In supernova spectroscopy relatively little attention has been given to the properties of optically thick spectral lines in epochs following the photosphere's recession. Most treatments and analyses of post-photospheric optical spectra of supernovae assume that forbidden-line emission comprises most if not all spectral features. However, evidence exists which suggests that some spectra exhibit line profiles formed via optically thick resonance-scattering even months or years after the supernova explosion. To explore this possibility we present a geometrical approach to supernova spectrum formation based on the "Elementary Supernova" model, wherein we investigate the characteristics of resonance-scattering in optically thick lines while replacing the photosphere with a transparent central core emitting non-blackbody continuum radiation, akin to the optical continuum provided by decaying 56Co formed during the explosion. We develop the mathematical framework necessary for solving the radiative transfer equation under these conditions, and calculate spectra for both isolated and blended lines. Our comparisons with analogous results from the Elementary Supernova code SYNOW reveal several marked differences in line formation. Most notably, resonance lines in these conditions form P Cygni-like profiles, but the emission peaks and absorption troughs shift redward and blueward, respectively, from the line's rest wavelength by a significant amount, despite the spherically symmetric distribution of the line optical depth in the ejecta. These properties and others that we find in this work could lead to misidentification of lines or misattribution of properties of line-forming material at post-photospheric times in supernova optical spectra.
Long-term optical and near-infrared photometric evolution of SN 2019vxm, an interacting Type IIn supernova
HUN-REN CSFK, Konkoly Observatory（匈牙利科学院研究网络恒星物理研究所孔科伊天文台）；MTA Centre for Excellence（匈牙利科学院卓越中心）；ELTE Eötvös Loránd University, Institute of Physics and Astronomy（厄特沃什·罗兰大学物理与天文学研究所）；MTA–HUN-REN CSFK Lendület “Momentum” Stellar Pulsation Research Group（匈牙利科学院-匈牙利科学院研究网络恒星物理研究所Lendület“动量”恒星脉动研究组）；Department of Experimental Physics, University of Szeged（塞格德大学实验物理系）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体科学系）
The 91T/99aa-like Type Ia Supernova 2019vrq, Part II: 3D, Non-LTE, Low-Amplitude, Pulsating Delayed-Detonation Models of a Promising Standard Candle
Florida State University（佛罗里达州立大学）；Tsinghua University（清华大学）；University of Texas（德克萨斯大学）；European Organisation for Astronomical Research in the Southern Hemisphere (ESO)（欧洲南方天文台）；Texas A&M University（德克萨斯农工大学）
