rp-process

<h2 id="conditions">Conditions</h2>
<p>The process has to occur in very high-temperature environments (above 109 <a href="/facts/Kelvin/E3trzC4C">kelvins</a>) so that the protons can overcome the large <a href="/facts/Coulomb_barrier/mAftHz1k">Coulomb barrier</a> for charged-particle reactions.  A hydrogen-rich environment is also a prerequisite due to the large proton flux needed.  The seed nuclei needed for this process to occur are thought to be formed during breakout reactions from the hot <a href="/facts/CNO_cycle/ClM5eAGc">CNO cycle</a>.  Typically proton capture in the rp-process will compete with (α,p) reactions, as most environments with a high flux of hydrogen are also rich in helium.  The time scale for the rp-process is set by β+ decays at or near the <a href="/facts/Proton_drip_line/k3PfJUoy">proton drip line</a>, because the <a href="/facts/Weak_interaction/f6upmKMs">weak interaction</a> is notoriously slower than the <a href="/facts/Strong_interaction/JjRsKcLg">strong interaction</a> and <a href="/facts/Electromagnetic_force/oAkmALHT">electromagnetic force</a> at these high temperatures.
</p>
<h2 id="possible-sites">Possible sites</h2>
<p>Sites suggested for the rp-process are <a href="/facts/Accretion_(astrophysics)/atcWRsDP">accreting</a> binary systems where one star is a <a href="/facts/Neutron_star/4enfoxBA">neutron star</a>.  In these systems the donor star is accreting material onto its compact partner star.  The accreted material is usually rich in hydrogen and helium because of its origin from the surface layers of the donor star.  Because such compact stars have high <a href="/facts/Gravitation/bqAN7DdQ">gravitational fields</a>, the material falls with a high <a href="/facts/Velocity/Q3o1LVDe">velocity</a> towards the compact star, usually colliding with other accreted material en route, forming an <a href="/facts/Accretion_disk/8zJXshat">accretion disk</a>.  In the case of accretion onto a neutron star, as this material slowly builds up on the surface, it will attain a temperature on the order of 108 K.
</p><p>Eventually, it is believed that thermonuclear instabilities arise in this hot atmosphere, allowing the temperature to continue to rise until it leads to a runaway <a href="/facts/Thermonuclear_explosion/BtpfgcUg">thermonuclear explosion</a> of the hydrogen and helium. During the flash, the temperature quickly rises, becoming high enough for the rp-process to occur. While the initial flash of hydrogen and helium lasts only a second, the rp-process typically takes up to 100 seconds. Therefore, the  rp-process is observed as the tail of the resulting <a href="/facts/X-ray_burst/hUAR3j1Q">X-ray burst</a>.
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<h2 id="see-also">See also</h2>
<ul>
<li>Astronomy portal</li><li>Physics portal</li></ul>
<ul><li><a href="/facts/P-nuclei/LheR8EQW">p-nuclei</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Bildsten, Lars (2010) [1998]. "Thermonuclear Burning on Rapidly Accreting Neutron Stars". In van Paradijs, J.; Alpar, M.A.; Buccheri, R. (eds.). The Many Faces of Neutron Stars. Springer. arXiv:astro-ph/9709094v1. ISBN 9789048150762. <a href="9789048150762" target="_blank">9789048150762</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Schatz, H.; A. Aprahamian; V. Barnard; L. Bildsten; A. Cumming; et al. (April 2001). "End Point of the rp Process on Accreting Neutron Stars". Physical Review Letters. 86 (16): 3471–3474. arXiv:astro-ph/0102418. Bibcode:2001PhRvL..86.3471S. doi:10.1103/PhysRevLett.86.3471. PMID 11328001. S2CID 46148449. Retrieved 2006-08-24. <a href="http://link.aps.org/abstract/PRL/v86/p3471" target="_blank">http://link.aps.org/abstract/PRL/v86/p3471</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Auranen, K.; et al. (2018). "Superallowed α decay to doubly magic 100Sn" (PDF). Physical Review Letters. 121 (18): 182501. Bibcode:2018PhRvL.121r2501A. doi:10.1103/PhysRevLett.121.182501. PMID 30444390. <a href="https://www.pure.ed.ac.uk/ws/files/77942573/PhysRevLett.121.pdf" target="_blank">https://www.pure.ed.ac.uk/ws/files/77942573/PhysRevLett.121.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Lahiri, S.; Gangopadhyay, G. (2012). "Endpoint of rp process using relativistic mean field approach and a new mass formula". International Journal of Modern Physics E. 21 (8). arXiv:1207.2924. Bibcode:2012IJMPE..2150074L. doi:10.1142/S0218301312500747. S2CID 119259433. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

rp-process open-in-new

rp-process