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arXiv 0705.4467astro-ph
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SN 2005 hj:两类正常亮Ia超新星的证据及其宇宙学意义

SN 2005hj: Evidence for Two Classes of Normal-Bright SNe Ia and Implications for Cosmology

Robert Quimby, Peter Höflich, J. Craig Wheeler

摘要:

本文给出了Ia型超新星SN 2005 hj的HET光谱,包括从最大光之前约6天到最大光之后约5周的演化,以及ROTSE-IIIb未过滤的光变曲线。宿主星系在z=0.0574的红移处显示出HII区域线,这使得峰值未过滤的绝对星等有点过亮-19.6。光谱显示出微弱而狭窄的SiII线,在最大光照开始的至少10天内,这些剖面的宽度或深度没有变化,它们表明恒定的膨胀速度约为10,600 km/s。我们分析了观测的基础上详细的辐射动力学模型在文献中。虽然延迟爆轰和爆燃模型已被用来解释大部分的超新星Ia,他们没有预测一个长的速度平台在SIII的最低与不变的线轮廓。脉动延迟爆轰和合并的情况下形成壳状密度结构的属性主要与质量的壳,M壳,我们讨论如何这些模型可以解释所观察到的硅线演变,但是,这些模型是基于球形计算和其他可能性可能存在。SN 2005 hj在稳定期的开始、持续时间和速度、峰值亮度以及在不确定性范围内与M_shell=0.2 M_sun模型的固有颜色是一致的。我们的分析表明,一个独特的类的事件隐藏在分支正常SNe Ia。如果观测量之间的预测关系得到证实,它们可能提供一种方法来区分这两组。我们讨论了两个不同的祖先类的宇宙学研究采用超新星Ia,包括可能的差异,在峰值光度的光变曲线宽度的关系。

英文摘要:

HET Optical spectra covering the evolution from about 6 days before to about 5 weeks after maximum light and the ROTSE-IIIb unfiltered light curve of the "Branch-normal" Type Ia Supernova SN 2005hj are presented. The host galaxy shows HII region lines at redshift of z=0.0574, which puts the peak unfiltered absolute magnitude at a somewhat over-luminous -19.6. The spectra show weak and narrow SiII lines, and for a period of at least 10 days beginning around maximum light these profiles do not change in width or depth and they indicate a constant expansion velocity of ~10,600 km/s. We analyzed the observations based on detailed radiation dynamical models in the literature. Whereas delayed detonation and deflagration models have been used to explain the majority of SNe Ia, they do not predict a long velocity plateau in the SiII minimum with an unvarying line profile. Pulsating delayed detonations and merger scenarios form shell-like density structures with properties mostly related to the mass of the shell, M_shell, and we discuss how these models may explain the observed SiII line evolution; however, these models are based on spherical calculations and other possibilities may exist. SN 2005hj is consistent with respect to the onset, duration, and velocity of the plateau, the peak luminosity and, within the uncertainties, with the intrinsic colors for models with M_shell=0.2 M_sun. Our analysis suggests a distinct class of events hidden within the Branch-normal SNe Ia. If the predicted relations between observables are confirmed, they may provide a way to separate these two groups. We discuss the implications of two distinct progenitor classes on cosmological studies employing SNe Ia, including possible differences in the peak luminosity to light curve width relation.

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