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Stay at University of Gottingen, from 03-08-2016 to 17-08-2016
My name is Pedro Figueira, and I am a researcher at the Institute of Astrophysics and Space Sciences, in Portugal. During my PhD I specialized in the measurement of precise Radial Velocities in the near infra-red, and after it I have been working in the usage and development of nIR instrumentation for planetary searches through RV. I have also been working in the impact of stellar activity on precise radial velocities, and studying the relation between planetary properties and their host properties.
We started to analyze the solar spectra obtained with HARPS through sunlight reflection on the Moon's surface. A first calculation of radial velocities (RV) from the Moon spectra was performed using the HARPS DRS (Data Reduction Software) in its version available from Geneva dedicated machine. This pipeline provides state-of-the-art RV precision, allowing the detection of the lightest exoplanets known to date by measuring the reflex RV motion induced on the parent star. Our objective is to associate the measured RV to the activity patterns identified on the surface of the Sun. However, our observation of the Moon uses a dramatically different set-up than used on observing other stars, and several effects surfaced. The first was the effect of our Earth's RV. When observing other stars one has to remove the signature of Earth's RV around the Sun along the line of sight of observation. This allows us to calculate heliocentric RVs that are time invariant and can be used to create a precise timeseries. When observing the Moon, this corrections is different, and we started by removing the correction as it applied by default, and implementing our own. Other than this, the only effect on RV should be that of Moon's orbital movement and rotation, and the latter effect is expected to be smaller than 10 cm/s and as such at the level of our current instrumental noise. We are currently working on developing the best model for the Moon orbital movement down to the RV precision of the acquired data (~50 cm/s).