS; TIC 454069765). We confirm the planet using radial velocities from the CORALIE spectrograph. Using NGTS and TESS full-frame image photometry combined with CORALIE radial velocities we determine NGTS-13b to have a radius of R_P_=1.142+/-0.046R_Jup_, mass of M_P_=4.84+/-0.44M_Jup_ and eccentricity e=0.086+/-0.034. Some previous studies suggest that ~4M_Jup_ may be a border between two separate formation scenarios (e.g., core accretion and disk instability) and that massive giant planets share similar formation mechanisms as lower-mass brown dwarfs. NGTS-13b is just above 4M_Jup_ making it an important addition to the statistical sample needed to understand the differences between various classes of substellar companions. The high metallicity, [Fe/H]=0.25+/-0.17, of NGTS-13 does not support previous suggestions that massive giants are found preferentially around lower metallicity host stars, but NGTS-13b does support findings that more massive and evolved hosts may have a higher occurrence of close-in massive planets than lower-mass unevolved stars.
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