  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
0.39, 0.89, and 0.49 Mjup, and radii of 1.28, 1.43, and 1.28 Rjup. The stellar
hosts have masses of 0.94, 1.26, and 1.28 Msun. 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 220 d and a minimum mass of
1.6 Mjup. Due to aliasing we cannot rule out an alternative solution for the
outer planet having a period of 438 d and a minimum mass of 3.7 Mjup. 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 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 d and a minimum mass of 2.0 Mjup, 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 RV 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.
