TESS Hunt for Young and Maturing Exoplanets (THYME). VI. An 11 Myr Giant Planet Transiting a Very-low-mass Star in Lower Centaurus Crux

Mature super-Earths and sub-Neptunes are predicted to be $\simeq$Jovian radius when younger than 10 Myr. Thus, we expect find 5-15$R_\oplus$ planets around young stars even if their older counterparts harbor none. We report the discovery validation of TOI 1227 b, a $0.85\pm0.05R_J$ (9.5$R_\oplus$) planet transiting very low-mass star ($0.170\pm0.015M_\odot$) every 27.4 days. TOI~1227's kinematics strong lithium absorption confirm it is member previously discovered sub-group in Lower Centaurus Crux OB association, which designate Musca group. derive an age 11$\pm$2 Myr for Musca, based on lithium, rotation, color-magnitude diagram members. The TESS data ground-based follow-up show deep (2.5\%) transit. use multiwavelength transit observations radial velocities from IGRINS spectrograph validate signal as planetary nature, obtain upper limit mass $\simeq0.5 M_J$. Because such large exceptionally rare mature stars, suggest that b still contracting will eventually turn into one more common $<5R_\oplus$ planets.