paper

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

arXiv:2301.09663 · doi:10.3847/1538-3881/acd197

Abstract

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

16 pages, 5 figures, 4 tables, Submitted to AAS Journals