KELT-24b: A 5<i>M</i><sub>J</sub> Planet on a 5.6 day Well-aligned Orbit around the Young <i>V</i>=8.3 F-star HD 93148

Rodriguez, Joseph E.; Eastman, Jason D.; Zhou, George; Quinn, Samuel N.; Beatty, Thomas G.; Penev, Kaloyan; Johnson, Marshall C.; Cargile, Phillip A.; Latham, David W.; Bieryla, Allyson; Collins, Karen A.; Dressing, Courtney D.; Ciardi, David R.; Relles, Howard M.; Murawski, Gabriel; Nishiumi, Taku; Yonehara, Atsunori; Ishimaru, Ryo; Yoshida, Fumi; Gregorio, Joao; Lund, Michael B.; Stevens, Daniel J.; Stassun, Keivan G.; Gaudi, B. Scott; Colon, Knicole D.; Pepper, Joshua; Narita, Norio; Awiphan, Supachai; Chuanraksasat, Pongpichit; Benni, Paul; Zambelli, Roberto; Garrison, Lehman H.; Wilson, Maurice L.; Cornachione, Matthew A.; Wang, Sharon X.; Labadie-Bartz, Jonathan; Rodriguez, Romy; Siverd, Robert J.; Yao, Xinyu; Bayliss, Daniel; Berlind, Perry; Calkins, Michael L.; Christiansen, Jessie L.; Cohen, David H.; Conti, Dennis M.; Curtis, Ivan A.; Depoy, D. L.; Esquerdo, Gilbert A.; Evans, Phil; Feliz, Dax; Fulton, Benjamin J.; Holoien, Thomas W. S.; James, David J.; Jayasinghe, Tharindu; Jang-Condell, Hannah; Jensen, Eric L. N.; Johnson, John A.; Joner, Michael D.; Khakpash, Somayeh; Kielkopf, John F.; Kuhn, Rudolf B.; Manner, Mark; Marshall, Jennifer L.; McLeod, Kim K.; McCrady, Nate; Oberst, Thomas E.; Oelkers, Ryan J.; Penny, Matthew T.; Reed, Phillip A.; Sliski, David H.; Shappee, B. J.; Stephens, Denise C.; Stockdale, Chris; Tan, Thiam-Guan; Trueblood, Mark; Trueblood, Pat; Villanueva, Steven, Jr.; Wittenmyer, Robert A.; Wright, Jason T.
2019
ASTRONOMICAL JOURNAL
DOI
10.3847/1538-3881/ab4136
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-eff = 6509(-49)(+50) K, a mass of M-* = 1.460(-0.059)(+0.055) M-circle dot, a radius of R-* = 1.506 +/- 0.022 R-circle dot, and an age of 0.78(-0.42)(+0.61) Gyr. Its planetary companion (KELT-24 b) has a radius of R-P = 1.272 +/- 0.021 R-J and a mass of M-P = 5.18(-0.22)(+0.21) M-J, and from Doppler tomographic observations, we find that the planet's orbit is well-aligned to its host star's projected spin axis (lambda = 2.6(-3.6)(+5.1)). 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.