2020/06/26 by Tomás E. Müller-Bravo, Claudia P. Gutiérrez, Mark Sullivan +20 · 1 citation
Physics and Astronomy · #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.1093/mnras/staa1932
Accepted for publication in MNRAS
arxiv created 2020/06/26 · arxiv updated 2020/07/15
Low-luminosity type II supernovae (LL SNe~II) make up the low explosion energy end of core-collapse SNe, but their study and physical understanding remain limited. We present SN 2016aqf, a LL SN~II with extensive spectral and photometric coverage. We measure a V-band peak magnitude of -14.58 mag, a plateau duration of ∼100 days, and an inferred 56Ni mass of 0.008 ± 0.002 \msun. The peak bolometric luminosity, L\rm bol ≈ 1041.4 erg s-1, and its spectral evolution is typical of other SNe in the class. Using our late-time spectra, we measure the [\ionOi] λλ6300, 6364 lines, which we compare against SN II spectral synthesis models to constrain the progenitor zero-age main-sequence mass. We find this to be 12 ± 3 \msun. Our extensive late-time spectral coverage of the [\ionFeii] λ7155 and [\ionNiii] λ7378 lines permits a measurement of the Ni/Fe abundance ratio, a parameter sensitive to the inner progenitor structure and explosion mechanism dynamics. We measure a constant abundance ratio evolution of 0.081+0.009-0.010, and argue that the best epochs to measure the ratio are at ∼200 -- 300 days after explosion. We place this measurement in the context of a large sample of SNe II and compare against various physical, light-curve and spectral parameters, in search of trends which might allow indirect ways of constraining this ratio. We do not find correlations predicted by theoretical models; however, this may be the result of the exact choice of parameters and explosion mechanism in the models, the simplicity of them and/or primordial contamination in the measured abundance ratio.