Constraining blazar distances with combined Fermi and TeV data: an empirical approach

We discuss a method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes. We assume that the VHE spectrum corrected for the absorption through the interaction with the Extragalactic Background Light can not be harder than the spectrum in the Fermi/LAT band. Starting from the observed VHE spectral data we derive the EBL-corrected spectra as a function of the redshift z and fit them with power laws to be compared with power law fits to the LAT data. We apply the method to all TeV blazars detected by LAT with known distance and derive an empirical law describing the relation between the upper limits and the true redshifts that can be used to estimate the distance of unknown redshift blazars. Using different EBL models leads to systematic changes in the derived upper limits. Finally, we use this relation to infer the distance of the unknown redshift blazar PKS 1424+240.Comment: 5 pages, 4 figures, accepted for publication in MNRAS, minor revisio

Theoretical and experimental assessment of the non-linear scattering functions for the cad of non-linear microwave circuits

The Non-Linear Scattering Functions have been theoretically defined and experimentally measured for the linear-equivalent design of non-linear circuits in arbitrary large signal conditions. Non-linear measures and simulations have been compared, with good agreement. Linear CAD concepts can therefore be extended to non-linear circuits in a rigorous way

Baseband Predistortion Lineariser Using Direct Spline Computation

A baseband predistorter is presented. Key features of the predistorter resides in the use of cubic splines interpolation to generate predistorted input data to the power amplifier, resulting in a reduction of computational effort with respect to traditional polynomial interpolators. Simulated behaviour of the proposed scheme is presented, demonstrating the effectiveness of the approach

Relativistic Doppler-boosted emission in gamma-ray binaries

Gamma-ray binaries could be compact pulsar wind nebulae formed when a young pulsar orbits a massive star. The pulsar wind is contained by the stellar wind of the O or Be companion, creating a relativistic comet-like structure accompanying the pulsar along its orbit. The X-ray and the very high energy (>100 GeV, VHE) gamma-ray emissions from the binary LS 5039 are modulated on the orbital period of the system. Maximum and minimum flux occur at the conjunctions of the orbit, suggesting that the explanation is linked to the orbital geometry. The VHE modulation has been proposed to be due to the combined effect of Compton scattering and pair production on stellar photons, both of which depend on orbital phase. The X-ray modulation could be due to relativistic Doppler boosting in the comet tail where both the X-ray and VHE photons would be emitted. Relativistic aberrations change the seed stellar photon flux in the comoving frame so Doppler boosting affects synchrotron and inverse Compton emission differently. The dependence with orbital phase of relativistic Doppler-boosted (isotropic) synchrotron and (anisotropic) inverse Compton emission is calculated, assuming that the flow is oriented radially away from the star (LS 5039) or tangentially to the orbit (LS I +61 303, PSR B1259-63). Doppler boosting of the synchrotron emission in LS 5039 produces a lightcurve whose shape corresponds to the X-ray modulation. The observations imply an outflow velocity of 0.15-0.33c consistent with the expected flow speed at the pulsar wind termination shock. In LS I +61 303, the calculated Doppler boosted emission peaks in phase with the observed VHE and X-ray maximum. Doppler boosting might provide an explanation for the puzzling phasing of the VHE peak in this system.Comment: 8 pages, 7 figures, accepted for publication in A&

Piezoelectric Rainfall Energy Harvester Performance by Advanced Arduino based Measuring System

This paper presents the performances of rainfall energy harvesting through the use of a piezoelectric transducer and an Arduino-based measuring system. Different studies agree on the possibility of generating electricity from rainfall, but to date, a study on measuring the quantity of energy produced during rainfall is still missing. The present study begins with results obtained from laboratory researchers using piezoelectric transducers and oscilloscopes, finalized to measure the energy produced from a single raindrop, and concludes with an ad hoc Arduino-based measuring system, aimed to measure the actual amount of electrical energy produced by a piezoelectric transducer that is exposed to rainfall of variable durations

TeV BL Lac objects at the dawn of the Fermi era

We reconsider the emission properties of the BL Lac objects emitting in the high-energy gamma-ray band exploiting the new information in the MeV-GeV band obtained by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope in its first three months of operation. To this aim we construct the spectral energy distribution of all the BL Lacs revealed by LAT and of the known TeV BL Lacs not detected by LAT, also including data from the Swift satellite, and model them with a simple one-zone leptonic model. The analysis shows that the BL Lacs detected by LAT (being or not already detected in the TeV band) share similar physical parameters. While some of the TeV BL Lacs not revealed by LAT have spectral energy distributions and physical parameters very similar to the LAT BL Lacs, a group of objects displays peculiar properties (larger electron energies and smaller magnetic fields) suggesting different physical conditions in the emission region. Finally, we discuss possible criteria to effectively select good new candidates for the Cherenkov telescopes among the LAT sources, presenting a list of predicted fluxes in the very high-energy band calculated including the effect of the absorption by the extragalactic background light.Comment: 18 pages, 8 figures, accepted for publication in MNRA

Signatures of the anomalous ZγZ\gamma and ZZ production at the lepton and hadron Colliders

The possible form of New Physics (NP) interactions affecting the ZZZ, $ZZ \gamma$ and $Z\gamma \gamma$ vertices, is critically examined. Their signatures and the possibilities to study them, through ZZ and $Z\gamma$ production, at the e^-e^+ Colliders LEP and LC and at the hadronic Colliders Tevatron and LHC, are investigated. Experimental limits obtained or expected on each coupling are collected. A simple theoretical model based on virtual effects due to some heavy fermions is used for acquiring some guidance on the plausible forms of these NP vertices. In such a case specific relations among the various neutral couplings are predicted, which can be experimentally tested and possibly used to constrain the form of the responsible NP structure.Comment: 17 pages and 9 figures, version to appear in Phys. ReV. e-mail: [email protected]

Long Term X-ray Monitoring Of The TeV Binary LS I +61 303 with RXTE

We report on the results of a long term X-ray monitoring campaign of the galactic binary LS I +61 303 performed by the Rossi X-ray Timing Explorer. This dataset consists of 1 ks pointings taken every other day between 2007 August 28 until 2008 February 2. The observations covered six full cycles of the 26.496 day binary period and constitute the largest continuous X-ray monitoring dataset on LS I +61 303 to date with this sensitivity. There is no statistically strong detection of modulation of flux or photon index with orbital phase; however, we do find a strong correlation between flux and photon index, with the spectrum becoming harder at higher fluxes. The dataset contains three large flaring episodes, the largest of these reaching a flux level of 7.2 (+0.1,-0.2)*10^-11 erg cm^-2 s^-1 in the 3-10 keV band, which is a factor of three times larger than flux levels typically seen in the system. Analysis of these flares shows the X-ray emission from LS I +61 303 changing by up to a factor of six over timescales of several hundred seconds as well as doubling times as fast as 2 seconds. This is the fastest variability ever observed from LS I +61 303 at this wavelength and places constraints on the size of the X-ray emitting region.Comment: 24 pages, 7 figures, 2 tables. Accepted for publication in Ap

The Core-like Nature of HST-1 in the M87 Jet

We investigate the total flux density, spectral, polarization, and Faraday rotation variability of HST-1 in the M87 jet during the outburst from 2003 to 2007 through multi-epoch VLA observations at 8, 15, and 22 GHz. Contrary to the general case for blazars, the flux densities of HST-1 rise earlier at lower frequencies from radio to X-ray, and the spectra are softening with the growth of outburst, indicating that the newly emerging subcomponents within HST-1 have relatively steep spectra. In particular, the intrinsic EVPA varies monotonically by $\sim90^\circ$ at the 3 wavebands during the period, and all but the stationary subcomponent in the eastern end of HST-1 move downstream superluminally deviating divergently from the overall jet direction, with the motion of the outmost subcomponent bending from one side of the jet axis to another. These strongly argue for the presence of helical magnetic fields around HST-1, which is also supported by the fact that the subcomponents might be accelerated in this region. The fractional polarization is relatively low in the rising stage, and in the decaying stage the polarization levels are almost comparable at the 3 wavebands. In view of the quite large RM values, Faraday rotation is expected to occur dominantly external to HST-1 in the decaying stage, which is well supported by the presence of diffuse emission around HST-1, and consistent with the scenario that RM decrease gets slower with time.Comment: 5 pages, 4 figures, Accepted for publication in MNRAS Lette

Identification of Ambient Molecular Clouds Associated with Galactic Supernova Remnant IC443

The Galactic supernova remnant (SNR) IC443 is one of the most studied core-collapse SNRs for its interaction with molecular clouds. However, the ambient molecular clouds with which IC443 is interacting have not been thoroughly studied and remain poorly understood. Using Five College Radio Astronomy Observatory 14m telescope, we obtained fully sampled maps of ~ 1{\deg} \times 1{\deg} region toward IC443 in the 12CO J=1-0 and HCO+ J=1-0 lines. In addition to the previously known molecular clouds in the velocity range v_lsr = -6 to -1 km/s (-3 km/s clouds), our observations reveal two new ambient molecular cloud components: small (~ 1') bright clouds in v_lsr = -8 to -3 km/s (SCs), and diffuse clouds in v_lsr = +3 to +10 km/s (+5 km/s clouds). Our data also reveal the detailed kinematics of the shocked molecular gas in IC443, however the focus of this paper is the physical relationship between the shocked clumps and the ambient cloud components. We find strong evidence that the SCs are associated with the shocked clumps. This is supported by the positional coincidence of the SCs with shocked clumps and other tracers of shocks. Furthermore, the kinematic features of some shocked clumps suggest that these are the ablated material from the SCs upon the impact of the SNR shock. The SCs are interpreted as dense cores of parental molecular clouds that survived the destruction by the pre-supernova evolution of the progenitor star or its nearby stars. We propose that the expanding SNR shock is now impacting some of the remaining cores and the gas is being ablated and accelerated producing the shocked molecular gas. The morphology of the +5 km/s clouds suggests an association with IC443. On the other hand, the -3 km/s clouds show no evidence for interaction.Comment: Accepted for publication in ApJ. 15 pages (with emulateapj.cls), 17 figures, and 2 table