The Evolution of Dusty Disks Around Low-Mass Pre-Main Sequence Stars.

Low-mass Pre-main Sequence Stars;Accretion Disks;T Tauri Stars;Astronomy;Science;Astronomy and Astrophysics

Espaillat, Catherine C.Miller, Jon Matthew ;

University of Michigan

关键词: Low-mass Pre-main Sequence Stars;    Accretion Disks;    T Tauri Stars;    Astronomy;    Science;    Astronomy and Astrophysics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/63766/ccespa_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The evolution of protoplanetary disks is intricately tied to the origin of planets. Thedetails of how these disks evolve from initially well-mixed distributions of gas anddust into systems composed mostly of rocky planets and gas giants like our own solarsystem is not well understood and is a fundamental question in astronomy. It iswidely accepted that dust grain growth and settling to the disk midplane play an integralpart in creating the planetesimals that amalgamate into planets. Newly formedplanets will then interact with the disk, clearing the material around themselves andcreating gaps and holes.Several disks which have nearly photospheric near-infrared emission but substantialexcesses above the stellar photosphere at wavelengths beyond ~20 μm have beenobserved and are referred to as ;;transitional disks.” This deficit of flux can be explainedby the presence of an inner disk hole that is mostly devoid of small dust. Herewe model the transitional disks of CS Cha and CVSO 224. We also present evidencefor a new class of ;;pre-transitional disks” around UX Tau A and LkCa 15. These objects have a deficit of flux in the mid-infrared (5–20 μm) and significant emissionat longer wavelengths, as is seen in transitional disks. However, pre-transitional diskshave significant near-infrared excesses (2–5 μm) relative to their stellar photospheres,indicative of an optically thick inner disk. This points to a gap within the disk ratherthan an inner disk hole.We also present simulated spectral energy distributions of ~240 disks aroundlow-mass classical T Tauri stars and find that the majority of observed disks withinTaurus, Chamaeleon, and Ophiuchus lie within the parameter space probed by themodels and are therefore ;;full disks.” However, we find that some disks cannot beexplained by full disk models and are not known to be transitional or pre-transitionaldisks. We propose that these objects are pre-transitional disks with smaller gaps thanpreviously observed, emphasizing that much still remains to be understood regardingthe dust component of disks.