1. Pre-Main Sequence Stars PHYS390 (Astrophysics) Professor Lee Carkner Lecture 13

2. Pre-Main Sequence   Start to the right of the main sequence  Characteristics:   Accretion   Magnetic activity

3. Stage 1 -- Protostellar Core  Age --  IR class -- 0  Infall --  Outflow -- possible  Disk --  Magnetic activity -- yes

4. IR Class   The more IR excess (and the longer its wavelength) the more circumstellar material, the younger the star

5. Stage 2 -- Protostar  Age --  IR class -- 1  Infall --  Outflow -- strong jet  Disk --  Magnetic activity -- strong hard X-ray emission

6. Outflow  PMS stars exhibit strong outflows   Winds are similar to scaled up solar wind   Jets are magnetically collimated polar outflows  Regulate angular momentum

7. Evolutionary Tracks   Hayashi track   Most important for low mass stars  Henyey track   Most important for high mass stars

8. Stage 4 -- Classical T Tauri Star  Age --  IR class -- 2  Infall --  Outflow -- strong winds  Disk --  Magnetic activity -- strong X-ray emission

9. T Tauri  T Tauri stars are variable stars located near clouds   Classified by width of H  line  W >  Classical T Tauri (CTT)  W <  Weak T Tauri (WTT)  H  may be due to disk- star interaction

10. Disks   Can interact with star and stellar magnetic field   Can magnetically brake star  Forms into planets

11. Stage 4 -- Weak T Tauri Star  Age --  IR class -- 3  Infall --  Outflow -- weak wind  Disk --  Magnetic activity -- strong X-ray activity and starspots

12. Magnetic Activity   Exhibited as:   Starspots   Wind

13. Stage 5 -- Zero Age Main Sequence  Age --  IR class -- No IR excess  Infall --  Outflow -- very weak wind  Disk --  Magnetic activity -- weak X-ray emission

14. High Mass Stars   Herbig Ae/Be stars are high mass version of T Tauri stars  Star forming regions can also contain OB associations   Strong winds can trigger more star formation

15. IMF   The exact relationship is called the initial mass function  Hard to determine the low mass end 

16. Next Time  Read 13.1, 13.3  Homework: 12.19, 13.2, 13.8