KMS of Xinjiang Astronomical Observatory, CAS
| Ia型超新星观测研究 | |
| Alternative Title | Observations and studies of type Ia supernovae |
曾祥云
| |
| Subtype | 博士 |
| Thesis Advisor | 艾力·伊沙木丁 |
| 2021-06-02 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学博士 |
| Degree Discipline | 天体物理 |
| Keyword | 超新星,Ia 型超新星,SN 2017hpa,SN 2017fgc |
| Abstract | Ia型超新星可能由双星系统中碳氧白矮星非稳定的热核爆炸而导致，有两种可能的前身星系统备受关注：双星系统中单个碳氧白矮星吸积而导致的热核爆炸，称为单简并模型；双星系统中两个碳氧白矮星的并合导致Ia型超新星爆炸，称为双简并模型。对Ia型超新星的多波段测光观测有助于探索其绝对光度与光变曲线形状之间的关系，有助于研究Ia型超新星的多样性，并为其爆发机制提供更多限制。Ia型超新星可用作标准烛光，并直接导致了宇宙加速膨胀的发现。对Ia型超新星的时域光谱观测有助于探究Ia型超新星抛射物各元素的演化，有助于分析Ia型超新星前身星系统和爆发机制。此外，对Ia型超新星的深入研究有助于推进星系化学演化、中子星与黑洞产生、暗能量、暗物质等多方面的研究。 本文第一项研究工作深入分析了富碳Ia型超新星SN 2017hpa的实测特性，本项研究对该星进行了大量的测光和光谱观测，发现SN 2017hpa属于正常且NUV-red的Ia型超新星，其光变曲线下降率为∆m15(B) = 1.02±0.07星等，且光极大时候B波段的绝对星等为Mmax(B) = -19.12±0.11星等。 SN 2017hpa早期光谱中存在明显而演化独特的C II吸收线，使得它有别于其他正常Ia型超新星。其光谱中碳和氧的吸收强度比其它正常Ia型超新星的强，且在光极大后约10天后才完全消失。其抛射物中碳和氧的速度都低于IMEs的膨胀速度，例如 Si II、Ca II。SN 2017hpa光极大时的膨胀速度大约为9,550 km/s，与正常Ia型超新星的速度相当，而其速度梯度却高达130 km/s，显著高于正常Ia型超新星的速度梯度。爆炸抛射物中存在较多未燃烧的碳和氧，相对于IMEs较低的膨胀速度以及光球层较大的速度梯度表明该超新星可能起源于暴力并合模型。 本文第二项研究工作深入分析了高速Ia型超新星SN 2017fgc的实测特性。本项研究对该星进行了大量的测光和光谱观测，发现该超新星具有较小的光变曲线下降率(即∆m15(B) = 1.05±0.07星等)，其光变曲线的上升时间大约为18.0±0.4天，B波段峰值绝对亮度为Mmax(B) = −19.32±0.13星等。SN 2017fgc光变曲线和颜色曲线的演化与高速Ia型超新星类似，例如SN 2002bo和 SN 2006X。SN 2017fgc的U和B波段后期光变曲线中观测到的超亮现象可能是其前身星系统中CSM的指示器。该超新星光谱演化与SN 2002bo、SN 2006X以及SN 2013gs类似，且在4400 Å附近 Fe II/Mg II有较强的混合吸收线，在4900 Å附近 Fe III/Fe II/Si II也有较强的混合吸收线。在R/r和I/i波段，SN 2017fgc与其他高速Ia型超新星还有更显著的二次极大/凸起特征。上述观测特性表明，SN 2017fgc以及高速Ia型超新星可能经历了更彻底的燃烧，或者具有更高金属丰度的前身星系统或者出生地环境。SN 2017fgc爆发于宿主星系中心于外部壳层的气体桥上，距离星系中心较远，研究推测SN 2017fgc前身星系统可能是从星系内部抛射出来的，或者是宿主星系于其伴星系并合时星系盘上残留的冷气体物质或恒星系统。 SN 2017hpa 与 SN 2017fgc特殊的观测特性使它们有别于其他正常Ia型超新 星，丰富了 Ia 型超新星的多样性。富碳Ia型超新星SN 2017hpa爆炸抛射物中，碳氧元素相对较低且类似的速度分布表明，该超新星有可能起源于双白矮星的暴力并合。高速Ia型超新星SN 2017fgc光谱中较宽的中等质量及铁族元素吸收线，以及 R/r/I/i 波段更为显著的二次极大表明该超新星可能有富金属的前身星系统或环境。 |
| Other Abstract | Type Ia supernovae (SN Ia) are widely believed to originate from thermonuclear explosions of carbon-oxygen (C-O) white dwarfs in binary systems. Currently, two possible models of progenitor systems are of interest: the thermonuclear explosion caused by the accretion of a single carbon-oxygen white dwarf in a binary system, called the single-degenerate (SD) scenario, and the merger of two carbon-oxygen white dwarfs in a binary system leading to a Type Ia supernova explosion, called the double- degenerate scenario. Multi-band photometric observations of SNe Ia help to explore the relationship between their absolute luminosity and the shape of the light curve, and to study the diversity of Type Ia supernovae. Varies method are used to reduce the dispersion of the luminosity-width relation of SNe Ia, which will improve accuracy in distance measurements using SNe Ia. The early photometric observations of SNe Ia can provide more effective constraints on their explosion mechanisms and help to distinguish between different explosion mechanisms. Time-domain spectroscopic observations of SNe Ia can help to investigate the evolution of the elements of the ejecta, which help to analyze the progenitor systems and explosion mechanisms of SNe Ia, and provide necessary constraints on their explosion mechanisms. Studies of SNe Ia can help develop the study of galaxy chemical evolution, neutron star and black holes, dark energy, dark matter, and other aspects. The observational characteristics of carbon-rich type Ia SN 2017hpa are studied as the first work in this paper, and we present extensive optical observations on the photometry and spectroscopy of it. This SN Ia can be put into the category of normal and NUV-red SNe Ia, with ∆m15(B) =1.02±0.07 mag and absolute B-band magnitude as Mmax(B) = -19.12±0.11 mag. The prominent C II absorption and abnormal velocity evolution make SN 2017hpa distinguish from other normal Ia SNe. The carbon (and oxygen) feature is apparently stronger than normal SNe Ia and lasted until about 10 days after the maximum light. Both carbon and oxygen have apparently lower velocity than the intermediate-mass elements (IMEs) such as Si II and Ca II. Although SN 2017hpa has a normal ejecta velocity, i.e. , ~9,550±70 km/s as measured near the maximum light, it has an unsually large velocity gradient (i.e., ~130±7 km/s/day) in comparison with other normal SNe Ia. The significant amount of unburned C and O in the ejecta, lower velocity relative to IMEs, and large velocity gradient are more consistent with merger model. The observational characteristics of high-velocity type Ia SN 2017hpa are studied as the second work in this paper, and we present extensive optical observations on the photometry and spectroscopy of it. The supernova has a small light curve decline rate (i.e., ∆m15(B) = 1.05±0.07 mag), and its light curve rise time is ~18.0±0.4 days with a peak absolute magnitude of Mmax(B) = -19.12±0.11 mag. The light curve and color curve evolution of SN 2017fgc are similar to those of HV SNe Ia, such as SN 2002bo and SN 2006X. The excess emission seen at near nebuler phase light curves of SN 2017fgc in UB bands could be CSM indicators of its progenitors. The spectral evolution of SN 2017fgc is similar to those of SN 2002bo, SN 2006X, and SN 2013gs, with stronger absorptions of Fe II/Mg II blends near 4400 Å and Fe III/Fe II/Si II blends near 4900 Å. Moreover, SN 2017fgc and other HV SNe Ia are found to have more pronounced secondary maximum peaks in Ii bands. All the above features indicate that SN 2017fgc and other HV SNe Ia likely have experienced more complete burning or their progenitors have higher metallicity. SN 2017fgc was born in a gas bridge which connecting the centre and the outer shell, and it is far away from the centre of the host galaxy. It is speculate that SN 2017fgc could be ejected from the inner part of the companion galaxy, or formed as a result of some cold gas remained in the companion disk. The special observational properties of SN 2017hpa and SN 2017fgc distinguish them from other normal SNe Ia and enrich the diversity of SNe Ia. The relatively low and similar velocity distribution of carbon and oxygen elements in the ejecta of the carbon-rich SN 2017hpa suggests that the supernova may be originated from a violent merger of binary white dwarfs. The broad IMEs and Fe-group absorption lines in the spectra of the high-velocity SN 2017fgc and the more significant secondary maximum in the R/r/I/i band suggest that this supernova may have a metal-rich progenitor system or environment. Further more observations and modeling will help to explore the explosion mechanisms of the carbon-rich and high-velocity SNe Ia. |
| Pages | 170 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/5157 |
| Collection | 研究生学位论文 |
| Affiliation | 中国科学院新疆天文台 |
| First Author Affilication | Xinjiang Astronomical Observatory, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | 曾祥云. Ia型超新星观测研究[D]. 北京. 中国科学院大学,2021. |
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| Ia型超新星观测研究_曾祥云.pdf（23385KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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