Actinide-Rich or Actinide-Poor, Same r-Process Progenitor
Erika M. Holmbeck
16 October 2019 --- DNP 2019
Anna Frebel, Gail C. McLaughlin, Rebecca Surman,
Trevor M. Sprouse, Matthew Mumpower 2019, ApJ, 881, 5
The r-Process Pattern
Hotokezaka+ (2018)
The r-Process Pattern
Hotokezaka+ (2018)
Actinides in r-II Stars
Thorium in J2038-0023 and Uranium in J0954+5246
Placco, Holmbeck+ (2017), Holmbeck+ (2018)
Thorium in Metal-Poor Stars
The actinide-to-lanthanide ratio (Th/Eu) is not the same in all r-process enhanced stars
Holmbeck+ (2018)
Actinide Variation
Actinide variations could be a hint to key r-process characteristics
Holmbeck+ (2019b)
Actinide Production and Ye
The electron fraction, Ye, is a key parameter determining the extent of an r-process event
Ye = [1+(n/p)]-1 1 = all protons; 0 = all neutrons
Actinide Production and Ye
Only a narrow Ye range reproduces observations of Th and U
Holmbeck+ (2019a)
Actinide Production and Ye
Only a narrow Ye range reproduces observations of Th and U
Holmbeck+ (2019a)
Actinide Boost Stars
Abundances of stars enhanced with Th and U can be reproduced by a combination of Ye
Going backwards
What would the abundances themselves suggest for this ejecta distribution?
Actinide-Dilution with Matching Model
Builds empirical mass ejecta distributions as a function of Ye (0.005-0.450)
To explain entire pattern using Zr, Dy, and Th only
ADM
Empirical ejecta mass distributions
Distributions differ in very low-Ye region
Holmbeck+ (2019b)
Astrophysical Variations
Holmbeck+ (2019b)
Nuclear Physics Variations
Holmbeck+ (2019b)
The low-Ye component
No discrete difference between actinide-rich and actinide-poor
Holmbeck+ (2019b)
Nuclear and Astrophysical Variations
Holmbeck+ (2019b)
Actinide-boost stars do not necessarily call for a separate r-process progenitor
Special Thanks
Rebecca Surman (ND), Trevor M. Sprouse (ND), Matthew Mumpower (LANL)
Timothy C. Beers (ND), Nicole Vassh (ND), Terese T. Hansen (TAMU), Chris Sneden (UT-Austin)
Vinicius M. Placco (ND), Ian U. Roederer (UMich.), Charli M. Sakari (UW), Rana Ezzeddine (MIT)
Grant Mathews (ND), Ani Aprahamian (ND), Toshihiko Kawano (LANL)
GW170817 lightcurve
Lanthanide-poor blue ejecta + Lanthanide-rich red ejecta
Cowperthwaite+ (2017)
Two ejecta components
Stellar Abundances
Xlan = 10-3.8 Xlan = 10-0.8 mred / mblue = 1.7
Holmbeck+ (2019b)
GW170817
Xlan = 10-4 Xlan = 10-1.5 mred / mblue = 1.6
Kasen+ (2017)
Results derived from r-enhanced stars are consistent with the GW170817 kilonova
Further evidence supporting that an NSM produced the material in r-enhanced stars
Actinide-Rich or Actinide-Poor,Same r-Process Progenitor
Erika M. Holmbeck
16 October 2019 --- DNP 2019
Anna Frebel, Gail C. McLaughlin, Rebecca Surman,
Trevor M. Sprouse, Matthew Mumpower2019, ApJ, 881, 5
Good afternoon everyone, and thanks for being here. I am very excited to present work my collaborators and I recently published about actinides in the r-process.
