# Saltire -- A model to measure dynamical masses for high-contrast binaries and exoplanets with high-resolution spectroscopy

**Authors:** Daniel Sebastian, Amaury H. M. J. Triaud, Matteo Brogi  
**arXiv:** [2312.01924](https://arxiv.org/abs/2312.01924)  
**Date:** 2023-12-04  
**Summary page:** https://www.summarizepaper.com/en/paper/2312.01924v1/

## Key points

- Study focuses on the use of high-resolution cross-correlation methods for discovering and characterizing atomic and molecular species in exoplanet atmospheres
- Introduces a model called Saltire that accurately reproduces the shape of cross-correlation signals
- Saltire provides a fast and simple way to fit data with minimum parameters
- Demonstrates application of Saltire in detecting atmospheric carbon monoxide (CO) in archival data of tau Bootis b
- Saltire can estimate semi-amplitude and rest velocity of high brightness-ratio binaries
- Robustly derives signal position up to 10 times more accurately compared to conventional methods by including signal shape
- Reliable tool for estimating systematic uncertainties on signal position affected by correlated noise
- Promising implications for analyzing high signal-to-noise data, studying atmospheric dynamics, and measuring dynamical masses for exoplanets and faint stellar companions
- Allows investigations into phase-dependent changes in signals while disentangling them from noise and data aliases
- Enhances ability to study exoplanet atmospheres and measure dynamical masses with high-resolution spectroscopy

## Summary

The study focuses on the use of high-resolution cross-correlation methods to discover and characterize atomic and molecular species in exoplanet atmospheres. These methods typically represent the characteristic cross-correlation signal as a function of the velocity of the system and the semi-amplitude of the planet's orbit. In this paper, the authors introduce a model called Saltire, which accurately reproduces the shape of these cross-correlation signals. Saltire is designed to provide a fast and simple way to fit data by using a minimum set of parameters. The researchers demonstrate how this model can be applied to detect atmospheric carbon monoxide (CO) in archival data of the hot Jupiter tau Bootis b. Additionally, they show that Saltire can estimate the semi-amplitude and rest velocity of high brightness-ratio binaries. One significant advantage of Saltire is its ability to robustly derive the signal position up to 10 times more accurately compared to conventional methods by including the shape of the signal. The authors also discuss how correlated noise impacts their model and demonstrate that Saltire is a reliable tool for estimating systematic uncertainties on signal position. The implications of Saltire are promising for analyzing high signal-to-noise data, enabling accurate studies on atmospheric dynamics and precise measurements of dynamical masses for exoplanets and faint stellar companions. By accurately reproducing the phase-resolved shape of atmospheric cross-correlation function (CCF) signals, Saltire allows for investigations into phase-dependent changes in signals while disentangling them from noise and data aliases. Overall, this research introduces an innovative model that enhances our ability to study exoplanet atmospheres and measure dynamical masses with high-resolution spectroscopy. The simplicity and accuracy offered by Saltire make it a valuable tool for future studies in this field.