Search for Keplerian periods in light variations of T Tauri stars and Herbig Ae stars

TL;DR

This study analyzes long-term light variations of T Tauri and Herbig Ae stars, revealing a relationship between variability timescales and stellar luminosity, and providing evidence for protoplanets in early star systems.

Contribution

It establishes a correlation between variability timescales and star+disk luminosity, and links observed periods to Keplerian orbits, suggesting protoplanets in young stellar disks.

Findings

Variability timescale scales linearly with luminosity.

Observed periods match Keplerian orbits at dust-sublimation radii.

Evidence supports presence of protoplanets in early star systems.

Abstract

Long-term, uniform series of UBVR observations of T Tauri and Herbig Ae stars obtained over 20 yr at the Maidanak Observatory as part of the ROTOR program are analyzed. We find a linear relationship between the characteristic variability time scale and the bolometric luminosity of the star+disk system: the higher the luminosity, the slower the brightness variations. This dependence is valid over a wide range of masses and luminosities, from T Tauri stars to Herbig Ae stars. On average, the variability time scale is one-quarter the Keplerian period at the dust-sublimation radius, which is known from interferometric observations. Some T Tauri stars have periods from 25 to 120 days, which are preserved over several observing seasons. These periods correspond to Keplerian orbits with semi-major axes from 0.14 to 0.52 AU. The results obtained provide indirect evidence for the existence of protoplanets in the gas-dust disks of stars in early stages of their evolution toward the main sequence.