The results of long-term monitoring of the quasar 3C 273 at wavelengths from radio to gamma rays between 1963 and 2011 are presented. The variations of the source flux density are studied using ...harmonic and wavelet analysis techniques. The values and frequency-time localizations of harmonic components in the flux-density variations are determined. The eight-year radio-variability period reported earlier had become gradually reduced and attenuated by 2000. The optical light curve has a component with a quasi-period of approximately 13 years. Cyclic variations whose periodicity gradually increased from approximately one to two years were observed in the X-ray between 1996 and 2006. The relative time delays between the light curves at different radio frequences are determined. The frequency dependence of time delays is approximated by the power law, Δ
T
(
ν
) ∝
ν
−1/
k
with
k
= 1.4 ± 0.1, which can be used to infer the corresponding core shift and estimate the core-region magnetic field as
B
1 pc
= 0.5 ± 0.1 G. This approach is preferable to other methods, since it does not require multi-frequency VLBI observations and is a simple and effective tool for studying Active Galactic Nuclei.
The WEBT BL Lacertae Campaign 2000 Villata, M.; Raiteri, C. M.; Kurtanidze, O. M. ...
Astronomy & astrophysics,
08/2002, Volume:
390, Issue:
2
Journal Article
Peer reviewed
Open access
We present UBVRI light curves of BL Lacertae from May 2000 to January 2001, obtained by 24 telescopes in 11 countries. More than 15 000 observations were performed in that period, which was the ...extension of the Whole Earth Blazar Telescope (WEBT) campaign originally planned for July–August 2000. The exceptional sampling reached allows one to follow the flux behaviour in fine detail. Two different phases can be distinguished in the light curves: a first, relatively low-brightness phase is followed by an outburst phase, after a more than $1\rm\,mag$ brightening in a few weeks. Both the time duration (about $100\rm\,d$) and the variation amplitude (roughly $0.9\rm\,mag$) are similar in the two phases. Rapid flux oscillations are present all the time, involving variations up to a few tenths of mag on hour time scales, and witnessing an intense intraday activity of this source. In particular, a half-mag brightness decrease in about $7\rm\,h$ was detected on August 8–9, 2000, immediately followed by a ~$0.4 \rm \, mag$ brightening in $1.7\rm\,h$. Colour indexes have been derived by coupling the highest precision B and R data taken by the same instrument within $20\rm\,min$ and after subtracting the host galaxy contribution from the fluxes. The 620 indexes obtained show that the optical spectrum is weakly sensitive to the long-term trend, while it strictly follows the short-term flux behaviour, becoming bluer when the brightness increases. Thus, spectral changes are not related to the host galaxy contribution, but they are an intrinsic feature of fast flares. We suggest that the achromatic mechanism causing the long-term flux base-level modulation can be envisaged in a variation of the relativistic Doppler beaming factor, and that this variation is likely due to a change of the viewing angle. Discrete correlation function (DCF) analysis reveals the existence of a characteristic time scale of variability of ~$7\rm\,h$ in the light curve of the core WEBT campaign, while no measurable time delay between variations in the B and R bands is found.
Chronic total occlusion of coronary arteries is a condition that is technically difficult to solve by the x-ray surgical methods of treatment, and that is one of the decisive factors in favor of ...coronary artery bypass grafting. The article presents the results about 27 retrograde recanalization of chronic coronary occlusions and the analysis of reasons of unsuccessful attempts, the frequency and severity of re-operative complications. Retrograde recanalization of chronic total coronary occlusions turned out to be effective in the condition of minimally invasive tactics of myocardial revascularization in single long occlusion. Good distal direction and class CC1 and CC2 collarile appeared to be the main criteria of successful retrograde recanalization. Retrograde recanalization complications are typical for x-ray surgical methods of diagnostics and treatment, they are easily predicted, and the prevention methods are well known and effective. Thus, retrograde recanalization of chronic total coronary occlusions is an efficient way of treatment in case of careful patients’ selection and it should be added to frequently used antegrade recanalization method. The key factors for development and widespread implementation of this method are integration of x-ray surgical methods of diagnostics and treatment together with visualization methods and fluoroscopy with IVUS.
Flux-density variations of the quasar S0528+134 (Nimfa) are analyzed based on long-term monitoring at five radio frequencies between 4.8 and 37 GHz, performed at the Crimean Astrophysical ...Observatory, the Metsähovi Radio Observatory of Aalto University, and the University of Michigan Radio Astronomy Observatory. The dynamics of a powerful flare in 1996 are analyzed using gamma-ray (0.1–300 GeV), X-ray (2–10 keV, 15–50 keV), and radio observations. The delays of the flare between different spectral ranges and between different radio wavelengths have been measured. The dependence for the delays at different radio wavelengths relative to the X-ray and optical flares is established based on long-term observations in the X-ray, optical, and radio obtained from 2004 to 2013. Multi-frequency monitoring in the radio is used to estimate the orbital and precession periods in the binary supermassive black hole system S0528+134 and the physical characteristics of this system.
Context. Since 2001, the radio quasar 3C 454.3 has undergone a period of high optical activity, culminating in the brightest optical state ever observed, during the 2004-2005 outburst. The Whole ...Earth Blazar Telescope (WEBT) consortium has carried out several multifrequency campaigns to follow the source behaviour. Aims. The GLAST-AGILE Support Program (GASP) was born from the WEBT to provide long-term continuous optical-to-radio monitoring of a sample of γ-loud blazars, during the operation of the AGILE and GLAST (now known as Fermi GST) γ-ray satellites. The main aim is to shed light on the mechanisms producing the high-energy radiation, through correlation analysis with the low-energy emission. Thus, since 2008 the monitoring task on 3C 454.3 passed from the WEBT to the GASP, while both AGILE and Fermi detected strong γ-ray emission from the source. Methods. We present the main results obtained by the GASP at optical, mm, and radio frequencies in the 2008-2009 season, and compare them with the WEBT results from previous years. Results. An optical outburst was observed to peak in mid July 2008, when Fermi detected the brightest γ-ray levels. A contemporaneous mm outburst maintained its brightness for a longer time, until the cm emission also reached the maximum levels. The behaviour compared in the three bands suggests that the variable relative brightness of the different-frequency outbursts may be due to the changing orientation of a curved inhomogeneous jet. The optical light curve is very well sampled during the entire season, which is also well covered by the various AGILE and Fermi observing periods. The relevant cross-correlation studies will be very important in constraining high-energy emission models.
Achiral, diamagnetic Ni(II) complexes 1 and 3 have been synthesized from Ni(II) salts and the Schiff bases, generated from glycine and PBP (7) and PBA (11), respectively, in MeONa/MeOH solutions. The ...requisite carbonyl-derivatizing agents pyridine-2-carboxylic acid(2-benzoyl-phenyl)-amide 7 (PBP) and pyridine-2-carboxylic acid(2-formyl-phenyl)-amide 11 (PBA) were readily prepared from picolinic acid and o-aminobenzophenone or picolinic acid and methyl o-anthranilate, respectively. The structure of 1 was established by X-ray crystallography. Complexes 1 and 3 were found to undergo C-alkylation with alkyl halides under PTC conditions in the presence of β-naphthol or benzyltriethylammonium bromide as catalysts to give mono- and bis-alkylated products, respectively. Decomposition of the complexes with aqueous HCl under mild conditions gave the required amino acids, and PBP and PBA were recovered. Alkylation of 1 with highly reactive alkyl halides, carried out under the PTC conditions in the presence of 10% mol of (S)- or (R)-2-hydroxy-2‘-amino-1,1‘-binaphthyl 31a (NOBIN) and/or its N-acyl derivatives and by (S)- or (R)-2-hydroxy-8‘-amino-1,1‘-binaphthyl 32a (iso-NOBIN) and its N-acyl derivatives, respectively, gave rise to α-amino acids with high enantioselectivities (90−98.5% ee) in good-to-excellent chemical yields at room temperature within several minutes. An unusually large positive nonlinear effect was observed in these reactions. The Michael addition of acrylic derivatives 37 to 1 was conducted under similar conditions with up to 96% ee. The 1H NMR and IR spectra of a mixture of the sodium salt of NOBIN and 1 indicated formation of a complex between the two components. Implications of the association and self-association of NOBIN for the observed sense of asymmetric induction and nonlinear effects are discussed.
Long-term monitoring data at five radio frequencies from 4.8 to 37 GHz obtained at the Crimean Astrophysical Observatory, Metsahovi Radio Observatory of Aalto University, and the University of ...Michigan Radio Astronomy Observatory are used to analyze variations of the flux of the Active Galactic Nucleus (AGN) 3C 454.3. The dynamical characteristics of the three latest powerful flares from 2004 to 2010 are analyzed in detail. Observations in the gamma-ray (0.1–300 GeV), X-ray (2–10 kev, 15–50 keV), and optical are also used. Delays in the development of flares at different frequencies are derived. An empirical frequency dependence for the delays of flares from the gamma-ray to the radio is determined, which can be fit using a logarithmic low and remains the same from flare to flare. The physical characteristics of the central region of the AGN 3C 454.3 are used to estimate the size of its Strömgren sphere, taking into account the relevant mechanisms for heating and cooling the medium, as well as the adopted laws for the variation of the density and temperature with distance from the source of ionization. A model for the location of the radiation regions in the jet at various frequency ranges during the development of flares is proposed.
Observations of various types of objects in the northern sky were obtained at 44 GHz in the 7
0
-6
1
A
+
methanol line on the 20-m Onsala radio telescope (Sweden), in order to search for Class I ...methanol maser emission in the interstellar medium: regions of formation of high-mass stars, dust rings around HII regions, and protostellar candidates associated with powerful molecular outflows and Galactic HII regions. Seven new Class Imethanolmasers have been discovered toward regions of formation of highmass stars, and the existence of two previously observed masers confirmed. The following conclusions are drawn: (1) neither the association of a bipolar outflow manifest in the wings of CO lines with a highmass protostellar object (HMPO) nor the presence of thermal emission in lines of complex molecules are sufficient conditions for the detection of Class I methanol emission; no association with HMPOs radiating at 44 GHz was found for EGOs (a new class of object tracing bipolar outflows); (2) the existence of H
2
O masers and Class II methanol masers in the region of aHMPOenhances the probability of detecting Class I methanol emission toward the HMPO; Class II methanol masers with stronger line fluxes are associated with Class I methanol masers.
Results of observations of the five candidate GPS sources J0626+8202, J0726+7911, J1044+8054, J1823+7938, and J1935+8130 are presented. GPS sources are extragalactic sources whose spectral peaks are ...near several GHz. These objects were observed on the RATAN-600 radio telescope from 1999 through 2010 at 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. These radio sources were selected from a complete sample (
S
v
≥ 200 mJy at 1.4 GHz) in the vicinity of the North Celestial Pole (+75° ≤
δ
≤ +88°); four are considered as GPS candidates for the first time here. Their spectral properties, variability and morphology are analyzed, and confirms that these can be classified as GPS sources. These four to five GPS sources probably comprise a complete sample of this class of object in this region of the celestial sphere.
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