Optimising spectroscopic observations of transiting exoplanets

• DOI: 10.48550/arxiv.2312.08320
• Publication Date: 2023-01-01
• Authors: L. Boldt-Christmas; F. Lesjak; Ansgar Wehrhahn; N. Piskunov; Adam D. Rains; L. Nortmann; O. Kochukhov
• Keywords: Cadence; Spectral resolution

When observing the atmospheres of transiting exoplanets using high-resolution spectroscopy, one aims to detect well-resolved spectral features with high signal-to-noise ratios (SNR) as is possible today modern spectrographs. However, obtaining such high-quality observations comes a trade-off: lower cadence fewer, longer exposures across transit collects more photons thanks reduced overheads, enhancing SNR each observation, while higher several, shorter minimises feature smearing due continuously changing radial velocity planet. Considering that maximising and minimising are both beneficial analysis, there need establish where optimal compromise lies. In this work, we model real events based on targets they would be observed VLT/CRIRES+ at Paranal Observatory. Creating four hypothetical scenarios, simulate observation 100 realisations same event in order vary time resolution only. We remove telluric stellar lines SYSREM algorithm analyse them through cross-correlation templates, measuring how successfully case detects planetary signal. demonstrate continuous change detection significance resolutions, function has clear maxima. The strength location maxima varies e.g. planet system parameters, instrumentation, no. removal iterations. discuss why observers should therefore take several factors into account, strategy akin 'exposure triangle' from traditional photography balance must struck by considering full context observation. Our method robust may employed estimate best observational strategies for other targets.