Bibcode
                                    
                            Jenkins, J. S.; Tuomi, M.; Brasser, R.; Ivanyuk, O.; Murgas, F.
    Bibliographical reference
                                    The Astrophysical Journal, Volume 771, Issue 1, article id. 41, 13 pp. (2013).
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                        7
            
                        2013
            
  Journal
                                    
                            Citations
                                    30
                            Refereed citations
                                    26
                            Description
                                    There are a growing number of multi-planet systems known to be orbiting
their host stars with orbital periods that place them in mean motion
resonances (MMRs). These systems are generally in first-order resonances
and dynamical studies have focused their efforts on understanding the
origin and evolution of such dynamically resonant commensurabilities.
Here we report the discovery of two super-Earths that are close to a
second-order dynamical resonance orbiting the metal-poor ([Fe/H] =
–0.43 dex) and inactive G2V star HD 41428. We analyzed 62 HARPS
archival radial velocities for this star that, until now, exhibited no
evidence for planetary companions. Using our new Bayesian Doppler signal
detection algorithm, we find two significant signals in the data, with
periods of 18.357 days and 25.648 days, indicating they could be part of
a 7:5 second-order MMR. Both semi-amplitudes are below 3 m
s–1 and the minimum masses of the pair are 12.3 and 8.6
M ⊕, respectively. Our simulations found that apsidal
alignment stabilizes the system, and even though libration of the
resonant angles was not seen, the system is affected by the presence of
the resonance and could still occupy the 7:5 commensurability, which
would be the first planetary configuration in such a dynamical
resonance. Given the multitude of low-mass multi-planet systems that
will be discovered in the coming years, we expect that more of these
second-order resonant configurations will emerge from the data,
highlighting the need for a better understanding of the dynamical
interactions between forming planetesimals.
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