M2K. II. A triple-planet system orbiting HIP 57274

Debra A. Fischer*, Eric Gaidos, Andrew W. Howard, Matthew J. Giguere, John A. Johnson, Geoffrey W. Marcy, Jason T. Wright, Jeff A. Valenti, Nikolai Piskunov, Kelsey I. Clubb, Howard Isaacson, Kevin Apps, Sebastien Lepine, Andrew Mann, John Moriarty, John Brewer, Julien F P Spronck, Christian Schwab, Andrew Szymkowiak

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


Doppler observations from Keck Observatory have revealed a triple-planet system orbiting the nearby K4V star, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with Msin i = 11.6 M (0.036M Jup), an orbital period of 8.135 0.004 days, 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 Msin i = 0.4M Jup with an orbital period of 32.0 0.02 days in a nearly circular orbit (e = 0.05 0.03). The third planet has Msin i = 0.53M Jup with an orbital period of 432 8 days (1.18 years) and an eccentricity e = 0.23 0.03. This discovery adds to the number of super-Earth mass planets with M sin i < 12 M that have been detected with Doppler surveys. We find that 56% 18% of 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.

Original languageEnglish
Article number21
Pages (from-to)1-8
Number of pages8
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 20 Jan 2012
Externally publishedYes


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