Transcript Modeling the Spectral Energy Distributions and Variability

Gamma-Ray
Telescopes
Brief History of Gamma Ray Astronomy
2008 Fermi (GLAST): All-sky monitoring of the MeV – GeV sky every 3 hr with
sensitivity a factor of > 10 better than EGRET.
2004 Swift: Dedicated g-ray burst mission: prompt X-ray/optical follow-up;
arcsecond localization of GRBs
2002 INTEGRAL: Major advances in high-resolution imaging and spectroscopy of
Galactic g-ray sources
1997 BeppoSAX: First high-precision localization of g-ray bursts;
cosmological origin of GRBs established
1991 CGRO: First all-sky survey of the g-ray sky; major discoveries in all areas of
g-ray astronomy; g-ray astronomy becomes an integral part of astronomy
1989 SIGMA: First high-resolution images (13’) in hard X-rays / soft g-rays
1987 Whipple (ACT): First credible detection of a TeV source (Crab Nebula)
1981 SMM: Studies of solar flare g-ray emission; 56Co-lines from SN 1987A
1979 HEAO-3: Discovery of radioactive 26Al emission in the Milky Way
1975 COS-B: First detailed g-ray map of the Milky Way with 24 point sources
1972 SAS-2: First high-energy g-ray images; discovery of Geminga pulsar
1968 OSO-3: Discovery of > 100 MeV g-ray emission from the Milky Way
1967 VELA satelllites: Discovery of g-ray bursts (not published until 1973)
1961 EXPLORER-II: First detection of high-energy g-rays from space
1) The Compton Gamma Ray Observatory (CGRO)
(1991 – 2000)
Oriented ScintillationSpectrometer Experiment
(OSSE): ~ 0.1 – 10 MeV
Compton Telescope (COMPTEL):
~ 1 – 30 MeV
Energetic Gamma-Ray
Experiment Telescope
(EGRET): pair conversion
telescope,
~ 20 MeV – 30 GeV
Burst and Transient Source
Experiment (BATSE):
0.015 – 110 MeV
2) The International Gamma-Ray Astrophysics
Laboratory (INTEGRAL)
Launched 2002
Two g-ray telescopes:
Imager on Board the
INTEGRAL Satellite (IBIS),
optimized for high spatial
resolution;
Spectrometer on INTEGRAL
(SPI), optimized for high
spectral resolution.
Energy range: ~ 20 keV – 8 MeV
Both use coded-mask technique for imaging.
3) AGILE
(Astro-rivelatore Gamma a Immagini LEggero)
Italian gamma-ray satellite
mission; launched April 23, 2007
Similar technology and capabilities as
EGRET, intended to bridge the gap
between EGRET and Fermi (GLAST)
Two instruments:
Gamma-Ray
Imaging
Detector (GRID):
SuperAGILE:
30 MeV – 50 GeV
18 – 60 keV
4) The Fermi Gamma-Ray Space Telescope
(formerly: Gamma Ray Large Area Space Telescope
(GLAST)
Launched June 11, 2008
Similar technology as EGRET
(pair conversion), but much
improved sensitivity, large field
of view (~ p sr), and slightly
extended energy range (~ 20
MeV – 300 GeV).
Will operate in constant
slewing mode to survey the
sky for flaring high-energy gray sources:
One full-sky scan every 3 hr.
Fermi
Two main science
instruments:
• LAT (Large
Area Telescope)
• GBM (GLAST
Burst Monitor)
The Large Area Telescope (LAT)
Pair Conversion Telescope
Quantity
LAT
EGRET
Energy Range
20 MeV – 300 GeV
20 MeV – 30 GeV
Peak Effective Area
> 8000 cm2
1500 cm2
Field of View
> 2 sr
0.5 sr
Angular Resolution
< 3.5o (at 100 MeV)
< 0.15o (at > 10 GeV)
5.8o (at 100 MeV)
Point Source Sensitivity
< 6*10-9 cm-2 s-1
10-7 cm-2 s-1
The LAT First-Light All-Sky Map
All-Sky Map
The GLAST Burst Monitor (GBM)
All-sky Monitor optimized
to detect X-ray / soft g-ray
flashes
(~ 8 keV – 30 MeV)
Source localization to < 15o
5) Atmospheric Cherenkov Telescopes
Experiment
Technique
Ethr (TeV)
Location
Whipple
IACT
0.25
Arizona, USA
HEGRA-IACT
IACT array
0.50
Canary Islands
CANGAROO-II
IACT
0.1
Woomera, Australia
HEGRA-AIROBICC
Wavefront
sampling
15
Canary Islands
Themistocle
Wavefront
sampling
3
Themis, France
STACEE
Solar Tower ACT
0.05
Albuquerque, NM, USA
HESS
IACT array
0.04
Gamsberg, Namibia
MAGIC
IACT
0.01
Canary Islands
VERITAS
IACT array
0.05
Arizona, USA