KELT-24b: A 5M$_{\rm J}$ Planet on a 5.6 day Well-Aligned Orbit around the Young V=8.3 F-star HD 93148
Creators: name: Rodriguez, Joseph E.
name: Eastman, Jason D.
name: Zhou, George
name: Quinn, Samuel N.
name: Beatty, Thomas G.
name: Penev, Kaloyan
name: Johnson, Marshall C.
name: Cargile, Phillip A.
name: Latham, David W.
name: Bieryla, Allyson
name: Collins, Karen A.
name: Dressing, Courtney D.
name: Ciardi, David R.
name: Relles, Howard M.
name: Murawski, Gabriel
name: Nishiumi, Taku
name: Yonehara, Atsunori
name: Ishimaru, Ryo
name: Yoshida, Fumi
name: Gregorio, Joao
name: Lund, Michael B.
name: Stevens, Daniel J.
name: Stassun, Keivan G.
name: Gaudi, B. Scott
name: Colón, Knicole D.
name: Pepper, Joshua
name: Narita, Norio
name: Awiphan, Supachai
name: Chuanraksasat, Pongpichit
name: Benni, Paul
name: Zambelli, Roberto
name: Garrison, Lehman H.
name: Wilson, Maurice L.
name: Cornachione, Matthew A.
name: Wang, Sharon X.
name: Labadie-Bartz, Jonathan
name: Rodríguez, Romy
name: Siverd, Robert J.
name: Yao, Xinyu
name: Bayliss, Daniel
name: Berlind, Perry
name: Calkins, Michael L.
name: Christiansen, Jessie L.
name: Cohen, David H.
name: Conti, Dennis M.
name: Curtis, Ivan A.
name: Depoy, D. L.
name: Esquerdo, Gilbert A.
name: Evans, Phil
name: Feliz, Dax
name: Fulton, Benjamin J.
name: Holoien, Thomas W. S.
name: James, David J.
name: Jayasinghe, Tharindu
name: Jang-Condell, Hannah
name: Jensen, Eric L. N.
name: Johnson, John A.
name: Joner, Michael D.
name: Khakpash, Somayeh
name: Kielkopf, John F.
name: Kuhn, Rudolf B.
name: Manner, Mark
name: Marshall, Jennifer L.
name: McLeod, Kim K.
name: McCrady, Nate
name: Oberst, Thomas E.
name: Oelkers, Ryan J.
name: Penny, Matthew T.
name: Reed, Phillip A.
name: Sliski, David H.
name: Shappee, B. J.
name: Stephens, Denise C.
name: Stockdale, Chris
name: Tan, Thiam-Guan
name: Trueblood, Mark
name: Trueblood, Pat
name: Villanueva, Steven
name: Wittenmyer, Robert A.
name: Wright, Jason T.
Publisher: name: arXiv
Year: 2019
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present the discovery of KELT-24 b, a massive hot Jupiter orbiting a bright (V=8.3 mag, K=7.2 mag) young F-star with a period of 5.6 days. The host star, KELT-24 (HD 93148), has a $T_{\rm eff}$ =$6509^{+50}_{-49}$ K, a mass of $M_{*}$ = $1.460^{+0.055}_{-0.059}$ $M_{\odot}$, radius of $R_{*}$ = $1.506\pm0.022$ $R_{\odot}$, and an age of $0.78^{+0.61}_{-0.42}$ Gyr. Its planetary companion (KELT-24 b) has a radius of $R_{\rm P}$ = $1.272\pm0.021$ $R_{\rm J}$, a mass of $M_{\rm P}$ = $5.18^{+0.21}_{-0.22}$ $M_{\rm J}$, and from Doppler tomographic observations, we find that the planet's orbit is well-aligned to its host star's projected spin axis ($λ$ = $2.6^{+5.1}_{-3.6}$). The young age estimated for KELT-24 suggests that it only recently started to evolve from the zero-age main sequence. KELT-24 is the brightest star known to host a transiting giant planet with a period between 5 and 10 days. Although the circularization timescale is much longer than the age of the system, we do not detect a large eccentricity or significant misalignment that is expected from dynamical migration. The brightness of its host star and its moderate surface gravity make KELT-24b an intriguing target for detailed atmospheric characterization through spectroscopic emission measurements since it would bridge the current literature results that have primarily focused on lower mass hot Jupiters and a few brown dwarfs.
description: 18 pages, 10 Figures, 6 Tables, Accepted to the Astronomical Journal