Title:

Recent Spitzer results on circumstellar disks: dissipation
timescales and disk-braking of T Tauri rotation




Lucas Cieza
IfA



Abstract:

It is now well established that circumstellar disks are
typical byproducts of stars formation and the sites where
planets are formed. Understanding their structure and
evolution is crucial for our understanding of planet
formation. This talk on circumstellar disks will have two
parts. The first part of the talk will focus on recent
Spitzer results on the dissipation timescale of disks around
Weak-line T Tauri Star (WTTSs), low-mass pre-main-sequence
(PMS) stars that occupy the same region of the H-R diagram
as Classical T Tauri stars but do not show clear evidence
for accretion. Since Spitzer observations probe
planet-forming regions of the disk (r ~0.1-10 AU), these
results impose much stronger constraints on the time
available for the formation of planets than those provided
by previous near-IR studies. The second part of the talk
will deal with the "disk-braking paradigm", which is
believed to solve the angular momentum problem in PMS star
evolution, one of the longest-standing problems in star
formation. Virtually every model of the rotational evolution
of PMS stars includes "disk-braking", the drain of angular
momentum from the star to its protoplanetary disk. However,
finding conclusive observational evidence for a connection
between stellar rotation and the presence of a disk has
proven to be a difficult task. I will present recent Spitzer
results that provide dramatic evidence supporting the idea
that, in fact, circumstellar disks regulate the angular
momentum evolution of PMS stars.