Saltire :ã model to measure dynamical masses for high-contrast binariesãnd exoplanets with high-resolution spectroscopy

Abstract

High-resolution cross-correlation methodsãre widely used to disco v erãnd to characteriseãtomicãnd molecular species in exoplanetãtmospheres. The characteristic cross-correlation signal is typically representedãsã function of the velocity of the system,ãnd the semi-amplitude of the planet's orbit. We present Saltire ,ã fastãnd simple model thatãccurately reproduces the shape of such cross-correlation signals,ãllowingã direct fit to the data by usingã minimum set of parameters. We show how to use this model on the detection ofãtmospheric carbon monoxide inãrchival data of the hot Jupiter ΤBoötis b,ãnd how Saltire can be used to estimate the semi-amplitudeãnd rest velocity of high brightness ratio binaries. By including the shape of the signal, we demonstrate that our modelãllows to robustly derive the signal position up to 10 times moreãccurate, compared to conventional methods. Furthermore, we discuss the impact of correlated noiseãnd demonstrate that Saltire isã robust tool for estimating systematic uncertainties on the signal position. Saltire opensã new door toãnalyse high signal-to-noise data toãccurately studyãtmospheric dynamicsãnd to measure precise dynamical masses for exoplanetsãnd faint stellar companions. We show that the phase-resolved shape of theãtmospheric cross-correlation signal canãccurately be reproduced,ãllowing studies of phase-dependent signal changesãnd to disentangle them from noiseãnd dataãliases.