Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

We report on long-term multiwavelengthmonitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007–2015, characterized by several extreme flares. The ratio between the optical, X-ray and γ -ray fluxes is very variable. The γ -ray flux variations show a fair correlation with the optical ones starting from 2012.We analyse spectropolarimetric data and find wavelengthdependence of the polarization degree (P), which is compatible with the presence of the host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA). Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of the EVPA.We build broad-band spectral energy distributions with simultaneous near-infrared and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite. They show strong variability in both flux and X-ray spectral shape and suggest a shift of the synchrotron peak up to a factor of ∼50 in frequency. The interpretation of the flux and spectral variability is compatible with jet models including at least two emitting regions that can change their orientation with respect to the line of sight.http://10.0.4.69/mnras/stx2185Accepted manuscrip

Synthesis, characterization and antitumor activity of novel N-substituted alpha-amino acids containing ferrocenyl pyrazole-moiety

A series of new N-[(3-ferrocenyl-1-phenylpyrazol-4-yl)methyl] alpha-amino acids were prepared and characterized by a range of spectroscopic techniques and cyclic voltammetry. The in vitro antitumor activity of all synthesized compounds was investigated against cervix adenocarcinoma HeLa, melanoma Fem-x and myelogenous leukemia K562 cell lines using the MTT method. Tryptophan derivative 11 exhibited the highest cytotoxic activity in the cell growth inhibition of all three types of cell lines. (C) 2009 Elsevier B.V. All rights reserved

Synthesis, spectral characterization and electrochemical properties of 1H-3-(o-, m- and p-ferrocenylphenyl)-1-phenylpyrazole-4-carboxaldehydes

New ferrocene derivatives - 1H-1-phenylpyrazole-4-carboxaldehydes containing o-, m- and p- ferrocenylphenyl group at position 3 - were synthesized and characterized. The electrochemical investigation showed that the position of the ferrocenyl group does not affect the redox potential of these compounds. The X-ray crystal structure of the ortho-derivative is also presented. The screening for the in vitro antimicrobial activity against eleven bacterial and three fungal/yeast strains exhibited complete inactivity of these aldehydes, but n-butyl imines of ortho and meta derivatives showed moderate activity compared to those of the used standards. (C) 2009 Elsevier B.V. All rights reserved

The beamed jet and quasar core of the distant blazar 4C 71.07

The object 4C 71.07 is a high-redshift blazar whose spectral energy distribution shows a prominent big blue bump and a strong Compton dominance. We present the results of a 2-yr multiwavelength campaign led by the Whole Earth Blazar Telescope (WEBT) to study both the quasar core and the beamed jet of this source. The WEBT data are complemented by ultraviolet and X-ray data from Swift, and by.-ray data by Fermi. The big blue bump is modelled by using optical and near-infrared mean spectra obtained during the campaign, together with optical and ultraviolet quasar templates. We give prescriptions to correct the source photometry in the various bands for the thermal contribution, in order to derive the non-thermal jet flux. The role of the intergalactic medium absorption is analysed in both the ultraviolet and X-ray bands. We provide opacity values to deabsorb ultraviolet data, and derive a best-guess value for the hydrogen column density of N-H(best) = 6.3 x 10(20) cm(-2) through the analysis of X-ray spectra. We estimate the disc and jet bolometric luminosities, accretion rate, and black hole mass. Light curves do not show persistent correlations among flux changes at different frequencies. We study the polarimetric behaviour and find no correlation between polarization degree and flux, even when correcting for the dilution effect of the big blue bump. Similarly, wide rotations of the electric vector polarization angle do not seem to be connected with the source activity.Peer reviewe

Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

In 2015 July 29-September 1, the satellite XMM-Newton pointed at the BL Lac object PG 1553+133 six times, collecting data for 218 h. During one of these epochs, simultaneous observations by the Swift satellite were requested to compare the results of the X-ray and optical-UV instruments. Optical, near-infrared and radio monitoring was carried out by the Whole Earth Blazar Telescope (WEBT) collaboration for the whole observing season. We here present the results of the analysis of all these data, together with an investigation of the source photometric and polarimetric behaviour over the last 3 yr. The 2015 EPIC spectra show slight curvature and the corresponding light curves display fast X-ray variability with a time-scale of the order of 1 h. In contrast to previous results, during the brightest X-ray states detected in 2015 the simple log-parabolic model that best fits the XMM-Newton data also reproduces reasonably well the whole synchrotron bump, suggesting a peak in the near- UV band. We found evidence ofa wide rotation of the polarization angle in 2014, when the polarization degree was variable, but the flux remained almost constant. This is difficult to interpret with deterministic jet emission models, while it can be easily reproduced by assuming some turbulence of the magnetic field.Peer reviewe