?

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!