We have trapped a cold sample of cesium atoms in a magneto-optical trap.The damped harmonic force of magneto-optical trap was used to capture and trap the cesium atoms directly from a room temperature vapor.About 1.5&...We have trapped a cold sample of cesium atoms in a magneto-optical trap.The damped harmonic force of magneto-optical trap was used to capture and trap the cesium atoms directly from a room temperature vapor.About 1.5×10^(7) cesium atoms with a density of 3×10^(9) atoms/cm^(3) formed a 4mm^(3) cesium atomic cloud with temperature below 500μK.展开更多
Using the high time-resolution and 64ms resolution data of the burst and transient source experiment,we performed an autocorrelation analysis of the energy dependence of burst pulse width in short gamma-ray bursts.A m...Using the high time-resolution and 64ms resolution data of the burst and transient source experiment,we performed an autocorrelation analysis of the energy dependence of burst pulse width in short gamma-ray bursts.A method free from potential cosmological effects has been proposed.This allows us to use a sample with a size comparable to that used for long and bright bursts.Our result shows that the profiles of short bursts exhibit a very good power-law between profile width and photon energy,with an index~-0.3.This result is consistent with a united origin of the bimodal distribution.展开更多
A new model of noise processes,the so-called dynamic model,is presentedin which all the five noise processes(White PW,White FM,Random Walk FM,FlickerPM and Flieker FM)are involved.Withsuch a model and a special method...A new model of noise processes,the so-called dynamic model,is presentedin which all the five noise processes(White PW,White FM,Random Walk FM,FlickerPM and Flieker FM)are involved.Withsuch a model and a special method,the autocorrelationfunctions of the five noise processes are deduced.展开更多
In the framework of BLR in AGNs, i.e. large number of small, cold and dense emission-line clouds immerging in an intercloud hot medium, a delicate radiation model for a typical emission cloud is established, in which ...In the framework of BLR in AGNs, i.e. large number of small, cold and dense emission-line clouds immerging in an intercloud hot medium, a delicate radiation model for a typical emission cloud is established, in which the backside photoionization of the cloud against the central continuum source by the scattered diffuse continuum in the hot medium is considered. Under the assumption of the radial kinematics of the BLR clouds, the line profiles for the two important UV emission-lines, Lya and CIV/11549 are computed; and based on these calculations, various physical factors that affect the properties of the emission-line profiles are discussed. It is concluded that: (i) when the BLR clouds is inflow, there exists a confining hot medium with density around 2 x 105 cm-3. In this case, theoretical line profiles agree well with the observational; (ii) both symmetric Lya and nearly symmetric CIV line profiles show blue velocity shifts, the quantities of which are sensitive to the cutoff of the outer radius of the BLR. It is suggested that this cutoff effect is physical background to explain the observations that high ionization lines in the spectra of AGNs have some systematic blue shifts relative to those low ionization lines which usually characterize their source system velocities.展开更多
The present paper derives the modified expression of broad emission line profiles for the kinematic model of radiation pressure driving BLR gas outflow in the BLR, and discusses the intrinsic emission difference betwe...The present paper derives the modified expression of broad emission line profiles for the kinematic model of radiation pressure driving BLR gas outflow in the BLR, and discusses the intrinsic emission difference between the two lines HeIλ5876 and Hβ. It is shown that the fact that the observed line width of HeIλ5876 is broader than that of Hβ cannot be explained by W. G. Mathews’ modified model. For comparison, line profiles of gravitational infall model and orbital disk model are also calculated; the latter is in good agreement with the observations. Thereupon, conclusion is reached that gravitational infall is an important process in the BLR gas motion.展开更多
基金Supported by the National Natural Science Foundation of China.
文摘We have trapped a cold sample of cesium atoms in a magneto-optical trap.The damped harmonic force of magneto-optical trap was used to capture and trap the cesium atoms directly from a room temperature vapor.About 1.5×10^(7) cesium atoms with a density of 3×10^(9) atoms/cm^(3) formed a 4mm^(3) cesium atomic cloud with temperature below 500μK.
文摘Using the high time-resolution and 64ms resolution data of the burst and transient source experiment,we performed an autocorrelation analysis of the energy dependence of burst pulse width in short gamma-ray bursts.A method free from potential cosmological effects has been proposed.This allows us to use a sample with a size comparable to that used for long and bright bursts.Our result shows that the profiles of short bursts exhibit a very good power-law between profile width and photon energy,with an index~-0.3.This result is consistent with a united origin of the bimodal distribution.
文摘A new model of noise processes,the so-called dynamic model,is presentedin which all the five noise processes(White PW,White FM,Random Walk FM,FlickerPM and Flieker FM)are involved.Withsuch a model and a special method,the autocorrelationfunctions of the five noise processes are deduced.
基金Project supported by Pangden Project FoundationNational Natural Science Foundation of China.
文摘In the framework of BLR in AGNs, i.e. large number of small, cold and dense emission-line clouds immerging in an intercloud hot medium, a delicate radiation model for a typical emission cloud is established, in which the backside photoionization of the cloud against the central continuum source by the scattered diffuse continuum in the hot medium is considered. Under the assumption of the radial kinematics of the BLR clouds, the line profiles for the two important UV emission-lines, Lya and CIV/11549 are computed; and based on these calculations, various physical factors that affect the properties of the emission-line profiles are discussed. It is concluded that: (i) when the BLR clouds is inflow, there exists a confining hot medium with density around 2 x 105 cm-3. In this case, theoretical line profiles agree well with the observational; (ii) both symmetric Lya and nearly symmetric CIV line profiles show blue velocity shifts, the quantities of which are sensitive to the cutoff of the outer radius of the BLR. It is suggested that this cutoff effect is physical background to explain the observations that high ionization lines in the spectra of AGNs have some systematic blue shifts relative to those low ionization lines which usually characterize their source system velocities.
基金Project supported by the National Natural Science Foundation of China
文摘The present paper derives the modified expression of broad emission line profiles for the kinematic model of radiation pressure driving BLR gas outflow in the BLR, and discusses the intrinsic emission difference between the two lines HeIλ5876 and Hβ. It is shown that the fact that the observed line width of HeIλ5876 is broader than that of Hβ cannot be explained by W. G. Mathews’ modified model. For comparison, line profiles of gravitational infall model and orbital disk model are also calculated; the latter is in good agreement with the observations. Thereupon, conclusion is reached that gravitational infall is an important process in the BLR gas motion.
