Search

We observed the blazar 0716+714with the VLBA during its active state in 2003–2004. In this paper we discuss multi-frequency analysis of the inner jet (first 1 mas) kinematics. The unprecedentedly dense time sampling allows us to trace jet components without misidentification and to calculate the component speeds with good accuracy. In the smooth superluminal jet we were able to identify and track three components over time moving outwards with relatively high apparent superluminal speeds (8.5–19.4 c), which contradicts the hypothesis of a stationary oscillating jet in this source. Component ejections occur at a relatively high rate (once in two months), and they are accompanied by mm-continuum outbursts. Superluminal jet components move along wiggling trajectories, which is an indication of actual helical motion. Fast proper motion and rapid decay of the components suggest that this source should be observed with the VLBI at a rate of at least once in one or two months in order to trace superluminal jet components without confusion.

In this first of a series of papers describing polarimetric multifrequency Very Long Baseline Array (VLBA) monitoring of 3C 273during a simultaneous campaign with the INTEGRAL γ-ray satellite in 2003, we present 5 Stokes Iimages and source models at 7 mm. We show that a part of the inner jet (1-2 milliarcsec from the core) is resolved in a direction transverse to the flow, and we analyse the kinematics of the jet within the first 10 mas. Based on the VLBA data and simultaneous single-dish flux density monitoring, we determine an accurate value for the Doppler factor of the parsec scale jet, and using this value with observed proper motions, we calculate the Lorentz factors and the viewing angles for the emission components in the jet. Our data indicates a significant velocity gradient across the jet with the components travelling near the southern edge being faster than the components with more northern path. We discuss our observations in the light of jet precession model and growing plasma instabilities.

This paper represents the work of several years of observation of CTA 102with both single dish telescopes and interferometric arrays, covering wavelengths from 1.2 cm to 1.3 mm. The resolution of the maps covers an order of magnitude from 0.5 mas to 50 μas. The images presented demonstrate the rapid structural changes in this source. These rapid structural changes correlates with the outbursts seen in the total flux, turnover frequency and in the spectral index. We have calculated the Brightness Temperatures of the components (TB) directly from the determined component sizes and also using the logarithmic variability amplitudes and timescales to calculate the $T_{\mathrm{B}}$s. Both the methods yielded measurements of source frame TBs no higher than ~a $\rm few\times 10^{12}$K. We find that the observed average proper motion is ~$0.4 \pm 0.07$mas/yr, which corresponds to an apparent transverse velocity of $11 \pm 2$c.

We compare total flux density variations in 27 γ-ray blazars with structural changes in their parsec-scale jets using multi-epoch VLBA observations at 22 and 43 GHz together with data from the Mets$\ddot{\rm a}$hovi quasar monitoring program at 22 and 37 GHz. There is a clear connection between total flux density outbursts and VLBI components emerging into the jet. For essentially every new moving VLBI component, there is a coincident total flux density flare, with evolution similar to that of the component. Furthermore, extrapolated ejection times of the new VLBI components correspond to the beginnings of associated flares. Our results suggest that it is possible to explain all the radio variations as shocks propagating down the jet. A large fraction of the shocks grow and decay within the innermost few tenths of a milliarcsecond and therefore we see them only as “core flares” in the VLBI images. However, with present data we cannot exclude the possibility that the core itself also brightens (and thus contributes to the flare) as a shock passes through it.

We report a successful VLBI observation at 147 GHz (2.1 mm) on the 3 100 km long baseline between the telescopes at Metsähovi (Finland) and Pico Veleta (Spain). The sources 3C 273B and 3C 279 were detected with a SNRof . For these sources we estimate that 25–30% of the total flux is detectable as correlated flux on the 3 100 km baseline, which gives at 147 GHz a lower limit of the brightness temperature of the inner VLBI jet region of ~1$\times$1010K.

We have observed a sample of 15 bright active galactic nuclei (AGN) three times during 1992-1996 using the global 22 GHz VLBI network. The sample consists of all sources in the complete 2 Jy catalog of Valtaoja et al. that were not observed at 22 GHz VLBI before the first epoch. We will present submilliarcsecond resolution VLBI images of these sources with description of the observations and data analysis techniques. Part II of this paper will contain a detailed analysis of the images.

We propose to use the linear diameters of the shocks in AGN jets as standard rods for estimating the geometry of the Universe. The unique feature of shocks is that we can directly estimate their linear diameters from total flux density monitoring data and light travel time arguments. We demonstrate this method by using a small sample of 14 22 GHz VLBI observations. The accuracy of the derived values ($q_\mathrm{0} \simeq 0, \Omega_\mathrm{m} \simeq 0$) compares favorably with traditional methods using much larger samples.

We compare the total flux density variations and the VLBI structural variations in a sample of 27 gamma-ray blazars. We find that all the radio variations are due to shocks; the flux of the underlying jet remains constant. A large fraction of the shocks grow and fade within the innermost 0.1 mas, appearing only as ‘core flares’. Comparisons with the EGRET data show that gamma-ray flares must come from the shocks, not from the jet. At the time of an EGRET flare, the shock is typically already over a parsec downstream from the radio core, beyond the accretion disk and/or the broad line region (BLR) photon fields. Thus, present models for gamma-ray production are inadequate, since they typically model the gamma-ray inverse Compton flux as coming from the jet, with significant disk or BLR external Compton components. Keywords: black hole physics — galaxies: active — galaxies: jets — X-rays: binaries — radio continuum: galaxies — radio continuum: stars

AbstractWe compare the total flux density variations and the VLBI structural variations in a sample of 27 gamma-ray blazars. We find that all the radio variations are due to shocks; the flux of the underlying jet remains constant. A large fraction of the shocks grow and fade within the innermost 0.1 mas, appearing only as ‘core flares’. Comparisons with the EGRET data show that gamma-ray flares must come from the shocks, not from the jet. At the time of an EGRET flare, the shock is typically already over a parsec downstream from the radio core, beyond the accretion disk and/or the broad line region (BLR) photon fields. Thus, present models for gamma-ray production are inadequate, since they typically model the gamma-ray inverse Compton flux as coming from the jet, with significant disk or BLR external Compton components.

The enthalpies of oxidation of CaMnO3-δ, Ca2MnO4-δ, and SrMnO3-δ have been determined by in situ oxidation in a high-temperature adiabatic calorimeter. CaMnO3, Ca2MnO4, and SrMnO3 were synthesized by the EDTA precursor or the ceramic method, and partly reduced materials were prepared by topotactic reduction in diluted H2 (5−10%) at 290−355 °C. Unit cell dimensions and oxygen stoichiometry of partly reduced and reoxidized materials were determined by powder X-ray diffraction, thermogravimetry, and iodometric titration. The enthalpy of oxidation of SrMnO3-δ was considerably less exothermic than the corresponding value for CaMnO3-δ, and the enthalpy of oxidation of Ca2MnO4-δ was more exothermic than for CaMnO3-δ. The enthalpy of oxidation is discussed in terms of the basicity of oxides, the Goldschmidt tolerance factor, and the crystal structures of the oxidized and reduced materials. Finally, based on the enthalpy of oxidation, the oxygen defect chemistry of these materials is estimated using simple thermodynamic models. Using the measured enthalpy of oxidation and estimated entropy of oxidation, the measured oxygen nonstoichiometry is reproduced rather well. A free fit of the same models to the experimental data gives enthalpies of oxidation that are far more exothermic than the measured values. The present findings demonstrate that simple models based on point defect equilibrium may give significant errors in the enthalpy and entropy of formation of point defects, despite a good fit to the free energy.

Not Available

Context.We study the jet kinematics of the blazar S5 0716+714 during its active state in 2003–2004 with multi-epoch VLBI observations.