Astr 8000 stellar atmospheres and spectroscopy
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ASTR 8000 STELLAR ATMOSPHERES AND SPECTROSCOPY. Introduction & Syllabus Light and Matter Sample Atmosphere. Introductions and Syllabus. Available on-line at class web site http://www.astro.gsu.edu/~gies/ASTR8000/

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ASTR 8000 STELLAR ATMOSPHERES AND SPECTROSCOPY

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Astr 8000 stellar atmospheres and spectroscopy

ASTR 8000STELLAR ATMOSPHERESAND SPECTROSCOPY

Introduction & Syllabus Light and MatterSample Atmosphere


Introductions and syllabus

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”


Rutten utrecht notes on line

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


Two courses in one

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


Introduction

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


First approximation

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 …


Two parts to the problem

Two Parts to the Problem

Radiation field as a function of frequency and depth to make sure energy flow is conserved

Physical description of gas with depth: example, T = T(τ)


Parameters

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


Key example robert kurucz and atlas

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


Astr 8000 stellar atmospheres and spectroscopy

geometric depth

optical depth

density

682 km


Astr 8000 stellar atmospheres and spectroscopy

30000 10000 6000 4286 3333 Å


Comparison with vega a0 v flux

Comparison with Vega (A0 V): Flux


Comparison with vega a0 v lines

Comparison with Vega (A0 V): Lines


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