First Observation of Planet-Induced X-ray Emission: The System HD 179949

TL;DR

This paper reports the first detection of X-ray emission from a star caused by its close-in giant planet, showing a 30% flux increase and hotter emission at specific orbital phases, using Chandra observations.

Contribution

It provides the first direct observational evidence of planet-induced stellar X-ray activity in the HD 179949 system.

Findings

30% increase in X-ray flux during planetary orbit phase

X-ray emission is hotter (~1 keV) during flux enhancements

Correlation between X-ray activity and planetary orbital phase

Abstract

We present the first observation of planet-induced stellar X-ray activity, identified for the HD 179949 system, using Chandra / ACIS-S. The HD 179949 system consists of a close-in giant planet orbiting an F9V star. Previous ground-based observations already showed enhancements in Ca II K in phase with the planetary orbit. We find an ~30% increase in the X-ray flux over quiescent levels coincident with the phase of the Ca II enhancements. There is also a trend for the emission to be hotter at increased fluxes, confirmed by modeling, showing the enhancement at ~1 keV compared to ~0.4 keV for the background star.