Transit timing effects due to an exomoon
Abstract
As the number of known exoplanets continues to grow, the question as to whether such bodies harbour satellite systems has become one of increasing interest. In this paper, we explore the transit timing effects that should be detectable due to an exomoon and predict a new observable. We first consider transit time variation (TTV), where we update the model to include the effects of orbital eccentricity. We draw two key conclusions. (i) In order to maintain Hill stability, the orbital frequency of the exomoon will always be higher than the sampling frequency. Therefore, the period of the exomoon cannot be reliably determined from TTV, only a set of harmonic frequencies. (ii) The TTV amplitude is ~ M_{S}a_{S} where M_{S} is the exomoon mass and a_{S} is the semimajor axis of the moon's orbit. Therefore, M_{S} and a_{S} cannot be separately determined. We go on to predict a new observable due to exomoons  transit duration variation (TDV). We derive the TDV amplitude and conclude that its amplitude is not only detectable, but the TDV signal will also provide two robust advantages. (i) The TDV amplitude is ~M_{S}a^{1/2}_{S} and therefore the ratio of TDV to TTV allows for M_{S} and a_{S} to be separately determined. (ii) TDV has a π/2 phase difference to the TTV signal, making it an excellent complementary technique.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2009
 DOI:
 10.1111/j.13652966.2008.13999.x
 arXiv:
 arXiv:0810.2243
 Bibcode:
 2009MNRAS.392..181K
 Keywords:

 techniques: photometric;
 methods: analytical;
 occultations;
 planets and satellites: general;
 planetary systems;
 Astrophysics
 EPrint:
 10 pages, 3 figures, 1 table, notation updated