I_a型超新星爆发理论(Ⅱ):理论研究中的重要疑难问题

介绍与评述了I_a型超新星理论研究中最为突出的8个尚未解决的重要疑难问题,并简单介绍了国内围绕SNI_a开展的某些物理探讨研究．     

微波Ⅲ型爆发的一些初步研究

云南天文台“四波段（１．４２ＧＨｚ,２．１３ＧＨｚ,２．８４ＧＨｚ和４．２６ＧＨｚ）太阳射电高时间同步观测系统”在１９９０．１～１９９４．１期间,观测到５个具有短时标漂移结构的射电爆发事件,也就是微波Ⅲ型爆发。本文从中选取较典型的１９９１年３月１３日事件,对Ⅲ型爆发的时间轮廓（持续时间,衰减时间）作了分析,并与米波,分米波和微波段其它观测结果作了一些比较,以求对长厘米～短分米波段（微波低端）Ⅲ型爆发的时间轮廓的特征有一个初步的了解,最后对爆发的物理参数作了估计。     

太阳射电微波爆发及其精细结构研究进展

太阳射电微波爆发携带着爆发源区的物理环境及辐射机制等诸多重要信息。其辐射频段较高，通常来自低日冕磁重联区，尤其是微波爆发的精细结构，持续时间短、变化快、结构复杂，可以反映重联过程复杂的磁场结构、高能粒子运动等许多特征。综述了太阳微波射电爆发分类研究的3个主要阶段，介绍了每一阶段的重要爆发类型、物理机制研究及相应的观测设备，讨论了进一步研究的方向。     

第二太阳光谱

在太阳大气中,共振散射可引起辐射的线偏振．用偏振度测量精度达10－5的仪器,已经探测出完整的偏振辐射谱,这称为第二太阳光谱．它具有大量的、与通常太阳光谱截然不同的特征和结构．已有的研究发现它们与量子力学干涉、同位素效应、分子散射等物理过程有关．利用第二太阳光谱,可以进一步开展太阳物理的多项研究．     

1986年2月4日特大耀斑的物理先兆

本文从光球、色球及源于日冕的射电噪暴观测资料出发,分析了1986年2月4日4日级低年大耀斑的爆发前兆特征,可供耀斑物理预报及低年大耀斑物理机制的研究参考。     

与高能质子共生的两类太阳微波爆发(英)

在分析了近年来对太阳射电爆发与高能质子观测的基础上指出，既非II型也非米波IV型而是强微波爆发几乎总是同高能质子共生的；这一结果否定了以前长期所持的观点。同高能质子共生的微波爆发可分成两类：强脉冲型和强微波IV型，前者共生的被俘质子或相互作用质子要多于逃逸质子，后者则常共生有更多的逃逸质子．作者对每种情况中质子的有效加速过程进行了考虑，并对强微波爆发为何几乎总是有高能质子共生的缘由作了解释．     

太阳微波低频段射电III型爆发的一些特性分析

本文介绍了云南天文台四波段（１．４２,２．１３,２．８４和４．２６ＧＨｚ）太阳射电高时间分辩率同步观测得到的五个微波ＩＩ型爆发事件,它们具有宽频带、长和短寿命、内向和外向快速频漂等特征．观测事例表明,非热电子束引起的等离子体辐射和电子回旋脉泽辐射两种机制都可能发生．这些观测特征既不完全同于米波—分米波ＩＩ型爆发,也不完全同于微波高频段ＩＩ型爆发,说明在微波低频段可能存在二重性或过渡现象     

新浮磁流触发暗条爆发的统计研究

观测研究表明有利于磁重联的新浮磁流与日冕物质抛射(CME)有密切关系．利用数值模拟的方法,新浮磁流触发CME的物理模型对观测结果进行了物理解释．基于这种模型,不考虑重力和热传导, 2．5维的数值模拟的理论结果显示:是否能够触发暗条爆发及CME,取决于新浮磁流磁通量的大小、浮现的位置以及其磁极走向,并给出了能够触发暗条爆发与不能触发爆发的参数空间．利用2002年和2003年的15个暗条爆发事例以及2002年的44个非爆发事例,对新浮磁流磁通量的大小、浮现的位置以及磁极走向进行了统计研究．结果表明并非所有的新浮磁流都能够使暗条失去平衡,形成CME．统计结果基本上支持了数值模拟的理论结果．这个结果可为空间天气预报研究提供有用的参考信息．     

伴随CME的微波爆发的特征

分析了与日冕物质抛射(CME)有关的太阳微波爆发(SMB)的特征,包括持 续时间、峰值流量、爆发类型、谱指数等．选取了从1999年11月至2003年9月的136 个事件,包括60个部分晕状CME(120°<宽度<360°)／晕状CME(宽度=360°)和 76个正常CME(20°<宽度<120°)／窄CME(0°<宽度<20°)． 研究发现: (1)与正常CME／窄CME有关的微波爆发持续时间较短,与部分晕状 ／晕状CME有关的微波爆发持续时间有长有短; (2)与慢CME有关的微波爆发持续时 间较短,与快CME有关的微波爆发持续时间可长可短;(3)与正常／窄CME有关的微 波爆发峰值辐射流量比较小,与部分晕状／晕状CME有关的微波爆发峰值辐射流量有大 有小;(4)与慢CME有关的微波爆发峰值辐射流量较小,与快CME有关的微波爆发峰 值辐射流量可长可短; (5)与正常／窄CME有关的微波爆发绝大多数为简单(simple) 型,与晕状CME有关的微波爆发绝大多数为复杂(C)／大爆发(GB)型; (6)与CME 有关的事件在频率,f相似文献   

太阳白光耀斑的射电辐射特征:运动Ⅳ型爆发和与耀斑后环共生的短周期脉动现象

通过１９９１ 年６ 月６ 日一个复杂的太阳活动事件（ 包括宽带射电运动Ⅳ型爆发、脉冲相伴生的白光耀斑、耀斑后环及其伴生的射电多重短周期（ 约１ － ４ 秒） 脉动现象等） 的分析,探讨了白光耀斑产生的射电辐射特征,根据太阳白光耀斑和射电运动Ⅳ型爆发产生的物理过程,着重讨论了射电运动Ⅳ型爆发、耀斑后环和短周期脉动现象,并认为它们可能是白光耀斑的对应物     

Estimation of 56Ni Needed in the Explosion Process of the Super Luminous Supernova ASASSN-15lh

ASASSN-15lh is a super luminous supernova, whose light curve is similar to that of the type Ia supernova (SN Ia). Since the luminosity of SN Ia is directly related to the decay of ⁵⁶Ni, in this paper, we consider the de-excitation energy of the new nuclei, and calculate the energy generated by the decay of ⁵⁶Ni in the explosive environment of ASASSN-15lh. The calculated mass of ⁵⁶Ni needed by the ASASSN-15lh explosion is 31.32 M_⊙. This result agrees with the estimation of the mass of ⁵⁶Ni ≥ 30 M_⊙ derived from the observed light curve of ASASSN-15lh. No agreement has reached for the explosion mechanism of supernova ASASSN-15lh so far. The calculation in this paper provides a reference for the further study on the progenitor and explosion mechanism of the supernova ASASSN-15lh.     

Monte‐Carlo simulation of a possible correlation between the estimated luminosity distances and internal extinctions of type Ia supernovae

This paper describes a Monte Carlo simulation of type Ia supernova data. It was shown earlier that the data of SNe Ia might contain a possible correlation between the estimated luminosity distances and internal extinctions. This correlation was shown by different statistical investigations of the data. In order to remove observational biases (for example the effect of the detection limit of the observing instrument) and to test the reality of the effect found earlier we developed a simple routine which simulates extinction values, redshifts and absolute magnitudes for Ia supernovae. We pointed out that the correlation found earlier in the real data between the internal extinction and luminosity distance does not occur in the simulated sample. Furthermore, it became obvious that the detection limit of the observing devices used in supernova projects does not affect the far end of the redshift‐luminosity distance relationship of Ia supernovae. This result strengthens the earlier conclusions of the authors that SN Ia supernovae alone do not support the existence of dark energy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and infrared observations of SN 2002dj: some possible common properties of fast-expanding Type Ia supernovae

As part of the European Supernova Collaboration, we obtained extensive photometry and spectroscopy of the Type Ia supernova (SN Ia) SN 2002dj covering epochs from 11 d before to nearly two years after maximum. Detailed optical and near-infrared observations show that this object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines. The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN 2002bo. The only significant difference is observed in the optical to near-infrared colours and a reduced spectral emission beyond 6500 Å. For high-velocity gradient SNe Ia, we tentatively identify a faster rise to maximum, a more pronounced inflection in the V and R light curves after maximum and a brighter, slower declining late-time B light curve as common photometric properties of this class of objects. They also seem to be characterized by a different colour and colour evolution with respect to 'normal' SNe Ia. The usual light curve shape parameters do not distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass elements and lower temperatures are the most prominent spectroscopic features of SNe Ia displaying high-velocity gradients. It appears that these events burn more intermediate-mass elements in the outer layers. Possible connections to the metallicity of the progenitor star are explored.     

A review of type Ia supernova spectra

SN 2011fe was the nearest and best-observed type Ia supernova in a generation, and brought previous incomplete datasets into sharp contrast with the detailed new data. In retrospect, documenting spectroscopic behaviors of type Ia supernovae has been more often limited by sparse and incomplete temporal sampling than by consequences of signal-to-noise ratios, telluric features, or small sample sizes. As a result, type Ia supernovae have been primarily studied insofar as parameters discretized by relative epochs and incomplete temporal snapshots near maximum light. Here we discuss a necessary next step toward consistently modeling and directly measuring spectroscopic observables of type Ia supernova spectra. In addition, we analyze current spectroscopic data in the parameter space defined by empirical metrics, which will be relevant even after progenitors are observed and detailed models are refined.     

The galactic evolution of the supernova rates

Supernova rates (hypernova, type II, type Ib/c and type Ia) in a particular galaxy depend on the metallicity (i.e. on the galaxy age), on the physics of star formation and on the binary population. In order to study the time evolution of the galactic supernova rates, we use our chemical evolutionary model that accounts in detail for the evolution of single stars and binaries. In particular, supernovae of type Ia are considered to arise from exploding white dwarfs in interacting binaries and we adopt the two most plausible physical models: the single degenerate model and the double degenerate model. Comparison between theoretical prediction and observations of supernova rates in different types of galaxies allows to put constraints on the population of intermediate mass and massive close binaries.

The temporal evolution of the absolute galactic rates of different types of supernovae (including the type Ia rate) is presented in such a way that the results can be directly implemented into a galactic chemical evolutionary model. Particularly for type Ia’s the inclusion of binary evolution leads to results considerably different from those in earlier population synthesis approaches, in which binary evolution was not included in detail.     

Revisiting the magnification of type Ia supernovae with SDSS

We cross-correlate the sample of type Ia supernovae from Riess A. G. et al. with the SDSS DR2 photometric galaxy catalogue. In contrast to recent work, we find no detectable correlation between supernova magnitude and galaxy overdensity on scales ranging between 1 and 10 arcmin. Our results are in accord with theoretical expectations for gravitational lensing of supernovae by large-scale structure. Future supernova surveys such as SNAP will be capable of detecting unambiguously the predicted lensing signal.     

A strategy for finding gravitationally lensed distant supernovae

Distant Type Ia and II supernovae (SNe) can serve as valuable probes of the history of the cosmic expansion and star formation, and provide important information on their progenitor models. At present, however, there are few observational constraints on the abundance of SNe at high redshifts. A major science driver for the Next Generation Space Telescope is the study of such very distant SNe. In this paper we discuss strategies for finding and counting distant SNe by using repeat imaging of supercritical intermediate redshift clusters whose mass distributions are well constrained via modelling of strongly lensed features. For a variety of different models for the star formation history and supernova progenitors, we estimate the likelihood of detecting lensed SNe as a function of their redshift. In the case of a survey conducted with Hubble Space Telescope ( HST ), we predict a high probability of seeing a supernova in a single return visit with either Wide Field Planetary Camera 2 or Advanced Camera for Surveys, and a much higher probability of detecting examples with     in the lensed case. Most events would represent magnified SNe II at     and a fraction will be more distant examples. We discuss various ways to classify such events using ground-based infrared photometry. We demonstrate an application of the method using the HST archival data and discuss the case of a possible event found in the rich cluster AC 114     .     

Probing Dark Energy with Supernova Searches

Four years ago, two teams presented independent analyzes coming from photometry of type Ia supernovae at various distances. The results presented back then shook-up the scientific community: the universe is accelerating with a positive repulsive fluid sometimes called dark energy. No significant work has disproved the fundamental results, yet some doubt subsists in the assumptions behind the full use of type Ia supernovae as perfect distance indicators. The uncertainty of the evolution problem, the explosion mechanisms and the diversity of the observed light curves properties are often cited problems. All these aspects are now being deeply investigated in to-come or already started supernova searches along with the on-going quest of determining the nature of dark energy. We will present here a brief introduction to the use of type Ia supernova in cosmology, the current status of supernova cosmology as well as an overview of the wide supernova surveys about to begin.     

A Check on the Cardassian Expansion Model with Type－IaSupernovae Data

We use the magnitude-redshift relation for the type Ia supernova datacompiled by Riess et al. to analyze the Cardassian expansion scenario. This sce-nario assumes the universe to be flat, matter dominated, and accelerating, but contains no vacuum contribution.The best fitting model parameters are H0=65.3kms^-1 Mpc^-1, n= 0.35 and Ω= 0.05. When the highest redshift supernova,SN 1997ck, is excluded, H0 remains the same, but n becomes 0.20 and Ωm, 0.15, and the matter density remains unreasonably low. Our result shows that this particular scenario is strongly disfavoured by the SNeIa data.