Goddard Space Flight Center E.R. Christian, G.A. de Nolfo, T.T. von - PowerPoint PPT Presentation

Elemental Composition Measurements W.R. Binns, M.H. Israel Washington University M.E. Wiedenbeck Jet Propulsion Laboratory A.C. Cummings, R.A. Leske, R.A. Mewaldt, E.C. Stone Caltech Goddard Space Flight Center E.R. Christian, G.A. de Nolfo, T.T. von Rosenvinge

es multiple dE/dx and total energy method determine charge, mass, and energy

ACE-CRIS Elements – 18.5 Years of Data zrms<0.5 Ni theta<45 • Data collected rng3-8:rpproj 25-5850 over period fro rng2: rpproj 25-2550 12/4/1997-5/24/ • Excellent Cu resolution in Zn charge for UH nuclei Ga Ge • Limited statis Se the highest Z Rb Sr Kr Y As Br Zr 28 29 30 31 32 33 34 35 36 37 38 39 40 41 Charge (Z)

Comparison with SuperTIGER Zn zrms<0.5 theta<45 rng3-8:rpproj 25-5850 rng2: rpproj 25-2550 Ga Ge Se Kr Rb Sr Y Br As Zr 30 31 32 33 34 35 36 37 38 39 40 41 Charge (Z) ACE resolution in charge shows complete separation of elements SuperTIGER has greater statistics, with still good resolution Number of nuclei with Z>30. ACE=280; SuperTIGER=1159 The two data sets are very complimentary to each other

Source Abundances • We see that there is generally agreement, but ACE appears t systematically a bit lower for Z=3 ACE GCRS and a bit higher for Z=37-40. SuperTIGER GCRS • The reason for this is not know xxDifferences in the data sets are • ACE measurements are in sp SuperTIGER measured at b altitudes • ACE data at ~150–700 MeV/ SuperTIGER starts at >800 MeV/nuc above the atmosph zzand extends to ~10 GeV/nuc • ACE data is averaged over years of solar modulation. Su 30 31 32 33 34 35 36 37 38 39 40 Charge (Z) TIGER data taken at a speci s\8_25_2016_Rng2-8\Final_Corrections\Plots modulation level (in early 20

GCRS/SS abundances vs mass • As we have see 100% Normal ISM with SuperTIGER Zr refractories and Ni Rb Ca volatiles are mi Refractories Fe at high atomic ma Mg Co Sr when source Cu Ga Si abundances are Zn taken relative to Se Ge Solar System Ne abundances (ISM) S N Volatiles and there is a l scatter 10 10 20 20 30 30 40 40 50 50 60 60 70 70 80 90 100 80 90 100 Mass (amu) Mass (amu) Meyer Drury & Ellison (1997) proposed that the refractories are over-abundant

Least chi-squared fit to data mparison of GCR source 6% MSM + 94% ISM dances with a mixture % SS and 6% Massive outflow + ejecta sley & Heger, ApJ Co GCRS/Mix Fraction GCRS/Mix Fraction Fe ). Ca Refractories 1 1 Mg Ni ring and separation of ctories and volatiles is Si Ga ly improved. Cu Zn re is an enhancement of ctories over volatiles by Ge S ctor of ~3-5 over the full N Ne of masses Volatiles 0.1 0.1 10 10 20 20 30 30 40 40 50 50 60 60 70 70 Mass (amu) Mass (amu)

Chi-squared Reduced Chi-squared 3.0 2.8 Volatiles 2.6 Refractories 2.4 2.2 Reduced Chi-squared 2.0 1.8 1.6 1.4 Volatiles 1.2 Refractories 1.0 Combined 0.8 0.6 0.4 Best fit=6 +6 -2.5 % 0.2 0.0 0.0 0.1 0.2 0.3 0.4 0.0 0.1 0.2 0.3 0.4 0.5 Mix fraction Mix fraction \ACE\UH elements & Isotopes\8_25_2016_Rng2-8\Final_Corrections\5.3.2017-Verified_correct_data\Chi-squared_plots5.5.2017 Best fit corresponds to 6 +6 -2.5 % massive star material mixed with 94% of normal ISM This compares with SuperTIGER best fit of 19 +11 -6 % massive star material mixed with 81% rmal ISM fferences between the two data sets were noted earlier The ACE data are inconsistent with zero massive star material at the 11.4 σ level.

SuperTIGER data Best fit is 19% MSM +81% SS Semi-log-Log plot Log-Log plot with Helium added

Conclusions • The ordering of the element source abundances is substantially improved if they are taken relative to a mix of massive star material (wind outflow and SN ejecta) plus normal ISM instead of just normal ISM (SS abundances). • ACE data show that a mix of 6 +6 -2.5 % massive star material with ~94% of normal ISM gives a best fit to the source abundances. The data are inconsistent with 0% massive star material at the 11.4 σ level . • The data show an enhancement of refractory elements over volatiles by a factor of ~4 as was seen by TIGER & SuperTIGER and a mass dependence of the abundances for both refractory and volatile elements. • This is consistent with an origin in associations of massive stars (OB associations).

Backups

Measured and Source Abundance per panel Error bars included in both measured and source abundances Source data points substantially lower than measured data indicates large secondary component er panel Elements having “Source/1AU” near 1 are mostly “primary” nuclei Ratios larger than 1 result from inaccuracies in nuclear interaction cross-sections and from approximations in models for interstellar propagation and solar modulation used Normalized to Fe=1.0

ACE data assuming an 20-80% mix Comparison of GCR ource abundances with 20% MSM + 80% ISM ixture of 80% SS nd 20% Massive Star flow + ejecta GCRS/Mix Fraction GCRS/Mix Fraction Fe oosley & Heger, ApJ Co Ca 1 1 2007). Ni Mg Refractories erestingly the slopes he refractory and Si Zn Ga atile elements for this 20 mix are nearly the e as they are in the Cu uperTIGER data N Ge S 0.1 0.1 Volatiles Ne 10 10 20 20 30 30 40 40 50 50 60 60 70 70 Mass (amu) Mass (amu)

Abundances “in-space” • We see that there is gene good agreement, but ACE ACE-In Space SuperTIGER-TOA appears to be systematica bit lower for Z=30-33 and higher for Z=37-40. • The reason for this is not known. Differences in the data sets are: • ACE measurement is in space, SuperTIGER is measured at bal altitudes • ACE measurements are at energ several hundred MeV/nuc; Supe measures elements with energy 30 31 32 33 34 35 36 37 38 39 40 Charge (Z) MeV/nuc, but most are >1 GeV/nuc • ACE data is averaged over 18.5 & Isotopes\8_25_2016_Rng2-8\Final_Corrections\Plots solar modulation. ST data taken specific solar modulation level.