School nuclear physicists' paper published in Physical Review Letters

Artist's impression of an X-ray burst.

In the latest issue of the prestigious Physical Review Letters journal, School nuclear physicists report on the measurement of a nuclear reaction that is key to the understanding of type I X-ray bursts.

X-ray bursts are among the most energetic explosions in the Universe. They are triggered by a thermonuclear runaway on the surface of a neutron star that is accreting hydrogen- and helium-rich material from a less evolved companion in binary star systems.

Type I X-ray bursters (XRBs) exhibit brief recurrent bursts of intense X-ray emission and represent a frequent phenomenon in our galaxy. Recent observations from space-borne X-ray satellites (BeppoSAX, RXTE, Chandra and XMM Newton) have provided a great wealth of data and have marked a new era in X-ray astronomy. However, detailed understanding of the specific nuclear reactions responsible for such bursts is still largely hampered by the lack of experimental data relating to the energies of astrophysical relevance.

Gamow energy window

In an experiment carried out at the international TRIUMF facility in Canada, a measurement of the 18Ne(a,p)21Na reaction using the time-reversal approach was carried out at the lowest energies measured so far, and for the first time within the energy region of interest for X-ray bursts, the so-called Gamow energy window.

The results indicate a lower reaction rate (up to a factor of 2) compared with previous theoretical estimates. This will impact the physical conditions of temperature at which the thermonuclear runaway can be initiated by the 18Ne(a,p)21Na.

Nuclear Physics at Edinburgh

The Edinburgh Nuclear Physics Group is internationally renowned for its work on explosive nuclear astrophysical reactions. The project was led by Dr Marialuisa Aliotta, within an international collaboration, and formed the focus of the PhD Thesis of (now Dr) Philip Salter (Supervisors: M. Aliotta and T. Davinson).