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Theory of the Fireball

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The radius R is given<br />

R3 = I"-<br />

P<br />

P<br />

J ;+ = m -<br />

Y - 1 - const.<br />

7<br />

(3.9)<br />

We shall set <strong>the</strong> constant equal to zero which amounts to <strong>the</strong> (incorrect)<br />

assmption that ( 3.8) holds dam to m = 0. Actually, <strong>the</strong> isot'nermal<br />

sphere gives <strong>the</strong> constant a finite, positive value.<br />

To find <strong>the</strong> temperature distribution, we note that <strong>the</strong> enthalpy<br />

H = 7' E<br />

Y 1 - l P<br />

We are using <strong>the</strong> enthalpy ra<strong>the</strong>r than <strong>the</strong> internal energy because <strong>the</strong><br />

interior <strong>of</strong> <strong>the</strong> shock is at constant pressure, not constant density.<br />

The <strong>the</strong>rmodynamic eqmtion for H is<br />

TdS=dH-~dp<br />

At given pressure, i.e., given time, (3.8) to (3.10) give<br />

22

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