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arXiv 0801.2898astro-ph
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寻找NGC 1316中两颗Ia型超新星的前身星

A Search for the Progenitors of Two Type-Ia Supernovae in NGC 1316

Dan Maoz, Filippo Mannucci

摘要:

最近的证据表明,许多Ia型超新星(SNe-Ia)的年轻祖先人口提出了可能性,进化的中等质量的祖先恒星可能会在爆炸前的图像检测。NGC 1316是天炉座星系团中的一个射电星系,是SNe-Ia的多产者,自1980年以来已经探测到四个。我们分析了哈勃太空望远镜(HST)在这个星系中爆炸的两个SNe-Ia的爆炸前图像,SN 2006 dd(正常的Ia型)和SN 2006 mr(可能是一个亚发光的,1991 bg样的,SN-Ia)。天体测量位置是从事件的光学和近红外地面图像中获得的。我们在这两个位置都没有找到候选点源,并对来自任何此类祖先的B、V和I中的通量设置上限。我们还估计了可能存在的消光量,基于对HST图像本身表面亮度不均匀性的分析。在NGC 1316的距离上,M_B、M_V和M_I的绝对星等分别约为-5.5、-5.4和-6.0等。通过与恒星演化模型的比较,我们认为在超新星爆发前3年,在超新星爆发前的SN位置,不存在初始质量大于6 Msun的正常恒星,初始质量大于4 Msun的年轻后AGB恒星,以及初始质量大于9 Msun的后红巨星。

英文摘要:

Recent evidence of a young progenitor population for many Type-Ia SNe (SNe-Ia) raises the possibility that evolved intermediate-mass progenitor stars may be detected in pre-explosion images. NGC 1316, a radio galaxy in the Fornax cluster, is a prolific producer of SNe-Ia, with four detected since 1980. We analyze Hubble Space Telescope (HST) pre-explosion images of the sites of two of the SNe-Ia that exploded in this galaxy, SN2006dd (a normal Type-Ia) and SN2006mr (likely a subluminous, 1991bg-like, SN-Ia). Astrometric positions are obtained from optical and near-IR ground-based images of the events. We find no candidate point sources at either location, and set upper limits on the flux in B, V, and I from any such progenitors. We also estimate the amount of extinction that could be present, based on analysis of the surface-brightness inhomogeneities in the HST images themselves. At the distance of NGC 1316, the limits correspond to absolute magnitudes of about -5.5, -5.4, and -6.0 mag in M_B, M_V, and M_I, respectively. Comparison to stellar evolution models argues against the presence at the SN sites, 3 years prior to the explosion, of normal stars with initial masses > 6 M_sun at the tip of their asymptotic-giant branch (AGB) evolution, young post-AGB stars that had initial masses > 4 M_sun, and post-red-giant stars of initial masses > 9 M_sun.

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