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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.

In December 2004, the soft gamma-ray repeater SGR 1806-20 emitted the most powerful giant flare ever observed. This probably involved a large-scale rearrangement of the magnetosphere leading to observable variations in the properties of its X-ray emission. Here we present the results of the first Suzakuobservation of SGR 1806-20, together with almost simultaneous observations with XMM-Newtonand INTEGRAL. The source seems to have reached a state characterized by a flux close to the pre-flare level and by a relatively soft spectrum. Despite this, SGR 1806-20  also remained quite active after the giant flare, allowing us to study several short bursts observed by Suzakuin the 1–100 keV range. We discuss the broad-band spectral properties of SGR 1806-20, covering both persistent and bursting emission, in the context of the magnetar model, and consider its recent theoretical developments.

We present a systematic analysis of all the BeppoSAXdata of the soft gamma-ray repeater SGR 1900+14: these observations allowed us to study the long term properties of the source quiescent emission. In the observation carried out before the 1998 giant flare the spectrum in the 0.8–10 keV energy range was harder and there was evidence for a 20–150 keV emission, possibly associated with SGR 1900+14. This possible hard tail, if compared with the recent INTEGRALdetection of SGR 1900+14, has a harder spectrum (power-law photon index ~1.6 versus ~3) and a 20–100 keV flux ~4 times larger. In the last BeppoSAXobservation (April 2002), while the source was entering the long quiescent period that lasted until 2006, the 2–10 keV flux was ~25% below the historical level. We also studied in detail the spectral evolution during the 2001 flare afterglow. This was characterized by a softening that can be interpreted in terms of a cooling blackbody-like component.

We present the catalog of X-ray afterglow observed by BeppoSAX from the launch of the satellite to the end of the mission. Thirty-three X-ray afterglows out of 39 observations were securely identified based on their fading behavior. We have extracted the continuum parameters (decay index, spectral index, flux, absorption) for all available afterglows. We point out a possible correlation between the X-ray afterglow luminosity and the energy emitted during the prompt γ-ray event. We do not detect a significant jet signature within the afterglows, implying a lower limit on the beaming angle, nor a standard energy release when X-ray fluxes are corrected for beaming. Our data support the hypothesis that the burst should be surrounded by an interstellar medium rather than a wind environment, and that this environment should be dense. This may be explained by a termination shock located near the burst progenitor. We finally point out that some dark bursts may be explained by an intrinsic faintness of the event, while others may be strongly absorbed.

The sky region containing the soft gamma-ray repeater SGR 1627-41 has been observed three times with XMM-Newton in February and September 2004. SGR 1627-41 has been detected with an absorbed flux of ~$9\times10^{-14}$erg cm-2s-1(2-10 keV). For a distance of 11 kpc, this corresponds to a luminosity of ~$3\times 10^{33}$erg s-1, the smallest ever observed for a Soft Gamma Repeater and possibly related to the long period of inactivity of this source. The observed flux is smaller than that seen with Chandra in 2001-2003, suggesting that the source was still fading and had not yet reached a steady quiescent level. The spectrum is equally well fit by a steep power law (photon index ~3.2) or by a blackbody with temperature $kT\sim0.8$keV. We also report on the INTEGRAL transient IGR J16358-4726 that lies at ~10'from SGR 1627-41. It was detected only in September 2004 with a luminosity of ~$4\times10^{33}$erg s-1(for $d=7$kpc), while in February 2004 it was at least a factor 10 fainter.

Two XMM-Newtonobservations of the black-hole binary GRS 1915+105 were triggered in 2004 (April 17 and 21), during a long “plateau” state of the source. We analyzed the data collected with EPIC-pn in timing and burst modes, respectively. Reflection Grating Spectrometers were used only on April 21st. The source 2–10 keV flux is ~0.6 (unabsorbed: $0.9\div1.1$) $\times$10-8in cgs units. While the light curves show only small amplitude variations (a few percent) at timescales longer than a few seconds, a QPO is seen at about 0.6 Hz – as expected in χvariability modes of GRS 1915+105, when the phenomenological correlation with the source flux is taken into account – possibly with a harmonic signal at 1.2 Hz. The pn spectrum is well fitted without invoking thermal disk emission, on the basis of four main components: a primary one (either a simple power law or thermal Comptonization models), absorbed by cold matter with abundances different than those of standard ISM; reprocessing from an ionized disk; emission and absorption lines; and a soft X-ray excess at ~1 keV. However, the last is not confirmed by the RGS spectra, whose difference from the EPIC-pn ones lacks a fully satisfactory explanation. If real, the soft X-ray excess may be due to reflection from an optically thin, photoionized disk wind; in this case it may lead to a way to disentangle intrinsic from interstellar absorption.

SGR 1806–20 has been observed for more than 2 years with the INTEGRALsatellite. In this period the source went from a quiescent state into a very active one culminating in a giant flare on December 27, 2004. Here we report on the properties of all the short bursts detected with INTEGRALbefore the giant flare. We derive their number-intensity distribution and confirm the hardness-intensity correlation for the bursts found by Götz et al. (2004a, A&A, 417, L45). Our sample includes a very bright outburst that occurred on October 5, 2004, during which over one hundred bursts were emitted in 10 minutes, involving an energy release of $3\times 10^{42}$erg. We present a detailed analysis of it and discuss our results in the framework of the magnetar model.

We report on BeppoSAX simultaneous X- and γ-ray observations of the bright γ-ray burst (GRB) 990123. We present the broad-band spectrum of the prompt emission, including optical, X- and γ-rays, confirming the suggestion that the emission mechanisms at low and high frequencies must have different physical origins. In the framework of the standard fireball model, we discuss the X-ray afterglow observed by the Narrow Field Instruments (NFIs) on board BeppoSAX and its hard X-ray emission up to 60 keV several hours after the burst, detected for about 20 ks by the Phoswich Detection System (PDS). Considering the $2{-}10$keV and optical light curves, the $0.1{-}60$keV spectrum during the 20 ks in which the PDS signal was present and the 8.46 GHz upper limits, we find that the multi-wavelength observations cannot be readily accommodated by basic afterglow models. While the temporal and spectral behavior of the optical afterglow is possibly explained by a synchrotron cooling frequency between the optical and the X-ray energy band during the NFIs observations, in X-rays this assumption only accounts for the slope of the $2{-}10$keV light curve, but not for the flatness of the $0.1{-}60$keV spectrum. Including the contribution of Inverse Compton (IC) scattering, we solve the problem of the flat X-ray spectrum and justify the hard X-ray emission; we also suggest that the lack of a significant detection of $15{-}60$keV emission in the following 75 ks and last 70 ks spectra, should be related to poorer statistics rather than to an important suppression of IC contribution. However, considering also the radio band data, we find the 8.46 GHz upper limits violated. On the other hand, leaving unchanged the emission mechanism requires modifying the hydrodynamics by invoking an ambient medium whose density rises rapidly with radius and by having the shock losing energy. Thus we are left with an open puzzle which requires further inspection.

We report on the BeppoSAXdata analysis of the afterglow of Gamma-Ray Burst (GRB) 990123, one of the brightest GRBs detected by BeppoSAX. Mainly due to its exceptional brightness, this is the only source for which the Wide Field Cameras have allowed an early detection of the X-ray afterglow between ~20 and 60 min after the GRB trigger. Besides, again for the first time, high-energy emission from the afterglow was detected up to 60 keV. For the X-ray afterglow we found a power-law decay with index $\alpha = 1.46 \pm 0.04$; the spectrum has a power-law shape with photon index $\Gamma \sim 1.9$. The backward extrapolation of the afterglow decay smoothly reconnects with the late GRB emission, thus suggesting that both emissions are produced by the same phenomenon. An extensive set of multiwavelength observations for the GRB 990123 afterglow made during the BeppoSAXpointing was collected from the literature. The hard X-ray to radio range coverage allowed to construct a spectral flux distribution and to perform an analysis of the GRB afterglow in the context of the “fireball” model. We also report the results of temporal and spectral analysis of an X-ray source serendipitously observed about 22'north of the GRB afterglow, along with the optical spectroscopy of its possible counterpart to establish the nature of this source.

GRB 020410 is by far the longest γ-ray burst (with a duration of about 1600 s) to have been followed up from the X-ray through the radio regime. Afterglow emission was detected in X-rays and at optical wavelengths whereas no emission was detected at 8 GHz brighter than 120 μJy. The decaying X-ray afterglow, back-extrapolated to 11 h after the burst, had a flux of 7.9 $\times$10-12erg cm-2s-1(2–10 keV); the brightest detected so far. No direct redshift determination is available yet for this GRB, but according to the empirical relationship between the peak energy in the $\nu F_\nu$spectrum and the isotropic energy output, zis constrained in the range 0.9–1.5. The reconstructed optical afterglow light curve implies at least two breaks in the simple power law decay. This may be related to emergence of an SN, or refreshment of the external shock by a variation in the circumstellar medium. Considering the backward extrapolation of the 2–10 keV afterglow decay, the prompt lightcurve variability and its spectral evolution, we conclude that the long duration of this event is due to a prolonged activity of the “central engine”.

We report on the X-ray observations of the X-ray flash (XRF) which occurred on 2002 April 27, three days before BeppoSAXwas switched off. The event was detected with the BeppoSAXWide Field Cameras but not with the Gamma ray Burst Monitor. A follow-up observation with the BeppoSAXNarrow Field Instruments was soon performed and a candidate afterglow source was discovered. We present the results obtained. We also include the results obtained from the observations of the XRF field with the ChandraX-ray satellite. The spectral analysis of the prompt emission shows that the peak energy of the $EF(E)$spectrum is lower than 5.5 keV, with negligible spectral evolution. The X-ray afterglow spectrum is consistent with a power law model with photon index of ~2, while the 2–10 keV flux fades as a power law with a decay index -1.33. Both these indices are typical of GRBs. A very marginal excess at ~4.5–5 keV is found in the afterglow spectrum measured by BeppoSAX. As for many GRBs, the extrapolation of the 2–10 keV fading law back to the time of the prompt emission is consistent with the X-ray flux measured during the second part of the event. We estimate a possible range of values of the redshift and discuss our results in the light of current models of XRFs.

We report on spectral and temporal results of the 40–700 keV observations, obtained with the Gamma-Ray Burst Monitor (GRBM) on board BeppoSAX, of the two large flares from the Soft Gamma-ray Repeater SGR 1900+14 occurred on August 27, 1998 and April 18, 2001. From their intensity, fluence and duration, the first one was classified as “giant” and the second as “intermediate”.The spectral results have been obtained with an improved response function of the GRBM. We find that the two events have similar spectral properties, but different temporal properties. The major difference concerns the time profiles of the light curves, whereas the lack of evidence in the 2001 flare for the erratic time variability found at high frequencies (10–1000 Hz) in the 1998 flare could be ascribed to lower counting statistics. We discuss these results in the light of the magnetar model proposed for SGR sources.

We summarize the inflight performance of JEM–X, the X–ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM–X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis.

The JEM–X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM–X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM–X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm2, and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3'across an effective field of view of about 10° diameter.

We present data from the first of six monitoring Open Time observations of GRS 1915+105 undertaken with the orbiting INTEGRAL satellite. The source was clearly detected with all three X-ray and gamma-ray instruments on board. GRS 1915+105 was in a highly variable state, as demonstrated by the JEM X-2 and ISGRI lightcurves. These and simultaneous RXTE/PCA lightcurves point to a novel type of variability pattern in the source. In addition, we fit the combined JEM X-2 and ISGRI spectrum between 3–300 keV with a disk blackbody + powerlaw model leading to typical parameter values found earlier at similar luminosity levels. A new transient, IGR J19140+098, was discovered during the present observation.

A long Gamma-Ray Burst (GRB) was detected with the instruments on board the INTEGRAL satellite on January 31 2003. Although most of the GRB, which lasted ~150 s, occurred during a satellite slew, the automatic software of the INTEGRAL Burst Alert System was able to detect it in near-real time. Here we report the results obtained with the IBIS instrument, which detected GRB 030131 in the 15 keV–200 keV energy range, and ESO/VLT observations of its optical transient. The burst displays a complex time profile with numerous peaks. The peak spectrum can be described by a single power law with photon index $\Gamma\simeq1.7$and has a flux of ~2 photons cm-2s-1in the 20–200 keV energy band. The high sensitivity of IBIS has made it possible for the first time to perform detailed time-resolved spectroscopy of a GRB with a fluence of $7\times10^{-6}$erg cm-2(20–200 keV).

We report on the prompt and afterglow emission observations of the dark burst GRB010214 with BeppoSAX. The prompt emission shows possible evidence of variable absorption from $N_{\rm H} = 3.0^{+5.1}_{-2.0} \times 10^{23}$cm-2in the first 6 s of the event to a value consistent with the Galactic column density ($N_{\rm H}^{\rm G} = 2.66\times 10^{20}$cm-2) in the GRB direction. An X–ray afterglow emission in the 2–10 keV energy band was detected with BeppoSAX, but an analogue search at lower wavelengths (optical, IR and radio) was unsuccessful. The X–ray afterglow spectrum is consistent with a power–law with Galactic absorption. The light curve shows a complex decay, if the tail of the prompt emission is assumed as the onset of the afterglow: if the origin of the afterglow is coincident with the GRB onset, a bump before ~$3\times10^4$s is inferred, while if the afterglow is assumed to start later, a steepening of the power–law light curve at $t\sim 3\times10^4$s is deduced. We discuss these results in the light of the current models of afterglows and the possible origin of the GRB darkness. Finally, we tentatively derive an estimate of the burst redshift.

We present the main results of a study of spectral and energetics properties of twelve gamma-ray bursts (GRBs) with redshift estimates. All GRBs in our sample were detected by BeppoSAX in a broad energy range (2–700 $\rm keV$). From the redshift estimates and the good-quality BeppoSAX time–integrated spectra we deduce the main properties of GRBs in their cosmological rest frames. All spectra in our sample are satisfactorily represented by the Band model, with no significant soft X–ray excesses or spectral absorptions. We find a positive correlation between the estimated total (isotropic) energies in the 1–10 000 $\rm keV$energy range (Erad) and redshifts z. Interestingly, more luminous GRBs are characterized also by larger peak energies Eps of their $EF(E)$spectra. Furthermore, more distant GRBs appear to be systematically harder in the X–ray band compared to GRBs with lower redshifts. We discuss how selection and data truncation effects could bias our results and give possible explanations for the correlations that we found.

We present the X- and γ-ray detection of GRB 990704 and the discovery and study of its X-ray afterglow, 1SAX J1219.5-0350. Two pointed BeppoSAX observations with the narrow field instruments were performed on this source, separated in time by one week. The decay of the X-ray flux within the first observation appears unusually slow, being best-fit by a power law with negative index $0.83 \pm 0.16$. Such a slow decay is consistent with the non-detection in our second observation, but its back-extrapolation to the time of the GRB largely underestimates the detected GRB X-ray prompt emission. In addition, the GRB prompt event shows, among the BeppoSAX-WFC detected sample, unprecedentedly high ratios of X- and gamma-ray peak fluxes (F2-10 keV/$F_{\rm 40-700 keV}\sim0.6$, and F2-26 keV/$F_{\rm 40-700 keV}\sim1.6$) and fluences (S2-10 keV/$S_{\rm 40-700 keV}\sim1.5$and S2-26 keV/$S_{\rm 40-700 keV}\sim2.8$), making it, among the BeppoSAX arcminute-localized GRBs, the closest to the recently discovered class of Fast X-ray Transients.

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.

In December 2004, the soft gamma-ray repeater SGR?1806-20?emitted the most powerful giant flare ever observed. This probably involved a large-scale rearrangement of the magnetosphere leading to observable variations in the properties of its X-ray emission. Here we present the results of the first Suzaku?observation of SGR?1806-20, together with almost simultaneous observations with XMM-Newton?and INTEGRAL. The source seems to have reached a state characterized by a flux close to the pre-flare level and by a relatively soft spectrum. Despite this, SGR?1806-20? also remained quite active after the giant flare, allowing us to study several short bursts observed by Suzaku?in the 1?100?keV range. We discuss the broad-band spectral properties of SGR?1806-20, covering both persistent and bursting emission, in the context of the magnetar model, and consider its recent theoretical developments.

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.

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.

GRS 1915+105 was observed by BeppoSAX  for about 10 days in October 2000. For about 80% of the time, the source was in the variability class ρ, characterised by a series of recurrent bursts. We describe the results of the timing analysis performed on the MECS (1.6–10 keV) and PDS (15–100 keV) data. The X-ray count rate from GRS 1915+105 showed an increasing trend with different characteristics in the various energy bands: in the bands (1.6–3 keV) and (15–100 keV), it was nearly stable in the first part of the pointing and increased in a rather short time by about 20%, while in the energy range (3–10 keV) the increase had a smoother trend. Fourier and wavelet analyses detect a variation in the recurrence time of the bursts, from 45–50 s to about 75 s, which appear well correlated with the count rate. From the power distribution of peaks in Fourier periodograms and wavelet spectra, we distinguished between the regularand irregularvariability modes of the ρclass, which are related to variations in the count rate in the 3–10 keV range. We identified two components in the burst structure: the slow leading trail, and the pulse, superimposed on a rather stable level. Pulses are generally structured in a series of peaks and their number is related to the regularity modes: the mean number of peaks is lower than 2 in the regular mode and increases up to values higher than 3 in the irregular mode. We found that the change in the recurrence time of the regular mode is caused by the slow leading trails, while the duration of the pulse phase remains far more stable. The evolution in the mean count rates shows that the time behaviour of both the leading trail and the baseline level are very similar to those observed in the 1.6–3 and 15–100 keV ranges, while that of the pulse follows the peak number. These differences in the time behaviour and count rates at different energies indicate that the process responsible for the pulses must produce the strongest emission between 3 and 10 keV, while that associated with both the leading trail and the baseline dominates at lower and higher energies.