Period04分析PKS1510-089射电流量变化周期

收集了PKS 1510-089从1990年到2005年射电37 GHz的观测数据.通过对数据的处理获得其长期光变曲线.从光变曲线可以看出PKS 1510-089的活动非常剧烈.首次运用Period04方法较好地分析类星体PKS 1510-089的光变周期.结果表明:PKS 1510-089在射电37 GHz有(1.87±0.13)yr和(0.87±0.07)yr的周期.这个结果与Xie等在2004、2005、2008年以及Wu等在2005年采取其他数据分析方法获得的结果是一致的.

TeV噪BlazarPKS2155-304中心双黑洞系统(英文)

PKS2155-304是一个典型的TeV源,在全波段都观测到光变.文章利用GeVγ辐射和X辐射观测资料确定GeVγ辐射的基本参量以及相关黑洞质量,利用光学光变周期分析中心双黑洞系统的结构参量,并利用TeV的光变时标确定TeV辐射的区域大小以及离中心的距离.从分析得到如下结论:①在中心有一个双黑洞系统,大黑洞的质量是80.8×107太阳质量,而次黑洞的质量为(3.35-5.20)×107太阳质量.该双黑洞系统的半轴和为(3.67-5.15)×1016cm.②GeVγ辐射的参量与因子来自于离中心黑洞(次黑洞)18～20斯瓦西半径处.GeVγ辐射的Doppler因子为0.31～0.45,视角为8.5°～9.4°.这里的两个值分别对应于不同的系数λ.③TeVγ辐射来自于距中心2.5～2.8斯瓦西半径处.

星系团PKS0745-191中射电气体对X射线气体的加热

对星系团中相对论性粒子的能量演化做了数值计算,在此基础上,联合分析Chandra卫星数据和VLA射电观测结果,计算了星系团PKS0745-191中高能射电气体对X射线气体的加热作用,发现在射电气体幂律谱能量下限为0.001erg时,射电气体对X射线气体的加热不足以补充X射线气体的辐射能损。然后在计算研究了不同能量下限时射电气体对X射线气体的加热作用,并估计了射电气体的能量下限。

Optical quasi-periodic oscillation and color behavior of blazar PKS 2155–304

PKS 2155-304 is a well studied BL Lac object in the southern sky. The historical optical data during different periods have been collected and compiled. Light curves spanning 35 yr have been constructed. The R-band light curve has been ana- lyzed by means of three methods： the epoch folding method, the Jurkevich method and the discrete correlation function method. It is derived that there is an evident periodic component of 317 d （i.e. 0.87 yr） superposed on a long-term trend with large- amplitude variation in the light curve. The variability of this source is accompanied by a slight color variation, and the brightness and color index are correlated with each other. On a long-term time scale, PKS 2155-304 exhibits a tendency of bluer-when- brighter, which means the spectrum becomes flatter when the source brightens.

The parameters of binary black hole system in PKS 1510-089

Observations of PKS 1510-089 indicate the existence of a deep flux minimum with a timescale of -35 min and an interval of about 336 ± 14 d. A binary black hole system is proposed to be at the nucleus of this object. The secondary black hole orbits around the primary black hole. The minimum is caused by the periodic eclipse of the primary black hole by the secondary black hole. Based on the observations of PKS 1510-089, we estimate the parameters of the binary black hole system. The masses for the primary and secondary black holes are 1.37 × 10^9M⊙（M⊙ is the solar mass） and 1.37 × 10^7M⊙, and the major axis for this pair being about 0.1 parsec（pc）.

A new estimation of manganese distribution for local dwarf spheroidal galaxies

The distribution of abundance for iron-peak elements in dwarf spheroidal galaxies （dSphs） is important for galaxy evolution and supernova （SN） nucleosynthesis. Nowadays, manganese （Mn） is one of the most observed iron-peak elements in local dSphs. Studies of its distributions allow us to derive and understand the evolution history of these dSphs. We improve a phenomenological model by a two-curve model including a new initial condition, that includes detailed calculations of SN explosion rates and yields. We compare the results with the observed Mn distribution data for three dSphs： Fornax, Sculpture and Sextans. We find that the model can describe the observed Fe and Mn distributions well simultaneously for the three dSphs. The results also indicate that the initial conditions should be determined by the low metallicity sam- ples in the beginning time of the galaxies and the previous assumption of metellicity-dependant Mn yield of SNIa is not needed when a wide mass range of core-collapse SNe is included. Our method is applicable to the chemical evolution of other iron-peak elements in dSphs and can be modified to provide more detailed processes for the evolution of dSphs.

Discovery of a variable broad absorption line in the BL Lac object PKS B0138-097

We report the discovery of a broad absorption line （BAL） of - 10^4 km s^-1 in width in the previously known BL Lac object PKS 0138-097, which we tentatively identified as an Mg II BAL. This is the first detection of a BAL, which is sometimes seen in powerful quasars with high accretion rates, in a BL Lac object. The BAL was clearly detected in its spectra spanning two epochs at a high luminosity state taken in the Sloan Digital Sky Survey （SDSS）, while it disappeared in three SDSS spectra taken at a low luminosity state. The BAL and its variability pattern were also found in its historical multi-epoch spectra in the literature, but have been overlooked previously. In its high resolution radio maps, PKS 0138-097 shows a core plus a one- sided parsec-scale jet. The BAL variability can be interpreted as follows： The optical emission is dominated by the core in a high state and by the jet in a low state and the BAL material is located between the core and jet so that the BAL appears only when the core is shining. Our discovery suggests that outflows may also be produced in active galactic nuclei at a low accreting state.

Luminosity Function of the Cluster of Galaxies Abell 566

We investigate the Luminosity Function （LF） of the cluster of galaxies Abell 566. The photometric data of 15 intermediate-bands are obtained from the Beijing-Arizona- Taiwan-Connecticut （BATC） photometric sky survey. For each of the 15 wavebands, the LF of cluster galaxies is well modelled by the Schechter function, with characteristic luminosities from -18.0 to -21.9 magnitude, from the α- to the p-band. Morphological dependence of the LF is investigated by separating the cluster members into ＇red＇ and ＇blue＇ subsamples. It is clear that late type galaxies have a steeper shape of LF than the early type galaxies. We also divided the sample galaxies by their local environment. It was found that galaxies in the sparser region have steeper shape of LF than galaxies in the denser region. Combining the results of morphological and environmental dependence of LFs, we show that Abell 566 is a well relaxed cluster with positive evidence of galaxy interaction and merger, and excess number of bright early type galaxies located in its denser region.

Chandra Observations of the Flat Spectrum Seyfert-2 Galaxies NGC 2110 and NGC 7582

Chandra observations of the Seyfert-2 galaxies NGC 2110 and NGC 7582 arepresented. With the superb spatial resolution of Chandra we found that in NGC 7582 the soft (≤2keV) and hard (2-10 keV) X-rays are emitted in different regions, consistent with the report by Xueet al. By comparing the present X-ray data with the previous infrared data, we determined that thesoft X-ray region is the site of starburst activities. We found no significant temporal variationsduring our observations. We confirm the previous finding that NGC 2110 and NGC 7582 areflat-spectrum sources. We argue that the flat spectra may result from a cold absorbing material suchas envisaged in the 'dual absorbed' model. Strong FeK_α emission feature is detected in 6～7keV.Its equivalent width is so large that it cannot be reproduced by using the Galactic column densityof ～ 10^(22) cm^(-2).

Are Seyfert 2 Galaxies without Polarized Broad Emission Lines More Obscured?

New XMM-Newton data of seven Seyfert 2 galaxies with optical spectropolarimetric observations are presented. An analysis of the 0.5 - 10 keV spectra shows that four Seyfert 2 galaxies with polarized broad lines （PBLs） are absorbed by NH 〈 1024 cm^-2, while two of three Seyfert 2 galaxies without PBLs show evidence of Compton-thick obscuration, supporting the conclusion that Seyfert 2 galaxies without PBLs are more obscured than those with PBLs, Adding the measured obscuration indicators （NH, T ratio, and Fe Kα line EW） of six luminous AGNs to our previous sample improves the significance level of the difference in absorption from 92.3% to 96.3% for NH, 99.1% to 99.4% for T ratio, and 95.3% to 97.4% for Fe Kα line EW. The present results support and enhance the suggestions that the absence of PBLs in Seyfert 2 galaxies can be explained by larger viewing angles of the line of sight to the putative dusty toms, which leads to the obscuration of the broad-line scattering screen, as expected in the unification model.

Detection of a high-confidence quasi-periodic oscillation in radio light curve of the high redshift FSRQ PKS J0805–0111

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.

The jet of FSRQ PKS 1229-02 and its misidentification as a γ-ray AGN

Flat-spectrum radio quasar PKS 1229-02 with a knotty and asymmetric radio morphology was identified as the optical and radio counterpart of a γ-ray source. In this paper, we study the properties(e.g.morphology, opacity, polarization and kinematics) of the jet in PKS 1229-02 using radio interferometry.With our results, we find that the knotty and asymmetric morphology of this source may probably shaped by the interaction between its anterograde jet and the nonuniform dense ambient medium. By reproducing a Spectral Energy Distribution of PKS 1229-02 with the obtained kinematic parameters, we find that the relativistic beaming effect in PKS 1229-02 is not strong enough to produce the reported γ-ray emission,i.e. PKS 1229-02 may not be a γ-ray AGN. The misidentification may probably be due to the poor spatial resolution of the γ-ray detector of the previous generation.

About 300 days Optical Quasi-periodic Oscillations in the Long-term Light Curves of the Blazar PKS 2155-304

Based on the long-term light curves collected from the Catalina Sky Survey(CSS)(from 2005 to 2013)and the All-Sky Automated Survey for Supernovae(ASAS-SN)(from 2014 to 2018),optical quasi-periodic oscillations(QPOs)about 300 days can be well determined in the well-known blazar PKS 2155-304 through four different methods:the generalized Lomb-Scargle periodogram(GLSP)method,the weighted wavelet Z-transform technique,the epoch-folded method and the redfit method.The GLSP determined significance level for the periodicity is higher than 99.9999%based on a false alarm probability.The redfit provided confidence level for the periodicity is higher than 99%in the ASAS-SN light curve,after considering the effects of red noise.Based on continuous autoregressive process created artificial light curves,the probability of detecting fake QPOs is lower than 0.8%.The determined optical periodicity of 300 days from the CSS and ASAS-SN light curves is well consistent with the reported optical periodicity in the literature.Moreover,three possible models are discussed to explain the optical QPOs in PKS 2155-304:the relativistic frame-dragging effect,the binary black hole model and the jet precession model.

Intra-day variability of three Seyfert galaxies measured with XMM-Newton

We present and analyze the variability of three Seyfert galaxies on intra-day timescales. We have analyzed in a uniform manner the 38 longest(> 30 ks) observations made for NGC 4051, MCG-06–30–15 and NGC 4151 by XMM-Newton between 2000 and 2015. The nuclei were quite active during essentially all of these observations and the overall X-ray fluxes(0.3–10 keV) varied by an order of magnitude. Most of the observations do appear to show characteristic timescales, estimated through their auto-correlation functions, ranging between ~2.9 ks and ~45.3 ks. The hard(2–10 keV) and soft(0.3–2.0 keV) bands are very well correlated but consideration of their hardness ratios shows that the sources typically soften during flares. We also provide new estimates of the central black hole masses for these three AGNs that support the hypothesis that Narrow Line Seyfert 1 galaxies have relatively small central black holes.

Clumpy metal concentrations in elliptical galaxies NGC 4374 and NGC 4636

We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers.

A Quasi-periodic Oscillation of ~4.6 yr in the Radio Light Curves of Blazar PKS 0607-157

We present periodicity search analyses on long-term radio light curves at 4.8,8,and 14.5 GHz of blazar PKS 0607–157 observed by the University of Michigan Radio Astronomical Observatory telescope.The highly variable radio emissions are approximately distributed as a log-normal probability distribution function.The Power Spectral Density for the radio light curves can be well characterized by a power-law model.Using the Weighted Wavelet Z-transform and Lomb-Scargle periodogram methods,significant Quasi-periodic Oscillation(QPO)of∼4.6 yr in the radio light curve has been observed above the 3σconfidence level,which presents an interesting case among blazar QPO phenomena.We explore three plausible physical models to explain the observed QPOs:a supermassive binary black hole system,Lense-Thirring precession of the disk,and helical motion of plasma blobs within the jet.

Star formation properties in barred galaxies (SFB) Ⅱ. NGC 2903 and NGC 7080

Stellar bars are important for the secular evolution of disk galaxies because they can drive gas into the galactic central regions. To investigate the star formation properties in barred galaxies, we presented a multi-wavelength study of two barred galaxies： NGC 2903 and NGC 7080. We performed the three-component bulge-diskbar decomposition using the 3.6 μm images, and identified the bulges in the two galaxies as pseudobulges. Based on the narrowband Hα images, the star formation clumps were identified and analyzed. The clumps in the bulge regions have the highest surface densities of star formation rates in both galaxies, while the star formation activities in the bar of NGC 2903 are more intense than those in the bar of NGC 7080. Finally, we compared our results with the scenario of bar-driven secular evolution in previous studies, and discussed the possible evolutionary stages of the two galaxies.

Resolving the inner jet of PKS 1749+096 with super-resolution VLBA images at 7 mm

High resolution imaging of inner jets in Active Galactic Nuclei(AGNs)with Very Long Baseline Interferometry(VLBI)at millimeter wavelengths provides deep insight into the launching and collimation mechanisms of relativistic jets.The BL Lac object,PKS 1749+096,shows a core-dominated jet pointing toward the northeast on parsec-scales revealed by various VLBI observations.In order to investigate the jet kinematics,in particular,the orientation of the inner jet on the smallest accessible scales and the basic physical conditions of the core,in this work we adopted a super-resolution technique,the Bi-Spectrum Maximum Entropy Method(BSMEM),to reanalyze VLBI images based on the Very Long Baseline Array(VLBA)observations of PKS 1749+096 within the VLBA-BU-BLAZAR 7 mm monitoring program.These observations include a total of 105 epochs covering the period from 2009 to 2019.We found that the stacked image of the inner jet is limb-brightened with an apparent opening angle of 50°.0±8°.0 and 42°.0±6°.0 at the distances of 0.2 and 0.3 mas(0.9 and 1.4 pc)from the core,corresponding to an intrinsic jet opening angle of 5°.2±1°.0 and 4°.3±0°.7,respectively.In addition,our images show a clear jet position angle swing in PKS 1749+096 within the last ten years.We discuss the possible implications of jet limb brightening and the connection of the position angle with jet peak flux density and gamma-ray brightness.

On the reality of broad iron L lines from the narrow line Seyfert 1 galaxies 1H0707–495 and IRAS 13224–3809

We performed time resolved spectroscopy of 1H0707-495 and IRAS 13224-3809 using long XMM-Newton observations. These are strongly variable narrow line Seyfert 1 galaxies and show broad features around 1 keV that have been interpreted as relativistically broad Fe Lc~ lines. Such features are not clearly observed in other active galactic nuclei despite sometimes having high iron abundance required by the best fitted blurred reflection models. Given the importance of these lines, we explore whether the rapid variability of spectral parameters may introduce broad bumps/dips artificially in the time averaged spectrum, which may then be mistaken as broadened lines. We tested this hypothesis by performing time resolved spectroscopy using long （〉 100 ks） XMM-Newton observations and by dividing them into segments with typical exposures of a few ks. We extracted spectra from each such segment and modeled them using a two component phenomenological model consisting of a power law to represent the hard component and a black body to represent the soft emission. As expected, both the sources showed variations in the spectral parameters. Using these variation trends, we simulated model spectra for each segment and then co-added to get a combined simulated spectrum. In the simulated spectra, we found no broad features below 1 keV and in particular no deviation near 0.9 keV as seen in the real averaged spectra. This implies that the broad Fe Lα line that is seen in the spectra of these sources is not an artifact of the variation of spectral components and, hence, provides evidence that the line is indeed genuine.

Populations of Bright X-ray Sources in the Starburst Galaxies NGC 4038/4039

Assuming a naive star formation history, we construct synthetic X-ray source populations, using a population synthesis code, for comparison with the observed X-ray luminosity function （XLF） of the interacting galaxies NGC 4038/4039. We have included highand intermediate-mass X-ray binaries, young rotation-powered pulsars and fallback disk-fed black holes in modeling the bright X-ray sources detected. We find that the majority of the X-ray sources are likely to be intermediate-mass X-ray binaries, but for typical binary evolu- tion parameters, the predicted XLF seems to be steeper than observed. We note that the shape of the XLFs depends critically on the existence of XLF break for young populations, and suggest super-Eddington accretion luminosities or the existence of intermediate-mass black holes to account for the high luminosity end and the slope of the XLF in NGC 4038/4039.