Transcript VHE Galactic Gamma Ray Source Populations F.A. Aharonian (MPI-K, Heidelberg)

VHE Galactic Gamma Ray
Source Populations
F.A. Aharonian (MPI-K, Heidelberg)
THE MULTI-MESSENGER APPROACH TO UNIDENTIFIED GAMMA-RAY SOURCES
Barcelona 4-7 July, 2006
TeV Galactic Sources
SNR
MSH 15-52
Cas A
PWN
XRB
TeV J2032+4130
unidentified
Vela X
Crab
LS I+61 303
RX J0852-4622
LS 5039
RX J1713-3946
plus four identified molecular clouds in the Galactic Center
J.Hinton/A.Kappes
Whipple (1), HEGRA (2), CANGAROO (2), MAGIC (1), H.E.S.S. (24)
H.E.S.S. galactic plane survey
TeV and CO data:
narrow distributions
in the Galactic Plane:
NANTEN
CO observations
Fukui et al.2005
because of GMCs ?
Star Formation Regions ?
or (most likely) both ?
Performance and Potential of HESS

Energy range
100 GeV - 100 TeV

Energy resolution
15 - 20%

Angular resolution
3 - 6 arcmin

10 Crab

30 sec
20min
25 hours
1 sec
Field of View 5o
Lg(>100 GeV)=2.5x1032 (d/1kpc) -2 (fg/10-12 erg/s)
0.003 Crab
requires 200 h
-13 erg/cm2 s level at 1 TeV
spectrometry
10

morphology
better than Chandra/XMM
for >0.1 deg objects !







Sensitivity:
1 Crab
0.1 Crab
0.01 Crab

0.1
Crab -multi-functional
min detectiontool
time
HESS
- effective
in for
broad energy
range (2+ decades) for
probing VHE sources
at thehour
level
Whipple/HEGRA
– 25-50
timing
surveys
10 Crab (i) strong flares of Mkn 421/501
extended(ii)
sources:
GMCs,
etc.
energySNRs,
flux PWNe,
of EGRET
sources
(iii) several orders of magnitude
compact variable (periodic) sources:
less than
typical
GRB fluxes
binary pulsars,
mQSOs,
...
Contribution
in several
topical
areas:
 Great
3 arcmin
- angular
resolution
of ASCA

5o FoV plus 0.1 Crab for < 1 h –
GCRs – SNRs,
strong shocks,
DSA, ... surveys !
sufficient
for effective
Pulsars – Pulsar Winds, Plerions

huge detection area
mQSOs – High Energy Processes in Jets,...
huge TeV photon statistics
Galactic TeVatrons and PeVatrons –
particle accelerators
responsible for CRs up to 1015 eV
SNRs ?
Pulsars/Plerions ?
O & B stars ?
Microquasars ?
Galactic Center ?
Gaisser 2001
...
* the source population responsible for the bulk of GCRs are PeVatrons ?
Origin of Cosmic Rays:
a mystery since the discovery in 1912 by V. Hess …
but now we are close (hopefully) to the solution of the
(galactic) component below the energy 1015 eV thanks to
IACT
arrays
capability for deep spectrometric and morphological
studies of g-rays from SNRs in the crucial energy band
100 GeV to 100 TeV
GLAST
will provide additional (complementary)
information in the energy domain 100 MeV-100 GeV
km3
scale TeV neutrino detectors will provide unambiguous
information about the hadronic component of radiation
Cosmic Ray Studies with Cosmic Rays
or what do we know about Cosmic Rays ?



flux is dominated by hadronic component
energy spectrum
dN/dE=kE-2.6-2.7 up to the “knee”
content of secondaries:
l=5 (E/10GeV)-0.6 g/cm2
source spectrum close to E-2.0-2.1
particle production rate
3 x 1040 erg/s
because of deflections in ambient random magnetic fields
the information about the production sites is lost …
SNRs – the most probable factories of GCRs ?
(almost) common belief based in two arguments:


necessary amount of available energy – 1051 erg
Diffusive Shock Acceleration – >10% efficiency and E-2 type
(talk of L. Drury)
spectrum up to at least 1015 eV
Straightforward proof: detection of gamma-rays and neutrinos from
pp interactions (as products of decays of secondary pions)
Objective: to probe the content of nucleonic component of CRs
in SNRs at d < 10 kpc at the level 1049 -1050 erg
Realization: sensitivity of detectors - down to 10-13 erg/cm2 s
crucial energy domain
-
VHE/UHE (up to 100 TeV)
Visibility of SNRs in high energy gamma-rays
for CR spectrum with a=2
Fg(>E)=10-11 A (E/1TeV)-1 ph/cm2s
p0 –decay (A=1)
1o
0.1o
sensitivity
Crab
A=(Wcr/1050erg)(n/1cm-3 )(d/1kpc) -2
1000 yr old SNRs (in Sedov phase)
Detectability ? compromise between
angle q (r/d) and flux Fg (1/d2)
typically A: 0.1-0.01 q: 0.1o - 1o
TeV g-rays – detectable if A > 0.1
po component
0.1 (Sx/10 mJ)(B/10
mGand
) -2 IC TeV g’s
if electron
spectrum >>dominates
10 TeV if A >synchrotron
X-rays
-2
nucleonicmain
component
of CRs field
- “visible”
TeV=0.1
(and
GeV) gamma-rays
!
target photon
2.7 K: through
Fg,IC/Fx,sinch
(B/10mG)
Cosmic Ray Accelerators ?
SNRs in our Galaxy: 231(Green et al. 2001
with nonthermal X-ray emission - 10
or so
best
candidates - young SNRs with
nonthermal synchrotron X-rays
SN1006
Diffusive source
30 arcmin
H.E.S.S. PSF
Tycho Kepler
TeV emission
CasA
SN 1006 - a good candidate for particle source acceleration
H.E.S.S. upper limits - an order of magnitude below
the flux reported by CANGAROO
a trouble ?
not at all …
HESS upper limits imply
IC : B > 25 mG
po : Wp<(0.2-2) x 1050 erg
no problem for the hypothesis
of SNR origin of Galactic CRs …
Cas A – a proton accelerator
Wp=2x1049 erg
, n=20 cm-3
5-6 sigma detection
B > 0.1 mG
IC origin is unlikely;
TeV gamma rays of hadronic origin ?
yes, although Wp =1049 erg (only)
Cas A is well designed to operate as a PeVatron ?
with a “right“ combination of B-field, shock speed and age to accelerate
and confine particles up to 1 PeV - a source of >10TeV g -rays and neutrinos?



very important target for VERITAS and MAGIC
GLAST should detect GeV gamma-ray emission in any case
no way to detect TeV neutrionos even with km3 scale detectors
two young “1Crab“ strength shell type SNRs
Vela Junior
flux and spectrum - similar,
talk of M. Lemoine
RXJ1713.7-3946
morphology – rather different
RX J1713.7-3946
structure of the entire remnant (XMM-Newton)
XMM FOV
0.7-2keV, resolution 15”
Chandra FOV
Chandra image
RXJ1713.7-3946 is a TeV source !
energy spectrum and morphology
G=2.1-2.1 with a
curvature cutoff (?)
at high energies
G=2.1-2.2 -evidence of DSA of protons ?
no significant spectral variation
RX 1713.7-3946:
interpretation
the key issue - identification of g-ray
emission mechanisms: – p0 or IC ?
energy spectra 150GeV-30 TeV
from different parts - NW, S W, E,C
coordinate-independent from 0.2 to 10 TeV
difficult to explain by IC (?)
implications ?
if p0 - hadronic component is detected !
estimate of Wp (with an uncertainty
related to the uncertainty in n/d2 )
TeV-keV correlations …
what this could mean?
if IC - model independent estimate of We
(multi-TeV electrons) Le=Lx and
model independent map of B-field
Origin of radiation ?

hadronic origin preferable given
the high density environment:
Wp (above 10 TeV) = 3x1049 (n/1 cm-3) -1 erg

IC origin is not (yet) excluded, but this model
requires B – field less than 10 mG
more complex scenarios ? e.g. g-rays from NW+SW are contributed by
protons while gamma-rays from remaining parts are due to IC g-rays …
HESS observations with 4 telescope in 2004 and 2005
provide higher quality data and … certain answers ?
IC model:
DSA time:
B-field cannot exceed 10 mG and …
does not provide good spectral fit
tacc t 1,000 (Ee/100TeV)(v/3000km/s)-2 (B/10mG) -1 yr
limit from synch. losses: Ee,max t 100 (B/10mG)-1/2 (v/300km/s) TeV
steeper electron acceleration spectra ? a better fit, but …
conflict with radio and 2 orders of magnitude larger energetics
older source ?
two zone model ?
tesc=50 tB (prop. 1/E); B1=3 mG, B2=15mG; R=3 pc
no evidence for
such component
of IC radiation
pp
po
gg – perfect spectral fits,
reasonable energetics !
protons:
dN/dE=K E-a exp[-(E/Ecut)b]
g-rays:
dN/dE v E-G exp[-(E/E0)bg]
Gw a+da, da w 0.1, bg w b/2, E0 . Ecut/20
Wp(>1 TeV) w 0.5x1050 (n/1cm-3)-1 (d/1kpc)2
spectrum of protons ?
GLAST, HESS Phase-2
Wp = 1050 (n/1cm-3)-1 erg ; n close to 1 cm-3 ? preferable –
can explain the production rate of GCRs by SNRs
One needs
fluxthan
measurement
below
100 GeV and above 10 TeV
Eo significantly
smaller
1000 TeV ?, yes,
although
that could be connected with the fast escape of protons from
accelerator, so RXJ 1713 still could be treated as a PeVatron
3 channels of information
about cosmic PeVatrons:
10-100 TeV gamma-rays
10-100 TeV m-neutrinos
10 -100 keV hard X-rays
sensitivities ?
better than 10-12 erg/cm2s
 g-rays: difficult, but possible with future “10km2“ area multi-TeV IACT arrays
 neutrinos: difficult, but KM3NeT should be able to see (marginal) signals from
SNRs RX 1713.7-3946 and Vela Jr (see poster b y Stegmann et al.)
 “prompt“ synchrotron X-rays: a very promising channel
(NexT, NuSTAR, SIMBOL-X)
energy spectra of secondary gamma-rays, electrons and neutrinois
total inelastic pp cross-section
and
production rates of g and nm for
power-law spectrum of protons:
nH =1 cm-3 , wp=1 erg/cm-3
Probing PeV protons with X-rays
SNRs shocks can accelerate CRs to <100 TeV (e.g. Cesarsky&Lagage 1984)
unless magnetic field significantly exceeds 10 mG
Recent theoretical developments: applification of the B-field up
to >100 mG is possible through plasma waves generated by CRs
(Bell and Lucek 2000)
>1015 eV protons
>1014 eV gamma-rays and electrons
“prompt“ synchrotron X-rays
cooling time:
t(e) w 1.5 (e/1keV) -1/2 (B/1mG) -3/2 yr << tSNR
energy range:
typically between 1 and 100 keV with the ratio Lx/Lg
larger than 20% (for E-2 type spectra)
“hadronic“ hard X-rays and (multi)TeV g-rays – similar morphologies !
Basic Features
acceleration spectrum of protons:
dN/dE=AE-a exp[(-E/Eo)b ]
production spectra of g-rays, electrons, nm :
Qi(Ei)=QoEi-a+da exp[(-E/Ei,o)d]
(i) Da w 0.05-0.1; (ii) d w b/2; (iii) Ei,ow (1/20-1/100)Eo
good news ! cutoffs in the g-ray (e, n) spectra are smoother;
(relatively) easy to detect, but for spectrometry
one needs good photon statistics up to 100 TeV
important to have: IACT arrays designed for 10-100 TeV band
complementary multi-TeV neutrino detectors
and detect hard X-ray synchrotron emision of secondary electrons
the index of the exponential cutoff in the production spectra of g-rays (dg)
and electrons (de) versus the power-law spectral index of of protons a for
3 different b (0.5, 1, 2) and two Eo (10 TeV – dashed, 103 TeV – solid curves)
“hadronic“ X-rays versus synchrotron radiation of primary electrons:
electron injection spectrum Qe(Ee)=QoEe-a exp[(-Ee/Ee,o)s ]
spectrum of synchrotron radiation of cooled electrons
e-(a/2+1) exp[(-e/eo)l]
eo :
l= s/s+2; b=1
s=0.5, l=1/5
characteristic synchrotron frequency proportional BEo2 ( prop. to B3 ) *
for Eo =1 PeV, B=1 mG
X-ray emission extends well beyond 10 keV
while the cutoff energy in the synchrotron spectrum from directly
accelerated electrons is expected around 1(vshock/3000 km/s)2 keV
simultaneous measurements of p0-decay g-rays and associated
synchrotron radiation provide unambiguous estimate of B-field
in the acceleration region !
* in the Bohm diffusion regime
protons
broad-band
GeV-TeV-PeV
gs
synch. hard X-rays
Broad-band emision initiated by pp interactiosn : Wp=1050 erg, n=1cm-3
searching for galactic PeVatrons ...
TeV gamma–rays from Cas A and RX1713.7-3946, Vela Jr –
a proof that SNRs are responsible for the bulk of GCRs ?– not yet
the hunt for galactic PeVatrons continues
unbiased approach – deep survey of the Galactic Plane – not to
miss any recent (or currently active) acceleration site:
SNRs, Pulsars/Plerions, Microquasars...
not only from accelerators, but also from nearby dense regions
Gamm-rays/X-rays from dense regions surrounding accelerators
the existence of a powerful accelerator by itself is not sufficenrt for
gamma radiation; an additional component – a dense gas target - is required
gamma-rays from surrounding regions add much to our knowledge about highest
energy protons which quickly escape the accelerator and therefotr do not significantly contribute to gamma-ray production inside the proton accelerator-PeVatron
older source – steeper g-ray spectrum
tesc=4x105(E/1 TeV) -1 k-1 yr (R=1pc); k=1 – Bohm Difussion
Qp /
E-2.1 exp(-E/1PeV)
Lp=1038(1+t/1kyr) -1 erg/s
Formation of extended TeV sources due to GMCs and 2.7 K
Giant Molecular Clouds (GMCs) as tracers of Galactic Cosmic Rays *
GMCs - 103 to 105 solar masses clouds physically connected with star formation regions - the likely sites of CR accelerators (with or without SNRs)
perfect objects to play the role of targets for hadronic component of GCRs
2.7K MBR - target leading to formation of extended TeV IC sources
morphology of g-ray sources
– information about spatial distribution
of Ee t 20 (Eg/1TeB)1/2 TeV electrons
flux/energy spectrum of g-rays - unambiguous information about energy
distribution and total energy of electrons
unique channel of informtion in Astrophysics
* talk by
S. Gabici
First Unidentified TeV source TeV J2032+4130
found by HEGRA seredipiously (6 sigma signal accumulated 100h from
the Cygnus region and confirmed in 2002 by pointing observations (130 h)
Basic features – hard power-law spectrum (photon index 1.9), constant flux
and slightly extended (about 5 arcmin) source
Origin ?
leptonic (IC) origin is almost excluded, possibly dense gas cloud(s)
illuminated by protons arriving from a recent nearby Pevatron ?
if this object is a representative of a large source population, the planned survey
of the Galactic Disk by H.E.S.S. will reveal (many ?) more new hot spots
HongKong 2004
Electrons: Inverse Compton ?
B-field smaller than 3 10-6 G (!)
Source age less than 1000 yr (!)
otherwise even for very slow (Bohm !)
diffusion gamma ray source should be
largder than 5 arcmin (for d=1.6 kpc) !
Electrons: Bremsstrahlung ?
typically at VHE energies IC
is the most effective gamma-ray
production channel:
e.g. for IC in 2.7K MBR:
tIC(Eg) t 6x105 (Eg/1TeV) -1/2 yr
the cooling time for bremsstrahlung
tbr(Eg) t 107 (n/1cm-3) -1 yr
in dense gaseous environments with
n >> 100 cm-3 bremsstrahlung can
well dominate over inverse Compton
more ”comfortable” parameters …
Protons ? spectrum should extend at least to 100 TeV
protons …
young source
Gamma-ray spectrum should strongly depend on the diffusion (escape)
unless the diffusion is energy independent or escape is due to convection
older source
conflict with radio ?
weak B-field ?
change
or low-energy cutoff ?
Warning ! if the gamma-ray source box is empty (“dark accelerator“) this
cannnot be interpreted as evidence that we deal with a hadronic source
Conclusions ?
the source should be young, CR confinement - effective,
but at the same time magnetic field cannot be very large ...
Solution ? low-energy cutoff in the proton spectrum
•
a hadron-dominated pulsar wind (talks by Bednarek, Horns)
•
a GRB remnant (Atoyan et al. 2006)
•
accelerator and target are separated:
effective confinement of low energy protons in the accelerator
faster propagation of highest energy particles (Bosch-Ramon et al. 2005)
•
effects related to energy-dependent propagation
of CRs towards the core of the cloud (talk by Gabici).
first unidentified sources found by HESS !
Feb 2004
March 2004
PSR1259-63
the zoo of the HESS galactic sources
talk by S. Funk
gamma-ray production mechanisms in Extended HESS sources
characteristic timescales:
p+p
p0
gg
e+2.7 K
eg
e-bremsstrahlung
tpp=1x1015 (n/1cm-3) -1 sec
tIC=4x1012 (E/10 TeV) -1 sec
tbr=3x1014 (n/1cm-3) -1 sec

IC is very effective as long as magnetic field B < 10 mG

Bremsstrahlung important in dense, n > 102 cm-3 , environments

pp interactions dominate over Bremsstrahlung if the ratio of energy
densities of protons to electrons wp/we > 10, and dominate over IC
component if wp/we > 500 (n/1cm-3) -1 (at energies above 10 TeV)
Morphology vs. Energy Spectrum
morphology: pp: depends on spatial distributions of CR and gas: nH(r)xNp(r)
IC: depends only on spatial distribution of electrons: Ne(r)
energy spectra: depends on acceleration spectrum Q(E), energy losses dE/dt,
age of accelerator to, and character of propagation/diffusion coefficient D(E)
pp: generally energy spectrum independent of morphology, but for young
objects energy spectrum could be harder at larger distances than near
the accelerator
angular size increases with energy *
IC: very important are synchrotrin energy losses;
weak B-field ( <10 mG) and/or fast diffusion
angular size increases with energy
strong B-field (100 mG) and/or slow diffusion
angular size decreases with energy
irregular shapes of g-ray images : because of inhomogeneous distrubition
of gas (pp) or unisotropic propagation of cosmic rays (pp or IC)
* however opposide morphology (“higher energy – smaller size“) also is possible if in the past
an activity of the source was accompanied with CR acceleration with soft(er) energy spectrum
Crab Nebula – a perfect PeVatron of electrons (and protons ?)
1-10MeV
Standard MHD theory
MAGIC (?)
.
100TeV
HEGRA
cold ultrarelativistc pulsar wind terminates
by a reverse shock resulting in acceleration
with an unprecedented rate: tacc=hrL/c, h < 100 *)
synchrotron radiation => nonthermal optical/X-ray nebula
Inverse Compton
=> high energy gamma-ray nebula
Crab Nebula – a very powerful W=Lrot=5x1038 erg/s
and extreme accelerator: Ee > 1000 TeV
Emax=60 (B/1G) -1/2 h-1/2 TeV and hncut=(0.7-2) af-1mc2 h-1 = 50-150 h-1 MeV
h=1 – minimum value allowed by classical electrodynamics
Crab: hncut= 10MeV: acceleration at 1 to 10 % of the maximum rate ( h=10-100)
maximum energy of electrons: Eg=100 TeV => Ee > 100 (1000) TeV
B=0.1-1 mG
– very close the value independently derived from the MHD treatment of the wind
* for comparison, in shell type SNRs DSA theory gives h=10(c/v)2=104-105
Crab is not only a standard candle for calibration
of detectors but should be treated as a highest
priority target for GLAST/MAGIC/VERITAS/HESS



Energy-dependent size
(MAGIC –II and VERITAS)
Energy spectrum around and below
100 GeV (GLAST,MAGIC,VERITAS)
detection or upper limits on the linetype emission due to Comptonization
of cold ultrarelativisic pulsar wind
(GLAST,MAGIC,VERITAS)

maximum energy in the spectrum
beyond 50 TeV (HESS)
EGRET
TeV gamm-rays from other Plerions ?
Crab Nebula is a very effective accelerator
but not an effective IC g-ray emitter
We see TeV gamma-rays from the Crab Nebula because of
very large spin-down flux
but gamma-ray flux << “spin-down flux“
because of large magnetic field
but the strength of B-field also depends on
less powerful pulsar
weaker magnetic field
higher gamma-ray efficiency
detectable gamma-ray fluxes from other plerions
HESS confirms this prediction ! ( ? ) – several famous PWN
already detected - MSH 15-52, PSR 1825, Vela X, ...
* Plerions – Pulsar Driven Nebulae
HESS J1825 (PSR J1826-1334)
keV image
TeV image
“offset morphology“ seen in X-rays
and, on larger scales, in TeV g-rays
Pulsar‘s period: 110 ms, age: 21.4 kyr,
distance: 3.9 +/- 0.4 kpc
Luminosities:
spin-down:
Lrot= 3 x 1036 erg/s
X: 1-10 keV
Lx=3 x 1033 erg/s (< 5 arcmin)
g: 0.2-40TeV
Lg=3 x 1035 erg/s (< 1 degree)
the g-ray luminosity is comparable to the TeV luminosity of the Crab Nebula, while the
spindown luminosity is two orders of magnitude less !
Implications ?
(a) magnetic field should be significantly less than 10mG.
but even for Le=Lrot this condition alone is not sufficient to achieve 10 % g-ray production
efficiency (Comton cooling time of electrons on 2.7K CMBR exceeds the age of the source)
(b) the spin-down luminosity in the past was much higher.
first direct evidence of energy dependent morphology in VHE g-rays!
red – below 0.8 TeV
yellow – 0.8-2.5 TeV
blue – above 2.5 TeV
Energy spectrum
of whole PWN
significant softening of g-ray spectrum
away from the position of the pulsar:
spatially resolved spectral analysis of
HESS J1825-137 : flux (>1 TeV) versus
photon index derived for 0.3-10 TeV
evidence in favor of IC origin of g-rays!
Energy-Angular distributions of Synch. and IC radiation components
TeV g-ray
X-ray
50
50
10
30’
10
30’
15’
15’
3’
3’
Le=1036 erg/s, Q(E)=Qo E-2 exp(-E/103 TeV), age T=10,000yr
D(E)=Do(E/10 GeV)b , Do=1027 cm2/s, b=1/3, d=1kpc, B=5mG
R=[2D(E) t(E)] ½ ; tr=a/E => R(E) = const only when b=1
Hong Kong 2004
MSH 15-52
dN/dE  E-G
G = 2.270.030.15
2/n = 13.3/12
Flux > 280 GeV
15% Crab Nebula
since 2.7 K MBR is the main target
field, TeV images reflect spatial
distributions of electrons Ne(E,x,y);
coupled with synchrotron X-rays, TeV
the energy spectrum - a perfect hard powerlaw with photon index G=2.2-2.3
over 2 decades !
images allow measurements of B(x,y)
(unless intense IR sources around)
• hadronic (po-decay) origin of g-rays ?
• cannot be easily explained by IC…
HESS J0835-456 (Vela X) –
the image of TeV electrons ! (?)
spectral index
break around
total energy
G=2 with a
70 TeV
We=2 x 1045 erg
do we see the Compton peak ?
photon index 1.45 with
exponential cutoff at 13.8 TeV
questions:
B-field – as weak as several mG or even less ?
energy in ultrarelativistic electrons only 2x1045 erg ?
integrated energy over 11kyr: >2.5x1048 erg – in which form the “dark energy“ is released?
(‘inisible‘) low energy electrons or in ultrarelativistic protons ? (!)
Vela X as a proton PeVatron ?
dN/dE=AE-1.5 exp[-(E/300TeV)2]
note: a=1.5, b=2 !
for d=300 pc, n < 1cm-1, Wp > 1049 erg –
protons from early epochs ?
pulsar wind consisting of protons and nuclei ?
Horns et al. 2006
dNp/dE=AE2 exp[-(E/80TeV)2]
B=10 mG
Wp = 1.3 x 1049 (n/0.6cm-3) erg
We=1045 (B/10mG) -2 erg
total spin down energy released over the
last 11kyr: 5 x1048 – 5 x1051 erg depending
on the braking index (time-history of Lrot)
for B=100 mG – half of X-ray flux can
be explained by secondary electrons
High Lrot in the past
PSR1259-63 - a unique high energy laboratory
binary pulsars - a special case with strong effects associated with the
optical star on both the dynamics of the pulsar wind
and the radiation before and after its termination
the same 3 components - Pulsar/Pulsar/Wind/Synch.Nebula - as in plerions*
both the electrons of the cold wind and shocke-accelerated electrons are illuminated by
optical radiation from the companion star
detectable IC g-ray emission
HESS: detection of TeV gamma-rays from PSR1259-63 at < 0.1Crab level
several days before the periastron and 3 weeks after the periastron
the photon field is a strong function of time, thus the only unknown parameter is B-field:
TeV electrons are cooled and and radiate in deep Klein-Nishina regime with
very interesting effects on both synchrotron X-ray and IC gamma-rays
* but with characteristic timescales much shorter - less than 1 h !
energy flux of starlight
close to the periastron
around
1 erg/cm3
B-field is estimated
between 0.1 to 1 G
predictable X and
gamma-ray fluxes ?
time evolution of fluxes and energy spectra of X- and g-rays contain unique
information about the shock dynamics, electron acceleration, B(r), ...
while the gamma-ray energy spectrum
can be explained by IC mechanism
the lightcurve is still a puzzle …
deep theoretical (in particular MHD)
studies needed to understand the source
an improvement of the HESS sensitivity by a factor of >3
for comprehensive study of the lightcurve of this source
Explanation of the TeV lightcurve within the IC model
time (position) dependent adiabatic losses
energy losses of electrons versus
separation distance D between
the pulsar and companion star:
B=0.05(Do/D) Gauss
minimum at periastron at all energies
see poster of M.Khangulyan
Explanation of the TeV lightcurve within the IC model
variation of the maximum energy of electrons
100 d
escape
+/-20 d
+/-10 d
periastron
Bo=0.05 (Do/D) Gauss,
tacc= h rL/c ; h=4x103
minimum at periastron at high energies,
but maximum – at low energoes
see poster by M.Khangulyan
Explanation of the TeV lightcurve by Comptonization of the wind
reduction of the Lorentz factor
of the electron-positron wind
Probing the unshocked wind Lorentz factor
GLAST
the effect is not negligible, but not
sufficient to explain the lightcurve
Loretz factors exceeding 106 are excluded
see poster by M. Khangulyan
Explanation of the TeV lightcurve by interactions with the wind
assuming a specific position of the stellar
disk the excess of the radio, X-ray and
TeV g-rays can be explained as result of
the entrance of the pulsar into the disk ...
pp interactions responsible for g-rays?
radio and X-ray – result of synchratron/IC
of low-energy electrons?
talk by A. Neronov
TeV Gamma Rays From Microquasars !
HESS, 2005
MAGIC, 2006
Predicting TeV g-rays from mQSOs? Why?





they are scaled-down versions of AGN, in particular blazars
no problem with d < 1; it is compensated by larger LEdd/d2 (MBH/d2 in
mQSOs is larger, by several orders of magnitude, than in BL Lacs)
relativistic outflows are very (most) effective sites for acceleration of
particles to TeV energies and beyond
large scale synchrotron jets discovered from mQSOs !
SSC modeling of GRS 1915 based on R and IR data, and assuming that the
electron spectrum extends to >10 TeV leads to detectable IC g-ray fluxes
provided that B-field is somewhat below its equipartiton value
no strong evidence of TeV gamma-rays from GRS1915
mQSOs in binary systems with very luminous optical companion stars
enhanced IC emision because of copious target (starlight)
we do see TeV gamma-rays from such systems !
gamma-rays from hadronic interactions ?
actually we do not need them, but who knows ...
LS 5039: X-ray
binary - BH + O7
presence of two basic components for TeV gamma-ray production !


0.2c jet as accelerates electrons (protons ?) to TeV energies
1039 erg/s companion star provides seed photons for IC or pg
or dense wind for pp interactions
scenario ?
both g-ray production region within (despite tgg >> 1)
and outside the binary system cannot be excluded
LS5039 as a (detectable) neutrino source ?
if TeV gamma-rays are produced within
the binary system (R < 1012cm)

severe absorption of >100 GeV
gamma-rays (g + starlight -> e+e-)
up to a factor of 10 to 100
higher initial luminosity
 severe radiative losses
difficult to accelerate
electrons to multi-TeV energies
Conclusions ? TeV gamma-rays of hadronic origin with high luminosity,
and consequently high detectable TeV neutrino fluxes (!?)
If gamma-rays are produced within the bunary system and cascading is
TeV
neutrino
depend TeV
o the
production
sitefrom
of g-rays:
prevented
byfluxes
strongstrongly
B-field (>10G),
neutrino
signals
LS5039
the jet/accretion
disk and/or
of the star
andthe
LSbase
I+61of
mQSOs
can be detected
by km3wind/atmosphere
volume scale (KM3NeT
and IceCube) Telescopes (talk by C. Distefano, poster by Stegmann et al.))
TeV g-rays from GC
GC – a unique site that
harbors many interesting
sources packed with unusually high density around
the most remarkable object
3x106 Mo SBH – Sgr A*
HESS:
FoV=5o
many of them are potential g-ray
emitters - Shell Type SNRs
Plerions, Giant Molecular Clouds
Sgr A * itself, Dark Matter …
all of them are in the FoV HESS !
and can be probed down to a flux
level 10-13 erg/cm2 s and
localized within << 1 arcmin
TeV g-rays from central <10 pc region of GC

Annihilation of DM ? mass of DM particles > 10 TeV ?

Sgr A* : 3 106 Mo BH ? yes, but lack of variability …
even the inner R < 10 Rg region is transparent for TeV g-rays !
 SNR Sgr A East ?
why not ?
 Plerionic (IC) source(s) why not ?

Interaction of CRs with GMCs ?
easily
Sagittarius A - point-like but not variable …
syst. error
power-law index 2.3
Colors: H.E.S.S.
Contours: Radio
pp gamma-rays in the central 10 pc region
Qp(E)=Qo E-a exp(-E/1 PeV), D(E)=1028(E/1GeV) b
k cm2/s; k=1,
b=0.5-0.6 -diffusion in GD
if tpp < tesc => po-decay g-ray production
-3 )
tinpp“saturated”
= 50 kyr regime
(n=103 cm
=> Lg
=1/3 Lp,
otherwise the flux and spectrum of gs
not
only on CR-1injection
power
tdepend
(E/100TeV)
(B/100mG)
kyr
esc =300
and spectrum,
butDiffusion)
also on the (energy
(Bohm
dependent) propagation of CRs in ISM
1. fast diffusion : G
a+b
Lp=7.5 x 1037 erg/s
2. slow diffusion: G
a
Lp=6.9 x 1036 erg/s
3. Diffusion-to-rectlinear prop.
G=a+b
G=a
Lp=1.1 x 1039 erg/s
Residuals after source subtraction
diffuse emission along the plane!
HESS J1745-303
HESS collaboration: Nature Feb 9, 2006
concluding remarks:
we are at the gates of Heaven of
GeV/TeV astrophysics and Cosmology

condition for entrance? FE => 10-14 erg/cm2 s (0.03-30TeV)

realization ?

timescales

price for the ticket
1 to 10 km2 scale IACT arrays
short (years) - no technological challenges
very reasonable, plus (almost) 100 % guarante
for success (great results and many discoveries)
30 GeV – 30 TeV array (“super-HESS“)
several tens of 10 to 15m diameter class 5 (to 10?) deg FoV
telescopes located on 3.5-4 km a.s.l.
sites ?
several good places in Argentina, Chile, Mexico
(in addition to Namibia and La Palma)
5@5 - a future GeV ground-based gamma-ray observatory

Detector :
several 20 to 30m diameter IACTs to study the sky at energies
from several GeV to several 100 GeV with unprecedented
photon and source statistics

Potential:

Targets:
can detect “standard“ EGRET sources with spectra extending
beyond 5 GeV for exposure time from 1 sec to 10 minutes
Gamma Ray Timing Explorer for study of nonthermal phenomena
AGN jets, Microquasars, GeV counterparts of GRBs, Pulsars ...
5@5 is complementary to GLAST,
in fact due to small FoV needs very much GLAST
and ... GLAST certainly needs a 5@5 type instrument
PeV astrophysics with 10 km2 area array of small IACTs
Detector:
Energy Interval:
tens of 10m2 area and 5 to 10 deg FoV IACTs
located at > 300 m distances from each other
10 TeV to 1000 TeV
Scientific Objective: search for Cosmic PeVatrons
Site:
Southern Hemisphere and low elevations
preferable – Australia
Timescales:
a few years