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arXiv 0906.2200astro-ph.HEastro-ph.SR
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2006 gy型异常I型In超新星的光谱演化

Spectral Evolution of the Extraordinary Type IIn Supernova 2006gy

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

摘要:

我们提出了一个非常明亮的IIn型超新星SN 2006 gy使用爆炸后的第36和237天之间获得的光谱的详细分析。我们得到的时间演化的有效温度,半径,膨胀速度,和测热光度,以及祖风密度和总扫过的冲击质量。SN 2006 gy可以在激波与致密CSM相互作用的背景下进行解释,但CSM质量为20 Msun,爆炸动能至少为5 e51 erg。SN 2006 gy和其他SNeIIn的一个关键区别是,由于它的大CSM质量,相互作用区域保持不透明的时间要长得多。在早期,H-α的宽度表明光球在激波之前,光子通过不透明的CSM扩散出去。在第110天左右,我们开始看到黑体半径的减小和激波后壳层示踪物的增强,开始向光学薄辐射转变。根据激波前速度的演化,我们推断CSM是在爆炸前8年的一次1 e49 erg的前兆事件中被祖先抛射出来的。大的CSM质量排除了涉及初始质量约为10 Msun的恒星的模型。在完整的质量预算下,即使是M_ZAMS=30-40 Msun的大质量祖星也是不够的。在近似太阳的金属丰度下,SN 2006 gy的质量可能在恒星的生命中发生了大量的损失,因此SN 2006 gy的前身更符合LBV爆发或初始质量超过100 Msun的恒星中的脉动对不稳定性喷射。这需要对当前的恒星演化范式进行重大修改。(节略)

英文摘要:

We present a detailed analysis of the extremely luminous Type IIn supernova SN2006gy using spectra obtained between days 36 and 237 after explosion. We derive the temporal evolution of the effective temperature, radius, expansion speeds, and bolometric luminosity, as well as the progenitor wind density and total swept-up mass overtaken by the shock. SN2006gy can be interpreted in the context of shock interaction with a dense CSM, but with quite extreme values for the CSM mass of 20 Msun and an explosion kinetic energy of at least 5e51 erg. A key difference between SN2006gy and other SNeIIn is that, owing to its large CSM mass, the interaction region remained opaque much longer. At early times, H-alpha widths suggest that the photosphere is ahead of the shock, and photons diffuse out through the opaque CSM. The pivotal transition to optically thin emission begins around day 110, when we start to see a decrease in the blackbody radius and strengthening tracers of the post-shock shell. From the evolution of pre-shock velocities, we deduce that the CSM was ejected by the progenitor in a 1e49 erg precursor event 8yr before explosion. The large CSM mass rules out models involving stars with initial masses around 10Msun. With the full mass budget, even massive M_ZAMS=30-40 Msun progenitor stars are inadequate. At roughly solar metallicity, substantial mass loss probably occurred during the star's life, so SN 2006gy's progenitor is more consistent with LBV eruptions or pulsational pair-instability ejections in stars with initial masses above 100 Msun. This requires significant revision to current paradigms of massive-star evolution. (abridged)

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