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					AGILE view on TGF
F. Fuschino, F. Longo,
M. Marisaldi, C. Labanti, M. Galli,
G. Barbiellini

on behalf of the AGILE team

                  F.Fuschino, F.Longo et al. -- 1

• The AGILE satellite
   – Brief introduction
• The AGILE Mini Calorimeter (MCAL)
   – Burst Trigger Mode
   – Gamma-ray Burst detection
• Terrestrial Gamma Flashes
   – Detection by AGILE-MCAL

                                 The AGILE first photon – May 10, 2007
                                                F.Fuschino, F.Longo et al. -- 2

        F.Fuschino, F.Longo et al. -- 3
Detection Technique

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AGILE instrument

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 AGILE: inside the cube…

                            HARD X-RAY IMAGER
                            (E.Costa, M. Feroci)

                           GAMMA-RAY IMAGER
                           SILICON TRACKER
INAF-IASF-Mi (F.Perotti)   (G.Barbiellini, M. Prest)

                           (MINI) CALORIMETER
                           INAF-IASF-Bo, Thales-
                           Alenia Space (LABEN)
                           (G. Di Cocco, C. Labanti)
                                 F.Fuschino, F.Longo et al. -- 7
The AGILE instrument
             Sriharikota launch base (India)
             PSLV-C8 launch, April 23, 2007

                          F.Fuschino, F.Longo et al. -- 8
                          AGILE results

• Vela, Geminga, Crab PSR timing
• Monitoring of many Galactic hard X-ray sources
• Blazar detections
   – 3C 279
   – 3C 273
   – 3C 454.3         (repeated gamma-ray flares)
   – PKS1510-089
   – 0716+714
   – W Comae, Mkn 421

• Several GRBs detected by SuperAGILE and MCAL (MCAL detects
  ~ 1/week)

• Discovery of transient gamma-ray sources in the Galactic plane.

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  AGILE gamma-ray sky: 22 Nov. 2007

               Cygnus region

3C 454.3

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                           AGILE view of the sky                       F.Fuschino, F.Longo et al. -- 11

                 F.Fuschino, F.Longo et al. -- 12
      The Mini-Calorimeter (MCAL)

                                                   40 cm

 30 CsI(Tl) bars with Photodiode readout
 1400 cm
           2 geometrical area
 ~360 cm
            2 effective area @ 1 MeV
 330 keV – 100 MeV energy range

 14% energy resolution FWHM @ 1.3 MeV

 2 ms timing accuracy in photon-by-photon

 Clever, fully-programmable GRB trigger logic

                                     F.Fuschino, F.Longo et al. -- 13
 The AGILE instrument

              BURST        T
           -GRB SEARCH
           -SA IMAGE       R
           DECONVOLUTION   Y

On Board AGILE Trigger
                            F.Fuschino, F.Longo et al. -- 14
                      MCAL Trigger Logic
                                       MCAL Burst Search logic:
                                        1ms, 16ms, 64ms, 256ms, 1.024s,

                                       8.192s Search Integration Time
                                        4 spatial zones and 3 energy

                                       ranges (<700 keV, 700-1400 keV,
                                       >1400 keV)‫‏‬
                                        static and dinamic thresholds for

                                       start and stop generation
                                        dedicated look-up tables to

                                       accept/reject triggers
                                        very flexible: more than 2000

                                       parameters for full configuration

Configured in November 2007, steadily active since February 2008

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                   The AGILE instrument

MCAL GRB search testing
(Tortona, June 2006)

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                 MCAL and its partners in space

  49 cosmic GRBs detected by AGILE-MCAL between 22nd June '07 - 11th
    June. '08. Most of them confirmed by other InterPlanetary Network
    (IPN) spacecrafts

Detector with superposition > 80%                           Detector with photon-by-photon
with the MCAL sample and good                               microsecond timing accuracy in
                                    Detectors with
spectral capabilities: cross-                               the MeV range
                                    spectral capabilities
calibration activity ongoing        in the MeV range

                    A warm welcome to GLAST-GBM!

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Latest news: GRB 080609

                 long, bright GRB,
                 out of FOV

    25 s                F.Fuschino, F.Longo et al. -- 18
    Latest news: GRB 080611

                 short/hard, very bright

100 ms
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Terrestrial Gamma Flashes by AGILE

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            Terrestrial Gamma-ray Flashes (TGF)

 Gamma-ray flashes with incoming direction compatible with
the Earth surface.
 Few millisecond typical duration; hard spectrum (detected

up to 20 MeV)‫‏‬
 Discovered by BATSE (1994) and confirmed by RHESSI

 Possibly associated to lightning during thunderstorms by

means of correlation with VLF spheric waves detection on

 Serendipitous detection of candidate TGF by MCAL after the
onset of the onboard trigger logic
 Undetectable without small “search integration

times” (<=64 ms) and photon-by-photon data
 About 20 candidates in 5 months operation

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        MCAL candidate TGF

                                                         trigger date
                                                         and time

10 ms      temporal bin: 100 ms!   time scale: < 5 ms

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                TGF energy/position distribution

Candidate TGF on 2007-12-11 00:03: 42 UT FOV

                                                        AGILE pointing at trigger time

Light curves in 2           Events distribution in 2
energy bands                energy bands

The position distribution pattern is compatible with
incoming direction from the Earth surface
                                                       AGILE position at trigger time

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              TGF energy/position distribution

Candidate TGF on 25/3/08 15:00:02      Earth

                                                AGILE pointing at trigger time

Light curves in         Events distribution
3 energy bands          in 3 energy bands
The position distribution pattern is
compatible with incoming direction from
the Earth surface                              AGILE position at trigger time
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Geographycal distribution

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   Are the observed MCAL events compatible with RHESSI spectra?

                                     Considering RHESSI and MCAL effective
                                    area ~12 counts/ms are expected in MCAL
                                    in the 500 – 700 keV band
                                     ~16 counts/ms are found: quite good

                                    agreement, refinement are expected with
                                    better calibration
                                     possibly selection effect toward bright

                                    events due to the trigger time window
                                    (64ms): expected improvements with
                                    <=16ms time windows

Smith et al. 2005

                                                     F.Fuschino, F.Longo et al. -- 26

• AGILE-MCAL is the 3rd instrument (after BATSE and
  RHESSI) that observed TGF from space. Serendipity: from
  astrophysics to geophysics!
• Observation of such fast events is only possible thanks to
  the clever trigger logic (~ms time scale) and photon-by-
  photon data download with ms time resolution.
• The energetics of observed events is compatible with that
  reported by RHESSI.
• Definitive proof needed: search for spheric waves
• Calibration activity ongoing: better spectral
• Last week: enabling <16 ms time window: new discovery
  space opening!
• HW trigger 1, 16 ms + 293 ms (<1 ms)
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      The end

thank you !
   F.Fuschino, F.Longo et al. -- 28
BackUp Slides

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                            BATSE TGF

                                               Fishman et al. 1994
                                               Ostgaard et al. 08

~ 70 TGF detected on 9 life-Years
typically 100 counts/TGF
On-Board Trigger Logic performances:
Shorter timescale => 64ms
Significance => 40 sigma above the background on two separate detector

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             RHESSI TGF

                                                TGF Distribution
                                                with lighting
                                                per km2 per Year

            Continuous time-tagged event list
            10– 20 TGF per month
            Typically 20-30

Distribution of average energy for the
RHESSI TGFs (histogram) along with a
simulated brehmstrahlung spectra.             Smith et al. 2005
                                         F.Fuschino, F.Longo et al. -- 31

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