Making FORS2 fit for exoplanet observations (again)
H.M.J. Boffin, G. Blanchard, O.A. Gonzalez, S. Moehler, E. Sedaghati,, N. Gibson, M.E. van den Ancker, J. Smoker, J. Anderson, C. Hummel, D., Dobrzycka, A. Smette, G. Rupprecht
TL;DR
This paper reports on modifications to the FORS2 instrument, specifically replacing the LADC prisms, which significantly reduced systematic errors and restored its capability for precise exoplanet transmission spectroscopy.
Contribution
The study identifies the LADC as the source of systematic errors and demonstrates that replacing its prisms improves FORS2's performance for exoplanet observations.
Findings
Reduced systematic noise in FORS2 data
Improved zero point stability
Restored suitability for transmission spectroscopy
Abstract
For about three years, it was known that precision spectrophotometry with FORS2 suffered from systematic errors that made quantitative observations of planetary transits impossible. We identified the Longitudinal Atmospheric Dispersion Compensator (LADC) as the most likely culprit, and therefore engaged in a project to exchange the LADC prisms with the uncoated ones from FORS1. This led to a significant improvement in the depth of FORS2 zero points, a reduction in the systematic noise, and should make FORS2 again competitive for transmission spectroscopy of exoplanets.
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Taxonomy
TopicsAtmospheric Ozone and Climate · Stellar, planetary, and galactic studies · Astronomy and Astrophysical Research