Multifrequency Method for Mapping Active Galactic Nuclei with Allowance for the Frequency-Dependent Image Shift

We consider the problem of multifrequency VLBA image synthesis and spectral-index mapping for active galactic nuclei related to the necessity of taking into account the frequency-dependent image shift. We describe our generalized multifrequency synthesis algorithm with a spectral correction based on the maximum entropy method. The results of our processing of multifrequency VLBI data for the radio sources J2202+4216, J0336+3218, and J1419+5423 are presented.Comment: 12 pages, 2 tables, 6 figure

Transverse effects in multifrequency Raman generation

The theory of ultrabroadband multifrequency Raman generation is extended, for the first time, to allow for beam-propagation effects in one and two transverse dimensions. We show that a complex transverse structure develops even when diffraction is neglected. In the general case, we examine how the ultrabroadband multifrequency Raman generation process is affected by the intensity, phase quality, and width of the input beams, and by the length of the Raman medium. The evolution of power spectra, intensity profiles, and global characteristics of the multifrequency beams are investigated and explained. In the two-dimensional transverse case, bandwidths comparable to the optical carrier frequency, spanning the whole visible spectrum and beyond, are still achievable

Multifrequency Observations of the Gamma-Ray Blazar 3C 279 in Low-State during Integral AO-1

We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent gamma-ray blazar 3C 279 during the first year of the INTEGRAL mission. The variable blazar was found at a low activity level, but was detected by all participating instruments. Subsequently a multifrequency spectrum could be compiled. The individual measurements as well as the compiled multifrequency spectrum are presented. In addition, this 2003 broadband spectrum is compared to one measured in 1999 during a high activity period of 3C 279.Comment: 4 pages including 6 figures, to appear in: 'Proc. of the 5th INTEGRAL Workshop', ESA SP-552, in pres

Multifrequency Behaviour of Galactic and Extragalactic Novae

The outbursts of novae are among the strongest explosions in the Universe. The eruptions involve physical processes that span the whole electromagnetic spectrum, demanding multifrequency observations. The photometric and spectroscopic observations in the optical domain are combined with radio, infrared, X-ray and gamma ray observations, allowing to discover new phenomena, like the GeV gamma ray emission.Comment: Proceedings of a talk given at the conference on "XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop", 2017, 12-17 June Palermo, Italy; 22 pages, 9 figures, 2 table

Efficient detection for multifrequency dynamic phasor analysis

Analysis of harmonic and interharmonic phasors is a promising smart grid measurement and diagnostic tool. This creates the need to deal with multiple phasor components having different amplitudes, including interharmonics with unknown frequency locations. The Compressive Sensing Taylor-Fourier Multifrequency (CSTFM) algorithm provides very accurate results under demanding test conditions, but is computationally demanding. In this paper we present a novel frequency search criterion with significantly improved effectiveness, resulting in a very efficient revised CSTFM algorithm

A multifrequency angular power spectrum analysis of the Leiden polarization surveys

The Galactic synchrotron emission is expected to be the most relevant source of astrophysical contamination in cosmic microwave background polarization measurements, at least at frequencies 30'. We present a multifrequency analysis of the Leiden surveys, linear polarization surveys covering essentially the Northern Celestial Hemisphere at five frequencies between 408 MHz and 1411 MHz. By implementing specific interpolation methods to deal with these irregularly sampled data, we produced maps of the polarized diffuse Galactic radio emission with pixel size of 0.92 deg. We derived the angular power spectrum (APS) (PI, E, and B modes) of the synchrotron dominated radio emission as function of the multipole, l. We considered the whole covered region and some patches at different Galactic latitudes. By fitting the APS in terms of power laws (C_l = k l^a), we found spectral indices that steepen with increasing frequency: from a = -(1-1.5) at 408 MHz to a = -(2-3) at 1411 MHz for 10 < l < 100 and from a = -0.7 to a = -1.5 for lower multipoles (the exact values depending on the considered sky region and polarization mode). The bulk of this steepening can be interpreted in terms of Faraday depolarization effects. We then considered the APS at various fixed multipoles and its frequency dependence. Using the APSs of the Leiden surveys at 820 MHz and 1411 MHz, we determined possible ranges for the rotation measure, RM, in the simple case of an interstellar medium slab model. Taking also into account the polarization degree at 1.4 GHz, we could break the degeneracy between the identified RM intervals. The most reasonable of them turned out to be RM = 9-17 rad/m^2.Comment: 18 pages, 14 figures. Astronomy and Astrophysics, in pres