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{\bf Introduction to Astrophysics II, 29:120\\
     Spring, 2007\\
Tenth Homework Set...April 20, 2007. Due April 26, 2007}\\
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{\bf (1)} The black hole in the Cygnus X-1 system has a mass of $10 M_{\odot}$ and an accretion rate (mass flow from the star into the accretion disk) of $1.8 \times 10^{-9} M_{\odot}$/year.  Calculate the temperature of the accretion disk at a distance $r=15R_s$.  In what part of the spectrum does this segment of the accretion disk radiate?  \\

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{\bf (2)} A meter stick is moved into a point $2.8 R_s$ from the ``center'' of a $5 M_{\odot}$ black hole, and aligned in the radial direction.  If we could measure its radial extent, what would it be?  \\

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{\bf (3)} Derive the equation on p664 of the textbook (presented in class as a roundtrip propagation time).  \\ 


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{\bf (4)} A radar transmitter on Earth bounces a signal off the planet Venus when it is at opposition.  The line of sight passes by the Sun at a closest heliocentric distance (impact parameter $b$) of $b=3 R_{\odot}$.  Compare the round-trip propagation time with that which occurs in the absence of the Sun.  Is the difference measurable?
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{\bf (5)} Look at Table 1 in Remillard and McClintock, Annual Reviews of Astronomy and Astrophysics, vol 44, p49, 2006.  Consider the case of 0422+32.  The mass function is given as $1.19 M_{\odot}$, but the mass of the degenerate object is given as $3.7 - 5.0 M_{\odot}$.  What factors must be accounted for to calculate the mass of the degenerate object?  
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{\bf (6)} Problem \# 16.17 from textbook
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{\bf (7)} Problem \# 16.18  \\

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{\bf (8)} Problem \# 16.21


 
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