Abstract
For the first few million years, one of the dominant sources of emission
from a low mass young stellar object is from accretion. This process
regulates the flow of material and angular moments from the surroundings
to the central object, and is thought to play an important role in the
definition of the long term stellar properties. Variability is a well
documented attribute of accretion, and has been observed on time-scales
of from days to years. However, where these variations come from is not
clear. Th current model for accretion is magnetospheric accretion, where
the stellar magnetic field truncates the disc, allowing the matter to
flow from the disc onto the surface of the star. This model allows for
variations in the accretion rate to come from many different sources,
such as the magnetic field, the circumstellar disc and the interaction
of the different parts of the system. We have been studying unbiased
samples of accretors in order to identify the dominant time-scales and
typical magnitudes of variations. In this way different sources of
variations can be excluded and any missing physics in these systems
identified. Through our previous work with the Long-term Accretion
Monitoring Program (LAMP), we found 10 accretors in the ChaI region,
whose variability is dominated by short term variations of 2 weeks. This
was the shortest time period between spectroscopic observations which
spanned 15 months, and rules out large scale processes in the disk as
origins of this variability. On the basis of this study we have gone
further to study the accretion signature H-alpha, over the time-scales
of minutes and days in a set of Herbig Ae and T Tauri stars. Using the
same methods as we used in LAMP we found the dominant time-scales of
variations to be days. These samples both point towards rotation period
of these objects as being an important time-scale for accretion
variations. This allows us to indicate which are the most likely sources
of these variations.
| Original language | English |
|---|---|
| Publication status | Published - 15 Jul 2013 |
| Event | Protostars and Planets VI - Heidelberg, Germany Duration: 15 Jul 2013 → 20 Jul 2013 |
Conference
| Conference | Protostars and Planets VI |
|---|---|
| Country/Territory | Germany |
| City | Heidelberg |
| Period | 15/07/13 → 20/07/13 |