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# N-body Retrievals | ||
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Coming soon to EXOTIC... | ||
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In the meantime checkout: https://github.com/pearsonkyle/Nbody-ai | ||
## Prior estimate | ||
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The lomb-scargle periodogram from our ephemeris fitting code can be used to estimate a prior for an N-body retrieval. Transit timing variations (TTV) alone are not sufficient to uniquely constrain a single solution, instead multiple modes can exist which give the same amplitude/periodicity of perturbation. The distinguishing factor will rely on radial velocity measurements but none the less this approach can help limit the search space for potential planets. Below is a figure highlighting results from a grid of N-body simulations where we construct a mask based on the amplitude and periodicity found in the O-C diagram. The mask is used to constrain the N-body retrieval (i.e. search space) which significantly reduces the number of simulations needed to find a solution. | ||
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![](ttv_prior.png) | ||
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Match your Lomb-Scargle periodicity to this chart to determine the mass and period of a potential outer planet. A digitized version of this plot is coming soon... Occasionally, the O-C perturbation will experience an additional periodicity with only a single perturber, it is suspected to be due to precession of the inner planet's orbit. For now, just worry about the 1st order solution when matching to your observations. | ||
The example code has recently been refactored from [Nbody-AI](https://github.com/pearsonkyle/Nbody-ai) and is still in development. Some retrievals not work entirely... please be paitent and report any issues to our slack. | ||
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![](grid_500_150.png) | ||
If you make use of this code please cite: | ||
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The example code is still in development and may not work entirely... please be paitent and report any issues to our slack. | ||
https://ui.adsabs.harvard.edu/abs/2019AJ....158..243P/abstract |