Erika Holmbeck

Hubble Postdoctoral Fellow

Observatories
email: 
eholmbeck@carnegiescience.edu
Telephone: 
6263040253


In a nutshell, I study some of the oldest stars in the Milky Way with high-resolution spectroscopy to obtain their chemical abundance signatures. Then, I run nucleosynthesis network simulations and compare their theoretical elemental yields with observations to place constraints on astrophysical events and nuclear data.

The r-process
The abundance of roughly half of the elements heavier than iron in the Solar System attribute their production to the rapid neutron-capture ("r-") process. Although first identified as an astrophysical production mechanism of the elements over sixty years ago, it wasn't until recently that a host site for the r-process was idenfied observationally: neutron star mergers. With one confirmed astrophysical environment for the r-process identified, many questions still remain: Do mergers account for the majority of r-process production over the history of the Galaxy? What is the extent of their elemental production?  Can mergers occur in dwarf galaxies and explain the observed r-process enrichment of some galaxies?

Kilonovae and metal-poor stars
With the rise of multi-messenger astronomy---reinvigorated by the same neutron-star merger detection in 2017---models of r-process production in merger sites can be put to the test by comparing modeled light curves with those associated with mergers. However, only one such merger-associated light curve exists. Not all hope is lost; another, less transient r-process observable exists: the chemical records of metal-poor stars. An r-process event occuring in the ancient history of the Galaxy would enrich its surrounding environment with a signature of its elemental production. Subsequent stars formed from that gas would show this signature in their photospheres. Nearly 100 metal-poor (low-iron) stars with imprints of the r-process have been found, notably through dedicated obsevational efforts by the R-Process Alliance (RPA), of which I am a Core member. These data are one of the primary observables for r-process studies, and questions surrounding the elemental production, extent, event rates, gas mixing, etc. of r-process sites must agree with observations of metal-poor stars.

Observation and theory
I use the observations of metal-poor stars to probe specific conditions of r-process sites, exploring how physical differences in the r-process environments manifest into unique elemental signatures.

Education: 


Ph.D. Physics, University of Notre Dame (2020)
M.S. Physics, University of Notre Dame (2019)
B.S. Astrophysics, University of California, Los Angeles (2014)

Interests: 
Nuclear Astrophysics, Galactic Archaeology, Stellar Spectroscopy, Compact Object Mergers