Accretion phenomena and theories
Accretion phenomena and theories
Accretion phenomena and theories
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<strong>Accretion</strong> onto a compact object<br />
• Principal mechanism for producing high-energy<br />
radiation<br />
• Most efficient of energy production known in the<br />
Universe.<br />
• Gravitational potential energy released for an object<br />
with mass M <strong>and</strong> radius R when mass m is accreted:<br />
– E acc = GMm/R = (R s /2R)mc 2<br />
where R sch<br />
= 3 M sun<br />
km<br />
– For a Neutron star, R ~ 10 km E acc ~ 0.15 mc 2<br />
Or ~ 20 x more efficient than nuclear fusion<br />
(H => He) ~ 0.007 mc 2 .<br />
– For a white dwarf, R ~ 10 4 km E acc ~ 1.5x10 -4 mc 2<br />
Or ~ 50 less efficient than nuclear fusion.
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