Exoplanet Exposure Triangle: Optimising spectroscopic observations of transiting exoplanets

Transiting exoplanets provide opportunities for us to observe their atmospheres and to analyse them using spectroscopy. As the characterisation of exoplanet atmospheres relies on the detection of spectrally resolved features, analysis can be improved with high signal-to-noise ratios (SNR) that are possible to obtain today with modern spectrographs. However, obtaining high SNR through adjusting exposure times comes with a trade-off. A higher cadence of several, shorter exposures minimises the spectral feature smearing that arises due to the continuously changing radial velocity of the planet; but a lower cadence of fewer, longer exposures collects more photons with reduced overheads and readout noise, enhancing the SNR of each observation. As such, there is a need to establish what the optimal compromise is between the SNR and time resolution for a given target. In this poster, I present a new method that will aid observational astronomers in establishing the optimal parameters for observing transiting exoplanets with spectroscopic instruments. The method is demonstrated using simulated spectra, cross-correlation, and other statistical techniques. This will be particularly relevant for planning ground-based observational studies to characterise atmospheres for objects around cooler stars with more complex stellar spectra.