Pre-Main Sequence Stars PHYS390 (Astrophysics) Professor Lee Carkner Lecture 13
Pre-Main Sequence Start to the right of the main sequence Characteristics: Accretion Magnetic activity
Stage 1 -- Protostellar Core Age -- IR class -- 0 Infall -- Outflow -- possible Disk -- Magnetic activity -- yes
IR Class The more IR excess (and the longer its wavelength) the more circumstellar material, the younger the star
Stage 2 -- Protostar Age -- IR class -- 1 Infall -- Outflow -- strong jet Disk -- Magnetic activity -- strong hard X-ray emission
Outflow PMS stars exhibit strong outflows Winds are similar to scaled up solar wind Jets are magnetically collimated polar outflows Regulate angular momentum
Evolutionary Tracks Hayashi track Most important for low mass stars Henyey track Most important for high mass stars
Stage 4 -- Classical T Tauri Star Age -- IR class -- 2 Infall -- Outflow -- strong winds Disk -- Magnetic activity -- strong X-ray emission
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
Disks Can interact with star and stellar magnetic field Can magnetically brake star Forms into planets
Stage 4 -- Weak T Tauri Star Age -- IR class -- 3 Infall -- Outflow -- weak wind Disk -- Magnetic activity -- strong X-ray activity and starspots
Magnetic Activity Exhibited as: Starspots Wind
Stage 5 -- Zero Age Main Sequence Age -- IR class -- No IR excess Infall -- Outflow -- very weak wind Disk -- Magnetic activity -- weak X-ray emission
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
IMF The exact relationship is called the initial mass function Hard to determine the low mass end
Next Time Read 13.1, 13.3 Homework: 12.19, 13.2, 13.8