Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session C3: Invited Session: Neutron Stars and Laboratories for Neutrino, Nuclear and Gravitational Physics |
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Sponsoring Units: GGR DNP Chair: Zach Etienne, West Virginia University Room: Holiday 2 |
Saturday, April 11, 2015 1:30PM - 2:06PM |
C3.00001: Measuring the neutron-star equation of state from gravitational-wave observations of coalescing compact binaries Invited Speaker: Benjamin Lackey Gravitational-wave observations of inspiralling binary neutron star (BNS) and black hole--neutron star (BHNS) systems can be used to measure the unknown neutron-star equation of state (EOS). The most reliable information is likely to come from tidal interactions that increase the rate of inspiral and lead to a phase shift in the waveform. The strength of tidal interactions is parameterized by the tidal deformability $\Lambda$ which is a function of the EOS and NS mass. The magnitude of the effect strongly depends on the mass ratio, so BNS systems, with nearly equal NS masses, are expected to provide the dominant source of information during the inspiral. Recent work has shown that when second generation detectors, now being commissioned, reach design sensitivity, they will be able to measure $\Lambda$ with statistical errors of $\mathcal{O}$(50\%). Furthermore, stacking observations from several BNS inspiral events dramatically decreases the statistical errors, and, for realistic event rates, it may possible to measure the NS tidal deformability to $\mathcal{O}$(10\%) from a year of observations. These tidal deformability measurements can also be combined with other constraints such as causality and high-mass observations to directly measure the EOS with statistical errors in the pressure of less than a factor of two. Current uncertainties in the post-Newtonian waveform model, however, lead to systematic errors in the EOS measurement that are as large as the statistical errors, and more accurate waveform models are needed to minimize this error. The merger dynamics of BNS and BHNS systems depend more strongly on the EOS than for the inspiral dynamics, and can potentially provide additional EOS information. However, the merger occurs at higher frequencies where gravitational-wave detectors are less sensitive. For BHNS systems, we found, using a large set of numerical simulations, that $\Lambda$ is also the best measured parameter during the merger and ringdown. With these simulations, we calibrated a phenomenological inspiral-merger-ringdown waveform model and found that matter effects can only be detected by second generation detectors for nearby systems with small BH masses and large BH spins. Third generation detectors such as the proposed Einstein Telescope, however, may be able to measure matter effects for more realistic BHNS systems. For BNS mergers, significant effort has gone into improving the accuracy of numerical simulations and understanding how the waveform depends on the EOS, but comparatively few works have examined the measurability of the EOS with gravitational-wave detectors. I will briefly review recent progress, and discuss future data-analysis work needed to reliably extract EOS information from the merger of BNS systems. [Preview Abstract] |
Saturday, April 11, 2015 2:06PM - 2:42PM |
C3.00002: Microphysical Aspects of Supernova and Compact Object Merger Modeling Invited Speaker: Evan O'Connor This talk will review the microphysics components essential to the modeling of compact object mergers (binary neutron stars and neutron star-black holes) as well as the birth place of neutron stars, core-collapse supernovae. I will begin with core-collapse supernovae. For these systems, the microphysics modeling has arguably matured to a level where basic consequences of the microphysics such as the baseline neutrino signal and black hole formation properties of failed supernovae are accurately reproducible by independent modelers. However, there are still many areas of core-collapse supernova modeling that are less established. This is especially true in multidimensional simulations, which are accompanied by many fluid instabilities. There is still not consensus between modelers on the explosion outcome (i.e. success or failure) of core collapse, and in cases where there is agreement on the outcome, the explosion properties (e.g. energy, explosion time, ...) are often disparate. I will briefly review the current status of state-of-the-art, multidimensional, computational models of core-collapse supernovae. For binary neutron star and neutron-star black hole mergers on the other hand, only recently are there simulations that use full general relativity and incorporate neutrino and nuclear microphysics in earnest. This has lead to higher fidelity predictions of the ejected material and its composition, the accretion disk formation and early evolution, and the gravitational wave signal and its dependence on the nuclear equation of state, and the neutrino signal. I will also review these microphysical aspects. [Preview Abstract] |
Saturday, April 11, 2015 2:42PM - 3:18PM |
C3.00003: Nuclear Physics of neutron stars Invited Speaker: Jorge Piekarewicz One of the overarching questions posed by the recent community report entitled ``Nuclear Physics: Exploring the Heart of Matter'' asks \emph{How Does Subatomic Matter Organize Itself and What Phenomena Emerge?} With their enormous dynamic range in both density and neutron-proton asymmetry, neutron stars provide ideal laboratories to answer this critical challenge. Indeed, a neutron star is a gold mine for the study of physical phenomena that cut across a variety of disciplines, from particle physics to general relativity. In this presentation---\emph{targeted at non-experts}---I will focus on the essential role that nuclear physics plays in constraining the dynamics, structure, and composition of neutron stars. In particular, I will discuss some of the many exotic states of matter that are speculated to exist in a neutron star and the impact of nuclear-physics experiments on elucidating their fascinating nature. [Preview Abstract] |
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