2023A&A...672L...7K

We present the discovery of a transiting massive giant planet around TOI-4603, a sub-giant F-type star from NASA's Transiting Exoplanet Survey Satellite (TESS). The newly discovered planet has a radius of $ 1.042^{+0.038}_{-0.035}\,R_{\mathrm{J}} $ and an orbital period of $ 7.24599^{+0.00022}_{-0.00021} $ days. Using radial velocity measurements with the PARAS and TRES spectrographs, we determined the planet's mass to be $ 12.89^{+0.58}_{-0.57}\,M_{\mathrm{J}} $, resulting in a bulk density of $ 14.1^{+1.7}_{-1.6} $ g cm^–3. This makes it one of the few known massive giant planets with an extreme density. It lies in the transition mass region of massive giant planets and low-mass brown dwarfs, an important addition to the population of fewer than five known objects in this mass range. The eccentricity of 0.325 ± 0.020 and an orbital separation of 0.0888 ± 0.0010 AU from its host star suggest that the planet is likely undergoing high-eccentricity tidal migration. We find a fraction of heavy elements of $ 0.13^{+0.05}_{-0.06} $ and metal enrichment of the planet (Z_P/Z_star) of $ 4.2^{+1.6}_{-2.0} $. Detection of such systems will enable us to gain valuable insights into the governing mechanisms of massive planets and improve our understanding of their dominant formation and migration mechanisms.