Astr 345 Assignment 7
Due before midnight Fri, Oct 17, 2008 (full credit), before midnight Fri Oct 24, 2008 (half credit)
1. Hartmann, chapter 4, problem #1, 2, 3, and 5. Notes: some reading is required for problems 1, 2, and 3.
You are not given the distance to the stars in problem 5, hence be careful about what conclusions you
draw.
2. Supplemental problem: the star Vega has a spectrum that peaks at 2,950 ˚
A. Determine the following
(include units throughout your calculations, use top-down logic exclusively:
(a) surface temperature,
(b) surface flux density,
(c) total luminosity (given radius = 2.5 solar radii),
(d) the flux reaching a distance of 1 AU,
(e) the surface flux density in the wavelength range 4000 to 4010 ˚
A.
3. Supplemental problem: the young stellar object GM Aurigae is in the
great Taurus-Auriga star forming region. The following table
represents the received flux from this object. Make a plot of power
(λF (λ)) versus wavelength (λ); this type of plot is called a “spectral
energy distribution” (SED). You can either use a logarithmic scale,
or plot log(λF (λ)) vs log(λ). On the graph, identify the stellar and
circumstellar blackbody components, and estimate the temperature
of each. Estimate the value of the slope (the “spectral index”) at 2
microns. Classify the object as one of Lada’s classes I, II, or III, and
state at what stage of evolution GM Aurigae is at.
Wavelength Flux
(microns) (W m−2m−1)
0.43 5.42E-007
0.55 4.51E-007
0.7 7.04E-007
1.25 6.09E-007
1.65 3.52E-007
2.2 1.85E-007
3.5 3.62E-008
10 1.24E-008
12 4.38E-009
25 5.66E-009
60 2.63E-009
100 1.18E-009
624 1.03E-011
769 4.31E-012
Grading:
•You can share concepts, but all work must be completely original
•Write neatly and legibly
•Line up equal signs in a straight vertical column, and never have more than one equal sign on a line
•Define all non-standard variables
•Do not skip essential lines of algebra
•Develop ideas logically from start to finish
•Include a statement at the end of each problem interpreting the result
•Label your diagrams; all plots must be computer plots
•Take pride in your work
•All assignments are out of 30 points
