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The CARMENES search for exoplanets around M dwarfs. The enigmatic planetary system GJ 4276: one eccentric planet or two planets in a 2:1 resonance?



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Cortés Contreras, Miriam and Montes Gutiérrez, David (2019) The CARMENES search for exoplanets around M dwarfs. The enigmatic planetary system GJ 4276: one eccentric planet or two planets in a 2:1 resonance? Astronomy and astrophysics, 622 . ISSN 1432-0746

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Official URL: http://dx.doi.org/10.1051/0004-6361/201834569


We report the detection of a Neptune-mass exoplanet around the M4.0 dwarf GJ 4276 (G 232-070) based on radial velocity (RV) observations obtained with the CARMENES spectrograph. The RV variations of GJ 4276 are best explained by the presence of a planetary companion that has a minimum mass of m_(b) sin i ≈ 16 M_(⊕) on a P_(b) = 13.35 day orbit. The analysis of the activity indicators and spectral diagnostics exclude stellar induced RV perturbations and prove the planetary interpretation of the RV signal. We show that a circular single-planet solution can be excluded by means of a likelihood ratio test. Instead, we find that the RV variations can be explained either by an eccentric orbit or interpreted as a pair of planets on circular orbits near a period ratio of 2:1. Although the eccentric single-planet solution is slightly preferred, our statistical analysis indicates that none of these two scenarios can be rejected with high confidence using the RV time series obtained so far. Based on the eccentric interpretation, we find that GJ 4276 b is the most eccentric (e_(b) = 0.37) exoplanet around an M dwarf with such a short orbital period known today.

Item Type:Article
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© ESO 2019. Artículo firmado por 28 autores. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max- Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Insitut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico HispanoAlemáan), with additional contributions by the Spanish Ministry of Science through projects AYA2016-79425-C3-1/2/3-P, AYA2015-69350-C3-2-P, ESP2017-87676-C05-02-R, ESP2014-54362P, and ESP2017-87143R, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. This work made use of observations collected at Sierra Nevada Observatory (SNO) supported by the Instituto de Astrofísica de Andalucía, CSIC, and from the LCOGT network. EN acknowledges support through DFG project CZ 222/1-1. S.C. acknowledges support from DFG project SCH 1382/2-1 and SCHM 1032/66-1. G.A-E research is funded via the STFC Consolidated Grants ST/P000592/1, and a Perren foundation grant. This work was prepared using PyAstronomy. This research has also made use of the corner.py package (Foreman-Mackey 2016).

Uncontrolled Keywords:Orbital solutions; Likelihood ratio; Stars
Subjects:Sciences > Physics > Astrophysics
ID Code:55227
Deposited On:28 May 2019 11:15
Last Modified:28 May 2019 11:43

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