A search for star-planet interactions in chromospheric lines

TL;DR

This study searched for star-planet interactions in chromospheric lines of 7 stars with close-in massive planets but found no clear recurring emission linked to the planets, except for a binary system showing potential interaction signs.

Contribution

First high-resolution spectroscopic search for star-planet interactions in chromospheric lines across multiple systems, highlighting the absence of clear SPI signals and identifying a promising binary system for future study.

Findings

No periodic chromospheric emission linked to planets detected.

Signs of cyclic variation in a binary system possibly related to star-star interactions.

Potential of the binary system HD 41004 AB for future SPI research.

Abstract

Massive planets in very close orbits around their central stars can induce so-called star-planet interactions (SPI), which may be of magnetic or gravitational nature. In both cases, SPI can potentially cause recurring chromospheric emission on the host star visible in Ca II H & K and/or H$\alpha$. The emission would be bound to the planetary orbit, not to the rotation period of the star. We searched for SPI in a sample of 7 stars with massive close-in planets using high-resolution spectroscopic data taken at HRS (HET) and FEROS (La Silla). We find no periodically recurring emission in the planet-hosting stars. In the case of HD 41004 AB, a binary system consisting of a K dwarf and an M dwarf, where the M dwarf is orbited by a brown dwarf companion, we find signs of cyclic variation in the Ca II K and H$\alpha$ emission lines that could be associated to interactions between the M dwarf and its companion. We present our first results of this interesting system that may become an important system for the understanding of SPI.