## Andrew W. Steiner

Research Assistant Professor at the Institute for Nuclear Theory at the University of Washington

## Research summary

On Jan. 1, 2015, I will be starting a joint position at the Univ. of Tennessee, Knoxville (Asst. Prof.) and Oak Ridge National Laboratory.

My research demonstrates that neutron star observations can be used to understand how neutrons and protons interact. Also, I have shown that nuclear physics is critical for describing neutron star observations and many astrophysical processes including core-collapse supernovae, X-ray bursts and giant flares in magnetars. Recently, I determined how neutron star radius observations improve our knowledge of nuclear three-body forces, the neutron skin thickness of lead, and the nuclear symmetry energy.

Five of my papers are listed in the top 100 articles cited by nucl-th preprints in 2013 (#13, #29, #33, #35, and #64). My 2005 review appeared as #13 on this list.

## July 2014: Going Beyond $\chi^2$ in Nuclei and Neutron Stars

In a new article, at arXiv:1407.0100, I describe how Bayesian analysis has been used to analyze neutron star observations and why the best fit and a covariance matrix is not enough to describe the likelihood. This leads to a proposal on improving fits to low-energy nuclear data and a method for modern constraints on the nuclear symmetry energy.

## Apr. 2014: Predicting Neutron Star Tidal Deformabilities and Moments of Inertia

In a collaboration with Stefano Gandolfi, Farrukh Fattoyev, and William Newton, we predicted neutron star tidal deformabilities and neutron star moments of inertia using

• up-to-date nuclear physics near the saturation density, and
• recent neutron star mass and radius measurements.
We found that neutron star tidal deformabilities are less than $3 \times 10^{36}~\mathrm{g}~\mathrm{cm}^2~\mathrm{s}^2$ to 95% confidence. Also, the fraction of the neutron star's moment of inertia contained in the crust can be as much as 10-11% of the total, depending on one's current interpretation of the mass and radius data. Our work is now posted at arXiv:1403.7546.

## Mar. 2014: Systematic Uncertainties in Masses and Radii from QLMXBs

My analysis (with Jim Lattimer) of distance and X-ray absorption uncertainties in quiescent low-mass X-ray binaries (QLMXBs) is now published in Ap. J 784 (2014) 123 (also at arXiv:1305.3242). We show how mass and radius constraints from QLMXBs can be reconciled with what we know about neutron star crusts from nuclear physics experiments. We also identify X-ray abosrption as the key systematic uncertainty for connecting observations to neutron star structure.

## Publications

My publications are listed at Inspirehep.net, ADS (all), ADS (refereed papers only), and Google scholar.

## Recent talks

My invited talk at the April 2014 APS meeting.

My talk at KIPAC@10 last September:

(If the video is too grainy, just click on the youtube button to watch the video on youtube.com)

## Feb. 2014: Our invited review article is on the front cover

Our review on the nuclear symmetry energy is featured on the front cover of the European Physical Journal A. See the contents of the full issue or just the article itself. I was also happy to be involved in a separate and also excellent invited review in the same issue led by Stefano Gandolfi.

## Dec. 2013: Discovery of a new cooling process in accreting neutron stars

See our work as published in Nature, the arXiv version, a summary for non-specialists, an article on the Chandra website, the press releases at Los Alamos and MSU Today, the article at Ars Technica, or the Astronomy magazine article.

## Mar. 2013: Probing extreme matter through observations of neutron stars

We present our new constraints on the neutron star mass-radius curve and the equation of state (EOS) of dense matter which shows that almost all neutron stars in the universe mostly likely have radii between 10 and 13 km. Our work was featured on the Chandra website, and described at Astronomy magazine. A more technical summary and the associated EOS table are also available.

## Jul. 2012: New equation of state tables for core-collapse supernovae released

In collaboration with Matthias Hempel and Tobias Fischer, we release two new supernova equation of state tables, SFHo and SFHx, which are more consistent with modern nuclear experiments and neutron star mass and radius observations.

## May 2012: Nuclear reactions in the inner neutron star crust

I show that the nuclear symmetry energy can modify the amount of deep crustal heating in an accreting neutron star by a factor of two.

## Feb. 2012: Nuclear symmetry energy and three-body forces in Phys. Rev. Lett.

In my new article with Stefano Gandolfi in Physical Review Letters, we show that neutron star mass and radius observations can constrain the three-neutron force and the density dependence of the symmetry energy.