Constraining nucleosythesis in neutrino-driven winds using the impact of $(\alpha, xn)$ reaction rates

Thanassis Psaltis (@psaltistha)
TU Darmstadt, Institut für Kernphysik Theoriezentrum

Based on A. Psaltis et al., Astrophys. J 935 27 (2022), arXiv: 2204.07136 [astro-ph]

How I see nuclear astrophysics


 

 

 

 

 

 

 
HD 122563 (DSS2/ Aladin Sky Atlas)

What do the old stars reveal to us?

See also: C. Sneden, J. J. Cowan and R. Gallino, Annu. Rev. Astron. Astrophys. 46, 241 (2008)
⚠️ Solar r-process = Solar total - Solar s-process - Solar p-process

How many "r-processes" contribute to the production of elements between Sr and Ag?

Nucleosynthesis
in neutrino-driven ejecta

Image Credit: NASA/CXC/DSS/Rutgers/K.Eriksen et al.

How I see nuclear astrophysics

The weak $r$-process and the role $(\alpha, n)$ reactions

Take-home message #1


Elements between Sr and Ag can be produced in $\nu$-driven outflows via the weak $r$-process

What is the impact of the
$\mathbf{(\alpha,xn)}$ reactions
in the weak $r$-process?

How I see nuclear astrophysics

How well do we know the $(\alpha,xn)$ reaction rates?

The $(\alpha,xn)$ reaction rates are sensitive to the $\alpha$-optical model potential and can differ by up to two orders of magnitude.

J. Pereira and F. Montes, Phys. Rev. C 93, 034611 (2016) • P. Mohr, Phys. Rev. C 94, 35801 (2016)

Enter the ATOMKI-v2 $\alpha$-nucleus potential

The rates are tabulated and available to the community ☺️
P. Mohr et al., At. Data Nucl. Data Tables 132, 101453 (2021)

How I see nuclear astrophysics

The framework of the impact study

The impact of new $(\alpha,n)$ reaction rates to
elemental abundances

A. Psaltis et al., Astrophys. J 935 27 (2022)

The impact of new $(\alpha,n)$ reaction rates
to elemental abundance ratios

A. Psaltis et al., Astrophys. J 935 27 (2022)

Combine observations, astrophysical modeling and nuclear physics uncertainties

A. Psaltis et al., Astrophys. J 935 27 (2022)

Which are the most important
$\mathbf{(\alpha,xn)}$ reactions
for the weak $r$-process?

The most important $(\alpha,n)$ reactions
for the weak $r$-process

  1. $\mathrm{^{84}Se}$, $\mathrm{^{87-89}Kr, ^{93}Sr}$
    Affect many elemental ratios in many astrophysical conditions

  2. $\mathrm{^{86}Br,^{86, 90}Kr, ^{87-89}Rb, ^{91, 92, 94}Sr, ^{94}Y}$
    Affect few elemental ratios in many astrophysical conditions

  3. $\mathrm{^{85}Se, ^{85}Br}$
    Affect many elemental ratios in few astrophysical conditions

  4. $\mathrm{^{63}Co, ^{67}Cu, ^{79, 81}Ga, ^{76}Zn, ^{80, 82}Ge, ^{83}As}$
    $\mathrm{^{87, 90, 91}Rb, ^{88-90}Sr, ^{95, 96}Y, ^{96-98}Zr}$
    Affect few elemental ratios in few astrophysical conditions

Take-home message #2


We combined observations, astrophysical modeling and nuclear theory
to study the impact of $(\alpha,xn)$ reactions to the weak $r$-process

Can we study these $\mathbf{(\alpha,xn)}$ reactions in the lab?

How I see nuclear astrophysics

What has been done so far?

  • $\mathrm{^{86}Kr(\alpha,n)^{89}Sr}$, $\mathrm{^{96}Zr(\alpha,n)^{99}Mo}$ and $\mathrm{^{100}Mo(\alpha,n)^{103}Ru}$ at ATOMKI
    G.G. Kiss et al., Astrophys. J 908, 202 (2021) • T.N. Szegedi et al., Phys. Rev. C 104, 035804 (2021)
    See talk by Szegedi, Friday Session 1
  • $\mathrm{^{75}Ga(\alpha,n)^{78}As}$, $\mathrm{^{85,86}Kr(\alpha,xn)}$, $\mathrm{^{85}Br(\alpha,xn)}$ at NSCL/FRIB (HabaNERO/SECAR)
    F. Montes, Z. Meisel et al.
    See poster by Garg, Tuesday & talk by Tsintari, Thursday Session 3
  • $\mathrm{^{86}Kr(\alpha,xn)^{89}Sr}$ and $\mathrm{^{100}Mo(\alpha,xn)^{103}Ru}$ at ANL/NSCL (MUSIC)
    M. L. Avila, J. Pereira et al.
    W. J. Ong et al., Phys. Rev. C 105, 055803 (2022)
  • $\mathrm{^{86}Kr(\alpha,n)^{89}Sr}$ and $\mathrm{^{94}Sr(\alpha,n)^{97}Zr}$ at TRIUMF (EMMA)
    C. Aa. Diget, A. M. Laird, M. Williams et al.
    See talk by Angus, this session

First measurement of the $\boldsymbol{\mathrm{^{93}Sr}(\alpha,xn)\mathrm{^{96-x}Zr}}$ reaction

$\mathrm{^{93}Sr}(\alpha,xn)\mathrm{^{96}Zr}$ at Argonne with MUSIC

M. L. Avila et al., Nucl. Instrum. Methods Phys. Res A 859, 63 (2017)

  • Re-accelerated $\mathrm{^{93}Sr}$ beam from CARIBU.
  • Close to 100% efficiency.
  • Measure a large range of excitation functions of angle and energy integrated cross sections using single beam energy
Proposal #1923, PI: Psaltis, co-PI: Ong

What we expect in the near future

More observations of metal-poor stars and measurements on the key $(\alpha, xn)$ reactions will help us constrain the production site of the elements between Sr and Ag.

Acknowledgements

Almudena Arcones   Melina Avila   Camilla Juul Hansen   Max Jacobi   Zach Meisel   Peter Mohr   Fernando Montes   Wei Jia Ong   Hendrik Schatz

Take-home messages

  1. Elements between Sr and Ag can be produced
    in neutrino-driven outflows via the weak $r$-process.

  2. We combined observations, astrophysical modeling and nuclear theory
    to study the impact of $(\alpha,xn)$ reactions to the weak $r$-process.

  3. Future $(\alpha,xn)$ experiments using rare isotope beams (RIBs)
    will shed light on the production of elements between Sr and Ag.

Backup slides

The importance of the $(\alpha, n)$ reactions

$\mathrm{Timescale}: \frac{1}{\langle{\tau_x}\rangle} = \frac{\sum_{Z,A} \lambda_x(Z,A) Y(Z,A)}{\sum_{Z,A} Y(Z,A)}$

A. Arcones and G. Martinez-Pinedo, Phys. Rev. C 83, 045809 (2011) • J. Bliss et al., J. Phys. G 44, 054003 (2017)

Most of the rare isotope beams are accessible now!

FRIB PAC2 expected beam rates

Finding the most important $(\alpha,n)$ reactions
for the weak $r$-process