HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star

We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting late B star, discovered by NASA's Transiting Exoplanet Survey Satellite TESS as TOI-588 b. b is large (R$_{b}$ = 1.580$_{-0.070}^{+0.074}$ R$_{J}$) on highly eccentric (e 0.560$_{-0.031}^{+0.029}$) orbit with 39-day period. The host star bright (V 7.3 mag), T$_{eff}$ 10,400$_{-660}^{+800}$ K mass M$_{*}$ 2.383$_{-0.095}^{+0.10}$ M$_{\odot}$ radius R$_{*}$ 1.863$_{-0.082}^{+0.087}$ R$_{\odot}$, making it hottest to date. obtained radial velocity measurements from CHIRON spectrograph confirming companion's M$_{b}$ 68.0$_{-7.1}^{+7.4}$ M$_{J}$ well star's rotation rate ($vsini_{*} 55.6 \pm 1.8$ km/s). also new comoving group stars, designated MELANGE-6, determine that member. use combination periods isochrone models fit cluster members estimate an age 150 $\pm$ 25 Myr. With measured mass, radius, age, becomes benchmark for substellar evolutionary models.