A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction...A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were extracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time intervals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by■subsequently yielding significantly underestimated cutoff energy E_(cut)and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fitΓ,E_(cut),and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3–12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.展开更多
Melted cast iron was inoculated by FeSi,then quenched to interrupt the dissolution, the non-metallic inclusions,in which the graphite phase was already occured,formed in the dissolution region,They dissolved into the ...Melted cast iron was inoculated by FeSi,then quenched to interrupt the dissolution, the non-metallic inclusions,in which the graphite phase was already occured,formed in the dissolution region,They dissolved into the melt soon,but the inclusions coated by graphite could exist for along time.The function of inoculant is to create an undercooling solution for carbon,thereby the non-metallic inclusions in the solution may be activated as the nuclei for graphite.展开更多
This study will see the resurgence of interest in precise velocity dispersion measurements, both for the study of galactic and active nuclei kinematics. As several works suggest, an excellent tactic to measure σ is t...This study will see the resurgence of interest in precise velocity dispersion measurements, both for the study of galactic and active nuclei kinematics. As several works suggest, an excellent tactic to measure σ is to use the absorption lines of the calcium triplet, as it is a spectral region relatively free from complications. The discovery of an empirical relationship between the mass of the central black hole (M•) and σ was the leading guide of my detailed study of the calcium triplet region. This search for more accurate methods to calculate the dispersion of velocities, in addition to the careful study of uncertainties. After investing so much time in the development and improvement of the method and its application to so many galaxies, it is time to reap the rewards of this effort, using my results to address a series of questions concerning the physics of galaxies.展开更多
The Tsinghua University-National Astronomical Observatories, Chinese Academy of Sciences （NAOC） Transient Survey is an automatic survey that conducts a systematic exploration of optical transients. This project util...The Tsinghua University-National Astronomical Observatories, Chinese Academy of Sciences （NAOC） Transient Survey is an automatic survey that conducts a systematic exploration of optical transients. This project utilizes a 60/90 cm Schmidt telescope at the Xinglong Station of NAOC. This survey repeatedly covers - 1000 square degrees of the northern sky with a cadence of 34 d. With an exposure of 60 s, the survey reaches a limiting unfiltered magnitude of about 19.5 mag, which enables us to discover supernovae in their relatively young stages. We describe the overall performance of our survey during the first year and present some preliminary results.展开更多
Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei （AGN） and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN. We ...Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei （AGN） and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN. We investigate a comprehensive sample of extragalactic H2O masers in a sample of 38 maser host AGN to check potential correlations of the megamaser emission with parameters of the AGN, such as X-ray luminosity and black hole （BH） masses. We find a relation between the maser luminosities and BH masses LH2O∝MBH^3.6±0.4 which supports basically the theoretical prediction. The relation between the maser emission and X-ray emission is also confirmed.展开更多
In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 J...In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 January 9 to 2019 May 9,using the weighted wavelet Z-transform(WWZ)and the Lomb-Scargle Periodogram(LSP)techniques.This is the first time to search for a periodic radio signal in the FSRQ PKS J0805-0111 by these two methods.Both methods consistently reveal a repeating signal with a periodicity of 3.38±0.8 yr(>99.7%confidence level).In order to determine the significance of the periods,the false alarm probability method was applied,and a large number of Monte Carlo simulations were performed.As possible explanations,we discuss a number of scenarios including the thermal instability of thin disks scenario,the spiral jet scenario and the binary supermassive black hole scenario.We expect that the binary black hole scenario,where the QPO is caused by the precession of binary black holes,is the most likely explanation.FSRQ PKS J0805-0111 thus could be a good binary black hole candidate.In the binary black hole scenario,the distance between the primary black hole and the secondary black hole is about 1.71×10^(16) cm.展开更多
Black hole mass is one of the fundamental physical parameters of active galactic nuclei （AGNs）, for which many methods of estimation have been proposed. One set of methods assumes that the broad-line region （BLR） ...Black hole mass is one of the fundamental physical parameters of active galactic nuclei （AGNs）, for which many methods of estimation have been proposed. One set of methods assumes that the broad-line region （BLR） is gravitationally bound by the central black hole potential, so the black hole mass can be estimated from the orbital radius and the Doppler velocity. Another set of methods assumes the observed variability timescale is determined by the orbital timescale near the innermost stable orbit around the Schwarzschild black hole or the Kerr black hole, or by the characteristic timescale of the accretion disk. We collect a sample of 21 AGNs, for which the minimum variability timescales have been obtained and their black hole masses （Mσ） have been well estimated from the stellar velocity dispersion or the BLR size-luminosity relation. Using the minimum variability timescales we estimated the black hole masses for 21 objects by the three different methods, the results are denoted by Ms, Mk and Md,respectively. We compared each of them with Mσ individually and found that： （1） using the minimum variability timescale with the Kerr black hole theory leads to small differences between Mσ and Mk, none exceeding one order of magnitude, and the mean difference between them is about 0.53 dex; （2） using the minimum variability timescale with the Schwarzschild black hole theory leads to somewhat larger difference between Mσ and Ms： larger than one order of magnitude for 6 of the 21 sources, and the mean difference is 0.74 dex; （3） using the minimum variability timescale with the accretion disk theory leads to much larger differences between Mσ and Md, for 13 of the 21 sources the differences are larger than two orders of magnitude; and the mean difference is as high as about 2.01 dex.展开更多
In this paper,we discuss properties of SDSS J1042-0018 which is a broad line active galactic nucleus(AGN)but misclassified as an H II galaxy in the BPT diagram(SDSS J1042-0018 is called a misclassified broad line AGN)...In this paper,we discuss properties of SDSS J1042-0018 which is a broad line active galactic nucleus(AGN)but misclassified as an H II galaxy in the BPT diagram(SDSS J1042-0018 is called a misclassified broad line AGN).The emission lines around Hαand around Hβare well described by different model functions,considering broad Balmer lines to be described by Gaussian or Lorentz functions.Different model functions lead to different determined narrow emission line fiuxes,but the different narrow emission line fiux ratios lead SDSS J1042-0018 as an H II galaxy in the BPT diagram.In order to explain the unique properties of the misclassified broad line AGN SDSS J1042-0018,two methods are proposed,the star-forming contributions and the compressed narrow emission line regions with high electron densities near to critical densities of forbidden emission lines.Fortunately,the strong star-forming contributions can be preferred in SDSS J1042-0018.The misclassified broad line AGN SDSS J1042-0018,well explained by star-forming contributions,could provide further clues on the applications of BPT diagrams to the normal broad line AGNs.展开更多
Large-amplitude X-ray variation is a special feature of AGN, reflecting possible extreme change in the central engine or the ab- sorption along the line of sight. Till now there are only a few relevant studies on indi...Large-amplitude X-ray variation is a special feature of AGN, reflecting possible extreme change in the central engine or the ab- sorption along the line of sight. Till now there are only a few relevant studies on individual sources or rather small samples. In this work we aim to perform a systematic study of AGNs with strong soft X-ray variations at timescale of 〉 10 years. To build the sample, we compare the soft X-ray fluxes of AGNs measured in ROSAT All-Sky Survey （RASS） during 1990-1991 with those measured by XMM-Newton during 2000-2009. This investigation bings forth to a sample of 13 AGNs, which appeared bright in RASS era, and went into low states （flux dropped by a factor of 〉 10） when they were caught by XMM-Newton. Most of the 13 sources are type I Seyfert galaxies. 5 of them are noticed to have strong X-ray vai＇iation for the first time. We study the nature of their variations through performing XMM-Newton spectral analyses and by collecting reports from the existing literature. We find the sample could be divided into three categories according to the possible causes of the strong X-ray variations. The variations in MRK 0478 and 1H 0419-557 are consistent with strong light-bending effect, i.e., the observed X-ray flux drops significantly as the X-ray emitting corona gets much closer to the central black hole. The variations in ESO 140-G043 and NGC 7158 are caused by absorption changes along the line of sight. For one special case MRK 0335, the variation can be explained by either light-bending or absorption variation. In the rest 8 sources （- 60%）, the strong soft X-ray variations are likely to exist due to intrinsic changes in the activities of the corona, although in some of them without high quality X-ray spectra we are unable to rule out alternative models. This sample provides good targets for future monitoring campaigns with more extensive studies.展开更多
A relativistic beaming model has been successfully used to explain the observed properties of active galactic nuclei (AGNs). In this model there are two emission components, a boosted one and an unbeamed one, shown up...A relativistic beaming model has been successfully used to explain the observed properties of active galactic nuclei (AGNs). In this model there are two emission components, a boosted one and an unbeamed one, shown up in the radio band as the core and lobe components. The luminosity ratio of the core to the lobe is defined as the core-dominance parameter (R = (L<SUB>Core</SUB>/L<SUB>Lobe</SUB>)). The de-beamed radio luminosity (L<SUB>jet</SUB><SUP>db</SUP>) in the jet is assumed to be proportional to the unbeamed luminosity (L<SUB>ub</SUB>) in the co-moving frame, i.e., f = (L<SUB>jet</SUB><SUP>db</SUP>/L<SUB>ub</SUB>), and f is determined in our previous paper. We further discuss the relationship between BL Lacertae objects (BLs) and flat spectrum radio quasars (FSRQs), which are subclasses of blazars with different degrees of polarization, using the calculated values of the ratio f for a sample of superluminal blazars. We found 1) that the BLs show smaller averaged Doppler factors and Lorentz factors, larger viewing angles and higher core-dominance parameters than do the FSRQs, and 2) that in the polarization-core dominance parameter plot (P-log R) the BLs and FSRQs occupy a scattered region, but in a revised plot (log (P/c(m)) ? log R), they gather around two different lines, suggesting that they have some different intrinsic properties.展开更多
In this paper we give a brief review of the astrophysics of active galactic nuclei （AGNs）. After a general introduction motivating the study of AGNs, we discuss our present understanding of the inner workings of the...In this paper we give a brief review of the astrophysics of active galactic nuclei （AGNs）. After a general introduction motivating the study of AGNs, we discuss our present understanding of the inner workings of the central engines, most likely accreting black holes with masses between 106 and 10^10M. We highlight recent results concerning the jets （collimated outflows） of AGNs derived from X-ray observations （Chandra） of kpc-scale jets and ~/-ray observations of AGNs （Fermi, Cherenkov telescopes） with jets closely aligned with the lines of sight （blazars）, and discuss tile interpretation of these observations. Subsequently, we summarize our knowledge about the cosmic history of AGN formation and evolution. We conclude with a description of upcoming observational opportunities.展开更多
Blazars are subclass of AGN （active galactic nuclei） with relativistic jet that is pointing in the general direction of the earth. The energy flux in the jet is about （10^44-10^47） erg/s. The γ-rays in the energy...Blazars are subclass of AGN （active galactic nuclei） with relativistic jet that is pointing in the general direction of the earth. The energy flux in the jet is about （10^44-10^47） erg/s. The γ-rays in the energy range 10 GeV-10 TeV emanating from blazar are examined and their effect on the IGM （intergalactic medium） is studied. The γ-ray emission is considered as due to inverse Compton scattering of relativistic electrons. There appears to be a gamma ray flux from blazar above 10 GeV having a line intensity of 1.5 × 10^-4 cm^-2 s^-1 sr^-1. The IGM is measured to large distances and it is found to be clumpy. It is found that at higher redshifl the density of IGM increases. The cosmological density parameter measured is found to lie within the suggested limit of 0.03 at redshift z = 3 for background intensity of radiation 10^-24 W·m^-2·Hz^-1·sr^-1. The iso-ΩIGM curve shows a kink in its profile which might be significant at the particular value of z equal to 2. Some more detailed studies are required for understanding the distribution of intergalactic medium at the unstable point at z = 2 as shown in inverse Compton radiation.展开更多
We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations ...We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations among the line width of HB, optical line strength of Fell and the soft X-ray slope are confirmed. We found no correlations between the UV line parameters, the equivalent widths of Lya and CIV and their ratio on one hand and the optical line parameters on the other. The UV and X-ray luminosities strongly correlate with the line widths of HB and the Fe II/HB ratio. No significant correlation is found between the infrared-soft X-my continuum slope aix and the line width of HB.展开更多
In a previous paper, it was suggested that contamination of the nuclear luminosity by the host galaxy plays an important role in determining the parameters of the standard a disk of AGNs. Using the nuclear absolute B ...In a previous paper, it was suggested that contamination of the nuclear luminosity by the host galaxy plays an important role in determining the parameters of the standard a disk of AGNs. Using the nuclear absolute B band magnitude instead of the total absolute B band magnitude, we have recalculated the central black hole masses, accretion rates and disk inclinations for 20 Seyfert 1 galaxies and 17 Palomar-Green (PG) quasars. It is found that a small value of a is needed for the Seyfert 1 galaxies than for the PG quasars. This difference in a possibly leads to the different properties of Seyfert 1 galaxies and quasars. Furthermore, we find most of the objects in this sample are not accreting at super-Eddington rates if we adopt the nuclear optical luminosity in our calculation.展开更多
With the support by the National Natural Science Foundation of China,a collaboration led by Prof.Wang Jianmin(王建民)from the Institute of High Energy Physics,Chinese Academy of Sciences proposes a new mechanism for t...With the support by the National Natural Science Foundation of China,a collaboration led by Prof.Wang Jianmin(王建民)from the Institute of High Energy Physics,Chinese Academy of Sciences proposes a new mechanism for the origin of the broad-line region in Active Galactic Nuclei,which was published展开更多
We present estimated ratios of the central black hole mass to the bulge mass (Mbh/Mbulge) for 15 Narrow Line Seyfert 1 galaxies (NLS1s). It is found that NLS1s apparently have lower mass ratios: the average mass ratio...We present estimated ratios of the central black hole mass to the bulge mass (Mbh/Mbulge) for 15 Narrow Line Seyfert 1 galaxies (NLS1s). It is found that NLS1s apparently have lower mass ratios: the average mass ratio is about 1 × 10-4 with a spread of 2, which is one order of magnitude lower than for Broad Line AGNs and quiescent galaxies. This lower value, as compared to that established essentially for all other types of galaxies, can be accounted for by an underestimation of the black hole masses and an overestimation of the bulge masses in the NLS1s.展开更多
The physics behind the spectral energy distribution （SED） of blazars remains open. We assembled 36 blazars to tackle the factors that control their SED. Now, many blazar spectra have the ＂double hump＂ feature in t...The physics behind the spectral energy distribution （SED） of blazars remains open. We assembled 36 blazars to tackle the factors that control their SED. Now, many blazar spectra have the ＂double hump＂ feature in the radio and far-IR frequencies. For these a parameter, △, is created to characterize the behavior of the SED. We found a significant correlation between the broad-line luminosity （LBLR） and △. Because L BLR is an indicator of the accreting power of the source in blazars, we derived a linear correlation, △ oc M1/3.18, which suggests that the SED of blazars may depend on the accretion rate, like that of BL Lac objects. We also found a significant correlation between m and △ for a sample of 11 blazars （out of one of 36） with available black hole masses. This implies the Eddington accretion ratio may influence the shape of the SED of blazars.展开更多
We used multi-component profiles to model the HE and [O Ⅲ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy （NLS1） in a sample of 150 NLS1 candidates selected from the Sloan Digital Sk...We used multi-component profiles to model the HE and [O Ⅲ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy （NLS1） in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey （SDSS）, Early Data Release （EDR）. After subtracting the HE contribution from narrow line regions （NLRs）, we found that its full width half maximum （FWHM） of broad H/3 line is nearly 2900km s^-1, significantly larger than the customarily adopted criterion of 2000 km s^-1. With its weak Fe II multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLSls, we should use the Hβ linewidth after subtracting the NLR component.展开更多
The study ofkiloparsec-scale dual active galactic nuclei （AGN） provides important clues for understanding the co-evolution between host galaxies and their central supermassive black holes undergoing a merging proces...The study ofkiloparsec-scale dual active galactic nuclei （AGN） provides important clues for understanding the co-evolution between host galaxies and their central supermassive black holes undergoing a merging process. We present long-slit spectroscopy of J0038 ＋4128, a kiloparsec-scale dual AGN candidate, discovered recently by Huang et al., using the Yunnan Faint Object Spectrograph and Camera （YFOSC） mounted on the Lijiang 2.4-m telescope administered by Yunnan Observatories. From the long-slit spectra, we find that the average relative line-of-sight （LOS） velocity between the two nuclei （J0038＋4128N and J0038＋4128S） is about 150 km s-1. The LOS velocities of the emission lines from the gas ionized by the nuclei activities and of the absorption lines from stars governed by the host galaxies for different regions of J0038＋4128 exhibit the same trend. The same trend in velocities indicates that the gaseous disks are co-rotating with the stellar disks in this ongoing merging system. We also find several knots/giant H II regions scattered around the two nuclei with strong star formation revealed by the observed line ratios from the spectra. Those regions are also clearly detected in images from HST F336W/U-band and HST F555W/V-band.展开更多
Cloud condensation nuclei(CCN)constitute a reservoir of latent ice-forming nuclei(IFN)active by conden sation-followed-by-freezing and by sorption.Two classes of aerosol particles active as IFN by sorption were found....Cloud condensation nuclei(CCN)constitute a reservoir of latent ice-forming nuclei(IFN)active by conden sation-followed-by-freezing and by sorption.Two classes of aerosol particles active as IFN by sorption were found.The first produces IFN concentrations which are dependent on temperature only.The IFN concen- tration consecutively increases with lowering of temperature and does not respond to the increasing partial water vapor pressure.The second produces IFN concentrations which are dependent on partial water vapor pressure only,The IFN concentration consecutively decreases with decreasing of the partial water vapor pres- sure that takes place with the lowering temperature. Sulfates(mostly ammonium sulfate)constitute an integral part of IFN active by condensation-followed-by- freezing and by sorption.Backward isentropic air parcel trajectories linked polluted air rich in sulfates and clean air with high and low concentrations of IFN active by condensation-followed-by-freezing at-19.7℃ and S_w=0.1%. The experiments were performed in a dynamic filter processing chamber with aerosol particles collected on membrane filters.展开更多
基金supported by the National Natural Science Foundation of China(12033006,12192221,123B2042).
文摘A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were extracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time intervals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by■subsequently yielding significantly underestimated cutoff energy E_(cut)and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fitΓ,E_(cut),and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3–12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.
文摘Melted cast iron was inoculated by FeSi,then quenched to interrupt the dissolution, the non-metallic inclusions,in which the graphite phase was already occured,formed in the dissolution region,They dissolved into the melt soon,but the inclusions coated by graphite could exist for along time.The function of inoculant is to create an undercooling solution for carbon,thereby the non-metallic inclusions in the solution may be activated as the nuclei for graphite.
文摘This study will see the resurgence of interest in precise velocity dispersion measurements, both for the study of galactic and active nuclei kinematics. As several works suggest, an excellent tactic to measure σ is to use the absorption lines of the calcium triplet, as it is a spectral region relatively free from complications. The discovery of an empirical relationship between the mass of the central black hole (M•) and σ was the leading guide of my detailed study of the calcium triplet region. This search for more accurate methods to calculate the dispersion of velocities, in addition to the careful study of uncertainties. After investing so much time in the development and improvement of the method and its application to so many galaxies, it is time to reap the rewards of this effort, using my results to address a series of questions concerning the physics of galaxies.
基金Supported by the National Natural Science Foundation of China
文摘The Tsinghua University-National Astronomical Observatories, Chinese Academy of Sciences （NAOC） Transient Survey is an automatic survey that conducts a systematic exploration of optical transients. This project utilizes a 60/90 cm Schmidt telescope at the Xinglong Station of NAOC. This survey repeatedly covers - 1000 square degrees of the northern sky with a cadence of 34 d. With an exposure of 60 s, the survey reaches a limiting unfiltered magnitude of about 19.5 mag, which enables us to discover supernovae in their relatively young stages. We describe the overall performance of our survey during the first year and present some preliminary results.
基金the National Natural Science Foundation of China
文摘Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei （AGN） and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN. We investigate a comprehensive sample of extragalactic H2O masers in a sample of 38 maser host AGN to check potential correlations of the megamaser emission with parameters of the AGN, such as X-ray luminosity and black hole （BH） masses. We find a relation between the maser luminosities and BH masses LH2O∝MBH^3.6±0.4 which supports basically the theoretical prediction. The relation between the maser emission and X-ray emission is also confirmed.
基金supported by the National Natural Science Foundation of China(Grant No.11663009)the High-Energy Astrophysics Science and Technology Innovation Team of Yunnan Higher School+1 种基金the OVRO40-m monitoring program(Fan&Wu 2018)which is supported in part by NASA grants NNX08AW31GNNX11A043G and NNX14AQ89G,and NSF grants AST-0808050 and AST-1109911。
文摘In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 January 9 to 2019 May 9,using the weighted wavelet Z-transform(WWZ)and the Lomb-Scargle Periodogram(LSP)techniques.This is the first time to search for a periodic radio signal in the FSRQ PKS J0805-0111 by these two methods.Both methods consistently reveal a repeating signal with a periodicity of 3.38±0.8 yr(>99.7%confidence level).In order to determine the significance of the periods,the false alarm probability method was applied,and a large number of Monte Carlo simulations were performed.As possible explanations,we discuss a number of scenarios including the thermal instability of thin disks scenario,the spiral jet scenario and the binary supermassive black hole scenario.We expect that the binary black hole scenario,where the QPO is caused by the precession of binary black holes,is the most likely explanation.FSRQ PKS J0805-0111 thus could be a good binary black hole candidate.In the binary black hole scenario,the distance between the primary black hole and the secondary black hole is about 1.71×10^(16) cm.
基金Supported by the National Natural Science Foundation of China.
文摘Black hole mass is one of the fundamental physical parameters of active galactic nuclei （AGNs）, for which many methods of estimation have been proposed. One set of methods assumes that the broad-line region （BLR） is gravitationally bound by the central black hole potential, so the black hole mass can be estimated from the orbital radius and the Doppler velocity. Another set of methods assumes the observed variability timescale is determined by the orbital timescale near the innermost stable orbit around the Schwarzschild black hole or the Kerr black hole, or by the characteristic timescale of the accretion disk. We collect a sample of 21 AGNs, for which the minimum variability timescales have been obtained and their black hole masses （Mσ） have been well estimated from the stellar velocity dispersion or the BLR size-luminosity relation. Using the minimum variability timescales we estimated the black hole masses for 21 objects by the three different methods, the results are denoted by Ms, Mk and Md,respectively. We compared each of them with Mσ individually and found that： （1） using the minimum variability timescale with the Kerr black hole theory leads to small differences between Mσ and Mk, none exceeding one order of magnitude, and the mean difference between them is about 0.53 dex; （2） using the minimum variability timescale with the Schwarzschild black hole theory leads to somewhat larger difference between Mσ and Ms： larger than one order of magnitude for 6 of the 21 sources, and the mean difference is 0.74 dex; （3） using the minimum variability timescale with the accretion disk theory leads to much larger differences between Mσ and Md, for 13 of the 21 sources the differences are larger than two orders of magnitude; and the mean difference is as high as about 2.01 dex.
基金the kind support of Starting Research Fund of Nanjing Normal Universitythe kind support of NSFC-12173020the kind support of Da Chuang project of Nanjing Normal University for undergraduate students。
文摘In this paper,we discuss properties of SDSS J1042-0018 which is a broad line active galactic nucleus(AGN)but misclassified as an H II galaxy in the BPT diagram(SDSS J1042-0018 is called a misclassified broad line AGN).The emission lines around Hαand around Hβare well described by different model functions,considering broad Balmer lines to be described by Gaussian or Lorentz functions.Different model functions lead to different determined narrow emission line fiuxes,but the different narrow emission line fiux ratios lead SDSS J1042-0018 as an H II galaxy in the BPT diagram.In order to explain the unique properties of the misclassified broad line AGN SDSS J1042-0018,two methods are proposed,the star-forming contributions and the compressed narrow emission line regions with high electron densities near to critical densities of forbidden emission lines.Fortunately,the strong star-forming contributions can be preferred in SDSS J1042-0018.The misclassified broad line AGN SDSS J1042-0018,well explained by star-forming contributions,could provide further clues on the applications of BPT diagrams to the normal broad line AGNs.
基金supported by the National Natural Science Foundation of China(Grant No.11233002)the Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences(Grant No.XDB09000000)support from Chinese Top-notch Young Talents Program
文摘Large-amplitude X-ray variation is a special feature of AGN, reflecting possible extreme change in the central engine or the ab- sorption along the line of sight. Till now there are only a few relevant studies on individual sources or rather small samples. In this work we aim to perform a systematic study of AGNs with strong soft X-ray variations at timescale of 〉 10 years. To build the sample, we compare the soft X-ray fluxes of AGNs measured in ROSAT All-Sky Survey （RASS） during 1990-1991 with those measured by XMM-Newton during 2000-2009. This investigation bings forth to a sample of 13 AGNs, which appeared bright in RASS era, and went into low states （flux dropped by a factor of 〉 10） when they were caught by XMM-Newton. Most of the 13 sources are type I Seyfert galaxies. 5 of them are noticed to have strong X-ray vai＇iation for the first time. We study the nature of their variations through performing XMM-Newton spectral analyses and by collecting reports from the existing literature. We find the sample could be divided into three categories according to the possible causes of the strong X-ray variations. The variations in MRK 0478 and 1H 0419-557 are consistent with strong light-bending effect, i.e., the observed X-ray flux drops significantly as the X-ray emitting corona gets much closer to the central black hole. The variations in ESO 140-G043 and NGC 7158 are caused by absorption changes along the line of sight. For one special case MRK 0335, the variation can be explained by either light-bending or absorption variation. In the rest 8 sources （- 60%）, the strong soft X-ray variations are likely to exist due to intrinsic changes in the activities of the corona, although in some of them without high quality X-ray spectra we are unable to rule out alternative models. This sample provides good targets for future monitoring campaigns with more extensive studies.
基金This work is partially supported by the National 973 projectthe National Science Fundfor Distinguished Young Scholars.
文摘A relativistic beaming model has been successfully used to explain the observed properties of active galactic nuclei (AGNs). In this model there are two emission components, a boosted one and an unbeamed one, shown up in the radio band as the core and lobe components. The luminosity ratio of the core to the lobe is defined as the core-dominance parameter (R = (L<SUB>Core</SUB>/L<SUB>Lobe</SUB>)). The de-beamed radio luminosity (L<SUB>jet</SUB><SUP>db</SUP>) in the jet is assumed to be proportional to the unbeamed luminosity (L<SUB>ub</SUB>) in the co-moving frame, i.e., f = (L<SUB>jet</SUB><SUP>db</SUP>/L<SUB>ub</SUB>), and f is determined in our previous paper. We further discuss the relationship between BL Lacertae objects (BLs) and flat spectrum radio quasars (FSRQs), which are subclasses of blazars with different degrees of polarization, using the calculated values of the ratio f for a sample of superluminal blazars. We found 1) that the BLs show smaller averaged Doppler factors and Lorentz factors, larger viewing angles and higher core-dominance parameters than do the FSRQs, and 2) that in the polarization-core dominance parameter plot (P-log R) the BLs and FSRQs occupy a scattered region, but in a revised plot (log (P/c(m)) ? log R), they gather around two different lines, suggesting that they have some different intrinsic properties.
文摘In this paper we give a brief review of the astrophysics of active galactic nuclei （AGNs）. After a general introduction motivating the study of AGNs, we discuss our present understanding of the inner workings of the central engines, most likely accreting black holes with masses between 106 and 10^10M. We highlight recent results concerning the jets （collimated outflows） of AGNs derived from X-ray observations （Chandra） of kpc-scale jets and ~/-ray observations of AGNs （Fermi, Cherenkov telescopes） with jets closely aligned with the lines of sight （blazars）, and discuss tile interpretation of these observations. Subsequently, we summarize our knowledge about the cosmic history of AGN formation and evolution. We conclude with a description of upcoming observational opportunities.
文摘Blazars are subclass of AGN （active galactic nuclei） with relativistic jet that is pointing in the general direction of the earth. The energy flux in the jet is about （10^44-10^47） erg/s. The γ-rays in the energy range 10 GeV-10 TeV emanating from blazar are examined and their effect on the IGM （intergalactic medium） is studied. The γ-ray emission is considered as due to inverse Compton scattering of relativistic electrons. There appears to be a gamma ray flux from blazar above 10 GeV having a line intensity of 1.5 × 10^-4 cm^-2 s^-1 sr^-1. The IGM is measured to large distances and it is found to be clumpy. It is found that at higher redshifl the density of IGM increases. The cosmological density parameter measured is found to lie within the suggested limit of 0.03 at redshift z = 3 for background intensity of radiation 10^-24 W·m^-2·Hz^-1·sr^-1. The iso-ΩIGM curve shows a kink in its profile which might be significant at the particular value of z equal to 2. Some more detailed studies are required for understanding the distribution of intergalactic medium at the unstable point at z = 2 as shown in inverse Compton radiation.
基金the National Natural Science Foundationof China and Chinese Panden Project.
文摘We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations among the line width of HB, optical line strength of Fell and the soft X-ray slope are confirmed. We found no correlations between the UV line parameters, the equivalent widths of Lya and CIV and their ratio on one hand and the optical line parameters on the other. The UV and X-ray luminosities strongly correlate with the line widths of HB and the Fe II/HB ratio. No significant correlation is found between the infrared-soft X-my continuum slope aix and the line width of HB.
基金Supported by the National Natural Science Foundation of China.
文摘In a previous paper, it was suggested that contamination of the nuclear luminosity by the host galaxy plays an important role in determining the parameters of the standard a disk of AGNs. Using the nuclear absolute B band magnitude instead of the total absolute B band magnitude, we have recalculated the central black hole masses, accretion rates and disk inclinations for 20 Seyfert 1 galaxies and 17 Palomar-Green (PG) quasars. It is found that a small value of a is needed for the Seyfert 1 galaxies than for the PG quasars. This difference in a possibly leads to the different properties of Seyfert 1 galaxies and quasars. Furthermore, we find most of the objects in this sample are not accreting at super-Eddington rates if we adopt the nuclear optical luminosity in our calculation.
文摘With the support by the National Natural Science Foundation of China,a collaboration led by Prof.Wang Jianmin(王建民)from the Institute of High Energy Physics,Chinese Academy of Sciences proposes a new mechanism for the origin of the broad-line region in Active Galactic Nuclei,which was published
基金Supported by the National Natural Science Foundation of China.
文摘We present estimated ratios of the central black hole mass to the bulge mass (Mbh/Mbulge) for 15 Narrow Line Seyfert 1 galaxies (NLS1s). It is found that NLS1s apparently have lower mass ratios: the average mass ratio is about 1 × 10-4 with a spread of 2, which is one order of magnitude lower than for Broad Line AGNs and quiescent galaxies. This lower value, as compared to that established essentially for all other types of galaxies, can be accounted for by an underestimation of the black hole masses and an overestimation of the bulge masses in the NLS1s.
基金This work was supported by the Natural Science Foundation of Yunnan Province of China.
文摘The physics behind the spectral energy distribution （SED） of blazars remains open. We assembled 36 blazars to tackle the factors that control their SED. Now, many blazar spectra have the ＂double hump＂ feature in the radio and far-IR frequencies. For these a parameter, △, is created to characterize the behavior of the SED. We found a significant correlation between the broad-line luminosity （LBLR） and △. Because L BLR is an indicator of the accreting power of the source in blazars, we derived a linear correlation, △ oc M1/3.18, which suggests that the SED of blazars may depend on the accretion rate, like that of BL Lac objects. We also found a significant correlation between m and △ for a sample of 11 blazars （out of one of 36） with available black hole masses. This implies the Eddington accretion ratio may influence the shape of the SED of blazars.
基金Supported by the National Natural Science Foundation of China.
文摘We used multi-component profiles to model the HE and [O Ⅲ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy （NLS1） in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey （SDSS）, Early Data Release （EDR）. After subtracting the HE contribution from narrow line regions （NLRs）, we found that its full width half maximum （FWHM） of broad H/3 line is nearly 2900km s^-1, significantly larger than the customarily adopted criterion of 2000 km s^-1. With its weak Fe II multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLSls, we should use the Hβ linewidth after subtracting the NLR component.
基金Funding for the telescope has been provided by CASthe People’s Government of Yunnan Province+2 种基金supported by the National Natural Science Foundation of China(Grant Nos.11133006 and 11361140347)the Strategic Priority Research Program“The Emergence of Cosmological Structures”of the Chinese Academy of Sciences(Grant No.XDB09000000)support by the National Key Basic Research Program of China(2014CB845700)
文摘The study ofkiloparsec-scale dual active galactic nuclei （AGN） provides important clues for understanding the co-evolution between host galaxies and their central supermassive black holes undergoing a merging process. We present long-slit spectroscopy of J0038 ＋4128, a kiloparsec-scale dual AGN candidate, discovered recently by Huang et al., using the Yunnan Faint Object Spectrograph and Camera （YFOSC） mounted on the Lijiang 2.4-m telescope administered by Yunnan Observatories. From the long-slit spectra, we find that the average relative line-of-sight （LOS） velocity between the two nuclei （J0038＋4128N and J0038＋4128S） is about 150 km s-1. The LOS velocities of the emission lines from the gas ionized by the nuclei activities and of the absorption lines from stars governed by the host galaxies for different regions of J0038＋4128 exhibit the same trend. The same trend in velocities indicates that the gaseous disks are co-rotating with the stellar disks in this ongoing merging system. We also find several knots/giant H II regions scattered around the two nuclei with strong star formation revealed by the observed line ratios from the spectra. Those regions are also clearly detected in images from HST F336W/U-band and HST F555W/V-band.
文摘Cloud condensation nuclei(CCN)constitute a reservoir of latent ice-forming nuclei(IFN)active by conden sation-followed-by-freezing and by sorption.Two classes of aerosol particles active as IFN by sorption were found.The first produces IFN concentrations which are dependent on temperature only.The IFN concen- tration consecutively increases with lowering of temperature and does not respond to the increasing partial water vapor pressure.The second produces IFN concentrations which are dependent on partial water vapor pressure only,The IFN concentration consecutively decreases with decreasing of the partial water vapor pres- sure that takes place with the lowering temperature. Sulfates(mostly ammonium sulfate)constitute an integral part of IFN active by condensation-followed-by- freezing and by sorption.Backward isentropic air parcel trajectories linked polluted air rich in sulfates and clean air with high and low concentrations of IFN active by condensation-followed-by-freezing at-19.7℃ and S_w=0.1%. The experiments were performed in a dynamic filter processing chamber with aerosol particles collected on membrane filters.
