HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star
Noah Vowell, Joseph E. Rodriguez, Samuel N. Quinn, George Zhou, Andrew Vanderburg, Andrew W. Mann, M. J. Hooton, Keivan G. Stassun, Saburo Howard, Allyson Bieryla, David W. Latham, Steve B. Howell, T. Guillot, Carl Ziegler, Karen A. Collins, Theron W. Carmichael, Jon M. Jenkins, Avi Shporer, Lyu Abe, Philippe Bendjoya, Jonathan L. Bush, Marco Buttu, Kevin I. Collins, Jason D. Eastman, Matthew J. Fields, T Gasparetto, Maximilian N. Günther, Veselin B. Kostov, Adam L. Kraus, Kathryn V. Lester, Alan M. Levine, Colin Littlefield, Wenceslas Marie-Sainte, D. Mékarnia, H. P. Osborn, David Rapetti, G. Ricker, Sara Seager, Ramotholo Sefako, Gregor Srdoč, Olga Suárez, Guillermo Torres, A. H. M. J. Triaud, R. Vanderspek, Joshua N. Winn
Abstract
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 as TOI-588 b. HIP 33609 b is a large ( R b = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>1.580</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.070</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.074</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> R J ) brown dwarf on a highly eccentric ( e = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.560</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.031</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.029</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ) orbit with a 39 days period. The host star is a bright ( V = 7.3 mag), T eff = 10,400 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>660</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>800</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> K star with a mass of M * = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.383</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.095</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ and radius of R * = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>1.863</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.082</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.087</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> 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 = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>68.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>7.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>7.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M J as well as the host star's rotation rate ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>v</mml:mi> <mml:mi>sin</mml:mi> <mml:msub> <mml:mrow> <mml:mi>i</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>55.6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.8</mml:mn> </mml:math> km s −1 ). 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 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.