Search

We present the first catalog of high-confidence γ-ray sources detected by the AGILE satellite during observations performed from July 9, 2007 to June 30, 2008. Cataloged sources were detected by merging all the available data over the entire time period. AGILE, launched in April 2007, is an ASI mission devoted to γ-ray observations in the 30 MeV–50 GeV energy range, with simultaneous X-ray imaging capability in the 18–60 keV band. This catalog is based on Gamma-Ray Imaging Detector (GRID) data for energies greater than 100 MeV. For the first AGILE catalog, we adopted a conservative analysis, with a high-quality event filter optimized to select γ-ray events within the central zone of the instrument field of view (radius of 40°). This is a significance-limited (4σ) catalog, and it is not a complete flux-limited sample due to the non-uniform first-year AGILE sky coverage. The catalog includes 47 sources, 21 of which are associated with confirmed or candidate pulsars, 13 with blazars (7 FSRQ, 4 BL Lacs, 2 unknown type), 2 with HMXRBs, 2 with SNRs, 1 with a colliding-wind binary system, and 8 with unidentified sources.

Context. AGILE is an Italian Space Agency mission dedicated to observing the gamma-ray Universe. The AGILE's very innovative instrumentation for the first time combines a gamma-ray imager (sensitive in the energy range 30 MeV–50 GeV), a hard X-ray imager (sensitive in the range 18–60 keV), a calorimeter (sensitive in the range 350 keV–100 MeV), and an anticoincidence system. AGILE was successfully launched on 2007 April 23 from the Indian base of Sriharikota and was inserted in an equatorial orbit with very low particle background.

Context. We report the detection by the AGILE satellite of an intense gamma-ray flare from the gamma-ray source 3EG J1255-0549, associated with the Flat Spectrum Radio Quasar 3C 279, during the AGILE pointings towards the Virgo Region on 2007 July 9-13.

Context. The mini-calorimeter (MCAL) instrument on-board the AGILE satellite is a non-imaging gamma-ray scintillation detector sensitive in the 300 keV–100 MeV energy range with a total on-axis geometrical area of 1400 cm2. Gamma-ray bursts (GRBs) are one of the main scientific targets of the AGILE mission and the MCAL design as an independent self-triggering detector makes it a valuable all-sky monitor for GRBs. Furthermore MCAL is one of the very few operative instruments with microsecond timing capabilities in the MeV range.

Aims. We report the detection by the AGILE satellite of a rapid ?-ray flare from the source 1AGL J1511-0908, associated with the powerful ?-ray quasar PKS 1510-089, during a pointing centered on the Galactic center region from 1 March to 30 March 2008. This source has been continuosly monitored in the radio-to-optical bands by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). Moreover, the ?-ray flaring episode triggered three ToO observations by the Swift satellite in three consecutive days, starting from 20 March 2008. The quasi-simultaneous radio-to-optical, UV, X-ray and ?-ray coverage allows us to make a detailed study of the multifrequency time evolution, the spectral energy distribution of this source, and its theoretical interpretation based on the synchrotron and inverse Compton?(IC) emission mechanisms.Methods. During the radio-to-optical monitoring provided by the GASP-WEBT, AGILE observed the source with its two co-aligned imagers, the gamma-ray imaging detector (GRID) and the hard X-ray imager (SuperAGILE), which are sensitive in the 30?MeV?30?GeV and 18?60?keV energy bands, respectively.Results. In the period 1?16?March 2008, AGILE detected ?-ray emission from PKS 1510-089 at a significance level of 6.2-? with an average flux over the entire period of (84 ?17) ?10-8?photons?cm-2s-1for photon energies above 100?MeV. After a predefined satellite re-pointing, between 17 and 21 March 2008, AGILE detected the source at a significance level of 7.3-?, with an average flux (E > 100?MeV) of (134 ?29) ?10-8?photons?cm-2?s-1and a peak level of (281 ?68) ?10-8?photons?cm-2?s-1with daily integration. During the observing period January-April 2008, the source also showed an intense and variable optical activity, with several flaring episodes and a significant increase in the flux was observed at millimetric frequencies. Moreover, in the X-ray band, the Swift/XRT observations seem to show a harder-when-brighter behavior of the source spectrum.Conclusions. The flat spectrum radio quasar PKS?1510-089 showed strong activity between January and April 2008, with episodes of rapid variability from radio to ?-ray energy bands, in particular with a rapid ?-ray flaring episode. The spectral energy distribution of mid-March 2008 is modeled with a homogeneous one-zone synchrotron self Compton (SSC) emission plus contributions from inverse Compton scattering of external photons from both the accretion disk and the broad line region. Indeed, some features in the optical-UV spectrum seem to indicate Seyfert-like components such as the little and the big blue bumps.

Context. ?We report the results of a 3-week multi-wavelength campaign targeting the flat spectrum radio quasar 3C?273 carried out with the AGILE gamma-ray mission, covering the 30?MeV?50?GeV and 18?60?keV, the REM observatory (covering the near-IR and optical), Swift (near-UV/Optical, 0.2?10?keV and 15?50?keV), INTEGRAL (3?200?keV) and Rossi XTE (2?12?keV). This is the first observational campaign including gamma-ray data, after the last EGRET observations, more than 8?years ago. Aims. This campaign has been organized by the AGILE team with the aim of observing, studying and modelling the broad band energy spectrum of the source, and its variability on a week timescale, testing the emission models describing the spectral energy distribution of this source. Methods. Our study was carried out using simultaneous light curves of the source flux from all the involved instruments, in the different energy ranges, to search for correlated variability. Then a time-resolved spectral energy distribution was used for a detailed physical modelling of the emission mechanisms. Results. The source was detected in gamma-rays only in the second week of our campaign, with a flux comparable to the level detected by EGRET in June?1991. We found an indication of a possible anti-correlation between the emission at gamma-rays and at soft and hard X-rays, supported by the complete set of instruments. Instead, optical data do not show short term variability, as expected for this source. Only in two preceding EGRET observations (in 1993 and 1997) 3C?273 showed intra-observation variability in gamma-rays. In the 1997 observation, flux variation in gamma-rays was associated with a synchrotron flare.?The energy-density spectrum with almost simultaneous data partially covers the regions of synchrotron emission, the big blue bump, and the inverse-Compton. We adopted a leptonic model to explain the hard X/gamma-ray emissions, although from our analysis hadronic models cannot be ruled out.?In the adopted model, the soft X-ray emission is consistent with combined synchrotron-self Compton and external Compton mechanisms, while hard X and gamma-ray emissions are compatible with external Compton from thermal photons of the disk. Under this model, the time evolution of the spectral energy distribution is well interpreted and modelled in terms of an acceleration episode of the electron population, leading to a shift in the inverse Compton peak towards higher energies.?

Context. We report the detection by the AGILE (Astro-rivelatore Gamma a Immagini LEggero) satellite of an intense gamma-ray flare from the source AGL?J1511-0909, associated with the powerful quasar PKS?1510-089, during ten days of observations from 23?August to 1?September?2007.Aims. During the observation period, the source was in optical decrease following a flaring event monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). The simultaneous gamma-ray, optical, and radio coverage allows us to study the spectral energy distribution and the theoretical models based on the synchrotron and inverse Compton (IC) emission mechanisms.Methods. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector and the hard X-ray imager Super-AGILE sensitive in the 30?MeV?[Formula: see text][Formula: see text] 50?GeV and 18?[Formula: see text][Formula: see text] 60?keV bands, respectively.Results. Between 23 and 27 August 2007, AGILE detected gamma-ray emission from PKS?1510-089 when this source was located ~50?off-axis, with an average flux of (270 ?65)?? 10-8?photons?cm-2?s-1for photon energy above 100?MeV. In the following period, 28?August-1?September, after a satellite re-pointing, AGILE detected the source at ~35?off-axis, with an average flux (E?> 100?MeV) of (195 ?30)?? 10-8?photons?cm-2?s-1. No emission was detected by Super-AGILE, with a 3-? upper limit of 45?mCrab in 200?ks.Conclusions. The spectral energy distribution is modelled with a homogeneous one-zone synchrotron self Compton (SSC) emission plus contributions by external photons: the SSC?emission contributes primarily to the X-ray band, whereas the contribution of the IC from the external disc and the broad line region match the hard gamma-ray spectrum observed.

GRB 080514B? is the first gamma ray burst (GRB), since the time of EGRET, for which individual photons of energy above several tens of MeV have been detected with a pair-conversion tracker telescope. This burst was discovered with the Italian AGILE gamma-ray satellite. The GRB was localized by a cooperation between AGILE and the interplanetary network (IPN). The gamma-ray imager (GRID) estimate of the position, obtained before the SuperAGILE-IPN localization, is found to be consistent with the burst position. The hard X-ray emission observed by SuperAGILE lasted about 7?s, while there is evidence that the emission above 30?MeV extends for a longer duration (at least?13?s). Similar behavior has been seen from a few other GRBs observed with EGRET. However, during the brightest phases, the latter measurements were affected by instrumental dead time effects, resulting in only lower limits to the burst intensity. Thanks to the small dead time of the AGILE/GRID we could assess that in the case of GRB 080514B?the gamma-ray to X-ray flux ratio changes significantly between the prompt and extended emission phase.

Aims. We report the ?-ray activity from the intermediate BL?Lac S5?0716+714 during observations acquired by the AGILE satellite in September and October?2007. These detections of activity were contemporaneous with a period of intense optical activity, which was monitored by GASP?WEBT. This simultaneous optical and ?-ray coverage allows us to study in detail the light curves, time lags, ?-ray photon spectrum, and Spectral Energy Distributions (SEDs) during different states of activity.Methods. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector (GRID) and the hard X-ray imager (Super-AGILE), which are sensitive to the 30?MeV?50?GeV and 18?60?keV energy ranges, respectively. Observations were completed in two different periods, the first between 2007 September?4?23, and the second between 2007 October?24?November?1.Results. Over the period 2007 September?7?12, AGILE detected ?-ray emission from the source at a significance level of 9.6-? with an average flux (E > 100?MeV) of (97 ? 15) ? 10-8?photons?cm-2?s-1, which increased by a factor of at least four within three days. No emission was detected by Super-AGILE for the energy range 18?60?keV to a 3-? upper limit of 10?mCrab in 335?ks. In October 2007, AGILE repointed toward S5?0716+714 following an intense optical flare, measuring an average flux of (47 ? 11) ? 10-8?photons?cm-2?s-1at a significance level of 6.0-?. Conclusions. The ?-ray flux of S5?0716+714 detected by?AGILE is the highest ever detected for this blazar and one of the most intense??-ray fluxes detected from a BL?Lac?object. The SED of mid-September appears to be consistent with the synchrotron self-Compton (SSC) emission model, but only by including two SSC components of different variabilities.

Context. We present the AGILE gamma-ray observations of the field containing the puzzling gamma-ray source 3EG?J1835+5918. This source is one of the most remarkable unidentified EGRET sources.Aims. An unprecedentedly long AGILE monitoring of this source yields important information on the positional error box, flux evolution, and spectrum.Methods. 3EG?J1835+5918 has been in the AGILE field of view several times in 2007 and?2008 for a total observing time of 138?days from 2007 Sep.?04 to 2008 June?30 encompassing several weeks of continuous coverage.Results. With an exposure time approximately twice that of EGRET, AGILE confirms the existence of a prominent gamma-ray source (AGL?J1836+5926) at a position consistent with that of EGRET, although with a remarkably lower average flux value for photon energies greater than 100?MeV. A 5-day bin temporal analysis of the whole data set of AGL?J1836+5926 shows some evidence for variability of the gamma-ray flux. The source spectrum between 100?MeV and 1?GeV can be fitted with a power law with photon index in the range 1.6?1.7, fully consistent with the EGRET value.Conclusions. The faint X-ray source RX?J1836.2+5925 that has been proposed as a possible counterpart of 3EG?J1835+5918 is well within the AGILE error box. Future continuous monitoring (both by AGILE and GLAST) is needed to confirm the gamma-ray flux variability and to unveil the source origin, a subject that is currently being pursued through a multiwavelength search for counterparts.

GRB 070724B is the first gamma ray burst localized by SuperAGILE, the hard X-ray monitor aboard the AGILE?satellite. The coordinates of the event were published ~19?h after the trigger. The Swift X-Ray Telescope pointed at the SuperAGILE location and detected the X-ray afterglow inside the SuperAGILE error circle. The AGILE gamma-ray Tracker and Minicalorimeter did not detect any significant gamma ray emission associated with GRB?070724B in the MeV and GeV range, neither prompt nor delayed. Searches for the optical afterglow were performed by the Swift UVOT and the Palomar automated 60-inch telescopes, resulting in no significant detection. Similarly, the Very Large Array did not detect any radio afterglow. This is the first GRB?event associated with an X-ray afterglow with a firm upper limit in the 100?MeV-30?GeV energy range.

Silicon Drift Detectors (SDDs) have been recently employed as detectors of scintillation light for γ-ray spectroscopy and imaging applications. Compared to conventional Photo Multiplier Tubes (PMTs), these devices offer the higher quantum efficiency to the scintillation light, typical of a silicon detector. Moreover, due to the low value of output capacitance, a SDD is characterized by a lower electronics noise with respect to a conventional silicon photodiode. This feature allows a detector based on the CsI(Tl)-SDD architecture to reach high energy and position resolution in gamma detection. In this work we present the results obtained in the development of the first prototypes of gamma detectors for energy measurements (single scintillator-SDD unit) and 1D or 2D position measurements (single scintillator coupled to an array of SDDs).

In this paper a procedure for analysing the seismic response of seabed anchored floating tunnels is presented. The first step of the research was the development of an ‘ad hoc’ finite element for modelling the behaviour of anchor elements, with particular reference to the problem of transverse oscillations under time varying axial loads. The element was subsequently inserted in a step-by-step procedure for the numerical analysis of non-linear response to multiple-support seismic input; the procedure encompasses simplified modelling of fluid–structure and soil–structure interaction effects. An example of an application is given concerning two 4680 m long floating tunnels with different seabed profiles. Copyright © 2000 John Wiley & Sons, Ltd.

During a balloon flight of the MISO telescope on the 30th September 1979, the Seyfert galaxies NGC 4151 and MGC 8-11-11 were studied in the hard X-ray range (EX > 20 keV) and low-energy γ-ray range up to 19 MeV. An emission at the 4.5 σ level above 20 keV (4 σ above 260 keV) was detected in the direction of NGC 4151. γ-ray emission at the 3.9 σ level above 90 keV was also observed from the direction of MCG 8-11-11. The emission photon spectrum shows a high-energy cutoff at about 3 MeV. A large amount of the observed low-energy γ-ray diffuse background could be produced by a few percent of the X-ray emitting Seyfert galaxies having a γ-ray luminosity comparable to that observed from the regions of NGC 4151 or MCG 8-11-11.

During a balloon flight in September 1979 of the MISO low-energy ?-ray telescope, the BL Lac-object MkN 501 was studied in the hard X-ray range above 30 keV and in the low energy ?-ray range up to 19 MeV. No statistically significant X- and ?-ray fluxes were detected. The implications of the upper limits obtained are discussed in the light of the relativistic jet theories recently proposed.

Three active galaxies, generally classified as Seyferts, have been discovered recently to be powerful, low energy γ-ray sources. The similarity between their spectral characteristics and those of the cosmic background at γ-ray energies suggests that these objects could make a significant contribution to this diffuse flux. This contribution has been assessed using two different number densities of γ-ray-emitting Seyfert galaxies based on optical and X-ray data. The comparison of the estimated and measured diffuse γ-ray background intensities is used to gain a deeper understanding of the metabolism of Seyfert galaxies.

A γ-ray detector consisting in a CsI(Tl) scintillator coupled to a Silicon Drift Chamber (SDC), has been realized and tested. Experimental results, obtained with a prototype based on a scintillator of 3mm diameter and 5mm thickness and on a SDC of the same diameter with on-chip electronics, are reported here. The peculiar noise characteristics of the SDC allow this γ-ray detector to operate on a wide energy range with high resolution. An energy threshold of about 10keV at room temperature and of few keV at 0°C has been measured. At 662keV the detector shows an energy resolution of 4.34% FWHM at room temperature, to our knowledge the best result ever obtained with a scintillator.

An array of 1-dimensional position sensitive detectors designed to operate over the photon energy range 0.2–10.0 MeV, so as to form an efficient 2-dimensional position sensitive detection plane is described. A series of experimental tests has been carried out to evaluate and confirm the computed capabilities.

The background which arises from the presence of a coded aperture. The major contributions which have been considered here are the interactions with the mask of the isotropic gamma-ray background, a parallel gamma-ray beam, neutrons and the effect of the mask element profile. It is shown that none of these factors contribute to a significant excess or modulation in the background counting rate over the detection plane. In this way the use of a passive rather than an active coded apertuer mask is seen to be suitable for use in a low energy gamma-ray telescope.

This paper refers to the attenuation of macroseismic intensity with epicentral distance. A new attenuation law is discussed, with particular reference to Italian conditions. The new formula shows a much better fit compared to traditional attenuation laws. A numerical example indicates that a proper choice of the attenuation law is a crucial step in local hazard evaluation.

Data on high energy electrons and protons in different energy windows are analyzed and compared for two solar flares which occurred at 37 W solar longitude on the 25th February 1969 and the 29th March 1970. While the data for the first of these flares can be interpreted in the framework of a diffusion model with suitable values of the parallel diffusion coefficient, in order to explain the time behaviour of the different particles after the second event, we are led to suppose that the coronal magnetic fields are such that particles of different rigidity are ejected at different longitudes and that there is no good magnetic connection of the Earth with the flare region.

The S 79 experiment on board of the HEOS-A1 European Satellite has been designed to electrons detection whose kinetic energies should be equal or greater than 7.5 MeV. From December 1968 to July 1970, 11 events were observed.

The galaxy MCG8 –11 –11 inside the 0.093 square degrees error-box of the X-ray source 2A0551 + 466 (ref. 1), was recently found to be a Type 1 Seyfert galaxy2. A 40-arcs error-box from the A3 experiment on HEAO1 has confined the X-ray emission to the nucleus or bar of this 14-mvgalaxy3. The redshift is z = 0.0205 (ref. 2), corresponding to a distance of 123 Mpc (H0= 50 km s−1Mpc−1). The 2–10 keV luminosity ranges from 5 × 1043erg s−1to 1.2 × 1044erg s−1(refs 1,3). Hard X-ray emission above 20 keV from the region of MCG8 –11 ‐11 has been recently reported4, and the A2 experiment on HEAO 1 has provided for the first time the emission spectrum of this object up to 30 keV (ref. 5). During a balloon flight on 30 September 1979 from Palestine, Texas of the Milan/Southampton (MISO) low-energy γ-ray telescope, an excess at the 3.9σ level in the flux above 90 keV was detected from a region of the sky containing MCG8 –11 –11. The emission spectrum, evaluated in the energy range 0.02–19 MeV, has similar spectral characteristics to those observed with the same telescope and associated with the Seyfert galaxy NGC4151 (ref. 6). Both spectra show evidence for a high-energy cutoff close to 3 MeV and this feature could be interpreted on the basis of the ‘Penrose–Compton scattering’ process7. A large amount of the observed low-energy γ-ray diffuse background8could be produced by a few per cent of the X-ray emitting Seyfert galaxies having a γ-ray luminosity comparable with that observed from the region of NGC4151 or MCG8 –11 –11.

Following the first detection of X-ray emission from the Seyfert galaxy NGC41511, later observations2–4have demonstrated that the X-ray spectrum up to 100 keV may be described by a power law having a differential spectral index 1<α<1.6 with a turnover at low energies caused by photoelectric absorption. Recently the results of an observation of this galaxy in the energy range 25–190 keV (ref. 5) have shown it to have a very hard spectrum with α≅0.9. Here more detailed results of the original observation of NGC4151 (ref. 6) using the MISO telescope are presented.

OBSERVATIONS of the Seyfert galaxy NGC4151 by Ariel V, OSOI VII and UCSD (refs 1–3 respectively) have demonstrated that it has a relatively flat X-ray spectrum up to photon energies greater than 100 keV. The X-ray luminosity of this object is of the order of 4 × 1043erg s−1if a distance of 20 Mpc is assumed, and exceeds the integrated luminosity at all the other observed greater wavelengths. Long-term observations4by Ariel V indicate that the X-ray emission may originate from a compact object with dimensions less than 8 × 1015cm, presumably the nucleus of the Galaxy. Here we present the preliminary results of a positive measurement in the low energy γ-ray region of the spectrum, which are in good agreement with the X-ray data and confirm the intense high energy luminosity of the object.

The COS-B source CG135+1 (ref. 1) is an extremely interesting object because of its possible identification with the QSO 0241+622. Radio observations have identified a strong point source within 2 arc s (ref. 2) of QSO 0241+622. X-ray emissions have also been observed from this region of the sky by the Uhuru (ref. 3), SAS-3 (ref. 2) and HEAO-A (ref. 4) telescopes. The HEAO-A (A1) data indicate that there are two soft X-ray sources in this region of the sky, H0241+62 which contains the QSO, and H0235+60 which includes the radio source GT0236+61 (ref. 5). The OSO-7 data in the energy range 1–40 keV (ref. 6) and measurements using the high-energy X-ray experiment on Ariel-V between 0.26 and 1.2 MeV (ref. 7) have indicated that the photon emission from this region of the sky is of an extremely hard nature, with a power law spectral index of γ≈1.0. However, the poor angular resolution of these telescopes make it uncertain whether the high-energy X-ray fluxes are due to the same celestial object. We now report the results of a balloon flight carried out on 8 October 1978 from Palestine, Texas, in which the region of the sky including the COS-B source CG135+1 was scanned by the Milan/Southampton telescope (MISO telescope). A 5σ excess in the counting rate of the telescope in the energy range 0.15–20 MeV was observed. The origin of this low-energy γ-ray emission is compatible with the measured position of CG135+1.

THE 3B flare of August 7, 1972, has been one of the largest of the present solar cycle and, thanks to the favourable conditions for particle propagation (the position of the flare on the Sun was 14° N, 37° W) and to the time of the day it occurred, one for which a large quantity of data is or will be available.

The observation of gamma ray bursts (GRBs) in the gamma ray band has been advanced by the AGILE and Fermi satellites after the era of the Compton Gamma-Ray Observatory. AGILE and Fermi are showing that the GeV-bright GRBs share a set of common features, particularly the high fluence from the keV up to the GeV energy bands, the high value of the minimum Lorentz factor, an extended emission of gamma rays, which is often delayed with respect to lower energies, and finally the possible multiple spectral components. GRB 100724B, localised in a joint effort by Fermi and the InterPlanetary Newtork, is the brightest burst detected in gamma rays so far by AGILE. Characteristic features of GRB 100724B are the simultaneous emissions at MeV and GeV, without delayed onset or any time lag as shown by the analysis of the cross correlation function, and the significant spectral evolution in hard X-rays over the event duration. In this paper we show the analysis of the AGILE data of GRB 100724B and discuss its features in the context of the bursts observed so far in gamma rays and the recently proposed models.

We report on the extreme γ-ray activity from the flat spectrum radio quasar (FSRQ) PKS 1510−089 observed by the AGILE satellite in March 2009. In the same period a radio-to-optical monitoring of the source was provided by the GASP–WEBT and REM facilities. In the radio band we made use also of multi-epoch 15-GHz Very Long Baseline Array data from the MOJAVE Program to get information on the parsec-scale structure. Moreover, several Swift target of opportunity observations were triggered, adding important information on the source behaviour from optical/UV to hard X-rays. We paid particular attention to the calibration of the Swift/UVOT data to make it suitable to the blazars spectra. Simultaneous observations from radio to γrays allowed us to study in detail the correlation among the emission variability at differentfrequencies and to investigate the mechanisms at work during this high activity state of the source.

Context.Identification of γ-ray-emitting Galactic sources is a long-standing problem in astrophysics. One such source, 1AGL J2022+4032, coincident with the interior of the radio shell of the supernova remnant Gamma Cygni (SNR G78.2+2.1) in the Cygnus region, has recently been identified by Fermi as a γ-ray pulsar, LAT PSR J2021+4026.

Context.We report the detection by the AGILE satellite of intense γ-ray activity from the source 1AGL J0538 − 4424, associated with the low-energy-peaked BL Lac PKS 0537 − 441, during a target of opportunity (ToO) observation performed on 2008 October 10–17, triggered by a Fermi-LAT alert, together with REM and Swift observations.

Context. Cygnus X-1 (Cyg X-1) is a high mass X-ray binary system, known to be a black hole candidate and one of the brightest sources in the X-ray sky, which shows both variability on all timescales and frequent flares. The source spends most of the time in a hard spectral state, dominated by a power-law emission, with occasional transitions to the soft and intermediate states, where a strong blackbody component emerges.Aims. We present the observation of Cyg X-1 in a hard spectral state performed during the AGILE science verification phase and observing cycle 1 in hard X-rays (with SuperAGILE) and gamma rays (with the gamma ray imaging detector) and lasting for about 160 days with a live time of ~6 Ms.Methods. We investigated the variability of Cyg X-1 in hard X-rays on different timescales, from ~300 s up to one day, and we applied different tools of timing analysis, such as the autocorrelation function, the first-order structure function, and the Lomb-Scargle periodogram, to our data (from SuperAGILE) and to the simultaneous data in soft X-rays (from RXTE/ASM). We concluded our investigation with a search for emission in the energy range above 100 MeV with the maximum likelihood technique.Results. In the hard X-ray band, the flux of Cyg X-1 shows its typical erratic fluctuations on all timescales with variations of about a factor of two that do not significantly affect the shape of the energy spectrum. From the first-order structure function, we find that the X-ray emission of Cyg X-1 is characterized by antipersistence(anticorrelation in the time series, with an increase in the emission likely followed by a decrease), indicative of a negative feedback mechanism at work. In the gamma ray data a statistically significant point-like source at the position of Cyg X-1 is not found, and the upper limit on the flux is 5 × 10-8ph cm-2s-1over the whole observation (160 days). Finally we compared our upper limit in gamma rays with the expectation of various models of the Cyg X-1 emission, both of hadronic and leptonic origin, in the GeV–TeV band.Conclusions. The time history of Cyg X-1 in the hard X-ray band over 13 months (not continuous) is shown. Different analysis tools do not provide fully converging results of the characteristic timescales in the system, suggesting that the timescales found in the structure function are not intrinsic to the physics of the source. While Cyg X-1 is not detected in gamma rays, our upper limit is a factor of two lower than the EGRET one and is compatible with the extrapolation of the flux measured by COMPTEL in the same spectral state.

Context. Cygnus X-1 (Cyg X-1) is a high mass X-ray binary system, known to be a black hole candidate and one of the brightest sources in the X-ray sky, which shows both variability on all timescales and frequent flares. The source spends most of the time in a hard spectral state, dominated by a power-law emission, with occasional transitions to the soft and intermediate states, where a strong blackbody component emerges.

Aims. Supernova remnants (SNRs) are believed to be the main sources of Galactic cosmic rays. Molecular clouds associated with SNRs can produce gamma-ray emission by means of the interaction of accelerated particles with the concentrated gas. The middle-aged SNR W28, because of its associated system of dense molecular clouds, provides an excellent opportunity to test this hypothesis.Methods. We present the AGILE/GRID observations of SNR W28, and compare them with observations at other wavelengths (TeV and 12CO (J=1$\rightarrow$0)molecular line emission). Results. The gamma-ray flux detected by AGILE from the dominant source associated with W28 is (14 ±5) × 10-8ph cm-2s-1for E > 400MeV. This source is positionally well correlated with the TeV emission observed by the HESS telescope. The local variations in the GeV to TeV flux ratio imply that there is a difference between the CR spectra of the north-west and south molecular cloud complexes. A model based on a hadronic-induced interaction and diffusion with two molecular clouds at different distances from the W28 shell can explain both the morphological and spectral features observed by both AGILE in the MeV-GeV energy range and the HESS telescope in the TeV energy range. The combined set of AGILE and H.E.S.S. data strongly support a hadronic model for the gamma-ray production in W28.

Aims. Supernova remnants (SNRs) are believed to be the main sources of Galactic cosmic rays. Molecular clouds associated with SNRs can produce gamma-ray emission by means of the interaction of accelerated particles with the concentrated gas. The middle-aged SNR W28, because of its associated system of dense molecular clouds, provides an excellent opportunity to test this hypothesis.

Context. SuperAGILE is the hard X-ray monitor of the AGILE gamma ray mission, in orbit since 23 April 2007. It is an imaging experiment based on a set of four independent silicon strip detectors, equipped with one-dimensional coded masks, operating in the nominal energy range 18–60 keV.

Context. SuperAGILE is the hard X-ray monitor of the AGILE gamma ray mission, in orbit since 23 April 2007. It is an imaging experiment based on a set of four independent silicon strip detectors, equipped with one-dimensional coded masks, operating in the nominal energy range 18–60 keV.Aims. The main goal of SuperAGILE is the observation of cosmic sources simultaneously with the main gamma-ray AGILE experiment, the Gamma Ray Imaging Detector (GRID). Given its ~steradian-wide field of view and its ~15 mCrab day-sensitivity, SuperAGILE is also well suited to the long-term monitoring of Galactic compact objects and the detection of bright transients.Methods. The SuperAGILE detector properties and design allow for a 6 arcmin angular resolution in each of the two independent orthogonal projections of the celestial coordinates. Photon by photon data are continuously available by means of experiment telemetry, and are used to derive images and fluxes of individual sources, with integration times depending on the source intensity and position in the field of view.Results. We report on the main scientific results achieved by SuperAGILE over its first two years in orbit, until April 2009. The scientific observations started in mid-July 2007, with the science verification phase, continuing during the complete AGILE Cycle 1 and the first ~half of Cycle 2. Despite the largely non-uniform sky coverage, due to the pointing strategy of the AGILE mission, a few tens of Galactic sources were monitored, sometimes for unprecedently long continuous periods, leading to the detection also of several bursts and outbursts. Approximately one gamma ray burst per month was detected and localized, allowing for prompt multiwavelength observations. A few extragalactic sources in bright states were occasionally detected as well. The light curves of sources measured by SuperAGILE are made publicly available on the web in almost real-time. To enable a proper scientific use of these, we provide the reader with the relevant scientific and technical background.

The title compounds, e.g. (VII), are evaluated for their activity against Leishmania infantum.