Starlib: A Next-Generation Reaction-Rate Library for Nuclear Astrophysics

Abstract

STARLIB is a next-generation, all-purpose nuclear reaction-rate library. For the first time, this library provides the rate probability density at all temperature grid points for convenient implementation in models of stellar phenomena. The recommended rate and its associated uncertainties are also included. Currently, uncertainties are absent from all other rate libraries, and, although estimates have been attempted in previous evaluations and compilations, these are generally not based on rigorous statistical definitions. A common standard for deriving uncertainties is clearly warranted. STARLIB represents a first step in addressing this deficiency by providing a tabular, up-to-date database that supplies not only the rate and its uncertainty but also its distribution. Because a majority of rates are lognormally distributed, this allows the construction of rate probability densities from the columns of STARLIB. This structure is based on a recently suggested Monte Carlo method to calculate reaction rates, where uncertainties are rigorously defined. In STARLIB, experimental rates are supplemented with: (1) theoretical TALYS rates for reactions for which no experimental input is available, and (2) laboratory and theoretical weak rates. STARLIB includes all types of reactions of astrophysical interest to Z = 83, such as (p, γ), (p, α), (α, n), and corresponding reverse rates. Strong rates account for thermal target excitations. Here, we summarize our Monte Carlo formalism, introduce the library, compare methods of correcting rates for stellar environments, and discuss how to implement our library in Monte Carlo nucleosynthesis studies. We also present a method for accessing STARLIB on the Internet and outline updated Monte Carlo-based rates.

Confronting uncertainties in stellar physics

“…This rises to around 30% in the high temperature wing of the Z-bump, because the OP data 13 A detailed discussion of the effects of reaction rates and opacities on a single stellar code can be found in Valle et al (2013). 14 See Sallaska et al (2013) for a detailed discussion concerning the meaning and determination of reaction rate uncertainties.…”

Nuclear astrophysics in the laboratory and in the universe

“…9. Experimental Monte Carlo-based reaction rates for the crucial 22 Ne(α,n) 25 Mg neutron source in the s-process at a temperature of 300 MK. The reaction rate is sampled 10,000 times.…”

“…These ideas turned out to be crucial for the design of a next-generation reaction rate library, called STARLIB. 22 Existing libraries contain values of only two parameters, temperature and recommended rate, either as analytical fit formulas (e.g., JINA REACLIB 60 ) or in tabular format (e.g., BRUSLIB 61 ). STARLIB also has a tabular format, but contains a third parameter, the factor uncertainty, which can be used for two purposes.…”

New measurements of low-energy resonances in theNe22(p,γ)Na23reaction

“…ratesmc calculates the lognormal parameters µ and σ that define the reaction rate probability distribution via the relations [44,[61][62][63] Median Rate = x med = e µ(T ) ,…”

“…See Refs. [44,[61][62][63] for more details on this formalism. A comparison of 22 Ne(p,γ) 23 Na reaction rate contribution plots calculated using the starlib rate (top panel) and the present rate (bottom panel) and is shown in Fig.…”