Relativistic opacities for astrophysical applications

Abstract

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.

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

“…For example, neutron-rich outflows from the NS merger form heavy elements via the r-process and undergo radioactive decay, resulting in a kilonova transient (Li & Paczyński 1998). In the absence of a long-lived magnetar, the signal is expected to peak in the near-IR band on ∼week timescales due to the large opacities of the heavy elements produced Kasen et al 2013;Tanaka & Hotokezaka 2013;Grossman et al 2014;Fontes et al 2015). In contrast, the large neutrino luminosity from a long-lived magnetar may inhibit the formation of very heavy elements, resulting in a bluer kilonova that peaks at optical wavelengths on ∼day timescales (Metzger & Fernández 2014;Kasen et al 2015).…”

Detailed Opacity Calculations for Astrophysical Applications

“…The ATOMIC-code [39,40] "full" calculations allow single-configuration fine-structure detail to be included in a relatively computationally inexpensive manner. They thus include intermediate coupling within a configuration but not complete interaction among the set of configurations.…”

“…Figure 7. Comparison between SCO-RCG and ATOMIC "full" (left) and "n5" (right) computations [39][40][41] of iron opacity at T = 23 eV and ρ = 2 mg/cm 3 . The ATOMIC calculations were kindly provided by J. Colgan.…”

“…The Rosseland means are rather close, although some differences exist around hν = 800 eV (maximum of the derivative of Planck's distribution with respect to temperature). [39,40] at the same conditions (right). The ATOMIC calculations were kindly provided by J. Colgan.…”

“…OP [42,43] 0.59 R-matrix [75,76] 0.51 ATOMIC [39,40] 0.60 OPAS [82][83][84] 0.70 SCO-RCG [17] 0.64 SCRAM [85] 0.77 TOPAZ [86,87] 0.62 Cold [72] 0.75…”