Opacity

Huebner, W. F.; Barfield, W. David

doi:10.1007/978-1-4614-8797-5

Cited by 27 publications

(22 citation statements)

References 894 publications

(1,420 reference statements)

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“…The b-b contribution was calculated via the linebinned expression in Equation (2). The f-f and scattering contributions were obtained from the simple, analytic formulas (Huebner & Barfield 2014) associated with Thomson and Kramers, respectively. The gap between the b-b features and the onset of the b-f edge occurring at ∼ 20 eV is due to missing lines that would be present if more excited configurations had been included in the model.…”

Section: Sample Opacities and Tablesmentioning

confidence: 99%

A line-binned treatment of opacities for the spectra and light curves from neutron star mergers

Fontes

Fryer

Hungerford

et al. 2020

Monthly Notices of the Royal Astronomical Society

126

108

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The electromagnetic observations of GW170817 were able to dramatically increase our understanding of neutron star mergers beyond what we learned from gravitational waves alone. These observations provided insight on all aspects of the merger from the nature of the gamma-ray burst to the characteristics of the ejected material. The ejecta of neutron star mergers are expected to produce such electromagnetic transients, called kilonovae or macronovae. Characteristics of the ejecta include large velocity gradients, relative to supernovae, and the presence of heavy r-process elements, which pose significant challenges to the accurate calculation of radiative opacities and radiation transport. For example, these opacities include a dense forest of bound-bound features arising from near-neutral lanthanide and actinide elements. Here we investigate the use of fine-structure, line-binned opacities that preserve the integral of the opacity over frequency. Advantages of this area-preserving approach over the traditional expansion-opacity formalism include the ability to pre-calculate opacity tables that are independent of the type of hydrodynamic expansion and that eliminate the computational expense of calculating opacities within radiation-transport simulations. Tabular opacities are generated for all 14 lanthanides as well as a representative actinide element, uranium. We demonstrate that spectral simulations produced with the line-binned opacities agree well with results produced with the more accurate continuous Monte Carlo Sobolev approach, as well as with the commonly used expansion-opacity formalism. Additional investigations illustrate the convergence of opacity with respect to the number of included lines, and elucidate sensitivities to different atomic physics approximations, such as fully and semi-relativistic approaches.

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Section: Sample Opacities and Tablesmentioning

confidence: 99%

A line-binned treatment of opacities for the spectra and light curves from neutron star mergers

Fontes

Fryer

Hungerford

et al. 2020

Monthly Notices of the Royal Astronomical Society

126

108

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“…For a more general discussion, see section 82 of Mihalas & Mihalas (1984), section 2.3 of Huebner & Barfield (2014), page 38 in Sturrock et al (1986), page 174 in Castor (2004), or section 15.2 in Modest (2013). The Planck or emission mean is…”

Section: B3 Mean Opacitiesmentioning

confidence: 99%

Double Compton and Cyclo-Synchrotron in Super-Eddington Discs, Magnetized Coronae, and Jets

McKinney

Chluba

Wielgus

et al. 2017

Mon. Not. R. Astron. Soc.

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We present an extension to the general relativistic radiation magnetohydrodynamic code HARMRAD to account for emission and absorption by thermal cyclo-synchrotron, double Compton, bremsstrahlung, low-temperature OPAL opacities as well as Thomson and Compton scattering. We approximate the radiation field as a Bose-Einstein distribution and evolve it using the radiation number-energy-momentum conservation equations in order to track photon hardening. We perform various simulations to study how these extensions affect the radiative properties of magnetically-arrested disks accreting at Eddington to super-Eddington rates. We find that double Compton dominates bremsstrahlung in the disk within a radius of r ∼ 15r g (gravitational radii) at a hundred times the Eddington accretion rate, and within smaller radii at lower accretion rates. Double Compton and cyclo-synchrotron regulate radiation and gas temperatures in the corona, while cyclo-synchrotron regulates temperatures in the jet. Interestingly, as the accretion rate drops to Eddington, an optically thin corona develops whose gas temperature of T ∼ 10 9 K is ∼ 100 times higher than the disk's black body temperature. Our results show the importance of double Compton and synchrotron in super-Eddington disks, magnetized coronae, and jets.

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“…The ATOMIC code was then used to process these fundamental data to calculate the level populations and a monochromatic opacity. The scattering and freeefree contributions to the opacity were obtained from the simple, analytic formulas [27] associated with Thomson and Kramers, respectively.…”

Section: Samariummentioning

confidence: 99%

Relativistic opacities for astrophysical applications

Fontes

Fryer

Hungerford

et al. 2015

High Energy Density Physics

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a b s t r a c tWe report on the use of the Los Alamos suite of relativistic atomic physics codes to generate radiative opacities for the modeling of astrophysically relevant plasmas under local thermodynamic equilibrium (LTE) conditions. The atomic structure calculations are carried out in fine-structure detail, including full configuration interaction. Three example applications are considered: iron opacities at conditions relevant to the base of the solar convection zone, nickel opacities for the modeling of stellar envelopes, and samarium opacities for the modeling of light curves produced by neutron star mergers. In the first two examples, comparisons are made between opacities that are generated with the fully and semirelativistic capabilities in the Los Alamos suite of codes. As expected for these highly charged, ironpeak ions, the two methods produce reasonably similar results, providing confidence that the numerical methods have been correctly implemented. However, discrepancies greater than 10% are observed for nickel and investigated in detail. In the final application, the relativistic capability is used in a preliminary investigation of the complicated absorption spectrum associated with cold lanthanide elements.

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Opacity

Cited by 27 publications

References 894 publications

A line-binned treatment of opacities for the spectra and light curves from neutron star mergers

A line-binned treatment of opacities for the spectra and light curves from neutron star mergers

Double Compton and Cyclo-Synchrotron in Super-Eddington Discs, Magnetized Coronae, and Jets

Relativistic opacities for astrophysical applications

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