The Weihai Observatory search for close-in planets orbiting giant stars

TL;DR

This study investigates whether tidal forces in giant stars can explain the scarcity of close-in planets, using high-precision radial velocity measurements from Weihai Observatory to detect such planets.

Contribution

It introduces a high-cadence observational program targeting bright giant stars to search for short-period planets and assesses the role of tidal forces in planet engulfment.

Findings

Confirmed precise radial velocity measurements with 7.3 m/s rms

Demonstrated capability to detect short-period planets around giants

Collected extensive observational data to test planet presence

Abstract

Planets are known to orbit giant stars, yet there is a shortage of planets orbiting within ~0.5 AU (P<100 days). First-ascent giants have not expanded enough to engulf such planets, but tidal forces can bring planets to the surface of the star far beyond the stellar radius. So the question remains: are tidal forces strong enough in these stars to engulf all the missing planets? We describe a high-cadence observational program to obtain precise radial velocities of bright giants from Weihai Observatory of Shandong University. We present data on the planet host Beta Gem (HD 62509), confirming our ability to derive accurate and precise velocities; our data achieve an rms of 7.3 m/s about the Keplerian orbit fit. This planet-search programme currently receives ~100 nights per year, allowing us to aggressively pursue short-period planets to determine whether they are truly absent.