Historical optical data are combined on the BL Lac object OQ 530. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate emission processes. To ...Historical optical data are combined on the BL Lac object OQ 530. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate emission processes. To examine the possible existence of a lag between variations in different optical bands from this source, a statistical analysis is performed through the discrete correlation function （DCF） method and the z-transformed discrete correlation function （ZDCF） method. Monte Carlo simulations called ＂flux redistribution/random subset selection＂ （FR/RSS） are performed to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties. The analysis confirms that the variations in different optical light curves are strongly correlated, with zero-lag within the errors. Long term variability of color indexes is also analyzed. The result suggests a strong correlation between color index and brightness. A clear bluer-when-brighter chromatism is found, in the sense that the spectrum steepens as the brightness decreases.展开更多
The post-1994 observations of the blazar OQ 530 in optical BVRI bands, and radio observations at 22 GHz and 37 GHz were collected. The date compensated discrete Fourier transform （DCDFr） and CLEANest methods were us...The post-1994 observations of the blazar OQ 530 in optical BVRI bands, and radio observations at 22 GHz and 37 GHz were collected. The date compensated discrete Fourier transform （DCDFr） and CLEANest methods were used to search for possible periodicities. Two possible periods of 456±100 days and 258±29 days were found in the optical bands. The existence of possible correlations between the optical and radio emissions was investigated by means of discrete correlation function （DCF） analysis, and no significant correlation was found. Some possible mechanisms for the periodic variability are discussed.展开更多
A periodicity analysis of the radio light curves of the blazar NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved phase dispersion mini- mization technique. The result, which shows two persistent pe...A periodicity analysis of the radio light curves of the blazar NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved phase dispersion mini- mization technique. The result, which shows two persistent periodic components of 6 and ~ 10 yr at all three frequencies, is consistent with the results obtained with the Lomb-Scargle periodogram and weighted wavelet Z-transform algorithms. The reliability of the derived periodicities is confirmed by the Monte Carlo numerical sim- ulations which show a high statistical confidence. （Quasi-）Periodic fluctuations of the radio luminosity of NRAO 530 might be associated with the oscillations of the accre- tion disk triggered by hydrodynamic instabilities of the accreted flow.展开更多
In this paper,the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8,8.0 and 14.5 GHz over a time baseline of three deca...In this paper,the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8,8.0 and 14.5 GHz over a time baseline of three decades.Two prominent periodicities on time scales of ～6.3 and ～9.5 a are identified at all three frequencies,in agreement with previous results derived from different numerical techniques,confirming the multiplicity of the periodicities in NRAO 530.In addition to these two significant periods,there is also evidence of shorter-timescale periodicities of ～5.0,～4.2,～3.4 and ～2.8 a showing lower amplitude in the periodograms.The physical mechanisms responsible for the radio quasi-periodic oscillations and the multiplicity of the periods are discussed.展开更多
We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz....We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz. The VLBI images show a core-jet structure with an oscillating trajectory on a scale of about 30 mas north of the strongest compact component （core）. Superluminal motions are detected in five of the jet components with apparent velocities in the range of 13.6 to 25.2c. A new component is detected at 15 GHz with the VLBA observations, which appears to be associated with the outburst in 2002. Significant polarized emission is detected around the core with the VLBA observations at 15 GHz. Rapid variations of the polarization intensity and angle are found between the epochs in 2002 and 2004. On the kpc-scale, a distant component （labelled as WL） located 11 arcsec west （PA=-86°） of the core is detected beyond the core-jet structure which extended to several hundreds of mas in the north-west direction （-50°）. A significant emission between the core-jet structure and the WL is revealed. A clump of diffuse emission （labelled EL, 12 arcsec long） at PA 70° to the core, is also detected in the VLA observations, suggesting the presence of double lobes in the source. The core component shows a fiat spectrum, while the distant components WL and EL have steep spectra. The steep spectra of the distant components and the detection of the arched emission suggest that the distant components are lobes or hot-spots powered by the core of NRAO 530. The morphologies from pc- to kpcscales and the bending of jets are investigated. The observed radio morphology from pc to kcp appears to favor the model in which precession or wobbling of the nuclear disk drives the helical motion of the radio plasma and produces the S-shaped structure on kpc scale.展开更多
To characterize the long-term service performance and predict the lifetime of heat-resistant steel applications,more than 300 test pieces can be loaded simultaneously at Baosteel to determine the relationship between ...To characterize the long-term service performance and predict the lifetime of heat-resistant steel applications,more than 300 test pieces can be loaded simultaneously at Baosteel to determine the relationship between stress and rupture duration at specific temperatures. In addition, versatile testing methods have been established that evaluate creep-rupture, stress-relaxation, and creep-fatigue, as well as state-of-the-art tensile testing at hyper-high temperatures exceeding 2 100 ~2. Based on the Larson-Miller method, according to API 530, the accumulation of large volumes of data with respect to stress, temperature, and rupture time of actually tested steels ensures the reliability of predicting the allowable working stress over 100 000 h at any given temperature. For examples ,the stress tendencies against rupture time of T/P91 and T/P92 steel tubes, as obtained by Baosteel, are consistent with those from NIMS and ECCC. As an accredited provider of the Proficiency Testing schemes in ISO/ IEC 17025 and ISO/IEC 17043, Baosteel has periodically organized national proficiency testing with respect to creep and rupture, thereby providing an efficient way for all parties to assess their technical competence when performing uniaxial creep testing by the methods in ISO 204 and ASTM E139.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 10975145)funded by Fuyang Normal College, the Research Foundation of the Department of Education of Anhui Province (KJ2010B159)
文摘Historical optical data are combined on the BL Lac object OQ 530. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate emission processes. To examine the possible existence of a lag between variations in different optical bands from this source, a statistical analysis is performed through the discrete correlation function （DCF） method and the z-transformed discrete correlation function （ZDCF） method. Monte Carlo simulations called ＂flux redistribution/random subset selection＂ （FR/RSS） are performed to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties. The analysis confirms that the variations in different optical light curves are strongly correlated, with zero-lag within the errors. Long term variability of color indexes is also analyzed. The result suggests a strong correlation between color index and brightness. A clear bluer-when-brighter chromatism is found, in the sense that the spectrum steepens as the brightness decreases.
基金the National Natural Science Foundation of China
文摘The post-1994 observations of the blazar OQ 530 in optical BVRI bands, and radio observations at 22 GHz and 37 GHz were collected. The date compensated discrete Fourier transform （DCDFr） and CLEANest methods were used to search for possible periodicities. Two possible periods of 456±100 days and 258±29 days were found in the optical bands. The existence of possible correlations between the optical and radio emissions was investigated by means of discrete correlation function （DCF） analysis, and no significant correlation was found. Some possible mechanisms for the periodic variability are discussed.
基金supported by the National Basic Research Programof China (973 Program,2009CB24900)the Guangxi Natural Science Foundation (0991018Z)+3 种基金the Science and Technology Commission of Shanghai Municipality (06DZ22101)supported by a grant from the Chinese Academy of Sciencesa visitor grant from the The Netherlands Science Foundationsupported by funds from the NSF,NASA,and the University of Michigan
文摘A periodicity analysis of the radio light curves of the blazar NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved phase dispersion mini- mization technique. The result, which shows two persistent periodic components of 6 and ~ 10 yr at all three frequencies, is consistent with the results obtained with the Lomb-Scargle periodogram and weighted wavelet Z-transform algorithms. The reliability of the derived periodicities is confirmed by the Monte Carlo numerical sim- ulations which show a high statistical confidence. （Quasi-）Periodic fluctuations of the radio luminosity of NRAO 530 might be associated with the oscillations of the accre- tion disk triggered by hydrodynamic instabilities of the accreted flow.
基金supported by the National Basic Research Program of China (Grant Nos.2009CB24900 and 2012CB821800)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA04060700)+1 种基金the National Natural Science Foundation of China (Grant No.61261017)The University of Michigan Radio Astronomy Observatory is supported by the funds from NSF,NASA,and the University of Michigan
文摘In this paper,the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8,8.0 and 14.5 GHz over a time baseline of three decades.Two prominent periodicities on time scales of ～6.3 and ～9.5 a are identified at all three frequencies,in agreement with previous results derived from different numerical techniques,confirming the multiplicity of the periodicities in NRAO 530.In addition to these two significant periods,there is also evidence of shorter-timescale periodicities of ～5.0,～4.2,～3.4 and ～2.8 a showing lower amplitude in the periodograms.The physical mechanisms responsible for the radio quasi-periodic oscillations and the multiplicity of the periods are discussed.
基金the National Natural Science Foundation of China
文摘We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz. The VLBI images show a core-jet structure with an oscillating trajectory on a scale of about 30 mas north of the strongest compact component （core）. Superluminal motions are detected in five of the jet components with apparent velocities in the range of 13.6 to 25.2c. A new component is detected at 15 GHz with the VLBA observations, which appears to be associated with the outburst in 2002. Significant polarized emission is detected around the core with the VLBA observations at 15 GHz. Rapid variations of the polarization intensity and angle are found between the epochs in 2002 and 2004. On the kpc-scale, a distant component （labelled as WL） located 11 arcsec west （PA=-86°） of the core is detected beyond the core-jet structure which extended to several hundreds of mas in the north-west direction （-50°）. A significant emission between the core-jet structure and the WL is revealed. A clump of diffuse emission （labelled EL, 12 arcsec long） at PA 70° to the core, is also detected in the VLA observations, suggesting the presence of double lobes in the source. The core component shows a fiat spectrum, while the distant components WL and EL have steep spectra. The steep spectra of the distant components and the detection of the arched emission suggest that the distant components are lobes or hot-spots powered by the core of NRAO 530. The morphologies from pc- to kpcscales and the bending of jets are investigated. The observed radio morphology from pc to kcp appears to favor the model in which precession or wobbling of the nuclear disk drives the helical motion of the radio plasma and produces the S-shaped structure on kpc scale.
文摘To characterize the long-term service performance and predict the lifetime of heat-resistant steel applications,more than 300 test pieces can be loaded simultaneously at Baosteel to determine the relationship between stress and rupture duration at specific temperatures. In addition, versatile testing methods have been established that evaluate creep-rupture, stress-relaxation, and creep-fatigue, as well as state-of-the-art tensile testing at hyper-high temperatures exceeding 2 100 ~2. Based on the Larson-Miller method, according to API 530, the accumulation of large volumes of data with respect to stress, temperature, and rupture time of actually tested steels ensures the reliability of predicting the allowable working stress over 100 000 h at any given temperature. For examples ,the stress tendencies against rupture time of T/P91 and T/P92 steel tubes, as obtained by Baosteel, are consistent with those from NIMS and ECCC. As an accredited provider of the Proficiency Testing schemes in ISO/ IEC 17025 and ISO/IEC 17043, Baosteel has periodically organized national proficiency testing with respect to creep and rupture, thereby providing an efficient way for all parties to assess their technical competence when performing uniaxial creep testing by the methods in ISO 204 and ASTM E139.
