Guillem Anglada-Escudé, Mikko Tuomi
Several M dwarfs are targets of systematical monitoring in searches for Doppler signals caused by low mass exoplanet companions. As a result, an emergent population of high multiplicity planetary systems around low mass stars starts to show up as well. We optimize classic data analysis methods and develop new ones to enhance the sensitivity towards lower amplitude planets in high multiplicity systems. We re-derive Doppler measurements from public HARPS spectra of GJ 676A using the recently developed template matching method (HARPS-TERRA software). We use refined versions of periodograms to assess the presence of additional low mass companions. We also analyse the same dataset using Bayesian statistics tools and compare the performance of both methods. We confirm the known massive gas giant candidate and the presence of a trend in the RVs. In addition to that, we find very secure evidence in favor of two new candidates in close-in orbits and masses in the super-Earth mass regime. Also, the increased time-span of the observations allows the detection of curvature in the ltrend suggesting the presence of a massive outer companion whose nature is still unclear. Even though the increased sensitivity of our new periodogram tools, we find that Bayesian methods are significantly more sensitive and reliable in the early detection of candidate signals but more works is needed to properly quantify their robustness against false positives. These new planetary system holds the record of minimum mass range (from 4.5Me to 5 Mjup) and period range (from 3.6 days to more than 10 years), being the first exoplanetary system with a general architecture similar to our Solar System. GJ 676A can be happily added to the family of high multiplicity planetary systems around M dwarfs.
View original:
http://arxiv.org/abs/1206.7118
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