A measurement of the equation of state of carbon envelopes of white dwarfs
Andrea Kritcher,Damian Swift,Tilo Döppner,Benjamin Bachmann,Lorin X. Benedict,Gilbert Collins,Jonathan L. DuBois,Fred Elsner,Gilles Fontaine,Jim Gaffney,Sebastien Hamel,Amy Lazicki,W. R. Johnson,Natalie Kostinski,Dominik Kraus,Dominik Kraus,Michael MacDonald,Brian Maddox,M. Martin,Paul Neumayer,A. Nikroo,Joseph Nilsen,Bruce Remington,Didier Saumon,P. A. Sterne,Wendi Sweet,Alfredo A. Correa,Heather D. Whitley,Roger Falcone,Siegfried Glenzer +29 more
TLDR
Researchers have measured the equation of state of hydrocarbon in a high-density regime, which is necessary for accurate modelling of the oscillations of white dwarf stars and predicts an increase in compressibility due to ionization of the inner-core orbitals of carbon.Abstract:
White dwarfs represent the final state of evolution for most stars1–3. Certain classes of white dwarfs pulsate4,5, leading to observable brightness variations, and analysis of these variations with theoretical stellar models probes their internal structure. Modelling of these pulsating stars provides stringent tests of white dwarf models and a detailed picture of the outcome of the late stages of stellar evolution6. However, the high-energy-density states that exist in white dwarfs are extremely difficult to reach and to measure in the laboratory, so theoretical predictions are largely untested at these conditions. Here we report measurements of the relationship between pressure and density along the principal shock Hugoniot (equations describing the state of the sample material before and after the passage of the shock derived from conservation laws) of hydrocarbon to within five per cent. The observed maximum compressibility is consistent with theoretical models that include detailed electronic structure. This is relevant for the equation of state of matter at pressures ranging from 100 million to 450 million atmospheres, where the understanding of white dwarf physics is sensitive to the equation of state and where models differ considerably. The measurements test these equation-of-state relations that are used in the modelling of white dwarfs and inertial confinement fusion experiments7,8, and we predict an increase in compressibility due to ionization of the inner-core orbitals of carbon. We also find that a detailed treatment of the electronic structure and the electron degeneracy pressure is required to capture the measured shape of the pressure–density evolution for hydrocarbon before peak compression. Our results illuminate the equation of state of the white dwarf envelope (the region surrounding the stellar core that contains partially ionized and partially degenerate non-ideal plasmas), which is a weak link in the constitutive physics informing the structure and evolution of white dwarf stars9. Researchers have measured the equation of state of hydrocarbon in a high-density regime, which is necessary for accurate modelling of the oscillations of white dwarf stars.read more
Citations
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Advances in NLTE Modeling for Integrated Simulations
TL;DR: In this paper, a simple screened-hydrogenic model was proposed to calculate ionization balance with surprising accuracy, at a low enough computational cost for routine use in radiation-hydrodynamics codes.
Journal ArticleDOI
First-principles equation of state database for warm dense matter computation.
Burkhard Militzer,Felipe González-Cataldo,Shuai Zhang,Shuai Zhang,Shuai Zhang,Kevin P. Driver,Kevin P. Driver,François Soubiran +7 more
TL;DR: A first-principles equation of state (FPEOS) database for matter at extreme conditions is put together by combining results from path integral Monte Carlo and density functional molecular dynamics simulations of the elements H, He, B, C, N, O, Ne, Na, Mg, Al, and Si.
Journal ArticleDOI
Accurate temperature diagnostics for matter under extreme conditions
Tobias Dornheim,Maximilian Böhme,Dominik Kraus,Tilo Döppner,T. R. Preston,Zh. A. Moldabekov,Jan Vorberger +6 more
TL;DR: In this paper , a simple approximation-free method was proposed to extract the temperature of arbitrarily complex materials in thermal equilibrium from X-ray Thomson scattering experiments, without the need for any simulations or an explicit deconvolution.
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An approach for the measurement of the bulk temperature of single crystal diamond using an X-ray free electron laser.
Adrien Descamps,Adrien Descamps,Benjamin K. Ofori-Okai,Karen Appel,Valerio Cerantola,Andrew Comley,Jon Eggert,Luke Fletcher,Dirk O. Gericke,Sebastian Göde,Oliver Humphries,O. Karnbach,Amy Lazicki,R. Loetzsch,R. Loetzsch,David McGonegle,David McGonegle,Charlotte Palmer,C. Plueckthun,T. R. Preston,Ronald Redmer,Debbie G. Senesky,C. Strohm,Ingo Uschmann,Ingo Uschmann,Thomas G. White,Lennart Wollenweber,Giulio Monaco,Justin Wark,Jerome B. Hastings,Ulf Zastrau,Gianluca Gregori,Siegfried Glenzer,Emma McBride +33 more
TL;DR: This technique could be used to determine the bulk temperature in transient systems with a temporal resolution of 50 fs and for which accurate measurements of thermodynamic properties are vital to build accurate equation of state and transport models.
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Electronic density response of warm dense matter
Tobias Dornheim,Zh. A. Moldabekov,Kushal Ramakrishna,Panagiotis Tolias,Andrew Baczewski,Dominik Kraus,T. R. Preston,David F. Chapman,Maximilian Böhme,Tilo Döppner,Frank Graziani,Michael Bonitz,Attila Cangi,Jan Vorberger +13 more
TL;DR: In this paper , the authors summarize the relevant theoretical background, covering the regime of linear response theory and nonlinear effects, the fully dynamic response and its static, time-independent limit, and the connection between density response properties and imaginary-time correlation functions (ITCF).
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