Spectral Evolution of the Extraordinary Type IIn Supernova 2006gy - Astrophysics > High Energy Astrophysical PhenomenaReport as inadecuate




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Abstract: We present a detailed analysis of the extremely luminous Type IIn supernovaSN2006gy using spectra obtained between days 36 and 237 after explosion. Wederive the temporal evolution of the effective temperature, radius, expansionspeeds, and bolometric luminosity, as well as the progenitor wind density andtotal swept-up mass overtaken by the shock. SN2006gy can be interpreted in thecontext of shock interaction with a dense CSM, but with quite extreme valuesfor the CSM mass of 20 Msun and an explosion kinetic energy of at least 5e51erg. A key difference between SN2006gy and other SNeIIn is that, owing to itslarge CSM mass, the interaction region remained opaque much longer. At earlytimes, H-alpha widths suggest that the photosphere is ahead of the shock, andphotons diffuse out through the opaque CSM. The pivotal transition to opticallythin emission begins around day 110, when we start to see a decrease in theblackbody radius and strengthening tracers of the post-shock shell. From theevolution of pre-shock velocities, we deduce that the CSM was ejected by theprogenitor in a 1e49 erg precursor event 8yr before explosion. The large CSMmass rules out models involving stars with initial masses around 10Msun. Withthe full mass budget, even massive M ZAMS=30-40 Msun progenitor stars areinadequate. At roughly solar metallicity, substantial mass loss probablyoccurred during the star-s life, so SN 2006gy-s progenitor is more consistentwith LBV eruptions or pulsational pair-instability ejections in stars withinitial masses above 100 Msun. This requires significant revision to currentparadigms of massive-star evolution. abridged



Author: Nathan Smith, Ryan Chornock, Jeffrey M. Silverman, Alexei V. Filippenko, Ryan J. Foley

Source: https://arxiv.org/



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