Andrew W. Steiner

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

The neutron star working group site for the town meeting is here.

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.

Aug 2014: How Superfluidity Affects Magnetar Flare Oscillations


In work led by Alex Deibel and in collaboration with Ed Brown (both at Michigan State), we show that superfluid entrainment resolves the standing issue of observed magnetar QPO frequencies predicting anomalously small values of the nuclear symmetry energy. Our work is now published in Physical Review C and available on the arXiv.

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.


A plot of my citation indices
	       over the past 13 years


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

See also my CV.

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

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

Mass and radius constraints from the five QLMXBs
		    for the Dickey et al. (1990) N_H values and
		    H or He atmospheres


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.

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

The cover of EPJA, 
	       volume 50 number 2


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

A plot of the nuclides
		 showing the new cooling process from Schatz et al.


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

A picture of the globular cluster 47 Tucanae  

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

The M-R curves for several EOS tables from
		      Steiner, Hempel, and Fischer (2013)  

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.

More information

May 2012: Nuclear reactions in the inner neutron star crust

The properties of the accreted crust
		 from Steiner (2012)  

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.

More information

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

Constraints on beta, b, and L from Steiner and
		      Gandolfi (2012)  

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.

More information