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Mass radius relationship for SIRIUS B

by cooper607
Tags: mass, radius, relationship, sirius
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Jul14-14, 06:37 AM
P: 49
hi guys, I have been doing a research on white dwarf stars and chanrashekhar limit. I need to plot a graph for the mass-radius relationship of the dwarfs. from the equalization of the hydrostatic equilibrium pressure and the electron degeneracy pressure I found out the radius -mass relationship for non relativistic fermi gas.

my final result is

R=3.58*10^16 M^(-1/3)

but when I take relativistic fermi gas, pressure comes in order of 4/3 and the radius cancels out leaving the equation to be
M(limit)=1.44 M(sun)

Now for this maximum limit how can I plot a graph for radius vs mass. which values should i input for different masses? please help me
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Jul14-14, 08:31 AM
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Matterwave's Avatar
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What do you mean plot a graph of radius vs mass for a limit? The limit is one value. It's a dot. What is the radius at this mass? If your final result is correct, you need only input this M(limit) into M.
Jul14-14, 12:37 PM
P: 49
But the relativistic fermi gas plot is different than the non relativistic, i want to know how do they get this graph?
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Jul14-14, 12:58 PM
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Chronos's Avatar
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Mass radius relationship for SIRIUS B

The formula can be found here - It is interesting to note that the radius actually shrinks as mass increases.
Jul15-14, 01:06 AM
P: 49
dear Chronos, I actually visited that page earlier, for relativistic fermi gas they derived the relation to be 1=M^(-1/3) , so radius actually cancels out from both sides. so how do they plot that graph where radius is zero when mass goes to 1.44? i didnt get any expression for the graph..can you tell me if there is any radius -mass relation for the relativistic curve ?

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