Tuesday 29 Aug 2017Extreme Variables in Star Forming Regions

Carlos Contreras - University of Exeter

4th Floor Interaction Area 11:15-11:45


Episodic accretion is thought to be common or even universal among young stellar objects (YSOs). If so, this would solve long standing problems in stellar evolution, i.e. the observed scatter around the best fitting isochrone of HR diagrams of pre-main-sequence (PMS) clusters, and the so-called “luminosity problem”, which is that typical luminosities of YSOs in clusters are lower than expected for Sun-like stars that should be above the main sequence. In addition, if it occurs, episodic accretion during the class II phase is predicted to have a strong impact in planet formation and evolution. However, the frequency and amplitude of the outbursts is not well constrained and there is controversy as to whether the very largest outbursts are associated with the Class II planet building phase at all, or are just limited to the pre-planet-forming (Class 0/I).



The abrupt increase in the mass accretion rate on to the central star, by a factor of up to a 1000, leads to a sudden rise of the luminosity of the object, of up to 6 magnitudes. Objects that display such variability are known as eruptive YSOs. These are usually classified according to the their spectral characteristics during outburst, the magnitude of the outburst, its duration and the shape of the light curve (the so-called FUors, EXors and MNors). However, the characteristics of individual objects do not always fully coincide with one of the classes.



In this talk I will present the results of the work conducted during my PhD of searching for high amplitude variability in the multi-epoch near-infrared data of the UKIDSS Galactic Plane Survey (GPS) and the Vista Variables in the Via Lactea (VVV) survey. I will connect these results with my current work of studying the photometric variability of class II YSOs using Gaia and the photographic Palomar and ESO/SRC surveys.



 

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