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Bayesian re-analysis of the radial velocities of Gliese 581. Evidence in favour of only four planetary companions
Earth and Planetary Astrophysics · Submitted 16 Feb 2011
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We conclude that based on the Bayesian model probabilities and the nature of the posterior densities of the different models, there is evidence in favour of four planets orbiting GJ 581.
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The abstract, sentence by sentence
The Gliese 581 planetary system has received attention because it has been proposed to host a low-mass planet in its habitable zone. We re-analyse the radial velocity measurements reported to contain six planetary signals to see whether these conclusions remain valid when the analyses are made using Bayesian tools instead of the common periodogram analyses. We analyse the combined radial velocity data set obtained using the HARPS and HIRES spectrographs using posterior sampling techniques and computation of the posterior probabilities of models with differing numbers of Keplerian signals. We do not fix the orbital eccentricities and stellar jitter to certain values but treat these as free parameters of our statistical models. Hence, we can take the uncertainties of these parameters into account when assessing the number of planetary signals present in the data, the point estimates of all of the model parameters, and the uncertainties of these parameters. We conclude that based on the Bayesian model probabilities and the nature of the posterior densities of the different models, there is evidence in favour of four planets orbiting GJ 581. The HARPS and HIRES data do not imply the conclusion that there are two additional companions orbiting GJ 581. We also revise the orbital parameters of the four companions in the system. Especially, according to our results, the eccentricities of all the companions in the system are consistent with zero.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The Gliese 581 planetary system has received attention because it has been proposed to host a low-mass planet in its habitable zone. | background 1.00 | 0.04 | 0.02 | hedged possibility 0.64 |
| s1 | We re-analyse the radial velocity measurements reported to contain six planetary signals to see whether these conclusions remain valid when the analyses are made using Bayesian tools instead of the common periodogram analyses. | contribution 0.94 | 0.84 | 0.03 | asserted 0.46 |
| s2 | We analyse the combined radial velocity data set obtained using the HARPS and HIRES spectrographs using posterior sampling techniques and computation of the posterior probabilities of models with differing numbers of Keplerian signals. | method 0.99 | 0.94 | 0.02 | asserted 0.98 |
| s3 | We do not fix the orbital eccentricities and stellar jitter to certain values but treat these as free parameters of our statistical models. | method 0.99 | 0.95 | 0.02 | asserted 0.99 |
| s4 | Hence, we can take the uncertainties of these parameters into account when assessing the number of planetary signals present in the data, the point estimates of all of the model parameters, and the uncertainties of these parameters. | method 0.79 | 0.81 | 0.03 | asserted 0.64 |
| s5 | We conclude that based on the Bayesian model probabilities and the nature of the posterior densities of the different models, there is evidence in favour of four planets orbiting GJ 581. | result 0.84 | 0.95 | 0.96 | hedged possibility 0.55 |
| s6 | The HARPS and HIRES data do not imply the conclusion that there are two additional companions orbiting GJ 581. | result 0.55 | 0.81 | 0.22 | asserted 0.98 |
| s7 | We also revise the orbital parameters of the four companions in the system. | result 0.55 | 0.96 | 0.04 | asserted 1.00 |
| s8 | Especially, according to our results, the eccentricities of all the companions in the system are consistent with zero. | result 0.99 | 0.95 | 0.06 | hedged possibility 0.94 |
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The paper
Original abstract
The Gliese 581 planetary system has received attention because it has been proposed to host a low-mass planet in its habitable zone. We re-analyse the radial velocity measurements reported to contain six planetary signals to see whether these conclusions remain valid when the analyses are made using Bayesian tools instead of the common periodogram analyses. We analyse the combined radial velocity data set obtained using the HARPS and HIRES spectrographs using posterior sampling techniques and computation of the posterior probabilities of models with differing numbers of Keplerian signals. We do not fix the orbital eccentricities and stellar jitter to certain values but treat these as free parameters of our statistical models. Hence, we can take the uncertainties of these parameters into account when assessing the number of planetary signals present in the data, the point estimates of all of the model parameters, and the uncertainties of these parameters. We conclude that based on the Bayesian model probabilities and the nature of the posterior densities of the different models, there is evidence in favour of four planets orbiting GJ 581. The HARPS and HIRES data do not imply the conclusion that there are two additional companions orbiting GJ 581. We also revise the orbital parameters of the four companions in the system. Especially, according to our results, the eccentricities of all the companions in the system are consistent with zero.
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How the literature uses it
Papers whose main result relates to this one's
States the same result 2 papers
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According to our analyses, the number of Keplerian signals favoured by the publicly available HARPS and HIRES radial velocity data of GJ 581 is four.
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This analysis is able to confirm the presence of four planets around GJ 581, but not the presence of GJ 581g.
An investigation into the radial velocity variability of GJ 581 - On the significance of GJ 581g · 0.97
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