Related papers: Disk-Star Alignment I: Pre-Main-Sequence Stellar P…
Protostellar disks are the product of angular momentum conservation during the protostellar collapse. Understanding their formation is crucial because they are the birthplace of planets and because their formation is tightly related to star…
Be stars are rapid rotators surrounded by a gaseous disk envelope whose origin is still under debate. This envelope is responsible for observed emission lines and large infrared excess. To progress in the understanding of the physical…
The temperature in most parts of a protoplanetary disk is determined by irradiation from the central star. Numerical experiments of Watanabe \& Lin (2008) suggested that such disks, also called `passive disks', suffer from a thermal…
Measuring stellar inclinations is fundamental to understand planetary formation and dynamics as well as physical conditions during star formation. Oscillation spectra of red giant stars exhibit mixed modes that have both a gravity component…
The understanding and modeling of the structure and evolution of stars is based on statistical physics as well as on hydrodynamics. Today, a precise identification and proper description of the physical processes at work in stellar…
(abridged) Thus far our impressions regarding the evolutionary time scales for young circumstellar disks have been based on small number statistics. Over the past decade, however, in addition to precision study of individual star/disk…
Most stars do not form in isolation, but as part of a star cluster or association. These young stars are initially surrounded by protoplanetary discs. In these cluster environments tidal interactions with other cluster members can alter the…
We present an investigation of spin-orbit angles for planetary system candidates reported by Kepler. By combining the rotational period $P_s$ inferred from the flux variation due to starspots and the projected rotational velocity $V\sin…
Based on a large number of observations carried out in the last decade it appears that the fraction of stars with protoplanetary disks declines steadily between ~1 Myr and ~10 Myr. We do, however, know that the multiplicity fraction of…
Recent observations uncover various phenomena around the protostar such as misalignment between the outflow and magnetic field, precession of the jet, and time variability of the ejected clumps, whose origins are under debate. We perform a…
Investigating the dust grain size and its dependence on substructures in protoplanetary disks is a crucial step in understanding the initial process of planet formation. Spectral indices derived from millimeter observations are used as a…
We study the structure and evolution of the very early protostellar disk (``protodisk'') just after protostar formation, where disk self-gravity dominates and the stellar contribution is dynamically minor. The disk redistributes angular…
The angle between the rotation and orbital axes of stars in binary systems -- the obliquity -- is an important indicator of how these systems form and evolve but few such measurements exist. We combine the sample of astrometric orbital…
Disks are a natural outcome of the star formation process in which they play a crucial role. Luminous, massive stars of spectral type earlier than B4 are likely to be those that benefit most from the existence of accretion disks, which may…
A detailed understanding of the physics of star and planet formation requires study of individual objects as well as statistical assessment of global properties and evolutionary trends. Observational investigations of circumstellar material…
(Edited) Many fast rotator stars (rotation periods of < 2 days) are found in unresolved binaries with separations of tens of au. This correlation leads to the question of whether the formation of binary stars inherently produces fast…
Spectroscopic follow-up of dozens of transiting planets has revealed the degree of alignment between the equators of stars and the orbits of the planets they host. Here we determine a method, applicable to spotted stars, that can reveal the…
We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability…
Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tens of percent. A standard explanation is that dippers host nearly edge-on (70 deg) protoplanetary discs that allow close-in (< 1…
Understanding the collapse of clouds and the formation of protoplanetary disks is essential to understanding the formation of stars and planets. Infall and accretion, the mass-aggregation processes that occur at envelope and disk scales,…