Post on 30-Dec-2015
Gamma-ray Astronomy of XXI Century 100 MeV – 10 TeV
1 keV 1MeV 1 GeV 1 TeV
Focusing Coded mask
Comptontelescopes
g-conversion + calorimeter EGRET, Fermi
Cherenkovtelescopes
Colli
mat
ors
Objects visible in gamma-rays:
- GRBs
- Blazars & AGNs
- Gamma-ray pulsars
- Supernova remnants
- Diffuse background
1991 – 2000 «Compton, EGRET» 30 MeV – 100 GeV
2008 Fermi 20 MeV – 300 GeV
2000 - Cherenkov telescopes 20 GeV - 50 TeV
Batse GRBs
Fermi
Pass 7 vs. Pass 6
Pass 6 Pass 7
The break is very close to the He II absorption threshold!
Pass 6 front/back
Gamma-ray bursts
Coincidence time + location
50 s
2o
Express search for transients in Fermi data
3-x coincidence
Near-polar horizon
Vela pulsarGeminga
3C454
GRB
GRB GRB
GRB
Fall 2009 (4 of 12 GRBs)
Now ~100
Short ~1.5 s
Time, s
> 30 GeV
QuasarsCyg A
3C 273
M 87
E > 1 GeV
E > 100 MeV
3C454.3
3C454.3
g – g -> e+ e-
He II Lya edge53 eV
Stern & Poutanen
Photon-photon absorption breaks in Fermi spectra of bright blazars
gGeV + gUV e+ e-
Poutanen & Stern 2010
Stern & Poutanen 2011
Stern & Poutanen 2014
Jet Broad line region
Pass6
Stacking analisys
Stern & Poutanen 2012
Fortunately
unpublished
medium ionization
x = 1.5
medium ionization
High ionization
x = 2.5
high ionization
g – g absorption He II Lya and H Lya
4s
6s
Broad line region~ 103 R
g
Infrared dust radiation~ 105 R
g
CMB 108 R
g
Where the GeV radiation comes from?
Looks like from ~ 103 RGG~ sqrt(R/Rc)
The jet launch is from the BH (Blandford-Znajek)Disk launch implies >104 RG
Emission mechanism is still unknown
1. Fermi acceleration in the jet due to internal perturbation (internal shocks, turbulence) + external Compton + some synchrotron
Don’t speak about synchrotron – self Compton!!!
2. Photon breeding Stern & Poutanen 2006 – 2008High energy photons produce a viscous friction between the jet and the external environment (works at G > 20 and a “strong” external environment)
The jet is decelerated down to G ~ 15 independently of initial G
FSRQs (broad emission lines, softer spectra, softer low energy hump, very powerful)
Versus
BL Lacs (no broad emission lines, harder spectra, harder low energy hump, less powerful)
BL Lacs z ~ 0.05 – 0.4
Гамма-пульсары
Gamma-pulsars
Absorbed spectra of gamma-pulsarsEa ~ 1 – 5 GeV
Fermi Yield
Blazars 1100 (650 – BL-Lacs + 450 – FSRQs)
AGNs 680
Gamma-ray pulsars 137 +29
Unidentified 1000
Diffuse emission from dark regions of the sky (0.25)
Galactic plane
po production?
The diffuse background
Galactic center 4o
Here people “observed” the dark matter annihilation line
Cosmic rays + gamma pulsars
Galactic emission
Galactic plane
Galactic center
CTA ~ 0.4 km2 (North) + 4 km2 (South)
H.E.S.S. II 105 m, energy threshold 20 GeV
MAGIC~104 m2
Threshold 25 GeV
Mkn 421
VERITAS 105 m2
50 GeV
Arizona
4100 kg
Calorimeter25 lr
Gamma-400
Conclusions:
1. Gamma-ray astronomy becomes a precise science due to Fermi.
2. The uncertainties in calibration much exceed statistical errors
3. The main task for Cherenkov telescopes is the cross-calibration with Fermi and coordinated observations (IMHO)
4. The gap between X-rays and 100 Mev should be covered by any means
5. Open data are of crucial importance