Week 5 Stellar Wind Bubbles & Spectral Lines Flashcards
what are the two types of radiation mechanisms involved in stellar winds
line emission/absorption
continuum process
what are the 3 key ideas behind line emission/absorption
> spectral lines are resultant of discrete energy transition of photons
happens in atoms, ions, molecules, lattice of orbitals
have bound-bound transitions
what are the 3 key ideas behind continuum process
> operates on a wide range of energy
bound free transitions so there is ionisation and recombination
free-free transitions are a possibility
how can ‘forbidden’ transitions take place for line emission
in the presence of another particle
what is often associated with line emission
fluorescence
what causes spectral lines
inner electron is kicked out due to absorption of high energy photon. Another electron fills up the hole giving rise to the spectral line
what are the 3 reasons that spectral lines are never infinitely sharp
Heisenberg uncertainty principle
doppler broadening
pressure broadening
what is the Lorentzian line profile equation
Φ(ν) = γ/4π^2 * 1/[(ν-ν0)^2 + (γ/4π)^2]
what does thermal broadening result in
Gaussian line profile
what are the two equivalent width equations
W = ∫(1-Iν/I0) dν = ∫(1-exp[-τν])dν
how does optical depth effect equivalent width
optically thin mediums have an equivalent width with a greater dependence on N
what is photoionisation
when a photon interacts with a particle and produces two charged particles
eg H + photon –> H+ + e-
what is the photoionisation rate equation
Ν = σnJ
σ is the cross section of photoionisation
n is the number density
J is the flux
