Constraining the Neutron Star Compactness: Extraction of the Al23(p,γ

Abstract

The 23 Al(p, γ) 24 Si reaction is among the most important reactions driving the energy generation in Type-I X-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The 23 Al(d, n) reaction was used to populate the astrophysically important states in 24 Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2 + 2 and (4 + 1 ,0 + 2) state in 24 Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.

First Direct Measurement of Mg22(α,p)AlRandhawa1, Ayyad2, Mittig3 et al. 2020Phys. Rev. Lett.Self Cite193470View full textAdd to dashboardCite

“…Type-I X-ray burst (XRB) light curves are sensitive to the model's nuclear input, consequently affects the model-observation comparisons. 22 Mg(α, p) 25 Al is among the most important reactions that directly impact the XRB light curve. We report the first direct measurement of 22 Mg(α, p) 25 Al using the Active Target Time Projection Chamber.…”

“…22 Mg(α, p) 25 Al is among the most important reactions that directly impact the XRB light curve. We report the first direct measurement of 22 Mg(α, p) 25 Al using the Active Target Time Projection Chamber. XRB light curve model-observation comparisons for the source GS1826 − 24 using new reaction rate imply a less-compact neutron star than previously inferred.…”

“…Accurate nuclear physics input plays an equally important role in predicting the burst ashes, which alter the composition of the crust of the neutron star, which in mass-accreting systems is made in part or entirely out of XRB ashes. Various sensitivity studies over the years have shown that the 22 Mg(α, p) 25 Al reaction rate is among the most significant reactions that directly impact the light curves and burst ashes [6,7,9]. Recently in a study to assess the impact of uncertainties in nuclear inputs on the extraction of the neutron star mass-radius relation, the 22 Mg(α, p) 25 Al reaction rate was shown to have a significant effect even when decreased by a factor of 10 [8].…”

“…Various sensitivity studies over the years have shown that the 22 Mg(α, p) 25 Al reaction rate is among the most significant reactions that directly impact the light curves and burst ashes [6,7,9]. Recently in a study to assess the impact of uncertainties in nuclear inputs on the extraction of the neutron star mass-radius relation, the 22 Mg(α, p) 25 Al reaction rate was shown to have a significant effect even when decreased by a factor of 10 [8].…”

Proton decays from $α$-unbound states in $^{22}$Mg and the $^{18}$Ne($α, p_{0}$)$^{21}$Na cross section

“…Recent developments have constrained some of these reaction rates [7,[10][11][12][13][14][15][16][17]. For example, the 22 Mg(α, p) 25 Al cross section has been measured using a time-projection chamber at NSCL [7].…”