A scenario of planet erosion by coronal radiation

TL;DR

This study investigates how coronal X-ray and EUV radiation from stars erodes planetary atmospheres by analyzing the distribution of planetary masses relative to stellar X-ray flux, providing observational evidence for atmospheric erosion.

Contribution

It offers the first observational assessment linking stellar coronal radiation to planetary atmosphere erosion, identifying a potential erosion threshold based on planetary mass and X-ray exposure.

Findings

Most massive planets have lower accumulated X-ray irradiation.

Evidence suggests a two-phase erosion process with a possible dividing line.

Distribution of planetary masses supports erosion by stellar coronal radiation.

Abstract

Context: According to theory, high-energy emission from the coronae of cool stars can severely erode the atmospheres of orbiting planets. No observational tests of the long term effects of erosion have yet been made. Aims: To analyze the current distribution of planetary mass with X-ray irradiation of the atmospheres in order to make an observational assessment of the effects of erosion by coronal radiation. Methods: We study a large sample of planet-hosting stars with XMM-Newton, Chandra and ROSAT; make a careful identification of X-ray counterparts; and fit their spectra to make accurately measurements of the stellar X-ray flux. Results: The distribution of the planetary masses with X-ray flux suggests that erosion has taken place: most surviving massive planets, (M_p sin i >1.5 M_J), have been exposed to lower accumulated irradiation. Heavy erosion during the initial stages of stellar evolution is followed by a phase of much weaker erosion. A line dividing these two phases could be present, showing a strong dependence on planet mass. Although a larger sample will be required to establish a well-defined erosion line, the distribution found is very suggestive. Conclusions: The distribution of planetary mass with X-ray flux is consistent with a scenario in which planet atmospheres have suffered the effects of erosion by coronal X-ray and EUV emission. The erosion line is an observational constraint to models of atmospheric erosion.