Gwenaël Boué, Mahmoudreza Oshagh, Marco Montalto, Nuno C. Santos
The transit timing variation (TTV) method allows the detection of
non-transiting planets through their gravitational perturbations. Since TTVs
are strongly enhanced in systems close to mean-motion resonances (MMR), even a
low mass planet can produce an observable signal. This technique has thus been
proposed to detect terrestrial planets. In this letter, we analyse TTV signals
for systems in or close to MMR in order to illustrate the difficulties arising
in the determination of planetary parameters. TTVs are computed numerically
with an n-body integrator for a variety of systems close to MMR. The main
features of these TTVs are also derived analytically. Systems deeply inside MMR
do not produce particularly strong TTVs, while those close to MMR generate
quasiperiodic TTVs characterised by a dominant long period term and a low
amplitude remainder. If the remainder is too weak to be detected, then the
signal is strongly degenerate and this prevents the determination of the
planetary parameters. Even though an Earth mass planet can be detected by the
TTV method if it is close to a MMR, it may not be possible to assert that this
planet is actually an Earth mass planet. On the other hand, if the system is
right in the center of a MMR, the high amplitude oscillation of the TTV signal
vanishes and the detection of the perturber becomes as difficult as it is far
from MMR.
View original:
http://arxiv.org/abs/1201.2080
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