Photoionization of Co⁺and electron-impact excitation of Co^{2 +}using the DiracR-matrix method

Abstract

Modelling of massive stars and supernovae (SNe) plays a crucial role in understanding galaxies. From this modelling we can derive fundamental constraints on stellar evolution, mass-loss processes, mixing, and the products of nucleosynthesis. Proper account must be taken of all important processes that populate and depopulate the levels (collisional excitation, de-excitation, ionization, recombination, photoionization, bound-bound processes). For the analysis of Type Ia SNe and core collapse SNe (Types Ib, Ic and II) Fe group elements are particularly important. Unfortunately little data is currently available and most noticeably absent are the photoionization cross-sections for the Fe-peaks which have high abundances in SNe. Important interactions for both photoionization and electron-impact excitation are calculated using the relativistic Dirac Atomic R-matrix Codes (darc) for low ionization stages of cobalt. All results are calculated up to photon energies of 45 eV and electron energies up to 20 eV. The wavefunction representation of Co iii has been generated using grasp0 by including the dominant 3d 7 , 3d 6 [4s, 4p], 3p 4 3d 9 and 3p 6 3d 9 configurations, resulting in 292 fine structure levels. Electron-impact collision strengths and Maxwellian averaged effective collision strengths across a wide range of astrophysically relevant temperatures are computed for Co iii. In addition, statistically weighted level-resolved ground and metastable photoionization cross-sections are presented for Co ii and compared directly with existing work.

Using late-time optical and near-infrared spectra to constrain Type Ia supernova explosion properties

“…rest wavelengths, transition probabilities) from the cmfgen compilation (Hillier & Miller 1998;Hillier & Dessart 2012), which includes the forbidden line data from and . For [Co iii] we use the atomic data from Tyndall et al (2016).…”

Monte Carlo radiative transfer for the nebular phase of Type Ia supernovae

“…In addition to the cmfgen database, we use updated collision strengths for Co + from Storey et al (2016), and Co + photoionisation cross sections, Co 2+ energy levels and bound-bound transition rates from Tyndall et al (2016).…”

A year-long plateau in the late-time near-infrared light curves of type Ia supernovae

“…We extracted the onedimensional spectrum from 1.0-1.7 µm in bins of 200 Å using sparse-matrix techniques Ryan et al (2018), but since only a single orient was available, we required additional steps to remove the contamination from the host galaxy Troja et al (2017). Next, we matched the emission features of the spectrum with iron-group forbidden lines from the National Institute of Standards and Technology's Atomic Spectra Database and the compilation of atomic data from CMFGEN (Hillier & Miller 1998;Hillier & Dessart 2012;Tyndall et al 2016), including forbidden line data for [Fe II] Quinet et al (1996) and [Fe III] Quinet (1996).…”