Analyses of the Light Variations of OJ 287, 0716+714 and BL Lacertae

OJ 287 is a BL Lac object which exhibits intense activities of low peak-frequencies. Its energy spectrum in low frequency band is quite similar with those of two other TeV BL Lac objects (i.e., 0716+714 and BL Lacertae). However, the Cerenkov telescope did not detect its TeV rays. By using the observational data of these three heavenly bodies and comparing the discrepan- cies of their minimal periods of light variations and delays at 22 GHz, 37 GHz and B-waveband, we have further investigated the possible reason why the TeV gamma-rays of OJ 287 have not been observed. The results of analyses are as fol- lows. (1) For the minimal periods of light variations, the periods of OJ 287 at 37 GHZ and B-waveband are short. At 22 GHz the results of OJ 287 and 0716+714 are comparable, but the period of OJ 287 is much shorter in comparison with that of BL Lacertae, and this shows that its activity is more intense. However, the TeV gamma-rays of OJ 287 have not been detected, which implies that the radiation of OJ 287 in TeV waveband may have no connection with the minimal periods of light variations in these three low-energy wavebands. (2) In respect of delays, the delay of OJ 287 in the B waveband with respect to 37 GHz is longer than that of 0716+714, but shorter than that of BL Lacertae. Its delay at 37 GHz in respect to 22 GHz is shorter than that of 0716+714. Meanwhile, the delay of BL Lacertae at 37 GHz in respect to 22 GHz is negative, which implies that 22 GHz precedes 37 GHz. Via the comparison and analysis of delays, no obvious differences between OJ 287 and 0716+714 as well as BL Lacertae have been found. On the side of energy spectra, it is quite possible that due to the steep energy spectrum of OJ 287 in TeV waveband, the Cerenkov telescope has not detected the gamma radiation of OJ 287. However, nowadays it is still not clear whether the steep energy spectrum in TeV energy range has some influence on the light variations in low energy realm.     

An Analysis of Light Periods of BL Lac Object S5 0716+714 with the MUSIC Algorithm

The multiple signal classi?cation (MUSIC) algorithm is introduced to the estimation of light periods of BL Lac objects. The principle of the MUSIC algorithm is given, together with a testing on its spectral resolution by using a simulative signal. From a lot of literature, we have collected a large number of effective observational data of the BL Lac object S5 0716+714 in the three optical wavebands V, R, and I from 1994 to 2008. The light periods of S5 0716+714 are obtained by means of the MUSIC algorithm and average periodogram algorithm, respectively. It is found that there exist two major periodic components, one is the period of (3.33±0.08) yr, another is the period of (1.24±0.01) yr. The comparison of the performances of periodicity analysis of two algorithms indicates that the MUSIC algorithm has a smaller requirement on the sample length, as well as a good spectral resolution and anti-noise ability, to improve the accuracy of periodicity analysis in the case of short sample length.     

Light Periodicity Analysis of Blazar Object OJ 287 Based on Empirical Mode Decomposition

Considering the shortages of classical methods in periodicity analysis, the method of empirical mode decomposition (EMD) for processing nonlinear and non-stationary signals is applied to the V-band fluxes of OJ 287 from 1891 to 2010, 10 intrinsic mode functions with different timescales and a residual function are obtained from the light curve. The result shows that there exists a period of 12.34 yr in the V-band light variation of OJ 287, where the contribution rate of variance is maximal, and confirms that OJ 287 has a long-period variability in the V-band, and that the mean flux of OJ 287 tends to gradually decrease with time.     

Characteristics of the Radiation from Blazars

We have collected short-timescale variability data of 47 blazars, estimated the masses of their central black holes and the sizes of their radiation regions at different wavebands, and made a statistical analysis on the calculated results. It is found that the central black hole mass of blazars falls in the range 10⁷M to 10¹⁰M, and that the BL Lac objects and the flat-spectrum radio quasars have very different central black hole masses (the latter being generally greater), while they have very similar sizes of radiation regions in the infrared and γ-ray wavebands. Also, using the collected bolometric luminosity data, we have analyzed the relationship between the bolometric luminosity of blazars and their short-timescale variability, and it is concluded that the radiations from the radio-selected BL Lac objects (RBLs) and flat-spectrum radio quasars (FSRQs) are strongly beam-confined, while the effect of relativistic beaming is relatively small for the X-ray-selected BL Lac objects (XBLs).     

A New Method for Processing the Correlation of Light Variation Time Delays

The method of time delay correlation function (TDCF) is a new method for calculating the sequential time delays. This method is utilized to calculate the time delays in 3 radio wave bands (4.8 GHz, 8 GHz and 14.5 GHz) of the blazar 0316 + 413 (NGC 1275) and to make the multi-band correlation analysis for other 7 blazar sources. The calculated result of the blazar 0316 + 413 shows that its light curve at 4.8 GHz lags by 410 d behind that at 8 GHz, or τ_4.8−8 = 410 d; the light curve at 4.8 GHz lags by 440 d behind that at 14.5 GHz, or τ_4.8−14.5 = 440 d; and the light curve at 8 GHz lags by 30 d behind that at 14.5 GHz, or τ_8−14.5 = 30 d. In comparison with the method of discrete correlation function (DCF), the time delay obtained by taking advantage of the TDCF method is much more rational for the multi-band correlation analysis of the 7 blazars.     

OJ 287,0716+714与BL Lacertae的光变分析

OJ 287是存在着剧烈活动的低峰频BL Lac天体,其低频段的能谱与另两个TeV BL Lac天体(0716+714和BL Lacertae)在低频段的能谱很相似,但是切仑科夫望远镜却没能探测到它的TeV射线.利用这3个天体的观测数据,比较它们在22 GHz、37 GHz和B波段的最小光变周期及延迟的异同,进一步寻找没有观测到OJ 287的TeV伽马射线的可能原因.分析结果显示:(1)最小光变周期方面,OJ 287在37 GHz和B波段的周期偏小,在22 GHz,OJ 287与0716+714的结果相当,但与BL Lacertae相比要小很多,OJ 287的周期更短表明其活动性更强,却没有探测到来自OJ 287的TeV伽马射线,这表明OJ 287在TeV波段的辐射与这3个低能波段最小光变周期之间可能没有联系;(2)延迟方面,OJ 287在B波段相对于37 GHz的延迟要长于0716+714,短于BL Lacertae;在37 GHz相对于22 GHz的延迟要短于0716+714,而BL Lacertae在37 GHz相对于22 GHz的时延为负值,表明22 GHz要超前于37 GHz.通过对延迟的比较分析,并没有发现OJ 287与0716+714和BL Lacertae之间存在明显的差异;从能谱来看,很可能是由于OJ 287在TeV波段的能谱较陡造成切仑科夫望远镜没有探测到来自OJ 287的伽马辐射,但TeV能段较陡的能谱对低能段光变的影响目前还不是很清楚.     

Computing the Light Periods of Blazars with the Periodogram Spectral Analysis Method

The periodogram spectral analysis method applicable to equallyspaced time series is discussed, and the method is tested first with a simulated data series. It is confirmed that this method is effective for noisy series. Then, applying this method to the analysis of the light periods of the quasars 3C 279 and 3C 345 as well as the BL Lac objects OJ 287 and ON 231, we obtain their light periods to be 7.14 yr, 10.00 yr, 11.76 yr and 6.80 yr, respectively. These results obtained by periodogram spectral analysis are consistent with those obtained by the Jurkevich method in the literature. We have analyzed the effects of different window functions, and commented on their correct selection in practical applications.     

A Periodicity Analysis of the Light Curve of 3C 454.3

We analyzed the radio light curves of 3C 454.3 at frequencies 22 and 37 GHz taken from the database of Metsahovi Radio Observatory, and found evidence of quasi-periodic activity. The light curves show great activity with very complicated non-sinusoidal variations. Two possible periods, a very weak one of 1.57±0.12 yr and a very strong one of 6.15±0.50 yr were consistently identified by two methods, the Jurkevich method and power spectrum estimation. The period of 6.15±0.50 yr is consistent with results previously reported by Ciaramella et al. and Webb et al. Applying the binary black hole model to the central structure we found black hole masses of 1.53×109M⊙and 1.86×108M⊙, and predicted that the next radio outburst is to take place in 2006 March and April.     

Calculating the Light Period of BL Lac Object S5 0716+714 by Wavelet Analysis Method

A kind of wavelet analysis method for identifying the light period of the BL Lac object S5 0716+714 is introduced. The rather complete observed data in the four optical wavebands B, V, R, I are collected, and the long-term light curves based on 10-day averaging are obtained. On these light curves, the periodicity analysis is performed by using a wavelet analysis method. The result demonstrates that the wavelet analysis method is preferable for searching and identifying the light periods of BL Lac objects. From the contour map of the real part of the wavelet transform coefficient, the periodical light variations of the BL Lac object S5 0716+714 can be precisely identified. By analyzing the wavelet variance curves at the 4 wavebands, it is found that the BL Lac Object S5 0716+174 has a stable light period of 1160 days. This result is consistent with the 3.3-year period given by Raiteri et al. It is predicted that the next outburst in this object will happen around the August of 2011.     

The Petrology and Mineralogy Analysis of Noble Metal Alloys in the Inclusions of a Chondrite: An Implication on the Evolution of the Solar Nebula

The calcium-aluminium-rich inclusions (CAIs) in chondrites are believed to be the most early solids formed in the solar system, and retain the original information of the early solar nebula. However, in-depth researches revealed that most inclusions had experienced a complex history of evolution, including partial melting and secondary alteration. Focused on the refractory and chemically stable noble metal particles in the CAI of a CV meteorite (NWA 2140), a study of astrochemistry is made in this paper. The petrology and mineralogy analysis as well as the composition determination have been made on the noble metal particles. Based on the result of composition analysis, the thermodynamic process experienced by the CAI is inferred, and two kinds of noble metal alloys are identified, which correspond to the early-stage condensation products and the secondary alteration products of primordial metals, respectively.     

Algorithm Analysis of Autonomous Navigation of Spacecraft Based on X-ray Pulsars

A pulsar has the very stable rotation and can be used as the time standard. The astrometric parameters and astrophysical parameters of many pulsars, such as the spatial position, proper motion, distance, rotation period and its derivative, etc., can be all accurately determined. Since the pulsar can provide the time signal and the coordinates of its spatial position simultaneously, the pulsar navigation system installed on a spacecraft enables the autonomous navigation of the spacecraft to be realized. Firstly, the position of the spacecraft is predicted based on the equation of orbit dynamics of the spacecraft and then the Kalman filtering is applied to calculating the estimation error of the spacecraft position through the difference between the pulse arrival time observed on the spacecraft and the predicted pulse arrival time, thereby modifying the position of the spacecraft. Finally, the effects of the initial error, measuring accuracy of the pulse arrival time and number of pulsars on the navigation accuracy are analyzed.     

3C 120射电光变曲线中的一个可能周期

本文利用两种周期分析方法(Jurkevich方法和功率谱方法)分析了赛弗特星系3C120五个射电波段的光变曲线(4.8,8,14.5,22和37 GHz)。结果发现了一个大约为4.2a(年)的周期共同存在于5个波段的光变曲线中。这个周期可能能用双黑洞模型来解释。     

An Analysis of UT1 Determined by IVS Intensive Observations

In this paper the history and status of the IVS (International VLBI Service for Astrometry and Geodesy) UT1 Intensive observations are briefly re- viewed, and the deficiencies and error sources in the current Intensive observa- tions are investigated. An in-depth analysis of the IVS Intensive observation data from February 1984 to August 2011 with different observation networks is carried out, and the progress of the UT1 accuracy obtained by the Intensive observations during this period is discussed. By comparing the results from dif- ferent networks, a difference of some dozens of microseconds between different networks is found. The results of the IVS Intensive observations with Sheshan Station participated in are analyzed, it shows that the Sheshan Station perfor- mance as well as other stations. Finally, from the comparison and analysis of different UT1 series, it is concluded that there is an uncertainty with a level of 10 microseconds between the UT1 values obtained from the IVS Intensive observations and the values of the IERS (International Earth Rotation Service) C04.     

Basic Functions of the Light Curve Analysis of Eclipsing Variables in the Frequency Domain

An analytically tractable method of transforming the problem of light curve analysis of eclipsing binaries from the time domain into the frequency domain was introduced by Kopal (1975, 1979, 1990). This method uses a new general formulation of eclipse functions α, the so-called moments A _2m , and their combinations as g _2m = A _2m+2/(A _2m A _2m+4) functions for the basic spherical model. In this paper, I will review the use of these functions in the light curve analysis of eclipsing binaries.     

Comparison and Analysis of the Light Variations of 3C 273, 3C 279 and 3C 345

The blazar 3C 345 is quite similar to the γ-ray blazar 3C 279 in respect of redshift, spectral energy distribution from the radio to the X-ray wave band, and so on. However, it was not detected by EGRET. We compared the differences and similarities between 3C 345 and the γ-ray sources 3C 279 and 3C 273 in respect of variation amplitudes (in the 8 GHz, 22 GHz, 37 GHz and B band), the smallest variation time scales in the optical and the time lags between different bands to search possible reason for the lack of the γ-ray radiation in 3C 345. From our analyses it is found that the variation amplitudes in the radio band for 3C 345 and 3C 279 are quite similar; the variation amplitudes in the optical wave band gradually decrease in the order 3C 279, 3C 345 and 3C 273, and variations on the order of days are found in these three sources. It is also found that the time lag in 3C 345 is much longer than that in 3C 279 and is approximately the same as that in 3C 273. Based on the similarity of other observational properties between 3C 345 and 3C 273, such as the presence of the big blue bump and their comparable infrared luminosities, it is proposed that the spectral energy distribution and the luminosity in the γ-ray band for 3C 345 are similar to those for 3C 273. It is indicated by our simple calculations that if 3C 273 has a similar redshift to that of 3C 345, then even at the burst state, EGRET could not detect any radiations from 3C 273. This might be the reason why 3C 345 had never been detected by EGRET.     

Computing the Periods of Light Variation of Blazar Objects 3C279 and OJ 287 with Autoregressive Spectral Analysis Method

The light variability is one of the main characteristics of blazar objects. Because of the complexity of their light curves, the present periodicity analysis methods are not yet perfect. Based on the modern spectral estimate theory, this paper has described in details the principles of the maximum entropy spectral estimate and autoregressive (AR) spectral estimate, analyzed the effect of the order number selection on the resultant model. Applying these methods to the periodicity analysis of the quasar 3C 279 and BL Lac object OJ 287, their light periods are obtained to be 7.14 and 11.76 yr, respectively. As is verified by experiments, the AR spectral estimate has a high resolution and is a rather good periodicity analysis method. Finally, the items noteworthy for the application of these spectrum estimation methods to the periodicity analysis of the light variations of blazars are mentioned.     

Light curve solutions of the ultrashort‐period Kepler binaries

We carried out light‐curve solutions of the ultrashort‐period binaries with MS components observed by Kepler. All six targets turned out almost in thermal contact with contact or slightly overcontact configurations. Two of them, KID 4921906 and KID 6309193, are not eclipsing but reveal ellipsoidal and spot variability. One of the components of KID 8108785 exhibits inherent, quasi‐sinusoidal, small‐amplitude variability. KID 12055255 turned out tobe a very rare case of ultrashort‐period overcontact binary consisting of two M dwarfs. Our modeling indicated that the variability of KID 9532219 is due to eclipses but not to δ Sct pulsations as it was previously supposed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

BLLac天体ON231的光变周期研究

从大量文献中收集了BLLac天体ON231光学B波段约100年的观测数据,在此基础上分析了光变周期。用两种不同的方法（Jurkevich方法和小波分析法）分析周期光变,发现其光变曲线中存在13．6±1．5及26．1年的周期。     

Blazar天体3C 66A光学波段准周期光变分析

研究了Blazar天体3C 66A光学波段的准周期光变行为.收集了3C 66A光学V波段将近18 yr (2003—2021年)的测光数据,观测数据主要来源是:上海天文台(ShAO)、 AAVSO (The American Association of Variable Star Observers)数据库、Steward天文台.使用了Jurkevich和Lomb-Scargle两种方法分析了光变数据.Jurkevich方法得到了(850±90) d (～2.3 yr)和(1150±140) d (～3.2 yr)的光变周期,而Lomb-Scargle方法在充分考虑了“红噪声”效应之后同样得到了(869±70) d和(1111±90) d的光变周期,它们的置信水平分别为>99%和> 95%.通过与之前的研究结果比较,发现～2.3 yr的光变周期在3C 66A的历史光变数据中是一个稳定的周期,而～3.2 yr的周期则是不稳定的.