Berkeley Supernova Ia Program – II. Initial analysis of spectra obtained near maximum brightness

摘要: In this second paper in a series, we present measurements of spectral features 432 low-redshift (z < 0.1) optical spectra 261 Type Ia supernovae (SNe Ia) within 20 d maximum brightness. The data were obtained from 1989 to the end 2008 as part Berkeley Supernova Program (BSNIP) and are presented BSNIP I by Silverman et al. We describe detail our method automated, robust feature definition measurement which expands upon similar previous studies. Using procedure, attempt measure expansion velocities, pseudo-equivalent widths (pEWs), depths fluxes at centre endpoints each nine major complexes. investigate how velocity pEW evolve with time they correlate other. Various classification schemes employed quantitative differences among subclasses investigated. Several ratios values calculated studied. so-called Si ii ratio, often used luminosity indicator, is found be well correlated SiFe ratio anticorrelated analogous ‘SSi ratio’, confirming results Furthermore, SNe that show strong evidence for interaction circumstellar material or an aspherical explosion have largest near-maximum velocities pEWs, possibly linking extreme observables specific progenitor scenarios. find purely spectroscopic useful identifying most peculiar Ia. However, almost all parameters investigated, full sample objects spans nearly continuous range values. Comparisons previously published theoretical models made conclude brief discussion performed herein possible correlations will important future SN surveys.