Demographics of Transition Discs in Ophiuchus and Taurus

TL;DR

This study compares the properties of transition discs and normal T Tauri stars in Taurus and Ophiuchus, revealing that transition discs likely host giant planets that influence accretion flows, thus shedding light on disc dispersal processes.

Contribution

It provides new insights into the nature of transition discs by analyzing stellar accretion rates and disc masses, suggesting giant planet formation impacts disc evolution.

Findings

Transition discs have higher average disc masses than normal T Tauri stars.

Transition discs exhibit lower accretion rates than normal T Tauri stars of similar disc mass.

Some non-transition T Tauri stars also show very low accretion rates for their disc masses.

Abstract

Transition disc systems are young stars that appear to be on the verge of dispersing their protoplanetary discs. We explore the nature of these systems by comparing the stellar accretion rates and disc masses of transition discs and normal T Tauri stars in Taurus and Ophiuchus. After controlling for the known dependencies of stellar accretion rate and disc mass and on age, stellar accretion rate on stellar mass, and disc mass on the presence of stellar or sub-stellar companions, we find that the normal T Tauri stars show a trend of stellar accretion rate increasing with disc mass. The transition discs tend to have higher average disc masses than normal T Tauri stars as well as lower accretion rates than normal T Tauri stars of the same disc mass. These results are most consistent with the interpretation that the transition discs have formed objects massive enough to alter the accretion flow, i.e., single or multiple giant planets. Several Ophiuchus T Tauri stars that are not known transition disc systems also have very low accretion rates for their disc masses. We speculate on the possible nature of these sources.