Actinide-Boost Stars Might Not
Suggest a Separate r-Process Site


Erika M. Holmbeck


17 April 2019

Elements in the Universe

processes

from data in Sneden+ (2008)

Neutron capture

processes

Site of the r-process?


Core-collapse supernovae

MHD-jet supernovae

Collapsars

Neutron-star mergers

???

r-process enhanced stars

from data in McWilliam+ (1995), Sneden+ (2003)

Reticulum II


Ji+ (2016)

A. Ji; Dark Energy Survey/Fermilab

Actinide variation among r-process enhanced stars

Holmbeck+ (2019); arXiv:1904.02139

Are stars boosted with actinides
made by a different source?


Can one site produce
the actinide variations?

Empirically characterize r-process events


Monte Carlo method to produce distributions as a function of Ye


Empirical ejecta mass distributions

Ye

Holmbeck+ (2019); arXiv:1904.02139

Actinide-boost stars do not call for
a separate r-process progenitor


Is this source an NSM?

NSM lightcurve


Lanthanide-poor blue ejecta + Lanthanide-rich red ejecta

Cowperthwaite+ (2017)

Two ejecta components

Two ejecta components

Ye

Results derived from r-enhanced stars
agree* with an NSM observation


Further evidence that an NSM produced
the material in r-enhanced stars like Ret II

Special Thanks


Rebecca Surman (ND), Gail C. McLaughlin (NC State), Anna Frebel (MIT)
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)