* Astronomy

Title: M2K: II. A Triple-Planet System Orbiting HIP 57274
Authors: Debra A. Fischer, Eric Gaidos, Andrew Howard, Matthew Giguere, John A. Johnson, Geoffrey W. Marcy, Jason T. Wright, Kelsey I. Clubb, Howard Isaacson, Kevin Apps, Sebastien Lepine, Andrew Mann, John Moriarty, John Brewer, Julien Spronck, Christian Schwab, Andrew Szymkowiak

Doppler observations from Keck Observatory have revealed a triple planet system orbiting the nearby mid-type K dwarf, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with \msini\ = 11.6 Earth masses (0.036 Jupiter masses), an orbital period of 8.135 ±0.004 d, and slightly eccentric orbit e=0.19 ±0.1. We calculate a transit probability of 6.5% for the inner planet. The second planet has \msini\ = 0.4 Jupiter masses with an orbital period of 32.0 ±0.02 d in a nearly circular orbit, and e = 0.05 ±0.03. The third planet has \msini\ = 0.53 Jupiter masses with an orbital period of 432 ±8 d (1.18 years) and an eccentricity e = 0.23 ±0.03. This discovery adds to the number of super Earth mass planets with \msini < 12 Earth masses  that have been detected with Doppler surveys. We find that 56 ±18% super-Earths are members of multi-planet systems. This is certainly a lower limit because of observational detectability limits, yet significantly higher than the fraction of Jupiter mass exoplanets, 20 ±8%, that are members of Doppler-detected, multi-planet systems.

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Position (J2000):     R.A. 11 44 40.96488  |  Dec. +30° 57' 33.4552''