Browsing by Author "Johnson, Marshall C."
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Item Kelt-19Ab: A P ~ 4.6-day Hot Jupiter Transiting a Likely Am Star with a Distant Stellar Companion(IOP Publishing Ltd, 2018-11-05) Siverd, Robert J.; Collins, Karen A.; Zhou, George; Quinn, Samuel N.; Gaudi, B. Scott; Stassun, Keivan G.; Johnson, Marshall C.; Penev, Kaloyan; Penev, KaloyanWe present the discovery of the giant planet KELT-19Ab, which transits the moderately bright (V similar to 9.9) A8V star TYC 764-1494-1 with an orbital period of 4.61 days. We confirm the planetary nature of the companion via a combination of. radial velocities, which limit the mass to less than or similar to 4.1 M-J (3 sigma), and a clear Doppler tomography signal, which indicates a retrograde projected spin-orbit misalignment of lambda = -179.7(-3.7)(+3.8) degrees. Global modeling indicates that the T-eff=7500. 110 K host star has M-star = 1.62(-0.20)(+0.25) M-star and R-star = 1.83 +/- 0.10 R-circle dot. The planet has a radius of R-P = 1.91 +/- 0.11 R-J and receives a stellar insolation flux of similar to 3.2 x 10(9) erg s(-1) cm(-2), leading to an inferred equilibrium temperature of T-eq similar to 1935 K assuming zero albedo and complete heat redistribution. With a v sin I-* = 84.8 +/- 2.0 km s(-1), the host. is relatively slowly rotating compared to other stars with similar effective temperatures, and it appears to be enhanced in metallic elements but deficient in calcium, suggesting that it is likely an Am star. KELT-19A would be the first detection of an Am host of a transiting planet of which we are aware. Adaptive optics observations of the system reveal the existence of a companion with late-G9V/early-K1V spectral type at a projected separation of approximate to 160 au. Radial velocity measurements indicate that this companion is bound. Most Am stars are known to have stellar companions, which are often invoked to explain the relatively slow rotation of the primary. In this case, the stellar companion is unlikely to have caused the tidal braking of the primary. However, it may have emplaced the transiting planetary companion via the Kozai-Lidov mechanism.Item KELT-22Ab: A Massive, Short-Period Hot Jupiter Transiting a Near-Solar Twin(IOP Publishing Ltd, 2019-01-21) Labadie-Bartz, Jonathan; Rodriguez, Joseph E.; Stassun, Keivan G.; Ciardi, David R.; Penev, Kaloyan; Johnson, Marshall C.; Gaudi, B. Scott; 0000-0003-4464-1371 (Penev, K); Penev, KaloyanWe present the discovery of KELT-22Ab, a hot Jupiter from the KELT-South survey. KELT-22Ab transits the moderately bright (V ~ 11.1) Sun-like G2V star TYC 7518-468-1. The planet has an orbital period of P = 1.3866529 ± 0.0000027 days, a radius of R_{P} = 1.285{_{-0.071}^{+0.12}} R_{J}, and a relatively large mass of M_{P} = 3.47{_{-0.14}^{+0.15}}, M_{J}. The star has R_{⋆} = 1.099{_{-0.046}^{0.079}} R_{⊙}, M_{⋆} = 1.092{_{-0.041}^{+0.045}} M_{⊙}, T_{eff} = 5767{_{-49}^{+50}} K, log g_{⋆} = 4.393{_{-0.060}^{+0.039}} (cgs), and [m/H] = +0.259{_{-0.083}^{+0.085}}; thus other than its slightly super-solar metallicity, it appears to be a near-solar twin. Surprisingly, KELT-22A exhibits kinematics and a Galactic orbit that are somewhat atypical for thin-disk stars. Nevertheless, the star is rotating rapidly for its estimated age, and shows evidence of chromospheric activity. Imaging reveals a slightly fainter companion to KELT-22A that is likely bound, with a projected separation of 6 '' (similar to 1400 au). In addition to the orbital motion caused by the transiting planet, we detect a possible linear trend in the radial velocity of KELT-22A, suggesting the presence of another relatively nearby body that is perhaps non-stellar. KELT-22Ab is highly irradiated (as a consequence of the small semimajor axis of a/R_{⋆}, and is mildly inflated. At such small separations, tidal forces become significant. The configuration of this system is optimal for measuring the rate of tidal dissipation within the host star. Our models predict that, due to tidal forces, the semimajor axis is decreasing rapidly, and KELT-22Ab is predicted to spiral into the star within the next Gyr.