Optical Spectral Variability of the Very-High-Energy Gamma-Ray Blazar 1ES 1011+496

We present results of five years of optical (UBVRI) observations of the very-high-energy gamma-ray blazar 1ES 1011+496 at the MDM Observatory. We calibrated UBVRI magnitudes of five comparison stars in the field of the object. Most of our observations were done during moderately faint states of 1ES 1011+496 with R > 15.0. The light curves exhibit moderate, closely correlated variability in all optical wavebands on time scales of a few days. A cross-correlation analysis between optical bands does not show significant evidence for time lags. We find a positive correlation (Pearson's r = 0.57; probability of non-correlation P(>r) ~ 4e-8) between the R-band magnitude and the B - R color index, indicating a bluer-when-brighter trend. Snap-shot optical spectral energy distributions (SEDs) exhibit a peak within the optical regime, typically between the V and B bands. We find a strong (r = 0.78; probability of non-correlation P (>r) ~ 1e-15) positive correlation between the peak flux and the peak frequency, best fit by a relation $\nu F_{\nu}^{\rm pk} \propto \nu_{\rm pk}^k$ with k = 2.05 +/- 0.17. Such a correlation is consistent with the optical (synchrotron) variability of 1ES 1011+496 being primarily driven by changes in the magnetic field.Comment: Accepted for publication in ApJ. 16 pages, including 7 figure

SNP haplotyping technique for evaluation of MGP 5� UTR power in osteoblast cells

Matrix Gla protein (MGP) is involved in calcium trafficking and arterial calcification. The aim of study was to investigate the role of three polymorphisms within the MGP gene promoter region on reporter gene (luciferase) expression level. The fragments containing rs1800799 (C/T), rs1800802 (T/C), and rs1800801 (G/A) sites were constructed and transferred into human G292 osteoblast cells using pGL3-Basic plasmid. The reporter gene expression was calculated for the high and low frequency polymorphic haplotypes (CTG and TCA, respectively). Results showed that the reporter gene expression levels are not statistically different (p > 0.3). We concluded that the investigated polymorphic sites are not able to change the gene expression pattern in human G292 osteoblast cells. © 2016, The Author(s)

Studies of active galactic nuclei with CTA

In this paper, we review the prospects for studies of active galactic nuclei (AGN) using the envisioned future Cherenkov Telescope Array (CTA). This review focuses on jetted AGN, which constitute the vast majority of AGN detected at gamma-ray energies. Future progress will be driven by the planned lower energy threshold for very high energy (VHE) gamma-ray detections to ~10 GeV and improved flux sensitivity compared to current-generation Cherenkov Telescope facilities. We argue that CTA will enable substantial progress on gamma-ray population studies by deepening existing surveys both through increased flux sensitivity and by improving the chances of detecting a larger number of low-frequency peaked blazars because of the lower energy threshold. More detailed studies of the VHE gamma-ray spectral shape and variability might furthermore yield insight into unsolved questions concerning jet formation and composition, the acceleration of particles within relativistic jets, and the microphysics of the radiation mechanisms leading to the observable high-energy emission. The broad energy range covered by CTA includes energies where gamma-rays are unaffected from absorption while propagating in the extragalactic background light (EBL), and extends to an energy regime where VHE spectra are strongly distorted. This will help to reduce systematic effects in the spectra from different instruments, leading to a more reliable EBL determination, and hence will make it possible to constrain blazar models up to the highest energies with less ambiguity.Comment: invited review article, 15 pages, 9 figures, Astroparticle Physics, Special Issue on Physics with the Cherenkov Telescope Array, in pres

The 72-Hour WEBT Microvariability Observation of Blazar S5 0716+714 in 2009

Context. The international whole earth blazar telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This object was chosen due to its bright apparent magnitude range, its high declination, and its very large duty cycle for micro-variations. Aims. We report here on the long continuous optical micro-variability light curve of 0716+714 obtained during the multi-site observing campaign during which the Blazar showed almost constant variability over a 0.5 magnitude range. The resulting light curve is presented here for the first time. Observations from participating observatories were corrected for instrumental differences and combined to construct the overall smoothed light curve. Methods. Thirty-six observatories in sixteen countries participated in this continuous monitoring program and twenty of them submitted data for compilation into a continuous light curve. The light curve was analyzed using several techniques including Fourier transform, Wavelet and noise analysis techniques. Those results led us to model the light curve by attributing the variations to a series of synchrotron pulses. Results. We have interpreted the observed microvariations in this extended light curve in terms of a new model consisting of individual stochastic pulses due to cells in a turbulent jet which are energized by a passing shock and cool by means of synchrotron emission. We obtained an excellent fit to the 72-hour light curve with the synchrotron pulse model

Another look at the BL Lacertae flux and spectral variability

The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) monitored BL Lacertae in 2008-2009 at radio, near-IR, and optical frequencies. During this period, high-energy observations were performed by XMM-Newton, Swift, and Fermi. We analyse these data with particular attention to the calibration of Swift UV data, and apply a helical jet model to interpret the source broad-band variability. The GASP-WEBT observations show an optical flare in 2008 February-March, and oscillations of several tenths of mag on a few-day time scale afterwards. The radio flux is only mildly variable. The UV data from both XMM-Newton and Swift seem to confirm a UV excess that is likely caused by thermal emission from the accretion disc. The X-ray data from XMM-Newton indicate a strongly concave spectrum, as well as moderate flux variability on an hour time scale. The Swift X-ray data reveal fast (interday) flux changes, not correlated with those observed at lower energies. We compare the spectral energy distribution (SED) corresponding to the 2008 low-brightness state, which was characterised by a synchrotron dominance, to the 1997 outburst state, where the inverse-Compton emission was prevailing. A fit with an inhomogeneous helical jet model suggests that two synchrotron components are at work with their self inverse-Compton emission. Most likely, they represent the radiation from two distinct emitting regions in the jet. We show that the difference between the source SEDs in 2008 and 1997 can be explained in terms of pure geometrical variations. The outburst state occurred when the jet-emitting regions were better aligned with the line of sight, producing an increase of the Doppler beaming factor. Our analysis demonstrates that the jet geometry can play an extremely important role in the BL Lacertae flux and spectral variability.Comment: 12 pages, 10 figures, accepted for publication in A&

Dual-frequency VLBI study of Centaurus A on sub-parsec scales

Centaurus A is the closest active galactic nucleus. High resolution imaging using Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on sub-parsec scales, providing essential information for jet emission and formation models. Our aim is to study the structure and spectral shape of the emission from the central-parsec region of Cen A. As a target of the Southern Hemisphere VLBI monitoring program TANAMI (Tracking Active Galactic Nuclei with Milliarcsecond Interferometry), VLBI observations of Cen A are made regularly at 8.4 and 22.3 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, and South Africa. The first dual-frequency images of this source are presented along with the resulting spectral index map. An angular resolution of 0.4 mas x 0.7 mas is achieved at 8.4 GHz, corresponding to a linear scale of less than 0.013 pc. Hence, we obtain the highest resolution VLBI image of Cen A, comparable to previous space-VLBI observations. By combining with the 22.3 GHz image, which has been taken without contributing transoceanic baselines at somewhat lower resolution, we present the corresponding dual-frequency spectral index distribution along the sub-parsec scale jet revealing the putative emission regions for recently detected gamma-rays from the core region by Fermi/LAT. We resolve the innermost structure of the milliarcsecond scale jet and counterjet system of Cen A into discrete components. The simultaneous observations at two frequencies provide the highest resolved spectral index map of an AGN jet allowing us to identify multiple possible sites as the origin of the high energy emission.Comment: 5 pages, 3 figures (1 color); A&A, accepte

Infections, inflammation, and risk of neuropsychiatric disorders: the neglected role of �co-infection�

Neuropsychiatric disorders (NPDs) have multiple etiological factors, mainly genetic background, environmental conditions and immunological factors. The host immune responses play a pivotal role in various physiological and pathophysiological process. In NPDs, inflammatory immune responses have shown to be involved in diseases severity and treatment outcome. Inflammatory cytokines and chemokines are involved in various neurobiological pathways, such as GABAergic signaling and neurotransmitter synthesis. Infectious agents are among the major amplifier of inflammatory reactions, hence, have an indirect role in the pathogenesis of NPDs. As such, some infections directly affect the central nervous system (CNS) and alter the genes that involved in neurobiological pathways and NPDs. Interestingly, the most of infectious agents that involved in NPDs (e.g., Toxoplasma gondii, cytomegalovirus and herpes simplex virus) is latent (asymptomatic) and co-or-multiple infection of them are common. Nonetheless, the role of co-or-multiple infection in the pathogenesis of NPDs has not deeply investigated. Evidences indicate that co-or-multiple infection synergically augment the level of inflammatory reactions and have more severe outcomes than single infection. Hence, it is plausible that co-or-multiple infections can increase the risk and/or pathogenesis of NPDs. Further understanding about the role of co-or-multiple infections can offer new insights about the etiology, treatment and prevention of NPDs. Likewise, therapy based on anti-infective and anti-inflammatory agents could be a promising therapeutic option as an adjuvant for treatment of NPDs. © 2020 Infection; Inflammation; Neuropsychiatric disorders; Co-infection; Immunology; Microbiology; Infectious disease; Psychiatry. © 202

The structure and emission model of the relativistic jet in the quasar 3C 279 inferred from radio to high-energy gamma-ray observations in 2008-2010

We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the gamma-ray emission by about 10 days. X-ray observations reveal a pair of `isolated' flares separated by ~90 days, with only weak gamma-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the gamma-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broad-band spectra during the gamma-ray flaring event by a shift of its location from ~ 1 pc to ~ 4 pc from the central black hole. On the other hand, if the gamma-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.Comment: 23 pages, 18 figures 5 tables, Accepted for publication in The Astrophysical Journa

Multiwavelength observations of 3C 454.3. III. Eighteen months of AGILE monitoring of the "Crazy Diamond"

We report on 18 months of multiwavelength observations of the blazar 3C 454.3 (Crazy Diamond) carried out in July 2007-January 2009. We show the results of the AGILE campaigns which took place on May-June 2008, July-August 2008, and October 2008-January 2009. During the May 2008-January 2009 period, the source average flux was highly variable, from an average gamma-ray flux F(E>100MeV) > 200E-8 ph/cm2/s in May-June 2008, to F(E>100MeV)~80E-8 ph/cm2/s in October 2008-January 2009. The average gamma-ray spectrum between 100 MeV and 1 GeV can be fit by a simple power law (Gamma_GRID ~ 2.0 to 2.2). Only 3-sigma upper limits can be derived in the 20-60 keV energy band with Super-AGILE. During July-August 2007 and May-June 2008, RXTE measured a flux of F(3-20 keV)= 8.4E-11 erg/cm2/s, and F(3-20 keV)=4.5E-11 erg/cm2/s, respectively and a constant photon index Gamma_PCA=1.65. Swift/XRT observations were carried out during all AGILE campaigns, obtaining a F(2-10 keV)=(0.9-7.5)E-11 erg/cm2/s and a photon index Gamma_XRT=1.33-2.04. BAT measured an average flux of ~5 mCrab. GASP-WEBT monitored 3C 454.3 during the whole 2007-2008 period from the radio to the optical. A correlation analysis between the optical and the gamma-ray fluxes shows a time lag of tau=-0.4 days. An analysis of 15 GHz and 43 GHz VLBI core radio flux observations shows an increasing trend of the core radio flux, anti- correlated with the higher frequency data. The modeling SEDs, and the behavior of the long-term light curves in different energy bands, allow us to compare the jet properties during different emission states, and to study the geometrical properties of the jet on a time-span longer than one year.Comment: Accepted for publication in ApJ. Adapted Abstract. 17 pages, 19 Figures, 5 Table

The Spectral Energy Distribution of Fermi bright blazars

(Abridged) We have conducted a detailed investigation of the broad-band spectral properties of the \gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48 LBAS blazars.The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual Log $\nu$ - Log $\nu$ F$_\nu$ representation, the typical broad-band spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SEDs to characterize the peak intensity of both the low and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broad-band colors (i.e. the radio to optical and optical to X-ray spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency $\nu_p^S$ is positioned between 10$^{12.5}$ and 10$^{14.5}$ Hz in broad-lined FSRQs and between $10^{13}$ and $10^{17}$ Hz in featureless BL Lacertae objects.We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron - inverse Compton scenarios. However, simple homogeneous, one-zone, Synchrotron Self Compton (SSC) models cannot explain most of our SEDs, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. (...)Comment: 85 pages, 38 figures, submitted to Ap