? Paolo Coppi Yale University GLAST X-Ray Follow-ups of GLAST AGN (Blazars)? Suzaku, SWIFT, RXTE,...
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Transcript of ? Paolo Coppi Yale University GLAST X-Ray Follow-ups of GLAST AGN (Blazars)? Suzaku, SWIFT, RXTE,...
?
Paolo CoppiYale University
GLAST
X-Ray Follow-ups of GLAST AGN (Blazars)?
Suzaku, SWIFT,RXTE, Astro-SAT,EXIST?
P. Coppi, Yale
CGRO/EGRET and the “GeV” Blazars
[but with jet pointed at you]
Unified Blazar Scheme?
Donato et al. 2002,Fossati et al. 1998
Fossati?
PKS 2155-304: multiwavelength coverage of flares …
Foschini et al. 2007 (astro-ph/07010868)
SWIFT??Uh, oh….
min
-3 4
9
min
-7
/
GRB :
10 sec / 10 M 10
2155 :
300 / 10 M
3 10
/
!
( t )
BH
Schwarzchild
t M
R c
Moderski et al. 2005
[~MeV]
When (external) photon field dominates energy density, be careful if Klein-Nishina effects important.
Spectral features such as “bumps” and break energies, alpha_x < 0.5! Interpretation not as obvious as in standard models!
Can get spectral Index harder than 0.5!
IC sync
ERC, UV blackbody seeds
EGRETblazars?
rad
B
U
U
sync IC
Hadronic models: generic energetics/time variability problems.External photons can help photo-meson production cooling rate … But need to be near core of AGN => high optical depth for gamma-rays! => proton-initiated cascade!
Generically gettoo many X/soft gamma-rays if not careful!
Need simultaneous X-ray coverage!
Origin of alpha_x < 0.5 in EGRET blazars never resolved (and seenin more blazars than EGRET ones) – “slow cooling” interpretation hasproblems during flares.
Watch out for Klein-Nishina effects! (alpha_x< 0.5, sync,peak -IC,peak mapping
messed up, x-ray bump does not imply new e- component)
Simultaneous X-ray luminosity/spectrum also constrains cascade/hadronic models.
Need X-rays! [Were guaranteed on EGRET, but not on GLAST. GBM?]
Question for organizers: what X-ray TOO programs are already in place?(TeV community routinely applies for these every cycle.)
Summary
Hadronic vs. Electronic models of TeV Blazars
SSC or external Compton – currently most favoured models: easy to accelerate electrons to TeV energies easy to produce synchrotron and IC gamma-rays recent results require more sophisticated leptonic
models
Hadronic Models: protons interacting with ambient plasma neutrinos very slow process: protons interacting with photon fields neutrinos* low efficiency + severe absorption of TeV -rays
proton synchrotron no neutrinos
very large magnetic field B=100 G + accelaration rate c/rg
“extreme accelerator“ (of EHE CRs) Poynting flux dominated
flow
unlik
ely
*detectable neutrinos from EGRET AGN but not from TeV blazars
F. Aharonian
(Buckley, Science, 1998)
Blazar Emission Mechanisms: Idealized vs. Real Life
“Zone of Avoidance” forpair jet -- Dark Energy!
GeV Blazar Models & Complications…
Blazejowski et al. 2000
Boettcher et al. 2001
vs.
3C279
Seed photons: IR from dust
Beamed from behind, reduced efficiency?
Which photon field(s) does jet interact with???
A Generic VHE Source ….
0 0
Compton scattering (e e )
synchrotron radiation (eB eB )
Bremsstrahlung (ee ee ,pe pe )
decay ( )
proton synchrotron (pB pB )
Process(es) directly responsible for observed X-ray/-ray emission?
lowest order, most “efficient”
almost always accompanied by ...e
IC or
Multiwavelength observations very powerful/critical!
E.g., if have synchrotron/ICmodel LIC/Lsyn=UB/Urad, constrain B if know Urad.Also, correlated IC/synch. spectra!
2peaksync peak B
2 (Thompson)
(Klein-Nishina)
peakIC peak soft
peakIC peak
Numerical simulations for 3C 279. Numerical simulations for 3C 279. Spada et al. 2001Spada et al. 2001
The “ Boring” TeV Blazars
Suzaku/EXIT
HESS VERITASMAGICCANGAROO
[N.B. Klein-Nishina effects important!]
The potential advantage of TeV blazars… they are much simpler?
SSC model
Internal, self-consistentlygenerated photon field…
Testablepredictions!
Coppi & Aharonian 1999
TeV blazar (Mkn 501-like) case?
[“flares”=varying electron accelerationluminosity]
2 (naive SSC)TeV xL L
(ERC, SSC,
hadronic model)
TeV xL L
Steady X-RayComponent??
N.B. June 1997 data (after main flaring) included!
Christmas Tree/Internal Shock Model … clearly not right for some objects
Mrk 501 X-TeVcorrelationSTABLEover 3+ months!
LinearAxes!
Key – 3 keV fluxtracks TeV fluxrelatively poorly
Krawczysnki, Coppi, & Aharonian 2002
O.K. So you can explain individual spectrum, but what about the variability data?
Varysourceluminosity
Vary E_max…
Oops!! -- 1ES1959 May-Aug 2002
Krawczynski et al. 2004
Multiple EmissionComponents!
In case you still thought things were simple…
Mkn 421 2002 X-ray/TeV campaign
(Dieter Horns, preliminary)
X-ray
TeV
X-ray hardness ratio (spectrum)
Counts
PKS 2155-304: remarkable flares in July/August 2006
see poster by L. Costamante
July 27
July 29
night by night lightcurve July-August 2006
prelim
inary prelim
inary
2 minute binning lightcurve
July 27
17 Crab
X-ray (RXTE, Swift, Chandra) observations available:Chandra – simultaneous coverage for 6 continuous hours ! strong variability - a factor of 2timescales – 10 minutes or so)
1Crab
strong evidence for variability on a few minute timescales ! on average 70 /min rate spectrometry on minute timescales
finally ! we do have simultaneously obtained keV/TeV
data for proper modelling of blazar jets (maybe)
Presentation by F. Aharonian, HEAD 2006
MAGIC : 10 min var. in Mkn 501?
Albert et al. 2007 (astro-ph/0702008)
TeV Blazars: Self-Consistent Modeling & Klein-Nishina Correction to Thomson Cross-Section Important!
E_p determined by t_cool=t_esc
Lots of soft target photons
IR/O Absorption(big effect!)
Fewer and fewersoft photons
E_p determined by E_min(t_esc=infinity)
Solid line models: Both fit April 16th Mrk 501 CAT gamma-ray and BeppoSax data above2 keV equally well…
Response to variations in electronacceleration luminosity.
HARD spectrum
concave up …
1ES 1426?
0.5
What if we try to add some external photons to boost IC flux?
If in KN limit, doesn’t work! If not, get too hard spectrum?
Theoretical Considerations [Complications] V.
Assume simplest scenario: e- directly accelerated, no protons, no photon-photon pair production.
UV/X-ray = synchrotronGeV/TeV = Compton
What are seed photons for Compton upscattering??
• Synchrotron Photons (SSC)• Accretion Disk Photons (ERC)• BLR Photons (reprocessed accretion disk photons) ..• IR photons from hot dust in central region ..• [Microwave background, probably not relevant, but .. always there ]
All possible => different gamma-ray spectra for same e- distribution!
Lots of uncertainty for generic blazar!!If you think you can a priori predict a gamma-ray spectrum, I have a deal for you…
Effect of EBL absorption on source modeling… TeV blazars, e.g., Mkn 501, are very nearby (z~0.03) => Absorption not important? Wrong … don’t ignore!
true observedpeak peak
1/ 2peak
EBL Abs: E 3 E
For standard SSC model
by up to
,
f
E
actor 9! [ =3
)
0
(
+?
/
]
B
B
kinet
peak peak
ic B
C
e-
I
Larger E Higher IC more in KN limit lower IC flux.
BUT... EBL abs also true
very out of equipL ! artU / U
L (another facto
ition
r 10)
! -
R
Mkn 501: absorption corrected spectrumEBL
[Coppi&Aharonian 1999]
[See alsoDwek &Krennrich ]
L. Costamante
Next Few Years Promising for Bright TeV Blazars …
Krawczynski, 2004
Mrk 501 (1ES 1959+650)Mrk 421
2 Years
3 hrs
EXIST GLAST VERITAS
1 Month
RXTE ASM
IACT
Model used for simulation (tcool) is slightly different at low energies comparedto fit model (high min).
Both models give excellent fit to current data – but not tosimulated HESSdata!
Example of Data Quality Expected for Next Generation Instruments –
Simulated 5hr observation of April 16,1997Mrk 501 flare as would be seen by HESS.
Two components!
Optical polarizedSynchrotron TeV+ electrons!
Uchiyama et al. 2007
Uchiyama et al. 2007
Another quasar jet (1136) …
GX339 - Corbel et al. 2004 AGN !? - Maccarone et al. 2003
The X-ray/Radio correlation …Are “low” luminosity AGN interesting? Yes….
A “boring” object in the sky: the nearby elliptical galaxy M87
Optical
Radio
HST M87 Superluminal Motion
M 87 – evidence for production of TeV -rays close to BH
Distance: ~16 Mpc
central BH: 3109 M
Jet angle: ~15-30° not a blazar!
discovery (>4) of TeV
-rays by HEGRA (1998)
confirmed by HESS (2003)
13
= 10-13 cm-2 s-1 TeV-1
F. Aharonian, HESS
M87: light curve and variabiliy
X-ray emission:knot HST-1
[Harris et al. (2005),ApJ, 640, 211]
nucleus(D.Harris private communication)
X-ray (Chandra)
HST-1
nucleus
knot A
I>73
0 G
eV [
cm-2 s
-1]
short-term variability within 2005 (>4)constrains size of emission region (R ~ 5x1015 j cm)
F. Aharonian, HESS
Aside: Can use M87 [Cen A?] to probe diffuse background at MIR /FIR wavelengths with E > 10 TeV -rays!
F. Aharonian
???
(e.g., Blanford-Znajekmechanism)
But…
[ Jet composition???]
38
TeV gamma-rays from Galactic Center
if extended source - size less than 3’ (7 pc)if point-like source – position within 1’ around Sgr A*
G0.9
Sgr A*
HESS, F. Aharonian
Most sources can think of, even decaying/annihilating CDM particles, trace large scale structure… look for clustering signal/cosmic web (anisotropy)!
Bromm et al. 2003,cosmological structureformation calculation
The rarer/more biased the source, the stronger the clustering signal!
Response to Change in IR/O Background
GeV background measurement= calorimeter for VHE universe!
Coppi & Aharonian 1997
Key GLAST measurement
“GZK”cutoff?
The big payoff from understanding AGN: Remove “spurious” sources and… An accurate measurement (upper limits) on the GeV-TeV extragalactic diffuse background.
Why so interesting?
GeV-TeV+ gamma-rays only produced in extreme environments or by “exotic” processes: e.g., black hole jets, supernova blast waves, cosmic strings, relict particle decays, or matter-antimatter annihilation.
Background is sum of all nearby GeV-TeV activity in the Universe + all > GeV activity at z > 1.
[ Gamma-ray pair production and cascading on intergalactic photon fields
GLAST = calorimeter for VHE-EHE Universe!
(best limits on BAU/matter-antimatter domains from gamma-rays) ]
Theorist’s Wish List (for AGN)
Rule of thumb: give a theorist a spectrum consistent with a power law(e.g., due to insufficient statistics) and he can fit any model/EBL you like.
Need to detect curvature! Ideally measure both sides of low and high energy peaks, simultaneously w/good (< hour-month) continuous time-sampling: UV-MeV, 100 MeV-TeV coverage. [Also very good to get below IR/O absorption threshold – N.B. EBL absorption not dependent.]
?
Pian et al. 1998
Find (HAWC) and follow low duty cycle flaring activity.
Monitor synchrotonpeak up to ~MeV!