4 spectroscopic bin Flashcards
how to calc radial vel from spectra?
name methods for measuring radial vel? analysing spectral bin?
model fitting
correlation
why cooler stars have more spectral lines
cooler stars: not iniozed– transitions bw states
what makes spectral line broadening?
many reason
doppler broadening: thermal motion
rotational broadening
why spectral lines must b narrow for correlation?
high spectral res req
why is it imp to take calibration spectra simultaneously?
to avoid time based inconsistneces, e.g instrument or environement
advantages and limitations of each
whats model fitting? what stars?
compare shift w a moel spectra– model from stellar evolution–
req fewer lines + good model
hot stars
why model fiiting is better for hot stars?
fewer lines + good model
cool stars = not modelled well + too many lines
OBAF?
whats correlation? why better for cooler stars?
compare w tempelate spectra –
error measurement propotional to # lines
more lines better – cooler stars
narrow lines – cooler stars
what stars not good for correlation?
what stars good for correlation?
cooler stars GKM
more lines + narrow lines:
less rotational broadening
no young stars / WD/ compact objs ( broad lines)
no early stars (#lines + broad lines)
stable atmosphere:
no pre MS
no active stars
good:
MS, giant, sub-giant GKM
types of errors in obs?
systematic
statistic (solve by multiple obs)
what is Extremely precise wavelength calibration?
in correlation method, the refrence spectrum. sample form the star should be very precisely callibrated fro high resolution spectra
how to measure Extremely precise wavelength calibration?
taking calibration spectra and observation simultanously
error because of earth motion?
v-orbital + v-rotation (precise location req)
