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

Erika M. Holmbeck

17 April 2019

Elements in the Universe


from data in Sneden+ (2008)

Neutron capture


Site of the r-process?

Core-collapse supernovae

MHD-jet supernovae


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


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


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)