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arXiv 0907.0246astro-ph.GAastro-ph.SR
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SN 2008年S前后壳层中尘埃的破坏与存活

The destruction and survival of dust in the shell around SN 2008S

R. Wesson, M. J. Barlow, B. Ercolano, J. E. Andrews, Geoffrey C. Clayton, J. Fabbri, Joseph S. Gallagher, M. Meixner, B. E. K. Sugerman, D. L. Welch, D. J. Stock

摘要:

SN 2008 S于2008年初在大设计螺旋星系NGC 6946中爆发。普列托等人在斯皮策太空望远镜拍摄的爆炸前四年的图像中发现了这一前身,但在深层光学图像中没有发现,他们从中推断出一个质量约为10 Msun的自遮蔽物体。我们在SN 2008 S被发现5天后获得了斯皮策的观测结果,以及在其爆发6个月后获得了双子座和斯皮策的光学和红外观测结果。我们建立了该天体在爆发前后的辐射转移尘埃模型,对所有时期都使用了相同的预先存在的无定形碳颗粒的r^-2密度分布,并考虑了爆发后早期的光旅行时间效应。我们排除了硅酸盐颗粒作为SN 2008 S周围尘埃的重要成分。尘埃壳的内半径从爆发前的85天文单位向外移动到爆发后的1250天文单位,这是由于SN 2008 S的闪光使颗粒蒸发。虽然这导致星周消光从爆发前的Av = 15下降到爆发后的0.8,但我们估计只有不到2%的星周尘埃质量被破坏。据估计,这颗祖星的总质量损失率为(0.5-1.0)x10^-4 Msun yr^-1。得出的尘埃质量损失率为5 × 10 ^-7 Msun/年,这意味着在自遮蔽阶段的建议持续时间内,向ISM注入的尘埃总量高达0.01 Msun。我们认为像SN 2008 S的对象的星系的尘埃富集的潜在贡献。

英文摘要:

SN 2008S erupted in early 2008 in the grand design spiral galaxy NGC 6946. The progenitor was detected by Prieto et al. in Spitzer Space Telescope images taken over the four years prior to the explosion, but was not detected in deep optical images, from which they inferred a self-obscured object with a mass of about 10 Msun. We obtained Spitzer observations of SN 2008S five days after its discovery, as well as coordinated Gemini and Spitzer optical and infrared observations six months after its outburst. We have constructed radiative transfer dust models for the object before and after the outburst, using the same r^-2 density distribution of pre-existing amorphous carbon grains for all epochs and taking light-travel time effects into account for the early post-outburst epoch. We rule out silicate grains as a significant component of the dust around SN 2008S. The inner radius of the dust shell moved outwards from its pre-outburst value of 85 AU to a post-outburst value of 1250 AU, attributable to grain vaporisation by the light flash from SN 2008S. Although this caused the circumstellar extinction to decrease from Av = 15 before the outburst to 0.8 after the outburst, we estimate that less than 2% of the overall circumstellar dust mass was destroyed. The total mass-loss rate from the progenitor star is estimated to have been (0.5-1.0)x10^-4 Msun yr^-1. The derived dust mass-loss rate of 5x10^-7 Msun yr^-1 implies a total dust injection into the ISM of up to 0.01 Msun over the suggested duration of the self-obscured phase. We consider the potential contribution of objects like SN 2008S to the dust enrichment of galaxies.

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