Optical Photometric Observations of 7-Ray Loud Blazars

We report results of our optical photometric observations of ten gamma-ray loud blazers, namely: 0219+428 (3C66A), PKS 0420-014 (OA 129), S5 0716+714, 0754+100 (OI 090.4), 0827+243 (OJ248), 1652+398 (Mrk 501), 2200+420 (BL Lacertae), 2230+114 (CTA 102), 2251+158 (3C 454.3) and 2344+514. The observations were carried out in September-October, 2000 using the 70 cm optical telescope at Abstumani Observatory, Georgia. We found intra-day variations in 0420-014, S5 0716+714, BL Lacertae and CTA 102. A variation of 0.3 magnitude over a time scale of about 3 hours was observed in the R passband in BL Lacertae on JD 2451827. We did not detect any variation in 3C 66A, Mrk 501, or 3C 454.3 during our observations. Nor did we detect any clear evidence of variation in 1ES 2344+514 during our two weeks' observing run of the TeV gamma-ray source.     

Detection of exceptional X-ray spectral variability in the TeV BL Lac 1ES 2344+514

We present the results of six BeppoSAX observations of 1ES 2344+514, five of which were taken within one week. 1ES 2344+514, one of the few known TeV BL Lac objects, was detected by the BeppoSAX Narrow Field Instruments (NFI) in the range 0.1 and ≈50 keV. During the first five closely spaced observations 1ES 2344+514 showed large-amplitude luminosity variability, associated with spectacular spectral changes: in particular, the last observation found the source to be several times fainter, with a much steeper X-ray spectrum . The energy-dependent shape of the light curve and the spectral changes both imply a large frequency shift (by a factor of 30 or more) of the peak of synchrotron emission. At maximum flux the peak was located at, or above, 10 keV, making 1ES 2344+514 the second blazar (after Mrk 501) to have a synchrotron peak in the hard X-ray band. The frequency shift, and the corresponding increase in luminosity, might be caused by the onset of a second synchrotron component extending from the soft to the hard X-ray band where most of the power is emitted. Rapid variability on a time-scale of approximately 5000 s has also been detected when the source was brightest.     

Variations in the flux from the blazar 1ES 2344+514 in 2003 and their correlation in the very-high-energy gamma-ray and X-ray ranges

We consider the very-high-energy (VHE) gamma-ray observations of the blazar 1ES 2344+514 in 2003 in comparison with the data of its ASM/RXTE X-ray monitoring. A VHE gamma-ray flux was detected from the observed object at a confidence level of ≈ 5σ and it was estimated to be 1.85 ± 0.68 Crab (E ≥ 1 TeV). The observations revealed a VHE gamma-ray burst from the object that occurred in September 2003 and that lasted for no more than 4 days. The burst was also confirmed in the X-ray (2–12 keV) energy range. Analysis of the observational data showed evidence of a correlation between the fluxes in the two energy ranges and invoking the previous observations of 1ES 2344+514 in 2002 allowed this correlation to be refined in a wide range of fluxes.     

Photometric variability of four coronally active stars

We present photometric observations of four stars that are optical counterparts of soft X-ray/EUV sources, namely 1ES 0829+15.9, 1ES0920-13.6, 2RE J1 10159+223509 and 1ES 1737+61.2. We have discovered periodic variability in two of the stars, viz., MCC 527 (1ES 0829+15.9; Period = 0 ^d .828 ± 0.0047) and HD 81032 (1ES 0920-13.6; Period = ∼ 57.02 ± 0.560 days). HD 95559 (2RE J1 10159+223509) is found to show a period of 3 ^d . HD 160934 (1ES1737+61.2) also shows photometric variability but needs to be monitored further for finding its period. These stars most likely belong to the class of chromospherically active stars.     

耀变体光学波段的微光变及能谱变化

耀变体在多个波段的微光变和能谱变化多年来是中外天文观测研究的热点课题.耀变体的微光变于20世纪60年代被发现,20世纪80年代以来发现很多源的微光变具有不同的特性,目前对其物理机制的认识和理论、模型的研究还处于发展阶段.该文总结了7个目前观测最多的耀变体(3C 66A,3C 279,3C 454.3,AO 0235+164,BL Lac,OJ 287,S5 0716+714)在光学波段的微光变和能谱变化的观测历史和最新进展,并对其理论模型作了简单介绍.     

Observational evidences of multiple shock waves in X-ray selected BL Lacerate objects

The results of optical R-band photometry of three X-ray selected BL Lacertae objects 1ES 0502+675, 1ES 0806+524 and 1ES 1959+650 from the Einstein Slew Survey are presented. The observations are performed during 1997–2006 with the 70-cm meniscus type telescope of Abastumani Astrophysical Observatory. The objects show clear long-term variability with time scales of 1–3 years without evident periodicity. The main results consist in the discovery of multiple-peak structures on historical light curves as predicted theoretically on the basis of the assumption that long-term variability of blazars are triggered by ultrarelativistic shock waves propagating through their jets. They are direct evidence of the existence of reverse shocks besides the main one arising by a single disturbance. Two-peak maxima are found for 1ES 0502+675 and 1ES 0806+524. The more complicated structure shows 1ES 199+650 - a maximum with four consequent peaks. The relative strengths of the main and reverse shocks are mainly equal according to the shape of the respective peaks. The brightness dip between them is on average 60% less than in the case of consequent main shocks. Optical maximum epochs, covered well by the observations, show that the main shocks are either not always accompanied by reverse ones or the later are not always strong enough to be discovered by the observations.     

Photometric variability of the protoplanetary nebula LSIV-12°111

We present our photometric observations of an early B supergiant with an infrared excess, the protoplanetary object LSIV-12°111, and the previously suspected variable star NSV 24971. We confirm its photometric variability. During two observing seasons (2000–2001), the star exhibited rapid irregular light variations with amplitudes $\Delta V \sim 0\mathop .\limits^m 3$ , $\Delta B \sim 0\mathop .\limits^m 3$ , and $\Delta U \sim 0\mathop .\limits^m 4$ and a time scale of ～1^d. There is no correlation between the colors and magnitudes of the star. The variability patterns of LSIV-12°111 and two other hot post-AGB stars, V886 Her and V1853 Cyg, are shown to be similar.     

CCD photometry of five X-ray selected BL Lacertae objects

We present the results of the monitoring of a sample of 5 HBLs in the B, V and R bands during 2003–2008. All sources in our monitoring project show significant rapid optical variations, except 1ES 1959+650, however; for 1ES 1959+650, the gamma-ray variability on a timescale of ～7 hours has been observed by Holder et al. (Astrophys. J. 583:L9, 2003). Using these variability timescales, we estimate the black hole masses for each source with the Kerr black hole theory.     

CCD Photometry and Long-Term Optical Variability of 3C 345

This paper presents evidence for long-term optical variability and colour behaviour of the blazar 3C 345 (1641+399, z=0.595). Our results show that the amplitude of the optical variations of 3C 345 has been only about 3 magnitudes from its photometric history; existent significant correlation between brightness and colours is found for 3C 345. Our recent CCD photometry of 3C 345 in May 1996 and May 1997 showed that they are in good agreement with our prediction of the optical variability period of about 10 years (see Zhang et al., 1998; Webb et al., 1988). This revised version was published online in July 2006 with corrections to the Cover Date.     

Monte Carlo Simulation of Solar Active-Region Energy

A Monte Carlo approach to solving a stochastic-jump transition model for active-region energy (Wheatland and Glukhov: Astrophys. J. 494, 858, 1998; Wheatland: Astrophys. J. 679, 1621, 2008) is described. The new method numerically solves the stochastic differential equation describing the model, rather than the equivalent master equation. This has the advantages of allowing more efficient numerical solution, the modeling of time-dependent situations, and investigation of details of event statistics. The Monte Carlo approach is illustrated by application to a Gaussian test case and to the class of flare-like models presented in Wheatland (Astrophys. J. 679, 1621, 2008), which are steady-state models with constant rates of energy supply, and power-law distributed jump transition rates. These models have two free parameters: an index (δ), which defines the dependence of the jump transition rates on active-region energy, and a nondimensional ratio ( ) of total flaring rate to rate of energy supply. For the nondimensional mean energy of the active-region satisfies , resulting in a power-law distribution of flare events over many decades of energy. The Monte Carlo method is used to explore the behavior of the waiting-time distributions for the flare-like models. The models with δ≠0 are found to have waiting times that depart significantly from simple Poisson behavior when . The original model from Wheatland and Glukhov (Astrophys. J. 494, 858, 1998), with δ=0 (i.e., no dependence of transition rates on active-region energy), is identified as being most consistent with observed flare statistics.     

Photometric monitoring of the blazar 3C 345 for the period 1996–2006

We present the results of the blazar 3C 345 monitoring in Johnson‐Cousins BVRI bands for the period 1996–2006. We have collected 29 V and 43 R data points for this period; the BI light curves contain a few measurements only. The accuracy of our photometry is not better than 0.03 mag in the VR bands. The total amplitude of the variability obtained from our data is 2.06 mag in the V and 2.25 mag in the R band. 3C 345 showed periods of flaring activity during 1998/99 and 2001: a maximum of the blazar brightness was detected in 2001 February – 15.345 mag in the V and 14.944 mag in the R band. We confirm that during brighter stages 3C 345 becomes redder; for higher fluxes the colour index seems to be less dependent on the magnitude. The intra‐night monitoring of 3C 345 in three consecutive nights in 2001 August revealed no significant intra‐night variability; 3C 345 did not show evident flux changes over timescales of weeks around the period of the intra‐night monitoring. This result supports the existing facts that intra‐night variability is correlated with rapid flux changes rather than with specific flux levels. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies of bright flat-spectrum radio quasar 3C 454.3 at high and very-high-energies

Blazars are the subclass of active galactic nuclei (AGNs) which includes the Flat Spectrum Radio Quasars (FSRQ) and BL Lacertae (BL Lac) objects. Variability on the short- and long-time scale in all the wide energy ranges from radio up to gamma-ray emission is a special characteristic of blazars. Multi-wavelength studies of the flaring activity and variability of blazars can serve as a tool to probe the physical properties of the near the core regions and processes responsible for the observed features. 3C 454.3 is a bright FSRQ that is intensively studied through the wide range of electromagnetic spectrum. It has shown remarkably high activity since 2000. The long-term observations of 3C 454.3 at 800 GeV–100 TeV energies with the SHALON telescope were started in 1998 year. A number of activity periods were found. The most significant flaring state of 3C 454.3 at TeV energies was detected in the SHALON observational period of November–December 2010. This increase is correlated with the flares at a lower energy range in observations of Fermi-LAT. The direct association of the significant changes of gamma-ray flux with strong core radio flares are not clear but observed correlations and lags in multi-wavelength activity may point to the complexity of the emission processes in blazars connected with disturbance propagating in the jet.     

Rapid photometric and spectroscopic evolution of the young planetary nebula Hen 3–1357 and its central star SAO 244567

We present the results of spectroscopic and photometric observations for the young compact planetary nebula Hen 3–1357 and its central star SAO 244567. High-resolution spectroscopy has allowed the expansion velocity of the nebula, V _exp = 8.4 ± 1.5 km s^?1, and the heliocentric velocity of the object, V _r = +12.6 ± 1.7 km s^?1, to be determined. The gas shell parameters (N _e , T _e ), the extinction in the Hβ line, and the O, N, Ne, Ar, S, Cl, He, and C abundances have been determined from low-resolution spectra taken in 1992 and 2011. We have found significant changes in the relative intensities of forbidden lines in the spectrum of Hen 3–1357 within the last 20 years: the low-excitation [O I], [O II], and [N II] lines became stronger relative to Hβ by a factor of ～2, while the [O III] lines weakened by a factor of ～ 2, suggesting a decrease in the excitation class of the nebula. The V-band photometry performed under the ASAS-3 program revealed a decline in the yearly mean brightness of SAO 244 567 from 2001 to 2009 by $0_.^m 5$ and rapid variability with an amplitude of a few tenths of a magnitude. Published observational data in a wide spectral range, from the near ultraviolet to the radio band, suggest an appreciable weakening of the flux from the star and the nebula.     

Optical R-band variability of seven X-ray-selected BL Lacertae objects

This paper presents the results of optical CCD photometry in the Cousins R band for seven X-ray-selected BL Lacertae objects. Observations have been performed with the 70-cm meniscus telescope of Abastumani Astrophysical Observatory, Georgia. The data obtained provide important information on sources that have been rarely observed in the optical band. The targets show clear long-term variability with time-scales of 1.5–5 yr. The maximum amplitudes are slightly greater than 1 mag. 1ES 0323+022, 0502+675 and 0806+524 show clear non-periodical behaviour. 1ES 1028+511 changes quasi-periodically but further monitoring for periodicity confirmation and period derivation is needed. Overall brightness variation is maximal for 1ES 0647+250 with  Δ R = 1.29  mag. Two-peak maxima, indicating the existence of reverse shocks in blazar jets, are observed for 1ES 0502+675, 0647+250, 0806+524 and 1517+656. The targets do not show intra-night variability. Day-to-day changes with amplitudes of 0.1–0.32 mag coincide mainly with short-term bursts. The latter are seen at faint (quiet) stages as during flaring activities. This fact leads to the suggestion that both hot-spot and shock-in-jet models explaining the origin of short-term bursts should be reasonable.     

Observations of active galactic nuclei with the GT-48 CrAO gamma-ray telescope in 2004

Observations of several active galactic nuclei were performed with the GT-48 gamma-ray telescope at CrAO in 2004: 3C 66A, Mk 421, Mk 501, 1H 1426, 1ES 1959, and BL Lac. Very-high-energy (E ≥ 10¹² eV) gamma-ray fluxes were recorded from 3C 66A, Mk 421, Mk 501, and 1H 1426 at a confidence level of more than 4σ. Upper limits for the flux of very-high-energy gamma rays are presented for 1ES 1959 and BL Lac. The 2004 observational data for 3C 66A (z = 0.44) confirm the results obtained previously at CrAO.     

Druse clinopyroxene in D'Orbigny angritic meteorite studied by single‐crystal X‐ray diffraction,electron microprobe analysis,and Mössbauer spectroscopy

Abstract— The crystal structure of druse clinopyroxene from the D'Orbigny angrite, (Ca_0.944 Fe²⁺_0.042 Mg_0.010Mn_0.004) (Mg_0.469Fe²⁺_0.317Fe³⁺_0.035Al_0.125Cr_0.010Ti_0.044) (Si_1.742Al_0.258) O₆, a = 9.7684(2), b = 8.9124(2), c = 5.2859(1) Å, β = 105.903(1)°, V = 442.58 ų, space group C2/c, Z = 2, has been refined to an R₁ index of 1.92% using single‐crystal X‐ray diffraction data. The unit formula, calculated from electron microprobe analysis, and the refined site scattering values were used to assign site populations. The distribution of Fe²⁺and Mg over the M1 and M2 sites suggests a closure temperature of 1000 °C. Mössbauer spectroscopy measurements were done at room temperature on a single crystal and a powdered sample. The spectra are adequately fit by a Voigt‐based quadrupole‐splitting distribution model having two generalized sites, one for Fe²⁺with two Gaussian components and one for Fe³⁺with one Gaussian component. The two ferrous components are assigned to Fe²⁺at the M1 site, and arise from two different next‐nearest‐neighbor configurations of Ca and Fe cations at the M2 site: (3Ca,0Fe) and (2Ca,1Fe). The Fe³⁺/Fe_tot ratio determined by Mössbauer spectroscopy is in agreement with that calculated from the electron microprobe analysis. The results are discussed in connection with the redox and thermal history of D'Orbigny.     

Rapid variability of active galactic nuclei: The 160min periodicity in NGC 3516, NGC 4151 and Quasar 3C 273

The analysis of all the available data between 1968 and 1991 on rapid variability of optical and X-ray luminosity of three AGNs, NGC 3516, NGC 4151 and 3C 273, shows the presence of small-amplitude (˜ 1 %) but statistically confident (≈︁ 5s̀) periodicity of 160.0105 (± 6) min. Within the error limits it coincides with the period P₀ = 160.0101 (± 1) min of global oscillations of the Sun. An independence of the observed period on AGN red shift z favours the hypothesis about a cosmological origin of the 160min oscillation.     

Peculiarities of 3C 454.3 as a superluminal source

This paper begins with a brief summary of the superluminal sources discovered so far. For one of the sources, the quasar 3C 454.3, the main observed results with VLBI at many frequencies and many epochs are then presented. The peculiarities of 3C 454.3 in relation to the general properties of the other superluminal sources are highlighted by means of a comparative table. Lastly, a preliminary discussion on possible explanations for the peculiarities is given.

This paper can be regarded as a supplement to the reports [12, 13] on the observations of 3C 454.3