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Astronomische Nachrichten
Article . 2013 . Peer-reviewed
License: Wiley Online Library User Agreement
Data sources: Crossref
https://dx.doi.org/10.48550/ar...
Article . 2012
License: arXiv Non-Exclusive Distribution
Data sources: Datacite
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Accretion, winds and outflows in young stars

Authors: Günther, Hans Moritz;

Accretion, winds and outflows in young stars

Abstract

AbstractYoung stars and planetary systems form in molecular clouds. After the initial radial infall an accretion disk develops. For classical T Tauri stars (CTTS, F‐K type precursors) the accretion disk does not reach down to the central star, but it is truncated near the co‐rotation radius by the stellar magnetic field. The inner edge of the disk is ionized by the stellar radiation, so that the accretion stream is funneled along the magnetic field lines. On the stellar surface an accretion shock develops, which is observed over a wide wavelength range as X‐ray emission, UV excess, optical veiling and optical and IR emission lines. Some of the accretion tracers, e.g. Hα, can be calibrated to measure the accretion rate. This accretion process is variable on time scales of hours to years due to changing accretion rates, stellar rotation and reconfiguration of the magnetic field. Furthermore, many (if not all) accreting systems also drive strong outflows which are ultimately powered by accretion. However, the exact driving mechanism is still unclear. Several components could contribute to the outflows: slow, wide‐angle disk winds, X‐winds launched close to the inner disk rim, and thermally driven stellar winds. In any case, the outflows contain material of very different temperatures and speeds. The disk wind is cool and can have a molecular component with just a few tens of km s–1, while the central component of the outflow can reach a few 100 km s–1. In some cases the inner part of the outflow is collimated to a small‐angle jet. These jets have an onion‐like structure, where the inner components are consecutively hotter and faster. The jets can contain working surfaces, which show up as Herbig‐Haro knots. Accretion and outflows in the CTTS phase do not only determine stellar parameters like the rotation rate on the main‐sequence, they also can have a profound impact on the environment of young stars. This review concentrates on CTTS in near‐by star forming regions where observations of high spatial and spectral resolution are available. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Keywords

Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Solar and Stellar Astrophysics (astro-ph.SR)

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    popularity
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    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
11
Top 10%
Average
Average
Green
bronze