Presented by Hendrik Schatz Michigan State University 2016 Submitted Presented by Hendrik Schatz Michigan State University National Superconducting Cyclotron Laboratory Joint Institute for Nuclear Astrophysics – CEE

Accreting Neutron Stars as Dense Matter Laboratories Rare Isotope Facilities Observe the same nuclei found inside neutron stars X-ray Observatories Observe thermal emission and bursts Chandra, XMM Newton NICER Mass Accretion Probe response of neutron star to mass accretion (varies!) Neutron Star - Thermonuclear explosions on the surface (bursts) - Cooling in transients FRIB, NSCL, FAIR, …

Burst lightcurve observable affected by nuclear physics Cyburt et al. 2016 Extract astrophysical parameters from model – observation comparison with accurate nuclear physics Accreted composition Neutron star surface temperature Neutron star mass, radius, compactness Peak luminosity (distance) Composition of the neutron star crust Remove nuclear uncertainties to learn about astrophysical unknowns

Burst ashes relates to observables and is affected by nuclear physics GRS 1741.9-2853 Possible Cr spectral feature in X-ray burst (Barriere et al. 2014)  Need nuclear physics to predict expected features and ejected composition Predicted crustal heating and cooling rate depending on the mass number of the burst ashes (Schatz et al. 2014)  Need nuclear physics to predict burst ashes and crustal heating/cooling NUSTAR Observatory

Burst nuclear physics depends strongly on burst system H/He-bursts: High accretion rate Accrete H/He He-bursts: Low accretion rate Accrete He This is good (sensitivity to astrophysics!) Must provide nuclear physics for all types of bursts

Proposal for Progress ✔ Goals: Translate rp-process nuclear physics work into an advance in X-ray burst science Create validation path for burst models Define 3 “standard” burst sources: GS 1826­‐24, 4U 1820-30, SAX J1808.4-3658 Sensitivity Study GS 1826­‐24 (H/He) Sensitivity Study 4U 1820-30 (He accretor) Sensitivity Study SAX J1808.4-3658 (Low accretion rate He) ✔ (This Talk) New Data Base by Summer 2018 As much experimental data as possible As much theoretical data as possible Evaluation effort Joint publication of all that contributed This workshop Benchmark of various group’s models Extract system parameters from observations Use as starting point to investigate other systems, time dependent accretion etc

Sensitivity Study Approach Study sensitivity of KEPLER model (Woosley, Heger, Keek, et al.) to reaction rates (not decays or masses) for typical mixed H/He burst Accreted solar composition Accretion: 1.75E-9 solar masses/year (about 10% Eddington) 1-zone model to ID potentially important rates Choose ignition conditions from 1D-KEPLER model Vary all 1931 rates (+ their inverse) by a factor of 100 up and down Select 84 top impacts on light curve and composition 1D KEPLER model Vary top reactions in KEPLER by a factor that is conservatively adapted to the possible uncertainty of the rate Identify rates that significantly impact light curve or composition

1-Zone Model Approximation Peak temperature: 1.2GK agrees

Sensitivity to Reaction Rates ap process (a,p) rates vs p-capture 1-Zone Light Curve Impact CNO Breakout 14O(a,p), 15O(a,g), 18Ne(a,p) Cycles and Major Waiting Points (p,a) rates vs p-capture; p-capture on WP+p

KEPLER

KEPLER: Light Curve Impact Use Average Light Curve

15O(a,g) Impact Fisker et al. 2006  Different result Decreased 15O(a,g) triggers burst later  Increased recurrence time  more He rich bursts Decreased 15O(a,g) increases CNO  more 3-alpha/HCNO runaway  decreased recurrence time  more He rich bursts

KEPLER: Light Curve Impact  Limited Set of Rates !

Comparison with Other Studies Parikh et al. 2008: Different bursts Postprocessing This work Conclusions: Some reactions are of general importance Sensitivity studies are model dependent and postprocessing has limitations Important result from Parikh et al.: From Monte Carlo study: Correlations have minor impact on rate selection In both studies Also in Parikh et al. for composition

KEPLER: Definition of final composition

Composition Impacts: Global

Composition Impacts: Local

X-ray Burst Sensitivity to Nuclear Reactions Sensitivity through 1-by-1 variation Varied 1931 rates in single zone model  ID 84 key rates Varied 84 rates in full 1D Model - sequence of ~12 bursts - variation inspired by possible uncertainty Composition Impact Lightcurve Impact No significant impact (Impact limited to single zone model) Never had the ressources for this without JINA-CEE – its truly intersectional work that would fall through the cracks Significant impact Identified reaction uncertainties that may affect: Light curve (19 reactions) Composition (47 reactions) Cyburt et al. 2016

Next Steps Sensitivity study for He accretor, and He bursts for mixed H/He accretor Expand mixed H/He burst analysis to all reactions Coordinated experimental and theoretical effort to address nuclear uncertainties as much as possible by summer 2018? Joint paper (in addition to individual papers) for all contributions before cutoff date Coordinated evaluation? Theory – Experiment needs coordination