Detecting exoplanets with the false inclusion probability

Hara, N.; Unger, N.; Delisle, J.-B.; Díaz, R. F.; Ségransan, D.

doi:10.1051/0004-6361/202140543

Cited by 19 publications

(26 citation statements)

References 97 publications

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“…From this model, the posterior distribution for the orbital periods is shown in the top panel of Fig. 3, where the count in each period bin was normalised by the ESS (thus resembling the TIP proposed by Hara et al 2022). The posterior shows two very clear peaks at 5.12 and 11.19 days.…”

Section: Results From the Joint Modelmentioning

confidence: 82%

A candidate short-period sub-Earth orbiting Proxima Centauri

Faria

Mascareño

Figueira

et al. 2022

A&A

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Context. Proxima Centauri is the closest star to the Sun. This small, low-mass, mid M dwarf is known to host an Earth-mass exoplanet with an orbital period of 11.2 days within the habitable zone, as well as a long-period planet candidate with an orbital period of close to 5 yr. Aims. We report on the analysis of a large set of observations taken with the ESPRESSO spectrograph at the VLT aimed at a thorough evaluation of the presence of a third low-mass planetary companion, which started emerging during a previous campaign. Methods. Radial velocities (RVs) were calculated using both a cross-correlation function (CCF) and a template matching approach. The RV analysis includes a component to model Proxima’s activity using a Gaussian process (GP). We use the CCF’s full width at half maximum to help constrain the GP, and we study other simultaneous observables as activity indicators in order to assess the nature of any potential RV signals. Results. We detect a signal at 5.12 ± 0.04 days with a semi-amplitude of 39 ± 7 cm s−1. The analysis of subsets of the ESPRESSO data, the activity indicators, and chromatic RVs suggest that this signal is not caused by stellar variability but instead by a planetary companion with a minimum mass of 0.26 ± 0.05 M⊕ (about twice the mass of Mars) orbiting at 0.029 au from the star. The orbital eccentricity is well constrained and compatible with a circular orbit.

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Section: Results From the Joint Modelmentioning

confidence: 82%

A candidate short-period sub-Earth orbiting Proxima Centauri

Faria

Mascareño

Figueira

et al. 2022

A&A

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“…In Gregory (2016), the number of planets is determined by checking that the Bayes factor comparing the n + 1 and n planets model is greater than a certain threshold. The significance of the planet can also be established with the false inclusion probability (FIP; Hara et al 2022), defined as follows. Considering a certain parameter space S (for instance, a period and eccentricity interval), the true inclusion probability (TIP) is the probability of having a planet with orbital elements in S marginalised over the number of planets in the system.…”

Section: Bayesian Approachmentioning

confidence: 99%

“…Gregory 2007b,a;Tuomi 2012;Faria et al 2016). Alternatively, one can use a detection criterion based on Bayesian model averaging (Hara et al 2022).…”

Section: Introductionmentioning

confidence: 99%

“…In RV data analysis, stellar activity is typically modelled with a Gaussian process. This approach is taken in Haywood et al (2014), Rajpaul et al (2015), Jones et al (2017), Gilbertson et al (2020), and Hara et al (2022). The stellar activity models are, however, imperfect, and another approach consists in being more agnostic to the form of stellar activity.…”

Section: Introductionmentioning

confidence: 99%

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Testing whether a signal is strictly periodic

Hara

Delisle

Unger

et al. 2022

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Searches for periodicity in time series are often done with models of periodic signals, whose statistical significance is assessed via false alarm probabilities or Bayes factors. However, a statistically significant periodic model might not originate from a strictly periodic source. In astronomy in particular, one expects transient signals that show periodicity for a certain amount of time before vanishing. This situation is encountered, for instance, in the search for planets in radial velocity data. While planetary signals are expected to have a stable phase, amplitude, and frequency – except when strong planet-planet interactions are present – signals induced by stellar activity will typically not exhibit the same stability. In the present article we explore the use of periodic functions multiplied by time windows to diagnose whether an apparently periodic signal is truly so. We suggest diagnostics to check whether a signal is consistently present in the time series and has a stable phase, amplitude, and period. The tests are expressed both in a periodogram and Bayesian framework. Our methods are applied to the solar HARPS-N data as well as HD 215152, HD 69830, and HD 13808. We find that the HARPS-N solar data exhibit signals at the solar rotation period and its first harmonic (~13.4 days). The frequency and phase of the 13.4 day signal appear constant within the estimation uncertainties, but its amplitude presents significant variations that can be mapped to activity levels. Secondly, as previously reported, we find four, three, and two planets orbiting HD 215152, HD 69830, and HD 13808, respectively.

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“…We tested POLYCHORD on the simulated datasets of Nelson et al (2020) and found its results closely matching those of the other nested samplers. In future works we aim to also use other techniques such as Bayesian model averaging, which was recently implemented as a detection criterion for exoplanet detection with radial velocities by Hara et al (2021).…”

Section: Introductionmentioning

confidence: 99%

The HARPS search for southern extra-solar planets

Unger

Ségransan

Queloz

et al. 2021

A&A

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Context. We present precise radial-velocity measurements of five solar-type stars observed with the HARPS Echelle spectrograph mounted on the 3.6-m telescope in La Silla (ESO, Chile). With a time span of more than 10 yr and a fairly dense sampling, the survey is sensitive to low mass planets down to super-Earths on orbital periods up to 100 days. Aims. Our goal was to search for planetary companions around the stars HD 39194, HD 93385, HD 96700, HD 154088, and HD 189567 and use Bayesian model comparison to make an informed choice on the number of planets present in the systems based on the radial velocity observations. These findings will contribute to the pool of known exoplanets and better constrain their orbital parameters. Methods. A first analysis was performed using the Data & Analysis Center for Exoplanets online tools to assess the activity level of the star and the potential planetary content of each system. We then used Bayesian model comparison on all targets to get a robust estimate on the number of planets per star. We did this using the nested sampling algorithm POLYCHORD. For some targets, we also compared different noise models to disentangle planetary signatures from stellar activity. Lastly, we ran an efficient Markov chain Monte Carlo algorithm for each target to get reliable estimates for the planets’ orbital parameters. Results. We identify 12 planets within several multiplanet systems. These planets are all in the super-Earth and sub-Neptune mass regime with minimum masses ranging between 4 and 13 M⊕ and orbital periods between 5 and 103 days. Three of these planets are new, namely HD 93385 b, HD 96700 c, and HD 189567 c.

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Detecting exoplanets with the false inclusion probability

Cited by 19 publications

References 97 publications

A candidate short-period sub-Earth orbiting Proxima Centauri

A candidate short-period sub-Earth orbiting Proxima Centauri

Testing whether a signal is strictly periodic

The HARPS search for southern extra-solar planets

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