• Volume 35, Issue 3

September 2014,   pages  201-593

• Preface

• Search for Binary Black Hole Candidates from the VLBI Images of AGNs

We have searched the core-jet pairs in the VLBI scales (&lt; 1 kpc), from several VLBI catalogues, and found out 5 possible Binary Black Hole (BBH) candidates. We present here the search results and analyse the candidates preliminarily. We plan to study with multi-band VLBI observation. We also plan to carry out optical line investigation in future.

• Multi-Frequency VLBA Studies of the Parsec-Scale Jets in 3C 66A and 3C 66B

We report multi-frequency VLBA phase-referencing observation results of 3C 66A and 3C 66B, including high resolution maps and relative position measurements. The resulting images show similar morphology with that presented in previous works. We find core shift variations in both sources, indicating some physical condition changes in the jets.

• Japanese VLBI Network Observations of a Gamma-Ray Narrow-Line Seyfert 1 Galaxy 1H 0323+342

We made simultaneous single-dish and VLBI observations of a gamma-ray narrow-line Seyfert 1 (NLS1) galaxy 1H 0323+342. We found significant flux variation at 8 GHz on a time scale of one month. The total flux density varied by 5.5% in 32 days, corresponding to a variability brightness temperature of 7.0 × 1011 K. We also obtained brightness temperatures of greater than 5.2 × 1010 K from the VLBI images. These high brightness temperatures suggest that the source has nonthermal processes in the central engine. The source structure could be modelled by two elliptical Gaussian components on the parsec scales. The flux of the central component decreases in the same way as the total flux density, showing that the short-term variability is mainly associated with this component.

• FAST Maser Surveys

FAST, the Five-hundred meter Aperture Spherical radio Telescope, will become the largest operating single-dish telescope in the coming years. It has many advantages: much better sensitivity for its largest collecting area; large sky coverage due to its innovative design of the active primary surface; extremely radio quiet from its unique location, etc. In this work, I will highlight the future capabilities of FAST to discover and observe both galactic and extragalactic masers.

• Bolometric Luminosity Correction of H2O Maser AGNs

For the H2O maser host AGN sample, we derived their bolometric luminosity corrections, based on their X-ray data and [O III] emission line luminosities. Our results for maser AGNs is comparable to that of non-maser AGNs.

• Dependence of Core and Extended Flux on Core Dominance Parameter for Radio Sources

Based on two extragalactic radio source samples, the core dominance parameter is calculated, and the correlations between the core/extended flux density and core dominance parameter are investigated. When the core dominance parameter is lower than unity, it is linearly correlated with the core flux density, but it is not correlated with the extended flux density. When the core dominance parameter is higher than unity, it is not correlated with the core flux density, but it is linearly correlated with the extended flux density. Therefore, there are different results from different samples. The results can be explained using a relativistic beaming model.

• Relativistic Beaming Effect in Fermi Blazars

The most identified sources observed by Fermi/LAT are blazars, based on which we can investigate the emission mechanisms and beaming effect in the 𝛾-ray bands for blazars. Here, we used the compiled around 450 Fermi blazars with the available X-ray observations to estimate their Doppler factors and compared them with the integral 𝛾-ray luminosity in the range of 1–100 GeV. It is interesting that the integral 𝛾-ray luminosity is closely correlated with the estimated Doppler factor, log 𝑣𝛾 𝐿𝑣𝛾 = (2.95 ± 0.09) log 𝛿 + 43.59 ± 0.08 for the whole sample. When the dependence of the correlation between them and the X-ray luminosity is removed, the correlation is still strong, which suggests that the 𝛾-ray emissions are strongly beamed.

• Multi-Wave Luminosity of High-Synchrotron-Peaked TeV BL Lacs Detected by Fermi LAT

We have studied the correlations between luminosities (𝐿R, 𝐿IR, 𝐿𝛾) in the radio, near-infrared and 𝛾-ray wave bands for HSP TeV BL Lacs. The results show that there are significant intrinsic correlations between 𝐿R and 𝐿𝛾 and between 𝐿IR and 𝐿𝛾 in all states (high/average/low), and suggest that for HSP TeV BL Lacs, the Synchrotron Self-Compton radiation (SSC) is the main mechanism of high energy 𝛾-ray emission, and the inverse Compton scattering of circum-nuclear dust is likely to be an important complementary mechanism.

• Optical Spectral Variability of Blazars

It is well established that blazars show flux variations in the complete electromagnetic (EM) spectrum on all possible time scales ranging from a few tens of minutes to several years. Here, we report the review of optical flux and spectral variability properties of different classes of blazars on IDV and STV time-scales. Our analysis show HSPs are less variable in optical bands as compared to LSPs. Also, we investigated the spectral slope variability and found that the average spectral slopes of LSPs showed a good agreement with the synchrotron self-Compton loss-dominated model. However, spectra of the HSPs and FSRQs have significant additional emission components. In general, spectra of BL Lacs get flatter when they become brighter, while for FSRQs the opposite trend appears to hold.

• Variability Study of the S5 Sample

We present the results of flux density monitoring of the S5 sample at 5GHz with the Urumqi 25-m radio telescope during Dec. 2008 and Nov. 2009. Most sources exhibited &gt; 2% rms variation in our one-year monitoring. Twenty-five highly variable sources were detected at a confidence level of 99%. Weaker sources show larger amplitude of variability. Sources that have a steep spectral index are not as variable in flux density as the flat spectrum objects. No galactic dependent variability was found. Supplemental IDV observations for several strong variables were performed in order to search for possible rapid variability, and to compare variability on different time-scales. The absence of short time-scale variability in S5 0633+73 indicates that mid time-scale variability is a main source of intrinsic origin.

• Error Analysis of Ia Supernova and Query on Cosmic Dark Energy

Some serious faults in error analysis of observations for SNIa have been found. Redoing the same error analysis of SNIa, by our idea, it is found that the average total observational error of SNIa is obviously greater than 0.55𝑚, so we can not decide whether the Universe is an accelerating expansion or not.

• Possible Lognormal Distribution of Fermi-LAT Data of OJ 287

OJ 287 is a BL Lac object at redshift 𝑧 = 0.306 that has shown double-peaked bursts at regular intervals of 12 yr during the last 40 yr according to previous research. Some of the AGN 𝛾 ray power density shows a white noise process, while some others shows a red noise process. Some AGN flux presents normal or log-normal distribution. The two processes have an intrinsic relationship with centre black hole emission mechanism. We present the results of the analysis of the Fermi-LAT data. We review some problems concerning the random process.

• Variability of OI 090.4

OI 090.4 was monitored on 21 nights from 2006 to 2012 for studying the variability. Strong variations occurred during the past 6 years. The long-term variability amplitude is consistent with previous results. Microvariability was analysed for 43 intra-night light curves. 30 out of 43 light curves showed microvariability by C and F test analysis.

• Statistical Properties of Gamma-Ray Burst Host Galaxies

A statistical analysis of gamma-ray burst host galaxies is presented and a clear metallicity-stellar mass relation is found in our sample. A trend that a more massive host galaxy tends to have a higher star-formation rate is also found. No correlation is found between 𝐴V and 𝑁H. GRB host galaxies at a higher redshift also tend to have a higher star formation rate, however, even in the same redshift, the star formation rate may vary for three orders of magnitude.

• 4.8 GHz Intra-Day Variability of FSRQ 0507+179

As one of the targets of many flux monitoring campaigns, FSRQ 0507 + 179 shows various flux variation properties at almost all observing wavelengths, from radio to 𝛾-ray. With Urumqi 25-m telescope, our study on this object is focussed mainly on its radio flux variability, especially the Intra-Day Variability (IDV). We carried out a total of six epochs of IDV observations on 0507+179 at 4.8 GHz since March 2010, and found clearly IDV behaviours in all observing sessions and considered it is likely a type-I IDV source by analysing the characteristics and the timescales of the light curves. Additionally, we found 0507+179 exhibited some different IDV behaviours after an optical flare.

• Light Curve Periodic Variability of Cyg X-1 using Jurkevich Method

The Jurkevich method is a useful method to explore periodicity in the unevenly sampled observational data. In this work, we adopted the method to the light curve of Cyg X-1 from 1996 to 2012, and found that there is an interesting period of 370 days, which appears in both low/hard and high/soft states. That period may be correlated with black hole physics and accretion disk geometry.

• Computing Optical Variable Periods of BL Lac Object S5 0716+714 with Period04 Analysis Method

From a large volume of literature, we have collected effective observation of BL Lac object S5 0716+714 in the optical band, and constructed its long-term light curve from 1994 to 2006 AD. The light curve shows that S5 0716+714 is very active and exhibits very complicated non-sinusoidal variations. We used Period04 to analyse the period of light curve variation. Our results show that for S5 0716+714, the long-term period of variation is 3.3 yr which is consistent with the result of Raiter et al. (2003).

• Optical Monitoring of OT 546 in 2009

We reported the monitoring results of OT 546 in V, R and I bands, observed on 22 nights from February 16 to July 1 in 2009 at Weihai Observatory, Shandong university. During our monitoring, its variability amplitude was small and a possible microvariability was detected on one night using both C and F tests.

• Optical Periodicity Analysis of 3C 446 using Period04

All the data of the blazar 3C446 at 8, 4.8, 14 and 22 GHz, presented in publications from 1977 to 2006, have been compiled to generate light curves. The light curves show violent activity of 3C446. Using Period04 analysis method, we have found that there is a period of 7.2 yr, which is consistent with the results that we found using wavelet analysis method. We get the instability region as 𝑟 = 123.83𝑟𝑔.

• Pilot 1.3-cm IDVObservation of Two Dozens of AGNs at Urumqi

We carried out a pilot 1.3-cm IDV observations of two dozens of AGNs at Urumqi from 23 to 25 November 2011. Six sources, namely J0136+4751, J0217+0144, J1058+0133, J1751+0939, J1833−2103 and DA193 were detected as IDV sources at a 99% confidence level (about 3𝜎 level). The weather was fine during the observation period, but the system noise after calibration remained which could be due to the data sampled are relatively sparse for each source in the observations.

• Fractal Property in the Light Curve of BL Lac Object S5 0716+714

In this paper, we compile the historical R-band data of S5 0716+714 from literature and obtain its fractal dimension by using a fractal method and then simulate the data with the Weierstrass–Mandelbrot (W–M) function. It is considered that the light curve has a fractal property.

• WISE Infrared Properties of Fermi AGNs

The infrared properties of Fermi AGNs were investigated using the survey data of the Wide-field Infrared Survey Explorer (WISE). The results showed:

1. BL Lacs tend to be brighter than FSRQs at 3.4 𝜇m. However, with increase of wavelength, FSRQs tend to be brighter than BL Lacs.

2. FSRQs colours are redder than BL Lacs;

3. A strong correlation exists between infrared and 𝛾-ray luminosity.

• Long Term Periodicity Analysis of OJ 287 at Optical V Waveband

BL Lacertae object OJ 287 is one of the blazar that shows convincing evidence to support periodic variations. We have collected V band data for OJ 287 from 1891 to 2010, from the University of Michigan Radio Observatory (UMRAO) database and the available literature. Based on the spectral estimate theory, this paper used the periodogram spectral estimate, the maximum entropy spectral estimate and bispectrum spectral estimate methods. Applying these methods to the periodic analysis of OJ 287, we find the most eminent period as 12.1 yr. The results confirm that the variability period of OJ 287 in the optical V band is in agreement with the radio variability period of about 12 years.

• Quasi Periodic Oscillations in Blazars

Here we report our recent discoveries of Quasi-Periodic Oscillations (QPOs) in blazars time series data in X-ray and optical electromagnetic bands. Any such detection can give important clues of the location and nature of the processes of emission mechanism. In the case of radio-quiet AGN, the detected QPOs are very likely to be associated with the accretion disk. But in the case of blazars, it may be associated with jets in the high and outburst states, and in the low-state, it is probably associated with the accretion disk. In this brief review, I summarize the recent QPO detections in blazars. There is one strong evidence of QPO detection in XMM–Newton time series data of narrow line Seyfert 1 galaxy RE J1034+396 about which we will also discuss briefly.

• Seven-Year Multi-Colour Optical Monitoring of BL Lacertae Object S5 0716+714

We monitored the BL Lac object S5 0716+714 in five intermediate optical passbands from 2004 September to 2011 April. The object was active most of the time and intra-day variability was frequently observed. The total variation amplitude tended to decrease with decreasing frequency. Strong bluer-when-brighter chromatism was observed on both long and short timescales.

• Arcsecond-Scale Radio Jets of Ultra-High-Energy Synchrotron Peak BL Lacs (UHBLs)

We present the arcsecond-scale jet structure and related radio properties for a sample of 9 UHBLs selected from Nieppola et al. (2006) with log(𝑣peak/Hz) &gt; 20. Our preliminary results show that most of the UHBLs have compact structures, and their core dominance parameters are much larger than FR-I radio galaxies, suggesting that beaming may be prevalent in the jets of these sources.

• A Non-Mainstream Viewpoint on Apparent Superluminal Phenomena in AGN Jet

The group velocity of light in material around the AGN jet is acquiescently one (𝑐 as a unit), but this is only a hypothesis. Here, we re-derive apparent superluminal and Doppler formulas for the general case (it is assumed that the group velocity of light in the uniform and isotropic medium around a jet (a beaming model) is not necessarily equal to one, e.g., Araudo et al. (2010) thought that there may be dense clouds around AGN jet base), and show that the group velocity of light close to one could seriously affect apparent superluminal phenomena and Doppler effect in the AGN jet (when the viewing angle and Lorentz factor take some appropriate values).

• Correlation Analysis of Multi-Wavelength Luminosity of Fermi Blazars

We have studied the correlations between luminosities (𝐿R, 𝐿O, 𝐿X, 𝐿𝛾) in radio, optical, X-ray and 𝛾-ray wave bands for Fermi blazars, and found that there are significant correlations between 𝐿R and 𝐿𝛾, 𝐿X and 𝐿𝛾 and 𝐿O and 𝐿𝛾 for blazars, BL Lacs and FSRQs, but no correlation between 𝐿𝛾 and 𝐿O for BL Lacs. These results suggest that for Fermi blazars, the high energy 𝛾-ray emission can be related with radio, X-ray and optical emissions.

• Broad Band Spectral Index TeV Blazars Detected by Fermi LAT

We collected the radio, K-band, optical, X-ray, and 𝛾-ray data for 35 TeV blazars detected by Fermi LAT and studied the possible correlation between different broad band spectral indices (𝛼r.o, 𝛼r.x, 𝛼ir.o, 𝛼ir.x, 𝛼o.𝛾, 𝛼x.𝛾) in all states (average/high/low). Based on our results, we suggested that the seed photons of the 𝛾-ray drive from the synchrotron radiation themselves.

• Blazar Sequence in Fermi Era

In this paper, we review the latest research results on the topic of blazar sequence. It seems that the blazar sequence is phenomenally ruled out, while the theoretical blazar sequence still holds. We point out that black hole mass is a dominated parameter accounting for high-power-high-synchrotron-peaked and low-power-low-sychrotron-peaked blazars. Because most blazars have similar size of emission region, theoretical blazar sequence implies that the break of Spectral Energy Distribution (SED) is a cooling break in nature.

• 𝛾-Ray Emission from the Extreme Blazar 1ES 0229+200

Based on the traditional Synchrotron Self-Compton (SSC) model, we consider a secondary γ -ray emission component to an extreme blazar 1ES 0229 + 200 for the multiwavelength radiation. By assuming a suitable electron spectra and Inter-Galactic Magnetic Field (IGMF), we obtained excellent fits to observed spectra of the source. This indicated that the observed excess GeV 𝛾-rays emission can be explained by secondary 𝛾-rays produced through inverse Compton scattering of 𝑒± pairs against Cosmic Microwave Background (CMB) photons.

• Relation between X-Ray and 𝛾-Ray Emissions for Fermi Blazars

Using 𝛾-ray band data detected by Fermi Large Area Telescope (LAT) and X-ray band data for 78 blazars, we find a medium correlation between X-ray and 𝛾-ray fluxes in the average state. A medium anticorrelation is also found between X-ray (1 KeV) mean spectral index 𝛼𝑥 and 𝛾-ray mean spectral index 𝛼𝛾 for blazars. Our results suggest that the most likely radiation mechanism for the high energy 𝛾-ray would be SSC. And that the 𝛾-ray emission mechanism may be somewhat different for BL Lacs and FSRQs.

• 𝛾-Rays Radiation of High Redshift Fermi Blazars

Based on the 31 high redshift (𝑧 &gt; 2) Flat Spectral Radio Quasars (FSRQs), which is from the second Fermi-LAT AGNs catalogue (2LAC), we studied the correlation between flux densities (𝐹R, 𝐹K, 𝐹𝛾) in the radio, infrared and 𝛾-ray wave bands. We found that there is a significant positive correlation between 𝐹𝛾 and 𝐹R, and a weak anticorrelation between 𝐹𝛾 and 𝐹K in the average state. For high redshift blazars, we argue that the seed photon of 𝛾-ray emission mainly comes from the jet itself and partially from the dusty torus.

• Correlation between 𝛾-Ray and Radio Bands for 𝛾-Ray Loud Blazars

The most identified sources observed by Fermi are blazars (Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BLs). In this paper, we obtained 124 𝛾-ray loud blazars with available 𝛾-ray and radio (core and total) data. It is interesting that the 𝛾-ray luminosity have a good correlation with the radio luminosity. This phenomenon exists in the core radio luminosity (𝐿c) and total radio luminosity (𝐿t). The correlation between the 𝛾-ray and the radio luminosities is still stronger even after we eliminated the redshift effect, which suggests that the 𝛾-ray radiations in the 𝛾-ray loud blazars are strongly beamed.

• What Governs Lorentz Factors of Jet Components in Blazars?

We use a sample of radio-loud Active Galactic Nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. Recent investigations suggested that the most super-massive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies. The correlation between black hole mass and bulk Lorentz factor of the jet components found in this work implies that the motion velocity of the jet components is probably governed by the black hole spin. The faster moving jets are magnetically accelerated by the magnetic fields threading the horizon of more rapidly rotating black holes.

• Models for Very Rapid High-Energy 𝛾-Ray Variability in Blazars

We present a family of models for rapid 𝛾-ray variability in blazars based on a two-component jet. Fast variability occurs when relativistic electron–positron pairs interact with small-scale perturbations in the inner jet. These perturbations are produced by Kelvin–Helmholtz instabilities. We fit the minute-scale strong variability displayed by the blazar PKS 2155−304 and present synthetic light-curves of the kind that might be observed with forthcoming instruments such as the Cherenkov telescope array.

• Spectral Variability in Radio-Loud Quasars

The spectral variability of a sample of 44 Flat-Spectrum Radio Quasars (FSRQs) and 18 Steep-Spectrum Radio Quasars (SSRQs) in SDSS stripe 82 region is investigated. Twenty-five of 44 FSRQs show a bluer-when-brighter trend (BWB), while only one FSRQ shows a redder-when-brighter trend, which is in contrast to our previous results. Eight of 18 SSRQs display a BWB. We found an anticorrelation between the Eddington ratio and the variability amplitude in the 𝑟 band for SSRQs, which is similar to that in radio-quiet AGNs. This implies that the thermal emission from the accretion disk may be responsible for the variability in SSRQs. The spectral variability from SDSS multi-epoch spectroscopy also shows BWB for several SSRQs, which is consistent with that from photometry.

• Fermi LAT View of a Sample of Flaring 𝛾-Ray AGNs

In the first 3.5 years of operations, Fermi detected several sources whose flaring activity brought them to exceed daily fluxes brighter than 𝐹(𝐸 &gt; 100MeV) &gt; 10-6 ph cm-2 s-1. These episodes were promptly reported to the scientific community by the Fermi collaboration by means of astronomer telegrams (ATels). We focus our attention on the sample composed by these flaring sources, most of which are blazars, known to be extremely variable over the whole electromagnetic spectrum, from radio to 𝛾-ray energies. We study properties of the selected sample and compare them to general characteristics of the Fermi source catalogue.

• Helical Magnetic Fields in AGN Jets

We establish a simple model to describe the helical magnetic fields in AGN jets projected on the sky plane and the line-of-sight. This kind of profile has been detected in the polarimetric VLBI observation of many blazar objects, suggesting the existence of helical magnetic fields in these sources.

• Debeamed Sequence of LBAS Blazars

We have collected a sample of 71 𝛾-ray blazars selected from the Fermi LAT Bright AGN Sample (LBAS). The correlation between synchrotron peak luminosities 𝐿p and synchrotron peak frequencies 𝑣p have been studied and there is a weak negative correlation. But after correcting the effect of redshift and Doppler boosting, the relation between intrinsic 𝐿'p and 𝑣'p show significant positive correlation.

• Delta-function Approximation SSC Model in 3C 273

We obtain an approximate analytical solution using 𝛿 approximate calculation on the traditional one-zone synchrotron self-Compton (SSC) model. In this model, we describe the electron energy distribution by a broken power-law function with a sharp cut-off, and non-thermal photons are produced by both synchrotron and inverse Compton scattering of synchrotron photons. We calculate the radiation energy spectrum of electrons by the 𝛿 function. We apply this model to the multi-wavelength Spectral Energy Distributions (SED) of the 3C 273 in different states, and obtain excellent fits to the observed spectra of this source.

• Spectral Energy Distributions of SDSS Blazars

We compiled the radio, optical and X-ray data for SDSS sample, and presented broad band spectral index. The broad band energy distribution reveals that FSRQs and LBLs objects have similar spectral properties. However, HBLs have a separate distinct property. Even so, a unified scheme was also revealed from colour–colour diagram.

• Are Radio-Loud Narrow-Line Seyfert 1 Galaxies Blazar-like?

The similarities between blazars and radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s) have received much attention. In this paper, by using the magnetized slim disk model, we calculate the jet power and disk luminosity. It is found that the jet power is only a very small fraction of the disk luminosity, &lt; 10%. This indicates that the jet orientation of RLNLS1 is close to the line-of-sight, which is similar to blazars.

• Position Angle Changes of Inner-Jets in a Sample of Blazars

We have carried out the Gaussian model-fitting to 15 GHz VLBAcores for a sample of blazars from the MOJAVE database, analysed the correlations in the model-fitted parameters and studied the variability properties for different group of sources. We found that the Fermi LAT-detected blazars have on an average higher position angle changes of cores than the non-LAT detected blazars, and that the LAT-detected ones are associated with more variable cores in flux density.

• Parametric Models of Periodogram

The maximum likelihood estimator is used to determine fit parameters for various parametric models of the Fourier periodogram followed by the selection of the best-fit model amongst competing models using the Akaike information criteria. This analysis, when applied to light curves of active galactic nuclei can be used to infer the presence of quasi-periodicity and break or knee frequencies. The extracted information can be used to place constraints on the mass, spin and other properties of the putative central black hole and the region surrounding it through theoretical models involving disk and jet physics.

• Spectral Index Changes with Brightness for 𝛾-Ray Loud Blazars

Based on Fermi 1FGL and 2FGL data, a sample of 572 𝛾-ray loud blazars are selected, in which each source has both 𝛾-ray flux and spectral index in 1FGL and 2FGL, respectively. Theoretic relation of spectral index changes depending on 𝛾-ray brightness is obtained. The correlations between the ratio of 𝛾-ray flux densities and the differences of the 𝛾-ray spectral indices are discussed for the three subclasses of HBL, LBL and FSRQs. Results show that the ratio is related with the differences for the three subclasses. It is consistent with the theoretical result and it indicates that the spectrum becomes flat as the source brightens in the 𝛾-ray band.

• Effective Spectral Indices of Core and Extended Emissions for Radio Sources

From some available literatures, a sample of 393 radio sources is selected. The core and extended spectral indices are calculated. Results show that the core spectral index is different from the extended spectral index with the middle values approximately being 0 and 0.8 respectively.

• Correlations between Optical Variability and Physical Parameters of Quasars

Optical variability is an important feature of quasars. Taking advantage of a larger sample of 7658 quasars from SDSS Stripe 82 and relatively more photometric data points for each quasar, we estimate their variability amplitudes and divide the sample into small bins of various parameters. An anticorrelation between variability amplitude and rest-frame wavelength is found. Variability increases as either luminosity or Eddington ratio decreases. The relationship between variability and black hole mass is uncertain. The intrinsic distribution of variability amplitudes for radio-loud and radio-quiet quasars are different. Both radio-loud and radio-quiet quasars exhibit a bluer-when-brighter chromatism. With the Shakura–Sunyaev disk model, we find that changes of accretion rate play an important role in producing the observed optical variability. However, the predicted positive correlation between variability and black hole mass seems to be inconsistent with the observed negative correlation between them in small bins of Eddington ratio, which suggests that other physical mechanisms may still need to be considered in modifying the simple accretion disk model. The different mechanisms in radio-loud and radio-quiet quasars are discussed.

• Toy Model of Frame-Dragging Magnetosphere for the M87 Jet

We make a toy model for M87 jet to interpret its parabolic structure and acceleration in the apparent speeds, according to observations in milli-arcsecond to arcsecond scales upstream of HST-1. The outermost layer of jet is driven by the frame-dragging effect in the Kerr spacetime with a slowly to moderately spinning black hole. The corresponding magnetosphere has a foot-point 𝑅0 in the vicinity of event-horizon, and rotating at a frequency 𝛺F equal to that of the frame-dragging 𝜔(𝑅0).

• Relation between Radio Polarization and Spectral Index of Blazars

University Michigan RAdio Observatory (UMRAO) supply many radio photometries and polarimetries. We select a sample of 81 blazars from UMRAO and analyse the correlations between their spectral index and polarizations. Out of 35 BL Lacs and 46 FSRQs in the sample, 8 and 15 show strong correlation.

• Joint Spectral Analysis for Early Bright X-ray Flares of 𝛾-Ray Bursts with Swift BAT and XRT Data

A joint spectral analysis for early bright X-ray flares that were simultaneously observed with Swift BAT and XRT are present. Both BAT and XRT lightcurves of these flares are correlated. Our joint spectral analysis shows that the radiations in the two energy bands are from the same spectral component, which can be well fitted with a single power-law. Except for the flares in GRBs 060904B and 100906A, the photon spectral indices are &lt; 2.0, indicating the peak energies (𝐸p) of the prompt 𝛾-rays should be above the high energy end of the BAT band.

• Estimating Black Hole Spin of PG 1322+659 with Observed Optical and X-ray Continuum Spectrum

We fit the observed Spectral Energy Distribution (SED) of a bright radio quite quasar PG 1322+659 in optical and hard X-ray bands with an accretion disk–corona model to estimate BH spin a.

• Orbital Signatures from Observed Light Curves of Blazars

Variability in active galactic nuclei is observed in UV to X-ray emission based light curves. This could be attributed to orbital signatures of the plasma that constitutes the accretion flow on the putative disk or in the developing jet close to the inner region of the central black hole. We discuss some theoretical models based on this view. These models include general relativistic effects such as light bending, aberration effects, gravitational and Doppler redshifts. The novel aspects relate to the treatment of helical flow in cylindrical and conical geometries in the vicinity of a Schwarzschild black hole that leads to amplitude and frequency modulations of simulated light curves as well as the inclusion of beaming effects in these idealized geometries. We then present a suite of time series analysis techniques applicable to data with varied properties which can extract detailed information for their use in theoretical models.

• Chemical Evolution of Mn in Three Dwarf Spheroidal Galaxies

Based on an improved model, more reasonable nucleosyn-thesis and explosion rate of SNeIa and CCSNe, we studied Mn evolution for three local dwarf spheroidal galaxies (dSphs), considering the detailed SNe yield and explosion rates for different types of progenitors. The results can explain the main observation ofMn abundance for tens stars in those dSphs, and give some constraints to the nucleosynthesis and explosion ratio of different types of supernovae and Star Formation Rates (SFR) in those dSphs.

• Generalized Langevin Equation Description of Stochastic Oscillations of General Relativistic Disks

We consider a description of the stochastic oscillations of the general relativistic accretion disks around compact astrophysical objects based on the generalized Langevin equation, which accounts for the general retarded effects of the frictional force, and on the fluctuation–dissipation theorems. The vertical displacements, velocities and luminosities of the stochastically perturbed disks are explicitly obtained for both the Schwarzschild and Kerr cases. The power spectral distribution of the luminosity is also obtained, and it is shown that it has non-standard values. The theoretical predictions of the model are compared with the observational data for the luminosity time variation of the BL Lac S5 0716+714 object.

• Multi-Wavelength Variability Properties of Fermi Blazar S5 0716+714

The multi-wavelength variability properties of blazar S5 0716 + 714 are reported. We construct multi-wavelength light curves of radio, optical, X-ray and 𝛾-ray including our optical observation at Yunnan Observatories. In all the bands, the light curves show intense variabilities. The variability amplitudes in 𝛾-ray and optical bands are larger than those in the hard X-ray and radio bands. The characteristic variability timescales at 14.5 GHz, optical, X-ray, and 𝛾-ray bands are comparable. The variations of the hard X-ray and 14.5GHz emissions are correlated with zero lag, and so are the V band and 𝛾-ray variations. The multi-wavelength variability behaviours can be naturally explained by the classic leptonic model. We model the average SED of S5 0716 + 714 by leptonic model. The SSC+ERC model using the external seed photons from hot dust or Broad Line Region (BLR) emission is probably favourable avoiding the extreme input parameters from the pure SSC model.

• Spectral Variation of NLS1 Galaxy PMN J0948+0022

Four well-sampled Spectral Energy Distributions (SEDs) of PMN J0948+0022 are fitted with the syn+SSC+EC model to derive the physical parameters of its jets and to investigate the spectral variations of its SEDs. A tentative correlation between the peak luminosity (𝐿c) and peak frequency (𝑣c) of its inverse Compton (IC) bump is found in both the observer and co-moving frames, indicating that the variations of luminosity are accompanied by the spectral shift. A correlation between 𝐿cs and 𝛿 is found, and thus the magnification of external photon field by the bulk motion of the radiation regions is an essential reason for the spectral variation since, IC bump of PMN J0948+0022 is dominated by the EC process.

• Spectral Energy Distributions of XBLs, RBLs and FSRQs

We have collected a sample of 86 blazars and analysed the redshift 𝑧, the accretion rate 4$\dot{m}$ and the spectral index of the sample.

• Microvariability Detection of Mrk 421

BL Lac object Mrk 421 was observed in optical bands from 2009 April to 2012 May with the 1.0-m telescope at Weihai Observatory of Shandong University. Microvariability was analysed by C and F tests, but no significant microvariability was detected during our observations.

• Core Dominance Parameter for 𝛾-Ray Loud Blazars

In this paper, we compiled 572 blazars that have known core dominance parameter (log 𝑅), out of which 121 blazars are 𝛾-ray loud blazars. We compared log 𝑅 between 121 blazars and the rest with non 𝛾-ray detections, and found that 𝛾-ray loud blazars showed a different distribution, and their average value of log 𝑅 is greater than that for non 𝛾-ray blazars. Our analysis suggests that the 𝛾-ray emissions are strongly beamed.

• Connections between the Radio, Optical and Soft X-ray Luminosities for Flat-Spectrum Radio Quasars

We investigate the connections between radio, optical and soft X-ray luminosities with a sample of 538 FSRQs. We find that the radio luminosity is strongly correlated with the optical luminosity, as well as with the soft X-ray luminosity. We also find that the optical luminosity is strongly correlated with the soft X-ray luminosity.

• Spectral Variability of Quasar SDSS J030639.57+000343.1

In a sample of 60 quasars selected from the Sloan Digital Sky Survey (SDSS) with at least six-epoch spectroscopy, we investigated the variability of emission lines and continuum luminosity. In this paper, we present the results of SDSS J030639.57+000343.1. We found a strong anticorrelation between the continuum luminosity at 5100 Å and the spectral index, implying a bluer-when-brighter trend. The luminosity of the broad 𝐻𝛼 line is in proportion to the continuum luminosity at 5100 Å. Correspondingly, we did not find a strong correlation between the equivalent width of broad 𝐻𝛼 and the continuum luminosity, i.e. no Baldwin effect of broad 𝐻𝛼 in this source.

• Recent Seven Years of Radio and Optical Variabilities of Quasar 1156+295

We analyzed the radio (4.8, 8.0 and 14.5 GHz) light curves from UMRAO database and the optical data of quasar 1156+295 and found that the quasar exhibited remarkable quasi-periodic long-term flux variations in both radio and optical bands with a similar variability timescale of 1.2 ± 0.3 yr. In addition, when a cross correlation analysis was adopted to the radio and optical light curves, we found that the optical variations may precede those of the radio e.g., at 14.5 GHz by ∼ 200 days.

• Correlation between Spectral Index and Doppler Factor for a Sample of Fermi Blazars

Relativistic beaming effect is important for blazars. In a very recent work, 𝛾-ray Doppler factors were calculated for a sample of Fermi blazars (Fan et al. 2013). In this work, we investigated the correlation between the Doppler factor and the effective spectral index, 4𝛼OX, and found an anticorrelation between them.

• Relation of Core Dominance Parameter and Extended Spectral Index for Radio Sources

The correlations between differences of two core dominance parameters and core/extended spectral index are investigated. The extended spectral index is associated with the differences very well, while there is a weak relationship between core spectral index and the differences. The average core spectral index tends to be a constant’ ∼ 0.0.

• Broad-Band Spectral Indices Variability of BL Lacertae by Wavelet Method

BL Lacertae is one of the famous AGN that shows convincing evidence to support periodic variability. We compile R-band data and radio 22 GHz database from the available literature to build the light curves and to calculate broad-band spectral indices. This paper employs the wavelet periodic estimation method. The analysis results indicate that the most possible period is 7.02–7.36 yr in the selected wave-bands. The broad-band spectral indices have a possible period of 4.11 yr as a half value in selected wave-bands. The results confirm that the variability period in the radio 22 GHz is in agreement with the optical R band of about 7.01 yr, as also mentioned in other literatures.

• Massive Star Formation: Accreting from Companion

We report the possible accretion from companion in the massive star forming region (G350.69–0.49). This region seems to be a binary system composed of a diffuse object (possible nebulae or UC HII region) and a Massive Young Stellar Object (MYSO) seen in Spitzer IRAC image. The diffuse object and MYSO are connected by the shock-excited 4.5 𝜇m emission, suggesting that the massive star may form through accreting material from the companion in this system.

• Scalar Condensation of Holographic Superconductors using Ginzburg–Landau Density with Quartic Term

We study holographic superconductors analytically by using the Ginzburg–Landau action with the 𝛾-quartic term |Ψ|4. Our results show that 𝛾-term plays a role in the scalar condensation. It is found that the system displays two kinds of critical temperatures. One is independent of 𝛾. But the other increases with increasing 𝛾, which suggests the onset of easier condensation.

• Training in Astronomy for Physics Students

In this paper, we describe what we have done with regard to astronomy training for physics students. More and more students are interested in astronomy, they spend their summer holidays and spare time in observations and studying the observation data. Some students are familiar with using the telescope for observations, dealing with absorption line features achieved from the observations. Astronomy was selected as the key subject in Guangzhou city and Guangdong province, the laboratory for astronomy science and technology was selected as the key laboratory of Guangzhou city and that for the education department of Guangdong Province. We also provide a master degree programme for astronomy.

• Black Hole Analogue in Bose–Einstein Condensation

We have proposed a black hole analogue in a Bose–Einstein condensation. By introducing the Painlevé co-ordinates and using K–G equations, we have obtained the critical temperature of the black hole analogue in a Bose–Einstein condensation.

• Visual Method for Spectral Energy Distribution Calculation of Blazars

In this work, we propose to use The Geometer’s Sketchpad’ to the fitting of a spectral energy distribution of blazar based on three effective spectral indices, 𝛼RO, 𝛼OX, and 𝛼RX and the flux density in the radio band. It can make us to see the fitting in detail with both the peak frequency and peak luminosity given immediately. We used our method to those sources whose peak frequency and peak luminosity are given and found that our results are consistent with those given in the work of Sambruna et al. (1996).

• Dense Molecular Gas and H2O Maser Emission in Galaxies

Extragalactic H2O masers have been found in dense gas circumstance in off-nuclear star formation regions or within parsecs of Active Galactic Nuclei (AGNs). HCN molecular (one of the best dense gas tracers) Emission has been detected in more than 60 galaxies. For HCN-detected galaxy sample, the relation of maser and gas emission was investigated here to identify physical observable properties that differentiate maser and non-maser galaxies. Our analysis results show that there is no significant difference on the infrared and gas emission between maser galaxies and galaxies without maser detection. For maser host HCN-galaxies, maser luminosity is found to be correlated to CO luminosity (a proxy of the total molecular gas) and HCN luminosity, i.e., kilomasers (𝐿H2O &lt; 10𝐿) with low maser luminosity having low gas emission luminosity, with respect to megamasers (𝐿H2O &gt; 10𝐿). For normalized maser and HCN luminosity (for removing distance effect), the correlation is still apparent. However, for normalized maser and CO luminosity, the correlation disappeared completely. Thus one proposition that the amount of dense molecular gas should be a good tracer of H2O maser emission can be made.

• Spectral Lag Evolution among 𝛾-Ray Burst Pulses

We analyse the spectral lag evolution of 𝛾-ray burst (GRB) pulses with observations by CGRO/BATSE. No universal spectral lag evolution feature and pulse luminosity-lag relation within a GRB is observed.Our results suggest that the spectral lag would be due to radiation physics and dynamics of a given emission episode, possibly due to the longer lasting emission in a lower energy band, and the spectral lag may not be an intrinsic parameter to discriminate the long and short GRBs.

• Evolution of Ly𝛼 Forest in Redshift Range 0.5 &lt; 𝑧 &lt; 3.4

We collect 23 spectral data from literature, which is regarded as a relatively sufficient sample. The evolution index 𝛾 was calculated to study the evolution of Ly𝛼 line density of Ly𝛼 forest. This paper discusses the relationship between the evolution with the redshift in different interval threshold of column density. The results are in accordance with the results of previous research.

• Conductivity of Holographic Superconductor within Ginzburg–Landau Theory

The frequency-dependent conductivity is obtained for the holographic superconductor by using the Ginzburg–Landau theory with a |Ψ|4 term. Our results show that |Ψ|4 term plays a role in the low-temperature behaviour of the conductivity.

• Entropy Spectrum of Modified Schwarzschild Black Hole via an Action Invariance

The entropy spectrum of a modified Schwarzschild black hole in the gravity’s rainbow are investigated. By utilizing an action invariance of the black hole with the help of Bohr–Sommerfield quantization rule, the entropy spectrum for the modified black hole are calculated. The result of the equally spaced-entropy spectrum being consistent to the original Bekenstein’s spectra is derived.

• Principal Component Analysis of Long-Lag, Wide-Pulse Gamma-Ray Burst Data

We have carried out a Principal Component Analysis (PCA) of the temporal and spectral variables of 24 long-lag, wide-pulse gamma-ray bursts (GRBs) presented by Norris et al. (2005). Taking all eight temporal and spectral parameters into account, our analysis shows that four principal components are enough to describe the variation of the temporal and spectral data of long-lag bursts. In addition, the first-two principal components are dominated by the temporal variables while the third and fourth principal components are dominated by the spectral parameters.

• Identification of Metal Absorption Lines on Quasar Spectra of SDSS DR9

Absorption lines are an important tool for probing the gas in the Universe. Our group aim to identify the metal absorption lines imprinted on the quasar spectra of the BOSS. In this work, we show the metal absorption lines identified in the spectrum of SDSS J160032.95+323638.7.

• Hawking Temperature of an Arbitrarily Accelerating Black Hole

Hawking temperature of an arbitrarily accelerating black hole with electric and magnetic charges are obtained based on the Klein–Gordon equation with a correct-dimension new tortoise coordinate transformation.

• Important Property of GRB Pulse: Power-Law Indices of Time Properties on Energy

The dependence of pulse temporal properties (pulse width, pulse rise width and pulse decay width) on energy is power-law function. Some correlated relationships between the power-law indices of the pulse time properties on energy and the spectral lags, relative spectral lags, spectral parameters of band function, and photon flux using a well-separated long-duration 𝛾-ray burst (GRB) pulse sample is demonstrated here. We argue that the curvature effect can explain the correlated properties.

• Outward Motions of SiO Masers around VX Sgr

We report the proper motions of SiO maser features around VX Sgr from the two-epoch VLBA observations (2006 December 15 and 2007 August 19). The majority of maser feature activities show a trend of outward motions. It is consistent with our previous finding that the outflow may play an important role for SiO maser pumping.

• CO and its Isotopomers Observation towards Sgr B2

We present our observations toward Sgr B2 region in 𝐽 = 1−0 lines of 12CO, 13CO, C18O and C17O using 13.7-m Delingha millimeter telescope with newly installed 9-beam SIS superconducting receiver. From the integrated line intensity, we derive the abundance ratio of C18O/C17O with a mean value of 3.11 ± 0.10, which is consistent with the previous results.

• Chandra and XMM–Newton Observations of H2O Maser Galaxy Mrk 348

For H2O megamaser galaxy Mrk 348, Chandra and XMM–Newton data are analysed. The nuclear fitting results of XMM–Newton data suggest the possible existence of a heavily obscured AGN. But the nuclear spectrum extracted from Chandra cannot be well-fitted by the best fitting model for XMM–Newton. Further optimal fitting and discussions are needed.

• Observations of Binary and Millisecond Pulsars at Xinjiang Astronomical Observatory

We present the first results of radio timing observations of binary and millisecond pulsars in China. We have timed four binary pulsars for 9 years, using Nanshan 25-m radio telescope. The long time span has enabled us to determine their rotation and orbital parameters.

• Hawking Temperature of Acoustic Black Hole

Using a new tortoise coordinate transformation, the Hawking radiation of the acoustic black hole was discussed by studying the Klein–Gordon equation of scalar particles in the curve space-time. It was found that the Hawking temperature is connected with time and position on the event horizon.

• Analysis of 𝐻𝛼(𝐷𝛼) Line Shape

The particles energy distribution is derived directly from the 𝐻𝛼(𝐷𝛼) line shape, which is measured by two sets of OMA. The dissociative excitation of molecular is dominating when the local electron temperature is &gt; 10 eV. The 𝐷𝛼 line shape is also simulated by the Monte–Carlo method, the molecular dissociation contributes to 57% neutral atoms and 53% emission intensity in front of the limiter, and 85% neutral atoms and 82% emission intensity in front of the wall. The processes of atoms and molecules influence on the energy balance is discussed in SOL, the power loss from molecular dissociation is 6 × 104 kW at SOL.

• Hawking Radiations from an Arbitrarily Accelerating Kerr Black Hole

The Hawking radiation from an arbitrarily accelerating Kerr black hole is calculated by using a new tortoise coordinate transformation and the improved Damour;Ruffini method.

• Different Luminosity Correlation of GRBs

We report our recent understanding about a tight correlation between relative spectral lag and luminosity (or redshift) for 𝛾-ray bursts. The latest investigations indicate that the empirical correlations got from BATSE bursts also exist for Swift/BAT ones. The special luminosity-lag correlation is much similar to that of the luminosity with pulse number proposed by Schaefer (2003), but largely different from most others ever discovered. Note that our newly built luminosity-lag correlation predicts that luminosity should evolve with cosmological redshift as 𝐿p ∝ (1 + 𝑧)2.4 ± 0.7 that is excellently confirmed by Salvaterra et al. (2012) and Geng &amp; Huang (2013). In addition, it is also surprisingly found that the luminosity-lag correlation can account for both long and short Swift/BAT bursts, which might be an evidence of the same radiation mechanism for diverse burst groups.

• Error Analysis on Plane-to-Plane Linear Approximate Coordinate Transformation

In this paper, the error analysis has been done for the linear approximate transformation between two tangent planes in celestial sphere in a simple case. The results demonstrate that the error from the linear transformation does not meet the requirement of high-precision astrometry under some conditions, so the linear approximate transformation should be taken seriously.

• Influence of Magnetic Field Decay on Electron Capture in Magnetars

The de-excited energy of electron capture (EC) induced by magnetic field decay may be a new source for heating magnetar crust, so we do a quantitative calculation on EC process near the outer crust and analyse their influence on persistent X-ray radiation of magnetars, adopting the experimental data or the results of theoretical model (including the large-scale shell model and quasi-particle random phase approximation).

• Canonical Ensemble Model for Black Hole Radiation

In this paper, a canonical ensemble model for the black hole quantum tunnelling radiation is introduced. In this model the probability distribution function corresponding to the emission shell is calculated to second order. The formula of pressure and internal energy of the thermal system is modified, and the fundamental equation of thermodynamics is also discussed.

• Canonical Ensemble Model for Black Hole Horizon of Schwarzschild–de Sitter Black Holes Quantum Tunnelling Radiation

In this paper, we use the canonical ensemble model to discuss the radiation of a Schwarzschild–de Sitter black hole on the black hole horizon. Using this model, we calculate the probability distribution from function of the emission shell. And the statistical meaning which compare with the distribution function is used to investigate the black hole tunnelling radiation spectrum.We also discuss the mechanism of information flowing from the black hole.

• Influence of Sudden Change of Solar Mass in the PN Stage on the Orbit of Earth-Like Planet

Assuming that the terminated mass is confined within the range 0.4551-0.5813𝑀 when the sun is going to evolve into a white dwarf, the velocity of the sun projecting the shell in the PN stage is much greater than the revolving velocity of the earth-like planet, therefore, we think that the solar mass change is instantaneous.

• Astronomy Education Project for Guangdong High Schools

Guangdong province is an active area in China for astronomy education and popularization. The current status and problems of astronomy education in high schools are reviewed. To tackle these problems, an astronomy education project for high school teachers and students was initiated by Guangzhou University in 2013. The purpose and key points of the projects are introduced in this paper.

• List of Participants

• Author Index

• # Journal of Astrophysics and Astronomy

Volume 41, 2020
All articles
Continuous Article Publishing mode

• # Continuous Article Publication

Posted on January 27, 2016

Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019