1 astr 8000 stellar atmospheres and spectroscopy introduction & syllabus light and matter sample...
DESCRIPTION
3 Rutten (Utrecht) Notes On-line Radiative Transfer in Stellar Atmospheres Good set of notes that emphasizes the physical aspects (versus the observational emphasis in Gray) We will use these notes frequentlyTRANSCRIPT
1
ASTR 8000STELLAR ATMOSPHERES
AND SPECTROSCOPYIntroduction & Syllabus
Light and MatterSample Atmosphere
2
Introductions and Syllabus
• Available on-line at class web sitehttp://www.astro.gsu.edu/~gies/ASTR8000/
• TextsGray “Stellar Photospheres” (older editions OK)Mihalas “Stellar Atmospheres” (out of print)Mihalas2 “Radiation Hydro” ($21)Collins “Fundamentals” available on-line athttp://ads.harvard.edu/books/1989fsa..book/Bohm-Vitense “Stellar Astrophysics Vol. 2”
3
Rutten (Utrecht) Notes On-line
• Radiative Transfer in Stellar Atmosphereshttp://www.astro.uu.nl/~rutten/Astronomy_lecture.html
• Good set of notes that emphasizes the physical aspects (versus the observational emphasis in Gray)
• We will use these notes frequently
4
Two Courses in One!
• Astr 8000 Stellar Atmospheresbasics, building model atmospheres, resulting continuous spectra, use to determine properties of starsGray Chapters 1 – 10
• Astr 8600 Stellar Spectroscopydetailed look at the line spectra of stars (bound-bound transitions), applications Gray Chapters 11 – 18
5
Introduction
• Understand stars from spectra formed in outer 1000 km of radius
• Use laws of physics to develop a layer by layer description of T temperatureP pressure andn densitythat leads to spectra consistent with observations
6
First Approximation
• Stellar spectra are similar to a Planck black body function characterized by T
• Actually assign an effective temperature to stars such that the integrated energy flux from the star = that from a Planck curve
• How good is this approximation? Depends on the type of star …
7
8
9
10
Two Parts to the Problem
Physical description of gas with depth: example, T = T(τ)
Radiation field as a function of frequency and depth to make sure energy flow is conserved
11
Parameters• Teff = Effective temperature defined by
integrated luminosity and radius • log g = logarithm (base 10) of the surface
gravitational acceleration• Chemical abundance of the gas• Turbulence of the gas• Magnetism, surface features, extended
atmospheres, and other complicationsAll potentially derivable from spectra
12
Key Example: Robert Kurucz and ATLAS
• Kurucz, R. L. 1979, ApJS, 40, 1(http://kurucz.harvard.edu/)
• Plane parallel, LTE, line-blanketed models• Current version ATLAS12 runs in Linux• Units: c.g.s. and logarithms for most• Example: Sun
13
682 km
geometric depth densityoptical
depth
14
30000 10000 6000 4286 3333 Å
15
16
Comparison with Vega (A0 V): Flux
17
Comparison with Vega (A0 V): Lines