How does the shape of the stellar spectrum affect the Raman scattering features in the albedo of exoplanets?

TL;DR

This paper explores how the spectral shape of different host stars influences Raman scattering features in exoplanet albedo spectra, revealing that stellar type significantly affects the detectability of atmospheric signatures.

Contribution

It provides a comprehensive analysis of how stellar spectral variations impact Raman features in planetary albedo spectra across different atmospheric compositions.

Findings

Raman features vary with host star spectral type

Alkali absorption can diminish Raman feature intensity

Different stellar types produce distinct Raman spectral signatures

Abstract

Diagnostic potential of the spectral signatures of Raman scattering imprinted in planetary albedo spectra at short optical wavelengths has been demonstrated in research on Solar System planets and has recently been proposed as a probe of exoplanet atmospheres, complementary to albedo studies at longer wavelengths. Spectral features caused by Raman scattering offer insight into the properties of planetary atmospheres, such as the atmospheric depth, composition, and temperature, as well as the possibility of detecting and spectroscopically identifying spectrally inactive species, such as H$_2$ and N$_2$, in the visible wavelength range. Raman albedo features, however, depend on both the properties of the atmosphere and the shape of the incident stellar spectrum. Identical planetary atmospheres can produce very different albedo spectra depending on the spectral properties of the host star. Here we present a set of geometric albedo spectra calculated for atmospheres with H$_2$/He, N$_2$, and CO$_2$ composition, irradiated by different stellar types ranging from late A to late K stars. Prominent albedo features caused by Raman scattering appear at different wavelengths for different types of host stars. We investigate how absorption due to alkali elements, sodium and potassium, may affect the intensity of Raman features, and discuss the preferred observing strategies for detecting Raman features in future observations.