Measuring the 15O(α, γ)19Ne reaction in Type I X-ray bursts using the GADGET II TPC: Hardware

T Wheeler ,D Bazin,E Argo,J Surbrook,A Psaltis,L Schaedig,A Chen,B Davids ,Lexanne Weghorn ,M Friedman ,J F Liang ,A M Rogers ,H Alvarez Pol ,Saiprasad Ravishankar ,D Pérez–Loureiro ,K A Chipps ,J Dopfer ,L J Sun ,J José ,Ruchi Mahajan ,R Grzywacz ,Y Ayyad ,Andrew Adams ,J M Allmond ,Tamas Budner ,D W Bardayan ,H O U Fynbo ,S D Pain ,E C Pollacco ,C Wrede

doi:10.1051/epjconf/202226011046

Abstract

Sensitivity studies have shown that the 15O(α, γ)19Ne reaction is the most important reaction rate uncertainty affecting the shape of light curves from Type I X-ray bursts. This reaction is dominated by the 4.03 MeV resonance in 19Ne. Previous measurements by our group have shown that this state is populated in the decay sequence of 20Mg. A single 20Mg(βp α)15O event through the key 15O(α, γ)19Ne resonance yields a characteristic signature: the emission of a proton and alpha particle. To achieve the granularity necessary for the identification of this signature, we have upgraded the Proton Detector of the Gaseous Detector with Germanium Tagging (GADGET) into a time projection chamber to form the GADGET II detection system. GADGET II has been fully constructed, and is entering the testing phase.

Highlights

Astrophysical MotivationWhen a neutron star is orbited by a low-mass population II star it will accrete hydrogen-rich material from this binary companion via a process called Roche lobe overflow
We would measure the 15O(α, γ)19Ne reaction directly, but given that 15O is radioactive (t1/2 ~ 122 s), beams of sufficient intensity are not currently available
When a neutron star is orbited by a low-mass population II star it will accrete hydrogen-rich material from this binary companion via a process called Roche lobe overflow

Summary

Astrophysical Motivation

When a neutron star is orbited by a low-mass population II star it will accrete hydrogen-rich material from this binary companion via a process called Roche lobe overflow. The temperatures and densities on the surface of the neutron star are such that the accreted hydrogen is continuously fused into helium. The helium is ignited and a thermonuclear runaway proceeds. This can lead to the synthesis of proton-rich nuclides up to mass number 100, and extremely powerful X-ray bursts [1]. Sensitivity studies have shown that for breakout temperatures of ~0.5 GK, the 15O(α, γ)19Ne reaction is the most important reaction rate uncertainty that needs to be determined to properly constrain the modelling of Type I X-ray burst light curves [3]

Measuring the Reaction

GADGET II