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Blazar天体的光变及多波段能谱特性
戴本忠
Subtype博士
Thesis Advisor谢光中
2001
Degree Grantor中国科学院云南天文台
Place of Conferral昆明
Degree Discipline天体物理
Keyword活动星系核-blazar天体 光变 多波段能谱特性 观测 -γ射线 统一模型
Abstract本文综述了活动星系核,特别是blazar天体的研究现状,对blazar天体的多波段观测与多波段能谱特性研究进行了较为详细的评述。主要的研究工作包括以下内容:(一)γ噪blazar天体的短时标光变研究,通过对16个γ噪blazar天体(其中包括全部已证认和观测到VHE γ射线爆发的可能甚高能γ射线源)自1998年的光学观测及光变分析研究表明,短时标光变(小时量级)是GeV γ噪blazar天体的普遍特性,光变幅度通常可达0.6星等/小时,对PKS 1510-089类星体的观测发现在一个小时内对象变暗2个星等,对如此激烈的光变变暗目前的理论还不能很好的解释,但它同样反映了辐射区域的内部结构;而对TBLs的监测表明,其光学波段的短时标光变没有其他对象激烈,出现的频度和振幅变化都 较小;(二)在研究γ噪blazar天体光变时,研究了寄主星系对光变的影响,得到了1ES 2344 + 514 的光变与 PSF 的关联,表明随着大气视宁度的下降(即FWHM变大),对象变暗,即由于寄主星系的影响从而导致假光变的产生;(三)引进两个多波段复合谱指数,α_(xox) = α_(ox) - α_x 及 α_(oro) = α_(or) - α_o。对样本的统计研究表明,RBLs是能谱特性界于XBLs和OVVs之间的一类中间态,所得结果支持了Sambruna et al. (1996)大样本波段能谱分布特性的统计研究结果。(四)我们对地面探测器对blazar 天体甚高能波段的观测做了较为详细的了解,由于blazar天体在全波段上都观测到光变,所以这类对象是多波段观测研究最完全的。地面望远镜对小时量级的光变很敏感,所以,对低流量源的直到10TeV或更高能谱的测量是多波段研究的重要扩展,特别地,如果γ射线的辐射是通过康普顿散射提升低能同步辐射光子产生的,即SSC模型产生,那么,VHE γ射线的观测和低能同步辐射的观测就可能估计喷流内的磁场强度、Doppler因子等。对我们今后的光学波段的观测工作提出了新的课题。
Other AbstractIn the present thesis, we reviewed the basic properties and studying results about the active galactic nuclei (AGNs), specially, we focus on the multiband observations and the properties of multiband spectral energy distributions (SEDs) of blazars that would constraint the emission models of blazars. Our main works and results are as follow: (1) studying on short timescale variability of γ-ray blazars. Our CCD monitoring campaign from 1998 have monitored the γ-ray blazars sample of 16 objects, including all TeV sources and some suspicious TeV objects. The observational results show that the short timescale (about 1 hour) variability is the common property for the GeV γ ray blazars, the amplitude variations in each optical band (B, V, R, I) reach to 0.6 mag/hour. The GeV γ-ray-loud source, PKS 1510-089, was very active during our observation period, it showed an apparent variation of 2.0 mag within 41 minutes in the R band. This is the most violently rapid variability in optical monitoring program since 1982 in our group. For this rapid dimming variability phenomenon, there is not any suitable theoretical explanation, but this is also the reflection of emission region structure. As for the TeV γ-ray blazars, the short timescale variability in optical band is less drastic than GeV γ-ray blazars in both the amplitude and timescale; (2) The influence of variable seeing conditions on the observations was investigated. There is weak correlation between the observed variability and the local seeing conditions for the objects 1ES 2344 + 514. This implies that the source brightness decreased, while the FWHM of PSF increased, removing more light from the aperture, e.g. there would be some spurious variation influenced by variable seeing conditions. (3) We introduce two composite color-color indices α_(xox) = α_(ox) - α_x and α_(oro) = α_(or) - α_o. The statistical results for selected sample show that RBLs are intermediate between XBLs and OVV quasars, which have been given by Sumbruna et al. (1996). (4) We present the overview of the VHE γ-ray observations by using the ground based Cerenkov imaging telescope and other detector. Because of their variability at all wavelengths, blazars can best be understood through multi-wavelength observations. The sensitivity of VHE telescopes to sub-hour scale variability, their ability to detect low source fluxes, and the measurement of spectra up to 10 TeV or more make the VHE observations an important addition to multi-wavelength campaigns. In particular, if the γ-ray emission arises from inverse Compton scattering of the same electron population which produces the low energy synchrotron emission, the combination of VHE γ-ray and synchrotron observations permit the estimation of the magnetic field strength and Doppler factor in the jet where the γ-ray emission is produced. It is a guide to our future optical observational campaign.
Subject Area天文学
Pages89
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/7148
Collection星系研究组
Recommended Citation
GB/T 7714
戴本忠. Blazar天体的光变及多波段能谱特性[D]. 昆明. 中国科学院云南天文台,2001.
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