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unpublished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