美国斯隆数字化巡天(SDSS)类星体光谱中存在明显的大气天光谱线，这对类星体光谱的分析尤其是吸收线的证认造成较大干扰.以SDSS D R 1 0 的光谱为样本，对光谱中的天光线进行研究，给出了[01]姿5577魡残差的分布.发现光谱[01]姿5577魡...美国斯隆数字化巡天(SDSS)类星体光谱中存在明显的大气天光谱线，这对类星体光谱的分析尤其是吸收线的证认造成较大干扰.以SDSS D R 1 0 的光谱为样本，对光谱中的天光线进行研究，给出了[01]姿5577魡残差的分布.发现光谱[01]姿5577魡残差处于5572.5586魡的范围内.这一结果为证认吸收线的工作提供参考，同时将有利于改进主成分分析减天光方法.展开更多
The narrowness of the distribution of the peak energy of the νF<SUB>ν</SUB> spectrum of gamma-ray bursts (GRBs) and the unification of GRB populations are great puzzles yet to be solved. We investigate t...The narrowness of the distribution of the peak energy of the νF<SUB>ν</SUB> spectrum of gamma-ray bursts (GRBs) and the unification of GRB populations are great puzzles yet to be solved. We investigate the two puzzles based on the global spectral behaviors of different GRB populations, the long GRBs, the short GRBs, and the X-ray flashes (XRFs), in the HR?E<SUB>p</SUB> plane (HR the spectral hardness ratio) with BATSE and HETE-2 observations. It is found that the long GRBs and the XRFs observed by HETE-2 seem to follow the same sequence in the HR?E<SUB>p</SUB> plane, with the XRFs at the low end of this sequence. We fit the sequence by a universal Band function, and find that this sequence is mainly defined by the low energy index α, and is insensitive to the high energy index, β. With fixed β = ?5, a best fit is given by α = ?1.00 with χ<SUP>2</SUP><SUB>min</SUB>/dof = 2.2. The long and short GRBs observed by BATSE follow significantly different sequences in the HR?E<SUB>p</SUB> plane, with most of the short GRBs having a larger hardness ratio than the long GRBs at a given E<SUB>p</SUB>. For the long GRBs a best-fit yields α = ?0.30 and β = ?2.05. For the short GRBs, a best fit gives α = ?0.60 with χ<SUP>2</SUP><SUB>min</SUB> = 1.1 (with β fixed at -2.0 because it is numerically unstable). The α value for the short GRBs is significantly greater than that for the long GRBs. These results indicate that the global spectral behaviors of the long GRB sample and the XRF sample are similar, while that of the short GRBs is different. The short GRBs seem to be a unique subclass of GRBs, and they are not the higher energy extension of the long GRBs.展开更多
We use a sample of type 2 active galactic nuclei （AGNs） from SDSS DR7 in which the [O Ⅲ] ）λ5007 emission line can be modeled by two Gaussian components, a broad wing plus a narrow core, to investigate the origin ...We use a sample of type 2 active galactic nuclei （AGNs） from SDSS DR7 in which the [O Ⅲ] ）λ5007 emission line can be modeled by two Gaussian components, a broad wing plus a narrow core, to investigate the origin of the broad wing and the connection between the velocity shift of the broad wing and the physical parameters of AGNs, as well as their host galaxies. We find that the flux of the wing components is statistically roughly equal to that of the core components. However, the velocity shift of the wing component has only weak, if any, correlations with the physical properties of AGNs and the host galaxies, such as bolometric luminosity, the Eddington ratio, the mass of supermassive black holes, D4000, H3A or stellar mass. Comparing the velocity shift from our type 2 AGN sample to that from the type 1 sample in Zhang et al., we suggest that the [O Ⅲ]] broad wing originates from outflow.展开更多
Broadband afterglow observations provide a probe of the density structure of the circumburst medium. In the spreading jet model, prompt and intense X-ray/UV radiation from the reverse shock may destroy and clear the d...Broadband afterglow observations provide a probe of the density structure of the circumburst medium. In the spreading jet model, prompt and intense X-ray/UV radiation from the reverse shock may destroy and clear the dust in the circumburst cloud out to about 30pc within the initial solid angle of the jet. As the jet expands significantly, optical radiation from the high-latitude part of the jet may suffer extinction by dust outside the initial solid angle, while radiation from the part within the initial solid angle can be observed without extinction. In previous studies, it is usually assumed that the extinction is complete. We calculate the extinction effect by taking the optical depth into account. Our numerical results show that a break appears in the light curve of optical afterglow but it extends over a factor of - 80 in time rather than a factor of - 10 in time for the case of strong dust extinction and a factor of - 60 in time for the case without dust extinction. These results may provide a way to judge how large the number density of the circumburst cloud is. Finally, we carry out a detailed modeling for the afterglow of GRB 000926. Our model can provide a good fit to the multi-color observations of this event.展开更多
We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations ...We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations among the line width of HB, optical line strength of Fell and the soft X-ray slope are confirmed. We found no correlations between the UV line parameters, the equivalent widths of Lya and CIV and their ratio on one hand and the optical line parameters on the other. The UV and X-ray luminosities strongly correlate with the line widths of HB and the Fe II/HB ratio. No significant correlation is found between the infrared-soft X-my continuum slope aix and the line width of HB.展开更多
Lithium is an ancient element that is almost as old as the universe itself. As one of the building blocks of our present-day universe though, the context of lithium observed in many celestial bodies often disaccord wi...Lithium is an ancient element that is almost as old as the universe itself. As one of the building blocks of our present-day universe though, the context of lithium observed in many celestial bodies often disaccord with predictions of classic theories.展开更多
文摘美国斯隆数字化巡天(SDSS)类星体光谱中存在明显的大气天光谱线，这对类星体光谱的分析尤其是吸收线的证认造成较大干扰.以SDSS D R 1 0 的光谱为样本，对光谱中的天光线进行研究，给出了[01]姿5577魡残差的分布.发现光谱[01]姿5577魡残差处于5572.5586魡的范围内.这一结果为证认吸收线的工作提供参考，同时将有利于改进主成分分析减天光方法.
基金the National Natural Science Foundation of China.
文摘The narrowness of the distribution of the peak energy of the νF<SUB>ν</SUB> spectrum of gamma-ray bursts (GRBs) and the unification of GRB populations are great puzzles yet to be solved. We investigate the two puzzles based on the global spectral behaviors of different GRB populations, the long GRBs, the short GRBs, and the X-ray flashes (XRFs), in the HR?E<SUB>p</SUB> plane (HR the spectral hardness ratio) with BATSE and HETE-2 observations. It is found that the long GRBs and the XRFs observed by HETE-2 seem to follow the same sequence in the HR?E<SUB>p</SUB> plane, with the XRFs at the low end of this sequence. We fit the sequence by a universal Band function, and find that this sequence is mainly defined by the low energy index α, and is insensitive to the high energy index, β. With fixed β = ?5, a best fit is given by α = ?1.00 with χ<SUP>2</SUP><SUB>min</SUB>/dof = 2.2. The long and short GRBs observed by BATSE follow significantly different sequences in the HR?E<SUB>p</SUB> plane, with most of the short GRBs having a larger hardness ratio than the long GRBs at a given E<SUB>p</SUB>. For the long GRBs a best-fit yields α = ?0.30 and β = ?2.05. For the short GRBs, a best fit gives α = ?0.60 with χ<SUP>2</SUP><SUB>min</SUB> = 1.1 (with β fixed at -2.0 because it is numerically unstable). The α value for the short GRBs is significantly greater than that for the long GRBs. These results indicate that the global spectral behaviors of the long GRB sample and the XRF sample are similar, while that of the short GRBs is different. The short GRBs seem to be a unique subclass of GRBs, and they are not the higher energy extension of the long GRBs.
基金supported by the National Natural Science Foundation of China (Grant Nos.11273015,11133001 and 11003007)the National Basic Research Program of China (973 program,No.2013CB834905)the Specialized Research Fund for the Doctoral Program of Higher Education (20100091110009)
文摘We use a sample of type 2 active galactic nuclei （AGNs） from SDSS DR7 in which the [O Ⅲ] ）λ5007 emission line can be modeled by two Gaussian components, a broad wing plus a narrow core, to investigate the origin of the broad wing and the connection between the velocity shift of the broad wing and the physical parameters of AGNs, as well as their host galaxies. We find that the flux of the wing components is statistically roughly equal to that of the core components. However, the velocity shift of the wing component has only weak, if any, correlations with the physical properties of AGNs and the host galaxies, such as bolometric luminosity, the Eddington ratio, the mass of supermassive black holes, D4000, H3A or stellar mass. Comparing the velocity shift from our type 2 AGN sample to that from the type 1 sample in Zhang et al., we suggest that the [O Ⅲ]] broad wing originates from outflow.
基金Supported by the National Natural Science Foundation of China
文摘Broadband afterglow observations provide a probe of the density structure of the circumburst medium. In the spreading jet model, prompt and intense X-ray/UV radiation from the reverse shock may destroy and clear the dust in the circumburst cloud out to about 30pc within the initial solid angle of the jet. As the jet expands significantly, optical radiation from the high-latitude part of the jet may suffer extinction by dust outside the initial solid angle, while radiation from the part within the initial solid angle can be observed without extinction. In previous studies, it is usually assumed that the extinction is complete. We calculate the extinction effect by taking the optical depth into account. Our numerical results show that a break appears in the light curve of optical afterglow but it extends over a factor of - 80 in time rather than a factor of - 10 in time for the case of strong dust extinction and a factor of - 60 in time for the case without dust extinction. These results may provide a way to judge how large the number density of the circumburst cloud is. Finally, we carry out a detailed modeling for the afterglow of GRB 000926. Our model can provide a good fit to the multi-color observations of this event.
基金the National Natural Science Foundationof China and Chinese Panden Project.
文摘We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations among the line width of HB, optical line strength of Fell and the soft X-ray slope are confirmed. We found no correlations between the UV line parameters, the equivalent widths of Lya and CIV and their ratio on one hand and the optical line parameters on the other. The UV and X-ray luminosities strongly correlate with the line widths of HB and the Fe II/HB ratio. No significant correlation is found between the infrared-soft X-my continuum slope aix and the line width of HB.
文摘Lithium is an ancient element that is almost as old as the universe itself. As one of the building blocks of our present-day universe though, the context of lithium observed in many celestial bodies often disaccord with predictions of classic theories.
