Title: Stars in adolescence: wild accretion, manic depression, fits of irrational outbursts, and pimply spots  

Speaker: Greg Herczeg (KIAA) 

Time & Place: Thursday, 3:00pm, June 26th, Lecture Hall, 3rd floor   

Abstract: Classical T Tauri stars are the adolescents of stellar evolution. They are nearly fully formed, with a remnant disk and ongoing accretion that usually lasts 2 - 5 Myr. Some stars refuse to grow up, taking as long as 10 Myr before losing their disks and emerging toward maturity. Strong magnetic activity leads to pimply spots on the stellar surfaces. Some T Tauri stars are still hidden inside their disks, not yet ready to emerge. Manic mood swings change the appearance of the star and are often explained with stochastic accretion. Depression has been seen in lightcurves on timescales of days to years. Sometimes every classical T Tauri star seems as uniquely precious as a snowflake, but all stars ultimately emerge from this wild period into the uniformity of adulthood. I will describe the physics that drives the evolution from birth to adulthood, efforts to understand the stellar properties despite the wild teenage facade, and recent observations that are starting to reveal how planets form in circumstellar disks around adolescent stars. 

Biog: Prof. Herzceg received his PhD from the University of Colorado in 2005, after which he took up postdoc positions at Caltech (with Lynne Hillenbrand) and MPE in Germany (with Ewine van Dishoeck). In 2011 he moved to KIAA in Beijing as a Youth Qianren. His research focusses on spectroscopic observations of the physics of protostellar evolution from the X-rays through far-IR.