A simple method to retrieve the complex eigenfrequency of the Earth's nearly diurnal-free wobble; application to the Strasbourg superconducting gravimeter data

International audienceWe have analysed more than four years of data from the Strasbourg superconducting gravimeter to retrieve the period and damping of the nearly diurnal-free wobble (NDFW). The removal of noise spikes is found to be crucial for an accurate determination of tidal-wave amplitudes and phases. A new simple algorithm is derived which allows an analytical solution for the NDFW pertod and damping using the complex gravimetric factors of three resonant diurnal waves. The results show a huge reduction of the confidence intervals when compared with a previous investigation from a Lacoste Romberg spring meter operated at the same station. Our results are in close agreement with values obtained from two other European superconducting gravimeters. The results are also compared with respect to values inferred from very long baseline interferometry (VLBI) measurements

Equilibrium Shapes of Large Trans-Neptunian Objects

International audienceThe large transneptunian objects (TNO) with radii larger than 400 km are thought to be in hydrostatic equilibrium. Their shapes can bring clues on their internal structures that would reveal information on their formation and evolution. In this paper we explore the equilibrium figures of five TNOs and we show that the difference between the equilibrium figures of homogeneous and heterogeneous interior models can reach several kilometers for fast rotating and low density bodies. Such a difference could be measurable by ground-based techniques. This demonstrates the importance of developing the shape up to second and third order when modeling the shapes of large and rapid rotators