Transit timing effects due to an exomoon
Article first published online: 27 NOV 2008
© 2008 The Author. Journal compilation © 2008 RAS
Monthly Notices of the Royal Astronomical Society
Volume 392, Issue 1, pages 181–189, January 2009
How to Cite
Kipping, D. M. (2009), Transit timing effects due to an exomoon. Monthly Notices of the Royal Astronomical Society, 392: 181–189. doi: 10.1111/j.1365-2966.2008.13999.x
- Issue published online: 18 DEC 2008
- Article first published online: 27 NOV 2008
- Accepted 2008 September 20. Received 2008 August 18; in original form 2008 July 15
- techniques: photometric;
- methods: analytical;
- planets and satellites: general;
- planetary systems
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 ∝MSaS where MS is the exomoon mass and aS is the semimajor axis of the moon's orbit. Therefore, MS and aS 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 ∝MSa−1/2S and therefore the ratio of TDV to TTV allows for MS and aS to be separately determined.
- (ii) TDV has a π/2 phase difference to the TTV signal, making it an excellent complementary technique.