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How to assemble a star? sheding light on outbursts, mass accretion and ejection Dirk Froebrich low mass star formation (protostellar) luminosity problem HR-diagram HR-diagram HR-diagram of NGC2264 (protostellar) luminosity problem Young stars are fainter than expected Young stars accrete not enough material T-Tauri accretion rates are 10-7MSUN/yr or lower.... it would take 10 million years to assemble the Sun Episodic/variable accretion can solve these problems! YSO variability one of the defining candidates of T-Tauri stars present on all time scales short time, mostly small changes: rotation ocultations from disk ‘flickering’ long time, larger amplitudes: EX Lup (EXor) FU Ori (FUor) duration for FUor unclear, frequency 5-50kyr from infrared monitoring with UKIDSS, VISTA, WISE vs Glimpse Currently GAIA, in future LSST, UoK Beacon Observatory … Some Questions What is the duration of the FUor bursts? What fraction of time do YSOs spend in outburst (of what strength and does it depend on mass, environment, etc)? What mass fraction is accreted in the bursts? YSO variability/outbursts McNeil’s Nebula YSO variability/outbursts McNeil’s Nebula YSO variability/outbursts McNeil’s Nebula YSO variability/outbursts YSO variability/outbursts YSO variability/outbursts YSO variability/outbursts YSO variability/outbursts YSO variability/outbursts models Some Questions What is the duration of the FUor bursts? What fraction of time do YSOs spend in outburst (of what strength and does it depend on mass, environment, etc)? What mass fraction is accreted in the bursts? How to answer some of these? Monitor the brightness of many YSOs over a long period of time. This does not have to be at regular intervals or specific filters/wavelengths. EVERY image is helpful! Young clusters are ideal as there are many YSOs in each field of view and we know their age. Can easily spot onset of eruption for detailed investigations.