Supernova PHYS390 Astrophysics Professor Lee Carkner Lecture 16.
Pre-Main Sequence Stars PHYS390 (Astrophysics) Professor Lee Carkner Lecture 13.
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Transcript of 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
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