AGILE WINS THE 2012 HEAD AAS BRUNO ROSSI PRIZE !
''The 2012 Rossi Prize has been awarded to astrophysicist Marco Tavani and the AGILE Team for the discovery of gamma-ray flares from the Crab Nebula. This finding has changed the understanding of this very important cosmic object.''
For a full coverage, see the:
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AGILE in a nutshell
AGILE (Astro-rivelatore Gamma a Immagini LEggero )
is an Italian Space Agency mission dedicated to the
observation of the gamma-ray Universe,
supported by the Italian Space Agency (ASI) with scientific and
programmatic participation by INAF, INFN, CNR, ENEA and several
Italian universities.
The main industrial contractors include Carlo Gavazzi Space,
Thales-Alenia-Space (formerly Laben), Rheinmetall Italia (formerly
Oerlikon-Contraves), Telespazio, Galileo Avionica, and Mipot.
AGILE was successfully launched on April
23, 2007 from the Indian base of Sriharikota and was inserted in
an equatorial orbit with very low particle background.
The AGILE very innovative instrumentation combines for the first time 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) together with a Calorimeter (sensitive in the range 300 keV - 100 MeV) and an Anticoincidence system.
AGILE provides crucial data for the study of:
An optimal angular resolution (reaching 0.1-0.2 degrees in gamma-rays and 1-2 arcminutes in hard X-rays) and very large fields of view (2.5 sr and 1 sr, respectively) are obtained by the use of Silicon detectors integrated in a very compact instrument.
Starting ftom 2009 November, a permanent failure in the reaction wheel imposed a change in the observing mode, shifting from a "pointed mode" to a "spinning mode". In spinning mode AGILE monitors about 80% of the sky during each orbit.
The AGILE imagers
The Gamma-ray Detector
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The Silicon Tracker (ST) is the AGILE gamma-ray imager based on photon conversion into electron-positron pairs. It consists of a total of 12 trays with a repetition pattern of 1.9 cm. The first 10 trays are capable of converting gamma-rays by a Tungsten layer. Tracking of charged particles is ensured by silicon microstrip detectors that are configured to provide the two orthogonal coordinates for each element (point) along the track. |
The Gamma-Ray Imaging Detector (GRID) is sensitive in the energy range 30 MeV - 50 GeV, and consists of a Silicon-Tungsten Tracker, a Cesium Iodide Calorimeter, and an Anticoincidence system. The GRID trigger logic and data acquisition system allows for an efficient background discrimination and inclined photon acceptance. The GRID is designed to achieve an optimal angular resolution (source location accuracy 6-12 arcmin for intense sources), a large field-of-view (2.5 sr), and a sensitivity comparable to that of CGRO/EGRET for sources within 10-20 degree from the main axis direction, and substantially better for larger off-axis angles.
The Hard X-ray Detector
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Super-AGILE (SA), the ultra-compact and light hard-X-ray imager of AGILE is a coded-mask system made of a Silicon detector plane and a thin Tungsten mask positioned 14 cm above it. The detection cabability of SA includes: (1) photon-by-photon transmission and imaging of sources in the energy range 18-60 keV, with a large field-of-view (FOV 1 sr); (2) an angular resolution of 6 arcmin; (3) a good sensitivity (15 mCrab between 18-60 keV for 50 ksec integration). |
Super-AGILE is aimed at the hard X-ray detection simultaneously with gamma-ray detection of high-energy sources with excellent timing capabilities (a few microseconds). The SA acquisition logic produces on-board essential GRB quantities such as time, coordinates and preliminary flux estimates. The AGILE satellite is equipped with an ORBCOMM transponder capable of trasmitting the GRB on-board processed physical quantities to the ground within 10-30 min.
Adapted from Tavani et al., 2009, A&A, 502, 995.
Scientific Results
AGILE is carrying an ambitious program of observations aimed
at covering the whole sky at gamma-ray energies above 100 MeV.
The unprecedentedly large FOV of the
gamma-ray detector (2.5 sr) allowed to complete this program. This Figure shows the gamma-ray
sky detected by AGILE since 2010 October 15.
The diffuse gamma-ray emission originating by cosmic-ray interactions in gaseous clouds in the Galaxy dominates the emission. However, many pointlike sources can be detected both in the Galactic plane as well as outside the plane.
Active Galactic Nuclei
Blazars emit across several decades of energy, from the radio to the TeV energy band, and thus are perfect candidates for simultaneous observations at different wavelengths.An example of the AGILE multiwavelength campaign is given in the following Figure, which shows the simultaneous light curves acquired during the 2009 November.
Blue circles represent AGILE/GRID data (E>100 MeV); red triangles represent Swift/XRT data (2 - 10 keV); blue, green, and red symbols represent Swift/XRT data (W2, M2, W1 bands); Black triangles represent R-band WEBT.
We note that the gamma-ray flaring event on MJD 55520 (2009 November 20) represents the maximum flux ever reached by a gamma-ray blazar, about 7E-5 ph/cm2/s (E>100 MeV). We also note what can be called an "gamma-ray orphan" UV-ptical flare on MJD 55510, 10 days prior to the gamma-ray one. A modeling of the evolution of the super-flare spectral energy distribution (SED), taking into account the evolution of the "gamma-ray orphan" UV-optical flare, challenges a model with a uniform external photon field. Moreover, the modeling places the gamma-ray emission region within the BLR.
Adapted from Vercellone et al., 2011, ArXiv 1111.0689.References
A list of accepted paper on AGNs with AGILE can be found at the following LINK.Pulsars
AGILE is contributing in a substantial way to PSR studies. A first contribution was possibile because of the excellent timing performance of the instrument, yielding lightcurves with unprecedented resolution for the Vela, Crab, Geminga and PSR B1706-44, as shown in this Figure.
The first surprise came with the detection of PSR J2021+3651 (through the AGILE Guest Observer Program) that is a young and energetic neutron star discovered after the end of the EGRET mission in the very complex Cygnus region. Other important gamma-ray PSRs were detected by AGILE including PSR J1513-5908 (B1509-58) previously detected only up to 10 MeV, PSR J2229+6114, and the remarkable millisecond pulsar J1824-2452 in the globular cluster M28.
With the firm detection of several new Crab-like and Vela-like gamma ray pulsars, AGILE nearly doubled the gamma-ray PSR family in one year of scientific operations implying that gamma-ray emission is a common feature for energetic and/or nearby radio PSRs. Indeed, our list encompasses the second youngest (J1513-5908) and by far the oldest non-recycled pulsar (J2043+2740) detected at gamma-ray energies.
Adapted from Pellizzoni et al., 2009, ApJ, 691, 1618.References
A list of accepted paper on PSRs with AGILE can be found at the following LINK.Galactic Sources
The large FOVs of the gamma-ray and hard X-ray imagers, the optimal angular resolution and good exposure achieved by AGILE near 100 MeV and 20 keV are particularly suited for the study of complex regions in the Galactic plane. During Cycle-1 AGILE monitored the Galactic plane regions accumulating exposure especially in the Carina-Vela and Cygnus regions.
An extensive observations of the Galactic region hosting the Carina nebula and the colliding wind binary Eta Carinae during the period 2007 July - 2009 January allowed us to detect a gamma-ray source (1AGL J1043-5931) consistent with the position of Eta Carinae. If 1AGL J1043-5931 is associated with the Carinae system our data provide the long sought first detection above 100 MeV of a colliding wind binary.
The Figure shows the AGILE gamma-ray intensity map in Galactic coordinates of the Eta Carinae region above 100 MeV summing all data collected from 2007 July to 2008 October. The central gamma-ray source that can be associated with Eta Carinae is 1AGL J1043-5931; we also indicate the prominent nearby gamma-ray source AGL J1046-5832 which is associated with the radio pulsar PSR B1046-58. The optical position of Eta Carinae is marked by a small black circle. The INTEGRAL sources are marked with cyan circles.
Adapted from Tavani et al., 2009, ApJL, 698, L142.References
A list of accepted paper on Gal. Sources with AGILE can be found at the following LINK.Gamma-ray Bursts
AGILE is optimally suited for a broad-band detection of gamma-ray bursts (GRBs) in the hard X-ray energies with Super-AGILE, in the MeV range with MCAL, and at gamma-ray energies with the GRID. During Cycle-1 several tens of GRBs were localized by Super-AGILE and detected above 300 keV by MCAL. However, only one GRB was unambigously detected in the energy range above 100 MeV.
This Figure shows the AGILE multiwavelength light curves for GRB080514B. This gamma ray burst showed also an afterglow counterpart at X-rays and in the optical, and a measured distance (from the photometric redshift) of z=1.8.
The hard X-ray emission observed by Super-AGILE 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 was seen in the past from a few other GRBs observed with EGRET. However, the latter measurements were affected, during the brightest phases, 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.
Adapted from Giuliani et al., 2008, A&AL, 491, 25.References
A list of accepted paper on GRBs with AGILE can be found at the following LINK.
IASF-Palermo Team, activities & related links
Team members
Currently, the only member of the AGILE Team at IASF-Palermo is:Activities
The main activities are:Other IASF-Palermo scientists involved in AGILE studies are:
all of them granted with AGILE Guest Observer sources.
Moreover, a strong support to multiwavelength studies comes from the IASF-Palermo Swift Team, actively collaborating to the planning of the coordinated campaign and to the Swift/XRT data analysis.
External links
The most relevant links are:Contact person at IASF-Palermo:
Edit by Stefano Vercellone