Understanding the variation of lags with respect to the X-ray flux is important to explore the geometry of the inner region of the accretion disk in AGNs.We performed frequency-lag,energy–lag and spectral studies for...Understanding the variation of lags with respect to the X-ray flux is important to explore the geometry of the inner region of the accretion disk in AGNs.We performed frequency-lag,energy–lag and spectral studies for two sets of observations,in order to investigate the variations in lags with respect to X-ray flux in the AGN source Mrk 704 using the XMM-Newton observatory.We divided one of the light curves into two sections which were noticed to exhibit a flux variation.The frequency-lag spectra in different energy domains revealed that reverberation(soft)lags varied along with the flux.For the first time,we show that the blurred reflection model can consistently explain the soft excess observed in the X-ray spectra for this source.The fluxes of soft(i.e.,reflection)and hard components were noted to vary by~18%and~9%respectively,across the sections.The soft lag amplitude was found to be larger at the high flux state than the amplitude at the low flux state.Most importantly,we found that both frequency-lag and energy–lag spectra do not display significant variation between two observational data sets despite a flux variation of 43%.This phenomenon cannot be explained by the reflection model because the soft lag amplitudes must be larger in the high flux state.The probable scenario is that,in the low flux state,the obscuring cloud delays the reflected soft photons which increases the soft lag amplitude.展开更多
The mid infrared regime is little affected by extinction, and it contains a plethora of spectroscopic information. The Infrared Space Observatory (ISO) has provided access to this wealth of information. Here I present...The mid infrared regime is little affected by extinction, and it contains a plethora of spectroscopic information. The Infrared Space Observatory (ISO) has provided access to this wealth of information. Here I present new results from a study of ISO SWS spectra of about 30 AGNs, concentrating on diagnostic digrams to distinguish between star formation and AGNs as energy source in dusty galaxies (such as ULIRGs), and to discuss the Starburst AGN connection in general. Further results and all details of this study can be found in Sturm et al. (2002).展开更多
Barbara Longhi of Ravenna(1552-1638)enjoyed creating small devotional paintings depicting holy saints,in particular Saint Agnes(c.291-304).This saint’s life and martyrdom was recorded by the Bishop of Milan,Saint Amb...Barbara Longhi of Ravenna(1552-1638)enjoyed creating small devotional paintings depicting holy saints,in particular Saint Agnes(c.291-304).This saint’s life and martyrdom was recorded by the Bishop of Milan,Saint Ambrose(339-397),a Doctor of the Church and theologian,in his book Concerning Virgins(374)and by Jacobus de Voragine,the Archbishop of Genoa,in his Golden Legend(Legenda Aurea,1275).The saint’s story continues to be imaged and recounted to the present day because she is an icon of a pure and virtuous adolescent female.Barbara Longhi,along with her father,Luca Longhi(1507-1580),painted several versions of Saint Agnes.In their many depictions they composed two types of images:a single-solo-image of the saint;and her presence in a group of saints-a theme known as holy conversation.In her paintings of Saint Agnes,however,Barbara Longhi preferred to depict the solo image of the saint as virgo,a young maiden of virtue.This essay is composed of two parts:(1)an account of the life and martyrdom of Saint Agnes;and(2)an iconographical interpretation of Barbara Longhi’s Saint Agnes of Rome.展开更多
The issue of destroying small polycyclic aromatic hydrocarbon （PAH） par- ticles by radiation from AGNs is examined through optical narrow-emission line ra- tios of a sample of type II AGNs. We find that narrow-line ...The issue of destroying small polycyclic aromatic hydrocarbon （PAH） par- ticles by radiation from AGNs is examined through optical narrow-emission line ra- tios of a sample of type II AGNs. We find that narrow-line ratios [OI]λ6300/Ha and [SII]λ6716, λ6731/Hα have prominent correlations with the PAH 11.3/7.7 ratio in our selected sample of AGNs. Because of the marginal （and in some cases no） dependence of the PAH ratio on the gas metallicity, a possible explanation for the correlations is the destruction of small PAH particles by the hard ionizing field associated with the AGNs.展开更多
基金K.S.acknowledges the financial support from the Indian Space Research Organisation(ISRO),Government of India。
文摘Understanding the variation of lags with respect to the X-ray flux is important to explore the geometry of the inner region of the accretion disk in AGNs.We performed frequency-lag,energy–lag and spectral studies for two sets of observations,in order to investigate the variations in lags with respect to X-ray flux in the AGN source Mrk 704 using the XMM-Newton observatory.We divided one of the light curves into two sections which were noticed to exhibit a flux variation.The frequency-lag spectra in different energy domains revealed that reverberation(soft)lags varied along with the flux.For the first time,we show that the blurred reflection model can consistently explain the soft excess observed in the X-ray spectra for this source.The fluxes of soft(i.e.,reflection)and hard components were noted to vary by~18%and~9%respectively,across the sections.The soft lag amplitude was found to be larger at the high flux state than the amplitude at the low flux state.Most importantly,we found that both frequency-lag and energy–lag spectra do not display significant variation between two observational data sets despite a flux variation of 43%.This phenomenon cannot be explained by the reflection model because the soft lag amplitudes must be larger in the high flux state.The probable scenario is that,in the low flux state,the obscuring cloud delays the reflected soft photons which increases the soft lag amplitude.
文摘The mid infrared regime is little affected by extinction, and it contains a plethora of spectroscopic information. The Infrared Space Observatory (ISO) has provided access to this wealth of information. Here I present new results from a study of ISO SWS spectra of about 30 AGNs, concentrating on diagnostic digrams to distinguish between star formation and AGNs as energy source in dusty galaxies (such as ULIRGs), and to discuss the Starburst AGN connection in general. Further results and all details of this study can be found in Sturm et al. (2002).
文摘Barbara Longhi of Ravenna(1552-1638)enjoyed creating small devotional paintings depicting holy saints,in particular Saint Agnes(c.291-304).This saint’s life and martyrdom was recorded by the Bishop of Milan,Saint Ambrose(339-397),a Doctor of the Church and theologian,in his book Concerning Virgins(374)and by Jacobus de Voragine,the Archbishop of Genoa,in his Golden Legend(Legenda Aurea,1275).The saint’s story continues to be imaged and recounted to the present day because she is an icon of a pure and virtuous adolescent female.Barbara Longhi,along with her father,Luca Longhi(1507-1580),painted several versions of Saint Agnes.In their many depictions they composed two types of images:a single-solo-image of the saint;and her presence in a group of saints-a theme known as holy conversation.In her paintings of Saint Agnes,however,Barbara Longhi preferred to depict the solo image of the saint as virgo,a young maiden of virtue.This essay is composed of two parts:(1)an account of the life and martyrdom of Saint Agnes;and(2)an iconographical interpretation of Barbara Longhi’s Saint Agnes of Rome.
基金Supported by the National Natural Science Foundation of China
文摘The issue of destroying small polycyclic aromatic hydrocarbon （PAH） par- ticles by radiation from AGNs is examined through optical narrow-emission line ra- tios of a sample of type II AGNs. We find that narrow-line ratios [OI]λ6300/Ha and [SII]λ6716, λ6731/Hα have prominent correlations with the PAH 11.3/7.7 ratio in our selected sample of AGNs. Because of the marginal （and in some cases no） dependence of the PAH ratio on the gas metallicity, a possible explanation for the correlations is the destruction of small PAH particles by the hard ionizing field associated with the AGNs.
