Recent studies reveal that weak Lyα emission line may be a ubiquitous feature of nearby BL Laceratae objects(BL Lacs). We present a survey of the Lyα emission lines in BL Lacs, with a focus on data obtained by the C...Recent studies reveal that weak Lyα emission line may be a ubiquitous feature of nearby BL Laceratae objects(BL Lacs). We present a survey of the Lyα emission lines in BL Lacs, with a focus on data obtained by the Cosmic Origins Spectrograph onboard the Hubble Space Telescope. Among the11 selected targets, seven show a clear detection of the intrinsic Lyα emission line, while one manifests a marginal detection. Two of these intrinsic Lyα lines are newly detected in this work(FBQS J1217+3007 and3 C 66 A). Most selected BL Lacs are either high or intermediate-frequency peaked BL Lacs, with the only exception being one low-frequency peaked BL Lac. A strong anti-correlation between the line equivalent width and the continuum luminosity was found. The possible sources of ionizing photons that are responsible for production of the Lyα emission line are studied based on a widely accepted detailed accretion-jet model. It is found that the clouds of the broad line region are unlikely to be located in the jet cone region with an inclination angle of less than 10 degrees. Contributions from the jet and disk to the emission lines are found to be comparable. Additionally, a possible way to constrain the accretion rate from the emission line is proposed.展开更多
S5 0716＋714 is one of the targets in our long term blazar monitoring program carried out with the 1.56-m telescope at Sheshan Station of Shanghai Astronomical Observatory, China. We report a very rapid variability of...S5 0716＋714 is one of the targets in our long term blazar monitoring program carried out with the 1.56-m telescope at Sheshan Station of Shanghai Astronomical Observatory, China. We report a very rapid variability of △I=0.611±0.102 mag over 3.6 min detected in our monitoring program during the period from December 2000 to March 2007. The rapid variability suggests that the mass for the central black hole is log（M/M⊙） = 7.68 - 8.38.展开更多
The broadband spectral energy distribution（SED） of blazars is generally interpreted as radiation arising from synchrotron and inverse Compton mechanisms. Traditionally,the underlying source parameters responsible fo...The broadband spectral energy distribution（SED） of blazars is generally interpreted as radiation arising from synchrotron and inverse Compton mechanisms. Traditionally,the underlying source parameters responsible for these emission processes,like particle energy density,magnetic field,etc.,are obtained through simple visual reproduction of the observed fluxes. However,this procedure is incapable of providing confidence ranges for the estimated parameters. In this work,we propose an efficient algorithm to perform a statistical fit of the observed broadband spectrum of blazars using different emission models. Moreover,we use the observable quantities as the fit parameters,rather than the direct source parameters which govern the resultant SED. This significantly improves the convergence time and eliminates the uncertainty regarding initial guess parameters. This approach also has an added advantage of identifying the degenerate parameters,which can be removed by including more observable information and/or additional constraints. A computer code developed based on this algorithm is implemented as a user-defined routine in the standard X-ray spectral fitting package,XSPEC. Further,we demonstrate the efficacy of the algorithm by fitting the well sampled SED of blazar 3 C 279 during its gamma ray flare in 2014.展开更多
The multiband nonthermal emissions in radio, X-ray, and very high-energy（VHE） γ-ray bands from two distant blazars, H 2356–309 and 1ES 1218＋304, havebeen detected, and, especially from recent observations with th...The multiband nonthermal emissions in radio, X-ray, and very high-energy（VHE） γ-ray bands from two distant blazars, H 2356–309 and 1ES 1218＋304, havebeen detected, and, especially from recent observations with the Suzaku, MAGICand VERITAS telescopes, clearly reveal nonthermal power-law spectra. We study thebroadband nonthermal spectra of the two sources by using a combination of a one-zone homogeneous synchrotron self-Compton （SSC） model and an inhomogeneousconical jet model, where the new external background light （EBL） model is taken intoaccount. The results show that （1） the nonthermal emissions of the two blazars, rang-ing from X-rays to VHE γ-rays, are from the homogeneous zone whereas the emis-sions in the radio bands can be explained as the radiation from the inhomogeneousconical jet; （2） a strict lower-limit EBL model can be used to explain their observedspectra well.展开更多
基金supported by the National Key R&D Program of China (2017YFA0402600)the National Natural Science Foundation of China (Grant Nos. 11525312 and U1531130)
文摘Recent studies reveal that weak Lyα emission line may be a ubiquitous feature of nearby BL Laceratae objects(BL Lacs). We present a survey of the Lyα emission lines in BL Lacs, with a focus on data obtained by the Cosmic Origins Spectrograph onboard the Hubble Space Telescope. Among the11 selected targets, seven show a clear detection of the intrinsic Lyα emission line, while one manifests a marginal detection. Two of these intrinsic Lyα lines are newly detected in this work(FBQS J1217+3007 and3 C 66 A). Most selected BL Lacs are either high or intermediate-frequency peaked BL Lacs, with the only exception being one low-frequency peaked BL Lac. A strong anti-correlation between the line equivalent width and the continuum luminosity was found. The possible sources of ionizing photons that are responsible for production of the Lyα emission line are studied based on a widely accepted detailed accretion-jet model. It is found that the clouds of the broad line region are unlikely to be located in the jet cone region with an inclination angle of less than 10 degrees. Contributions from the jet and disk to the emission lines are found to be comparable. Additionally, a possible way to constrain the accretion rate from the emission line is proposed.
基金the National Natural Science Foundationof China(Grant Nos.10633010 and 11173009)the National Basic Research Program of China(973 program,2007CB815405)+2 种基金the Bureau of Education of Guangzhou Municipality(No.11 Sui-Jiao-Ke[2009])Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(GDUPS)(2009)Yangcheng Scholar Funded Scheme(10A027S) and the Joint Laboratory for Optical Astronomy of Chinese Academy of Sciences
文摘S5 0716＋714 is one of the targets in our long term blazar monitoring program carried out with the 1.56-m telescope at Sheshan Station of Shanghai Astronomical Observatory, China. We report a very rapid variability of △I=0.611±0.102 mag over 3.6 min detected in our monitoring program during the period from December 2000 to March 2007. The rapid variability suggests that the mass for the central black hole is log（M/M⊙） = 7.68 - 8.38.
文摘The broadband spectral energy distribution（SED） of blazars is generally interpreted as radiation arising from synchrotron and inverse Compton mechanisms. Traditionally,the underlying source parameters responsible for these emission processes,like particle energy density,magnetic field,etc.,are obtained through simple visual reproduction of the observed fluxes. However,this procedure is incapable of providing confidence ranges for the estimated parameters. In this work,we propose an efficient algorithm to perform a statistical fit of the observed broadband spectrum of blazars using different emission models. Moreover,we use the observable quantities as the fit parameters,rather than the direct source parameters which govern the resultant SED. This significantly improves the convergence time and eliminates the uncertainty regarding initial guess parameters. This approach also has an added advantage of identifying the degenerate parameters,which can be removed by including more observable information and/or additional constraints. A computer code developed based on this algorithm is implemented as a user-defined routine in the standard X-ray spectral fitting package,XSPEC. Further,we demonstrate the efficacy of the algorithm by fitting the well sampled SED of blazar 3 C 279 during its gamma ray flare in 2014.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10778702 and 10803005)the 973 Program (2009CB824800)Yunnan Province under grant 2009 OC
文摘The multiband nonthermal emissions in radio, X-ray, and very high-energy（VHE） γ-ray bands from two distant blazars, H 2356–309 and 1ES 1218＋304, havebeen detected, and, especially from recent observations with the Suzaku, MAGICand VERITAS telescopes, clearly reveal nonthermal power-law spectra. We study thebroadband nonthermal spectra of the two sources by using a combination of a one-zone homogeneous synchrotron self-Compton （SSC） model and an inhomogeneousconical jet model, where the new external background light （EBL） model is taken intoaccount. The results show that （1） the nonthermal emissions of the two blazars, rang-ing from X-rays to VHE γ-rays, are from the homogeneous zone whereas the emis-sions in the radio bands can be explained as the radiation from the inhomogeneousconical jet; （2） a strict lower-limit EBL model can be used to explain their observedspectra well.
