How Does Spectral Resolution Influence Net Doppler Shifts?

Abstract

Exoplanets orbit stars beyond our Solar System. To investigate their atmospheres, astronomers analyze the light they emit or block, especially during transits. When spread into a spectrum, this light reveals spectral lines showing what gases are present. If the gases are moving, the lines shift slightly due to the Doppler effect. By measuring these shifts, astronomers can detect winds and other atmospheric motions. At high spectral resolution, these subtle shifts are clear, allowing precise velocity measurements. But at lower resolution, the lines blur, making Doppler shifts harder to detect. This limits our ability to study atmospheric dynamics using low-resolution data. In this project, I analyze simulated exoplanet spectra across spectral resolutions to investigate how Doppler shift retrieval changes. I also compare models with and without magnetic fields to assess their effects on measured velocities. Using cross-correlation techniques, I examine how resolution and magnetic fields impact the interpretation of atmospheric motion across orbital phases. Preliminary analysis shows that magnetic fields can change the measured Doppler velocities, even at the same orbital phase. I’ve identified consistent velocity differences between magnetic-on and magnetic-off models and am currently analyzing how these differences vary with spectral resolution. This work will aid astronomers in detecting atmospheric motions and understanding how spectral resolution influences the interpretation of exoplanet spectra.