Image Details
Caption: Figure 1.
The S/N of the spectra (red) near the Na I λλ5891,5898 Å doublet lines and the airmass (blue) as a function of the planet phase. Two vertical black dashed lines mark the first and fourth contacts of the transit event. The first three spectra (black crosses) are discarded due to their low S/Ns.
© 2026. The Author(s). Published by the American Astronomical Society.