BL Lacertae objects（BL Lacs） are the dominant population of Te V emitting blazars. In this work, we investigate whether there are any special observational properties associated with Te V sources.To do so, we will c...BL Lacertae objects（BL Lacs） are the dominant population of Te V emitting blazars. In this work, we investigate whether there are any special observational properties associated with Te V sources.To do so, we will compare the observational properties of Te V detected BL Lacs（Te V BLs） with non-Te V detected BL Lac objects（non-Te V BLs）. From the 3rd Fermi/LAT source catalog（3FGL）, we can obtain662 BL Lacs, out of which 47 are Te V BLs and 615 are non-Te V BLs. Their multi-wavelength flux densities（FpR, FO, FX and Fγ）, photon spectral indexes（α^phXand α^phγ）, and effective spectral indexes（αRO and αOX）are compiled from the available literature. Then the luminosities（log ν LR, log ν LO, log ν LX, log ν Lγ）are calculated. From comparisons, we find that Te V BLs are different from low synchrotron peaked BLs and intermediate synchrotron peaked BLs, but Te V BLs show similar properties to high synchrotron peaked（HSP） BLs. Therefore, we concentrated on a comparison between Te V HSP BLs and non-Te V HSP BLs.Analysis results suggest that Te V HSP BLs and non-Te V HSP BLs exhibit some differences in their αRO and αphγ, but their other properties are quite similar.展开更多
The geometry of broad-line regions （BLRs） in active galactic nuclei （AGNs） is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolut...The geometry of broad-line regions （BLRs） in active galactic nuclei （AGNs） is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolute magnitude at R-band, MR, by using the empirical relation between MR and black hole mass Mbh. The sizes of the broad-line regions for MglI are derived from the widths of MglI lines and the black hole masses. Compared with the empirical relation between BLR size RBLR and MgII line luminosity LMglI, it is found the BLR sizes in the BL Lac objects derived in this paper are 2-3 orders of magnitude higher. If the BLR geometry of these sources is disklike, then the viewing angle between the axis and the line of sight is in the range of - 2° - 15°, which is consistent with the unification scheme.展开更多
We present a large sample which includes 82 BL Lac objects with red- shifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A...We present a large sample which includes 82 BL Lac objects with red- shifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A). The correlations in other bands are very weak. Five TeV BL Lacs and two suspect sources are found to have similar properties as high- frequency- peaked BL Lacs (HBLs). Our results suggest that both the radio and optical emissions are from the same radiation mech- anism in the SSC model. The TeV BL Lac candidates should be HBLs or HBL-like objects with small redshifts.展开更多
BL Lacertae （BL Lac） objects at high redshifts （z ≥ 2） are rarely detected. Through careful analysis of its Sloan Digital Sky Survey spectrum, BZB J1450＋5201 is confirmed to be a high-z BL Lac object with z ≥ 2...BL Lacertae （BL Lac） objects at high redshifts （z ≥ 2） are rarely detected. Through careful analysis of its Sloan Digital Sky Survey spectrum, BZB J1450＋5201 is confirmed to be a high-z BL Lac object with z ≥ 2.471 by identifying the Lyα 1216 and CIV 1548/1550 absorption lines. This indicates that BZB J1450＋5201 is the most distant BL Lac object discovered to date. Careful analysis of the five-year Fermi-LAT data of 2FGL J1451.0＋5159 shows that its γ-ray emission is robust with a confidence level of 6.2σ at 1-3 GeV and 6.7σ at 3-10 GeV. This analysis with the five-year data overcomes confusion with its bright neighbor, which is a problem when analyzing the two-year data. In addition, 2FGL J 1451.0＋5159 is confirmed to be associated with BZB J1450＋5201 using the five-year data. The analysis of multiwavelength data, from radio to γ-ray energies, indicates that BZB J1450＋5201 is an intermediate synchrotron peaked （ISP） source. Its multiwavelength properties are consistent with distributions of other ISP sources at lower redshifts in the second Fermi-LAT AGN catalog. The pure synchrotron self-Compton （SSC） model seems to be disfavored, but the scattering of weak external emission plus the SSC process can provide a satisfactory description of the broadband emission.展开更多
In this work, we collected a sample of 69 TeV blazars from TeVCat, obtained their multi-wavelength observations, and fitted their spectral energy distributions by using a second degree poly-nomial function. The struct...In this work, we collected a sample of 69 TeV blazars from TeVCat, obtained their multi-wavelength observations, and fitted their spectral energy distributions by using a second degree poly-nomial function. The structure parameters of synchrotron bumps for 68 blazars and those of inverse- Compton bumps for 56 blazars were derived. Then, we conducted statistical analysis on the parame-ters （curvature, peak frequency, peak luminosity, bolometric luminosity and X/γ-ray spectral indexes）. From our analysis and discussions, we can conclude the following： （1） There is a clear positive correla-tion between the synchrotron peak frequency, log （Vp）^s, and the inverse-Compton peak frequency, log （Vp）^IC, and between the synchrotron peak luminosity, log （Vp）^sL（Vp）^s, and the inverse-Compton peak luminosity,log（Vp）^IC L（Vp）^IC. （2） The correlation between the peak frequency and the curvature of synchrotron bump is clearly different from that of the inverse-Compton bump, which further indicates that there are differ-ent emission mechanisms between them. （3） There is a correlation between log （Vp）^IC and γ-ray spectral index, αγ, for the TeV blazars： log （Vp）^IC = -（4.59 ± 0.30）αγ ＋ （32.67 ±0.59）, which is consistent with previous work. （4） An ＂L-shape＂ relation is found between log（Vp）^s Up and αx for both TeV blazars and Fermi blazars. A significant correlation between log（Vp）^s and X-ray photon index （αx） is found for the TeV blazars with high synchrotron peak frequency： log（Vp）^s = -（3.20 ± 0.34）αx ＋ （24.33 ± 0.79）, while the correlation is positive for low synchrotron peaked TeV sources. （5） In the αx -αγ diagram, there is also an ＂L-shape.＂ The anti-correlation is consistent with results available in the literature, and we also find a positive correlation between them. （6） Inverse-Compton dominant sources have luminous bolometric luminosities.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
Observations suggest that γ-ray loud blazars are strongly beamed. The Fermi mission has detected many of blazars, which provide us with a good opportunity to investigate the emission mechanism and the beaming effect ...Observations suggest that γ-ray loud blazars are strongly beamed. The Fermi mission has detected many of blazars, which provide us with a good opportunity to investigate the emission mechanism and the beaming effect in the γ-ray region. We compiled the X-ray observations for 138 Fermi blazars （54 flat spectrum radio quasars, 36 low-peaked BL Lacertae objects, and 48 high-peaked BL Lacertae objects） and calculated their Doppler factors, δγ. It is interesting that the calculated Doppler factors, δγ, are strongly correlated with the γ-ray luminosity.展开更多
The beaming effect is important for understanding the observational properties of blazars.In this work, we collect 91 Fermi blazars with available radio Doppler factors. γ-ray Doppler factors are estimated and compar...The beaming effect is important for understanding the observational properties of blazars.In this work, we collect 91 Fermi blazars with available radio Doppler factors. γ-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. The intrinsic（de-beamed）γ-ray flux density（fγin）, intrinsic γ-ray luminosity（Lγin） and intrinsic synchrotron peak frequency（VPin）are calculated. Then we study the correlations between finγand redshift and find that they follow the theoretical relation： log f =-2.0 log z ＋ const. When the subclasses are considered, we find that stationary jets are perhaps dominant in low synchrotron peaked blazars. Sixty-three Fermi blazars with both available short variability time scales（？T） and Doppler factors are also collected. We find that the intrinsic relationship between Lγin and ？Tinobeys the Elliot ＆ Shapiro and Abramowicz ＆ Nobili relations. Strong positive correlation between fγinand VPinis found, suggesting that synchrotron emissions are highly correlated with γ-ray emissions.展开更多
We compiled the radio, optical and X-ray data of blazars from the Sloan Digital Sky Survey database, and presented the distribution of luminosities and broadband spectral indices. The distribution of luminosities show...We compiled the radio, optical and X-ray data of blazars from the Sloan Digital Sky Survey database, and presented the distribution of luminosities and broadband spectral indices. The distribution of luminosities shows that the averaged luminosity of flat spectrum radio quasars（FSRQs） is larger than that of BL Lacertae（BL Lac） objects. On the other hand, the broadband spectral energy distribution reveals that FSRQs and low energy peaked BL Lac objects have similar spectral properties,but high energy peaked BL Lac objects have a distinct spectral property. This may be due to the fact that different subclasses of blazars have different intrinsic environments and are at different cooling levels. Even so, a unified scheme is also revealed from the color-color diagram, which hints that there are similar physical processes operating in all objects under a range of intrinsic physical conditions or beaming parameters.展开更多
We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02m optical teles...We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is -8.0 mJy in the R band, i.e., the AGN has a magnitude of R - 13.96 mag.展开更多
Using the database of the University of Michigan Radio Astronomy Observatory （UMRAO） at three radio frequencies （4.8, 8 and 14.5 GHz）, we determined the short-term variability timescales for 166 radio sources. The...Using the database of the University of Michigan Radio Astronomy Observatory （UMRAO） at three radio frequencies （4.8, 8 and 14.5 GHz）, we determined the short-term variability timescales for 166 radio sources. The timescales are 0.15d （2007＋777） to 176.17 d （0528-250） with an average timescale of Atobs = 17.1 4- 16.5 d for the whole sample. The timescales are used to calculate the brightness temperatures, TB. The value of log TB is in the range of log TB = 10.47 to 19.06 K. In addition, we also estimated the boosting factor for the sources. The correlation between the polarization and the Doppler factor is also discussed.展开更多
We analyze the spectral variability and spectral evolution in the optical en- ergy region by using multiband （BVRI） optical observations of S5 0716＋714 spanning 1994 to 2005. The spectrum hardens when the source be...We analyze the spectral variability and spectral evolution in the optical en- ergy region by using multiband （BVRI） optical observations of S5 0716＋714 spanning 1994 to 2005. The spectrum hardens when the source becomes brighter, which is con- sistent with general BL Lac objects. The spectral evolution parameter implies that the spectral variability is small in optical bands over 10 years. A simple model represent- ing the variability of a synchrotron component can explain the spectral changes. In addition, we employ the z-transformed discrete correlation function （ZDCF） to ana- lyze the optical multiband flux correlation. The long-term light curve behavior reveals that the variability time scales are 3.5 yr in the B-band, 3.3 yr in the V-band, 3.4 yr in the R-band and 3.5 yr in the/-band. The time lags between any two optical bands were not found when considering statistical errors.展开更多
基金partially supported by the National Natural Science Foundation of China(Grant Nos.10633010,11173009,U1431112 and U1531245)the Innovation Foundation of Guangzhou University(IFGZ)+2 种基金Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(GDUPS,2009)Yangcheng Scholar Funded Scheme(10A027S)support for Astrophysics Key Subjects of Guangdong Province and Guangzhou City
文摘BL Lacertae objects（BL Lacs） are the dominant population of Te V emitting blazars. In this work, we investigate whether there are any special observational properties associated with Te V sources.To do so, we will compare the observational properties of Te V detected BL Lacs（Te V BLs） with non-Te V detected BL Lac objects（non-Te V BLs）. From the 3rd Fermi/LAT source catalog（3FGL）, we can obtain662 BL Lacs, out of which 47 are Te V BLs and 615 are non-Te V BLs. Their multi-wavelength flux densities（FpR, FO, FX and Fγ）, photon spectral indexes（α^phXand α^phγ）, and effective spectral indexes（αRO and αOX）are compiled from the available literature. Then the luminosities（log ν LR, log ν LO, log ν LX, log ν Lγ）are calculated. From comparisons, we find that Te V BLs are different from low synchrotron peaked BLs and intermediate synchrotron peaked BLs, but Te V BLs show similar properties to high synchrotron peaked（HSP） BLs. Therefore, we concentrated on a comparison between Te V HSP BLs and non-Te V HSP BLs.Analysis results suggest that Te V HSP BLs and non-Te V HSP BLs exhibit some differences in their αRO and αphγ, but their other properties are quite similar.
基金Supported by the National Natural Science Foundation of China.
文摘The geometry of broad-line regions （BLRs） in active galactic nuclei （AGNs） is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolute magnitude at R-band, MR, by using the empirical relation between MR and black hole mass Mbh. The sizes of the broad-line regions for MglI are derived from the widths of MglI lines and the black hole masses. Compared with the empirical relation between BLR size RBLR and MgII line luminosity LMglI, it is found the BLR sizes in the BL Lac objects derived in this paper are 2-3 orders of magnitude higher. If the BLR geometry of these sources is disklike, then the viewing angle between the axis and the line of sight is in the range of - 2° - 15°, which is consistent with the unification scheme.
基金the NationalNatural Science FOundation of China and NaturaI Science Foundation of Yunnan Province(2000A004M).
文摘We present a large sample which includes 82 BL Lac objects with red- shifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A). The correlations in other bands are very weak. Five TeV BL Lacs and two suspect sources are found to have similar properties as high- frequency- peaked BL Lacs (HBLs). Our results suggest that both the radio and optical emissions are from the same radiation mech- anism in the SSC model. The TeV BL Lac candidates should be HBLs or HBL-like objects with small redshifts.
基金Supported by the National Natural Science Foundation of China
文摘BL Lacertae （BL Lac） objects at high redshifts （z ≥ 2） are rarely detected. Through careful analysis of its Sloan Digital Sky Survey spectrum, BZB J1450＋5201 is confirmed to be a high-z BL Lac object with z ≥ 2.471 by identifying the Lyα 1216 and CIV 1548/1550 absorption lines. This indicates that BZB J1450＋5201 is the most distant BL Lac object discovered to date. Careful analysis of the five-year Fermi-LAT data of 2FGL J1451.0＋5159 shows that its γ-ray emission is robust with a confidence level of 6.2σ at 1-3 GeV and 6.7σ at 3-10 GeV. This analysis with the five-year data overcomes confusion with its bright neighbor, which is a problem when analyzing the two-year data. In addition, 2FGL J 1451.0＋5159 is confirmed to be associated with BZB J1450＋5201 using the five-year data. The analysis of multiwavelength data, from radio to γ-ray energies, indicates that BZB J1450＋5201 is an intermediate synchrotron peaked （ISP） source. Its multiwavelength properties are consistent with distributions of other ISP sources at lower redshifts in the second Fermi-LAT AGN catalog. The pure synchrotron self-Compton （SSC） model seems to be disfavored, but the scattering of weak external emission plus the SSC process can provide a satisfactory description of the broadband emission.
基金supported by the National Natural Science Foundation of China(11733001 and U1531245)Guangdong Innovation Team(2014KCXTD014)+1 种基金Natural Science Foundation of Guangdong Province(2017A030313011)support from Astrophysics Key Subjects of Guangdong Province and Guangzhou City
文摘In this work, we collected a sample of 69 TeV blazars from TeVCat, obtained their multi-wavelength observations, and fitted their spectral energy distributions by using a second degree poly-nomial function. The structure parameters of synchrotron bumps for 68 blazars and those of inverse- Compton bumps for 56 blazars were derived. Then, we conducted statistical analysis on the parame-ters （curvature, peak frequency, peak luminosity, bolometric luminosity and X/γ-ray spectral indexes）. From our analysis and discussions, we can conclude the following： （1） There is a clear positive correla-tion between the synchrotron peak frequency, log （Vp）^s, and the inverse-Compton peak frequency, log （Vp）^IC, and between the synchrotron peak luminosity, log （Vp）^sL（Vp）^s, and the inverse-Compton peak luminosity,log（Vp）^IC L（Vp）^IC. （2） The correlation between the peak frequency and the curvature of synchrotron bump is clearly different from that of the inverse-Compton bump, which further indicates that there are differ-ent emission mechanisms between them. （3） There is a correlation between log （Vp）^IC and γ-ray spectral index, αγ, for the TeV blazars： log （Vp）^IC = -（4.59 ± 0.30）αγ ＋ （32.67 ±0.59）, which is consistent with previous work. （4） An ＂L-shape＂ relation is found between log（Vp）^s Up and αx for both TeV blazars and Fermi blazars. A significant correlation between log（Vp）^s and X-ray photon index （αx） is found for the TeV blazars with high synchrotron peak frequency： log（Vp）^s = -（3.20 ± 0.34）αx ＋ （24.33 ± 0.79）, while the correlation is positive for low synchrotron peaked TeV sources. （5） In the αx -αγ diagram, there is also an ＂L-shape.＂ The anti-correlation is consistent with results available in the literature, and we also find a positive correlation between them. （6） Inverse-Compton dominant sources have luminous bolometric luminosities.
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 Natural Science Foundation of China (Grant No. 11173009)the National Basic Research Program of China (973 program, 2007CB815405)+3 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)the Joint Laboratory for Optical Astronomy of Chinese Academy of Sciences
文摘Observations suggest that γ-ray loud blazars are strongly beamed. The Fermi mission has detected many of blazars, which provide us with a good opportunity to investigate the emission mechanism and the beaming effect in the γ-ray region. We compiled the X-ray observations for 138 Fermi blazars （54 flat spectrum radio quasars, 36 low-peaked BL Lacertae objects, and 48 high-peaked BL Lacertae objects） and calculated their Doppler factors, δγ. It is interesting that the calculated Doppler factors, δγ, are strongly correlated with the γ-ray luminosity.
基金supported by the National Natural Science Foundation of China (Grant Nos. U1531245, U1431112, 11203007, 11403006, 10633010, 11173009 and 11403006)the Innovation Foundation of Guangzhou University (IFGZ)+3 种基金Guangdong Innovation Team (2014KCXTD014)Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (GDUPS) (2009)Yangcheng Scholar Funded Scheme (10A027S)support for Astrophysics Key Subjects of Guangdong Province and Guangzhou City
文摘The beaming effect is important for understanding the observational properties of blazars.In this work, we collect 91 Fermi blazars with available radio Doppler factors. γ-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. The intrinsic（de-beamed）γ-ray flux density（fγin）, intrinsic γ-ray luminosity（Lγin） and intrinsic synchrotron peak frequency（VPin）are calculated. Then we study the correlations between finγand redshift and find that they follow the theoretical relation： log f =-2.0 log z ＋ const. When the subclasses are considered, we find that stationary jets are perhaps dominant in low synchrotron peaked blazars. Sixty-three Fermi blazars with both available short variability time scales（？T） and Doppler factors are also collected. We find that the intrinsic relationship between Lγin and ？Tinobeys the Elliot ＆ Shapiro and Abramowicz ＆ Nobili relations. Strong positive correlation between fγinand VPinis found, suggesting that synchrotron emissions are highly correlated with γ-ray emissions.
基金Supported by the National Natural Science Foundation of China
文摘We compiled the radio, optical and X-ray data of blazars from the Sloan Digital Sky Survey database, and presented the distribution of luminosities and broadband spectral indices. The distribution of luminosities shows that the averaged luminosity of flat spectrum radio quasars（FSRQs） is larger than that of BL Lacertae（BL Lac） objects. On the other hand, the broadband spectral energy distribution reveals that FSRQs and low energy peaked BL Lac objects have similar spectral properties,but high energy peaked BL Lac objects have a distinct spectral property. This may be due to the fact that different subclasses of blazars have different intrinsic environments and are at different cooling levels. Even so, a unified scheme is also revealed from the color-color diagram, which hints that there are similar physical processes operating in all objects under a range of intrinsic physical conditions or beaming parameters.
基金financial supports of the Key Research Program of the CAS(Grant No.KJZD-EW-M06)the National Natural Science Foundation of China(NSFC+3 种基金Grant No.11433004)the Ministry of Science and Technology of China(2016YFA0400700)the financial supports of the NSFC(Grant Nos.11273052 and U1431228)the Youth Innovation Promotion Association,CAS
文摘We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is -8.0 mJy in the R band, i.e., the AGN has a magnitude of R - 13.96 mag.
基金supported by the National Natural Science Foundation of China (10573005 and 10633010)the 973 project (2007CB815405)+1 种基金support from the Guangzhou Education Bureau and Guangzhou Science and Technology BureauDr. Margo Aller for allowing us to use data from the University of Michigan Radio Astronomy Observatory which has been supported by the University of Michigan and the National Science Foundation
文摘Using the database of the University of Michigan Radio Astronomy Observatory （UMRAO） at three radio frequencies （4.8, 8 and 14.5 GHz）, we determined the short-term variability timescales for 166 radio sources. The timescales are 0.15d （2007＋777） to 176.17 d （0528-250） with an average timescale of Atobs = 17.1 4- 16.5 d for the whole sample. The timescales are used to calculate the brightness temperatures, TB. The value of log TB is in the range of log TB = 10.47 to 19.06 K. In addition, we also estimated the boosting factor for the sources. The correlation between the polarization and the Doppler factor is also discussed.
基金supported by the National Natural Science Foundation of China (Grant No. 10778702)the Natural Science Foundation of Yunnan Province (2007A026M)
文摘We analyze the spectral variability and spectral evolution in the optical en- ergy region by using multiband （BVRI） optical observations of S5 0716＋714 spanning 1994 to 2005. The spectrum hardens when the source becomes brighter, which is con- sistent with general BL Lac objects. The spectral evolution parameter implies that the spectral variability is small in optical bands over 10 years. A simple model represent- ing the variability of a synchrotron component can explain the spectral changes. In addition, we employ the z-transformed discrete correlation function （ZDCF） to ana- lyze the optical multiband flux correlation. The long-term light curve behavior reveals that the variability time scales are 3.5 yr in the B-band, 3.3 yr in the V-band, 3.4 yr in the R-band and 3.5 yr in the/-band. The time lags between any two optical bands were not found when considering statistical errors.
