Discovery of New Dipper Stars with K2: A Window into the Inner Disk Region of T Tauri Stars

TL;DR

This study identifies 125 young stellar objects exhibiting dipper and burster behaviors in star-forming regions using machine learning, providing insights into inner disk structures of T Tauri stars.

Contribution

The paper presents a new large sample of dippers and bursters identified via machine learning, linking their properties to inner disk regions of young stars.

Findings

21% of stars with disks are dippers.

Dippers are exclusively late-type (KM) stars.

Inner disk temperature estimates align with interferometric data.

Abstract

In recent years a new class of Young Stellar Object has been defined, referred to as dippers, where large transient drops in flux are observed. These dips are too large to be attributed to stellar variability, last from hours to days and can reduce the flux of a star by 10-50\%. This variability has been attributed to occultations by warps or accretion columns near the inner edge of circumstellar disks. Here we present 95 dippers in the Upper Scorpius association and $\rho$ Ophiuchus cloud complex found in K2 Campaign 2 data using supervised machine learning with a Random Forest classifier. We also present 30 YSOs that exhibit brightening events on the order of days, known as bursters. Not all dippers and bursters are known members, but all exhibit infrared excesses and are consistent with belonging to either of the two young star forming regions. We find 21.0 $\pm$ 5.5\% of stars with disks are dippers for both regions combined. Our entire dipper sample consists only of late-type (KM) stars, but we show that biases limit dipper discovery for earlier spectral types. Using the dipper properties as a proxy, we find that the temperature at the inner disk edge is consistent with interferometric results for similar and earlier type stars.