Misc,
Exploring the robustness of Keplerian signals to the removal of active and telluric features
(2020)cite arxiv:2010.11208Comment: 12 pages, 6 figures. Accepted for publication in MNRAS.
Abstract
We examine the influence of activity- and telluric-induced radial velocity
signals on high resolution spectra taken with an iodine absorption cell. We
exclude 2 Angstrom spectral chunks containing active and telluric lines based
on the well characterised K1V star Alpha Centauri B and illustrate the method
on Epsilon Eridani - an active K2V star with a long period low amplitude
planetary signal. After removal of the activity- and telluric-sensitive parts
of the spectrum from the radial velocity calculation, the significance of the
planetary signal is increased and the stellar rotation signal disappears. In
order to assess the robustness of the procedure, we perform Monte Carlo
simulations based on removing random chunks of the spectrum. Simulations
confirm that the removal of lines impacted by activity and tellurics provides a
method for checking the robustness of a given Keplerian signal. We also test
the approach on HD 40979 which is an active F8V star with a large amplitude
planetary signal. Our Monte Carlo simulations reveal that the significance of
the Keplerian signal in the F star is much more sensitive to wavelength. Unlike
the K star the removal of active lines from the F star greatly reduces the
radial velocity precision. In this case, our removal of a K star active lines
from an F star does not a provide a simple useful diagnostic because it has far
less radial velocity information and heavily relies on the strong active lines.
