; this program does the work for problem 3.9 in Carroll and Ostlie, 2nd ed
; using the equations given in chapter 3 of the text.
; The output given here is just to the screen, and no files are read nor 
; written to.  Modifications will need to be made.
; magnitudes are not bolometric magnitudes

PRO PROBLEM3_9
;
; bring in constants
@physical_constants.inc			; use your file name
;  we'll deal with fixed quantities here
  lum_sun = 3.839D+26			; luminosity of the Sun in watts -- note decimal points
  teff_star = 28000.			; effective temp of star Dschubba
  radius_star = 5.16D+9			; radius in m
  dist_star_pc = 123.			; distance to star in parsecs
  dist_star = dist_star_pc * 3.0857D+16  ; distance in m
  absmag_sun = 4.76

; on to the problem!
  lum_star = 4. * pi * radius_star^2 * sigma * teff_star^4
  absmag_star = absmag_sun - 2.5 * alog10(lum_star / lum_sun)
  appmag_star = absmag_star + 5. * alog10(dist_star_pc) - 5.
  dist_mod_star = appmag_star - absmag_star
  fluxstar_surf = sigma * teff_star^4
  fluxstar_earth = lum_star / (4. * pi * dist_star^2)
  print, lum_star, absmag_star, appmag_star, dist_mod_star, fluxstar_surf, fluxstar_earth
  help				; spits out types and values of all variables onto screen
  END