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satcand

DOI

Tools to apply theoretical constraints of orbital stability and tidal migration to KOI exomoon candidates.

This is a repository for tools to apply known theoretical constraints of orbital stability and tidal migration to KOI exomoon candidates, which reproduce the figures in Quarles, Li, & Rosario-Franco (2020). Orbital stability analysis from Rosario-Franco et al. (2020) can provide the critical semimajor axis (a_c) of exomoons in terms of the host planet's Hill radius R_H (in AU), where this can be scaled/converted into units of the planetary radius R_p (in AU). Using our knowledge of the solar system planets, we can evaluate the orbital evolution due to tidal migration considering a constant Q tidal model (e.g., Sasaki, Barnes & O'Brien (2012)). In addition to the theoretical constraints, observational constraints can be applied using results from Kipping (2020).

Included in this repository are:

  • KOI_stab.py
    • produces Figure 1 from Quarles, Li, & Rosario-Franco (2020)
  • tidal_migration.py
    • evaluates the tidal migration within a Sun-Earth-Moon system using initial conditions from Sasaki, Barnes & O'Brien (2012) (see their Fig. 1)
    • plots angular velocity over time, which includes the time evolution of the spin angular momentum of the planet (omega_p), the orbital mean motion of the planet n_p, and the orbital mean motion of the satellite n_sat (SBO_tide_evol.png). Both T1 and T are calculated and plotted as vertical within the angular velocity evolution plot.
  • SBO_tidal_tree.py
    • implements the decision tree algorithm from Sasaki, Barnes & O'Brien (2012) to calculate the migration time scale (T1) and the total migration time scale (T).
  • Calc_tidal_limit.py
    • demonstrates the calculation of the minimum Q_p so that stable moon parameters (mass and separation) can be inferred
  • plot_Q_crit.py
    • produces Figure 2 from Quarles, Li, & Rosario-Franco (2020) using output from Calc_tidal_limit.py
  • plot_tide_evol.py
    • produces Figure 3 from Quarles, Li, & Rosario-Franco (2020) using the output in KOI1925 folder
    • assumes that the satellite is initially separaterd by 5 R_p and the host planet spin period is 10 hours
  • plot_combined_constraints.py
    • combines theoretical and observational constraints for the 6 KOI candidates proposed by Fox & Wiegert (2020).
    • uses 3\sigma curves from Kipping (2020)
    • uses output from Calc_tidal_limit.py
    • produces Figure 4 from Quarles, Li, & Rosario-Franco (2020)

These python scripts assume that the basic dependencies (e.g., Numpy, Scipy, Matplotlib) are already installed or the user is in an Anaconda environment.

Attribution

Please use the following citation, if you find these tools useful in your research.

@ARTICLE{Quarles2020,
       author = {{Quarles}, Billy and {Li}, Gongjie and {Rosario-Franco}, Marialis},
        title = "{Application of Orbital Stability and Tidal Migration Constraints for Exomoon Candidates}",
      journal = {\apjl},
     keywords = {Exoplanet dynamics, Exoplanet tides, Natural satellites (Extrasolar), Exoplanet systems, 490, 497, 483, 484, Astrophysics - Earth and Planetary Astrophysics},
         year = 2020,
        month = oct,
       volume = {902},
       number = {1},
          eid = {L20},
        pages = {L20},
          doi = {10.3847/2041-8213/abba36},
archivePrefix = {arXiv},
       eprint = {2009.14723},
 primaryClass = {astro-ph.EP},
       adsurl = {https://ui.adsabs.harvard.edu/abs/2020ApJ...902L..20Q},
      adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}