FIG. 12.
(a) Flux differences (in ppm) for transit transmission spectra and (b) equivalent widths (in nm) for reflected spectra for the O2 A band and the 1.06 μm dimer feature at various pressures and O2 concentrations. In transmission, for the Earth-like planet orbiting an M5V star considered here, only the top 0.9 bar can be probed, meaning the dimer and A band equivalent widths are roughly constant with pressure above 1.0 bar for a given O2 concentration. In comparison to the reflected spectra, the dimer equivalent widths are extremely sensitive to pressure. (Color graphics available online at www.liebertonline.com/ast)