2014MNRAS.437.3482I

In the framework of the parametrized post-Newtonian (PPN) formalism, we calculate the long-term preferred location (PL) effects, proportional to the Whitehead parameter ξ, affecting all the Keplerian orbital elements of a localized two-body system, apart from the semimajor axis a. They violate the gravitational local position invariance, fulfilled by general relativity. We obtain preliminary bounds on ξ by using the latest results in the field of the Solar system planetary ephemerides. The non-detection of any anomalous perihelion precession for Mars allows us to indirectly infer {verbar}ξ{verbar} ≤ 5.8x10^–6. Such a bound is close to the constraint, of the order of 10^–6, expected from the future BepiColombo mission to Mercury. As a complementary approach, the PL effects should be explicitly included in the dynamical models fitted to planetary data sets to estimate ξ in a least-squares fashion in a dedicated ephemerides orbit solution. The ratio of the anomalous perihelion precessions for Venus and Jupiter, determined with the EPM2011 ephemerides at the <3σ level, if confirmed as genuine physical effects needing explanation by future studies, rules out the hypothesis ξ ≠ 0. A critical discussion of the {verbar}ξ{verbar} ≲ 10^–6-10^-7 upper bounds obtained in the literature from the close alignment of the Sun's spin axis and the total angular momentum of the Solar system is presented.