### Abstract

We investigate biases in the measurement of exoplanet orbital parameters - especially eccentricity - from radial velocity (RV) observations. In this contribution we consider single-planet systems. We create a mock catalog of RV data, choosing planet masses and orbital periods, and observing patterns to mimic those of actual RV surveys. Using Markov chain Monte Carlo (MCMC) simulations, we generate a posterior sample for each mock data set, calculate best-fit orbital parameters for each data set, and compare these to the true values. We find that the precision of our derived eccentricities is most closely related to the effective signal-to-noise ratio, K√N/σ, where K is the velocity amplitude, cr is the effective single-measurement precision, and N is the number of observations. We also find that eccentricities of planets on nearly circular (e < 0.05) orbits are preferentially overestimated. While the Butler et al. (2006) catalog reports e < 0.05 for just 20% of its planets, we estimate that the true fraction of e < 0.05 orbits is about 50%. We investigate the accuracy, precision, and bias of alternative sets of summary statistics and find that the median values of h = esinω and k = ecosω (where ω is the longitude of periapse) of the posterior sample typically provide more accurate, more precise, and less biased estimates of eccentricity than traditional measures.

Original language | English (US) |
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Title of host publication | Extrasolar Planets in Multi-Body Systems |

Subtitle of host publication | Theory and Observations |

Pages | 169-173 |

Number of pages | 5 |

DOIs | |

State | Published - Dec 1 2010 |

Event | International Conference Eztrasolar Planets in Multi-Body Systems: Theory and Observations - Torun, Poland Duration: Aug 25 2008 → Aug 29 2008 |

### Publication series

Name | EAS Publications Series |
---|---|

Volume | 42 |

ISSN (Print) | 1633-4760 |

ISSN (Electronic) | 1638-1963 |

### Other

Other | International Conference Eztrasolar Planets in Multi-Body Systems: Theory and Observations |
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Country | Poland |

City | Torun |

Period | 8/25/08 → 8/29/08 |

### Fingerprint

### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Engineering(all)
- Space and Planetary Science

### Cite this

*Extrasolar Planets in Multi-Body Systems: Theory and Observations*(pp. 169-173). (EAS Publications Series; Vol. 42). https://doi.org/10.1051/eas/1042018

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*Extrasolar Planets in Multi-Body Systems: Theory and Observations.*EAS Publications Series, vol. 42, pp. 169-173, International Conference Eztrasolar Planets in Multi-Body Systems: Theory and Observations, Torun, Poland, 8/25/08. https://doi.org/10.1051/eas/1042018

**Observational biases in determining extrasolar planet eccentricities.** / Pan, M.; Zakamska, N. L.; Ford, Eric B.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

TY - GEN

T1 - Observational biases in determining extrasolar planet eccentricities

AU - Pan, M.

AU - Zakamska, N. L.

AU - Ford, Eric B.

PY - 2010/12/1

Y1 - 2010/12/1

N2 - We investigate biases in the measurement of exoplanet orbital parameters - especially eccentricity - from radial velocity (RV) observations. In this contribution we consider single-planet systems. We create a mock catalog of RV data, choosing planet masses and orbital periods, and observing patterns to mimic those of actual RV surveys. Using Markov chain Monte Carlo (MCMC) simulations, we generate a posterior sample for each mock data set, calculate best-fit orbital parameters for each data set, and compare these to the true values. We find that the precision of our derived eccentricities is most closely related to the effective signal-to-noise ratio, K√N/σ, where K is the velocity amplitude, cr is the effective single-measurement precision, and N is the number of observations. We also find that eccentricities of planets on nearly circular (e < 0.05) orbits are preferentially overestimated. While the Butler et al. (2006) catalog reports e < 0.05 for just 20% of its planets, we estimate that the true fraction of e < 0.05 orbits is about 50%. We investigate the accuracy, precision, and bias of alternative sets of summary statistics and find that the median values of h = esinω and k = ecosω (where ω is the longitude of periapse) of the posterior sample typically provide more accurate, more precise, and less biased estimates of eccentricity than traditional measures.

AB - We investigate biases in the measurement of exoplanet orbital parameters - especially eccentricity - from radial velocity (RV) observations. In this contribution we consider single-planet systems. We create a mock catalog of RV data, choosing planet masses and orbital periods, and observing patterns to mimic those of actual RV surveys. Using Markov chain Monte Carlo (MCMC) simulations, we generate a posterior sample for each mock data set, calculate best-fit orbital parameters for each data set, and compare these to the true values. We find that the precision of our derived eccentricities is most closely related to the effective signal-to-noise ratio, K√N/σ, where K is the velocity amplitude, cr is the effective single-measurement precision, and N is the number of observations. We also find that eccentricities of planets on nearly circular (e < 0.05) orbits are preferentially overestimated. While the Butler et al. (2006) catalog reports e < 0.05 for just 20% of its planets, we estimate that the true fraction of e < 0.05 orbits is about 50%. We investigate the accuracy, precision, and bias of alternative sets of summary statistics and find that the median values of h = esinω and k = ecosω (where ω is the longitude of periapse) of the posterior sample typically provide more accurate, more precise, and less biased estimates of eccentricity than traditional measures.

UR - http://www.scopus.com/inward/record.url?scp=78751668100&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78751668100&partnerID=8YFLogxK

U2 - 10.1051/eas/1042018

DO - 10.1051/eas/1042018

M3 - Conference contribution

AN - SCOPUS:78751668100

SN - 9782759804856

T3 - EAS Publications Series

SP - 169

EP - 173

BT - Extrasolar Planets in Multi-Body Systems

ER -