HAT-P-44b, HAT-P-45b, and HAT-P-46b: Three Transiting Hot Jupiters in Possible Multi-planet Systems

We report the discovery by the HATNet survey of three new transiting extrasolar planets orbiting moderately bright (V = 13.2, 12.8, and 11.9) stars. The planets have orbital periods of 4.3012, 3.1290, and 4.4631 days, masses of 0.35, 0.89, and 0.49 M _J, and radii of 1.24, 1.43, and 1.28 R _J. The stellar hosts have masses of 0.94, 1.26, and 1.28 M _⊙. Each system shows significant systematic variations in its residual radial velocities, indicating the possible presence of additional components. Based on its Bayesian evidence, the preferred model for HAT-P-44 consists of two planets, including the transiting component, with the outer planet having a period of 872 days, eccentricity of 0.494 ± 0.081, and a minimum mass of 4.0 M _J. Due to aliasing we cannot rule out alternative solutions for the outer planet having a period of 220 days or 438 days. For HAT-P-45, at present there is not enough data to justify the additional free parameters included in a multi-planet model; in this case a single-planet solution is preferred, but the required jitter of 22.5 ± 6.3 m s^-1 is relatively high for a star of this type. For HAT-P-46 the preferred solution includes a second planet having a period of 78 days and a minimum mass of 2.0 M _J, however the preference for this model over a single-planet model is not very strong. While substantial uncertainties remain as to the presence and/or properties of the outer planetary companions in these systems, the inner transiting planets are well characterized with measured properties that are fairly robust against changes in the assumed models for the outer planets. Continued radial velocity monitoring is necessary to fully characterize these three planetary systems, the properties of which may have important implications for understanding the formation of hot Jupiters.

Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO (A284Hr) and NASA (N154Hr, N108Hr).