# Presentation: 931980

## X-Ray Follow-ups of  GLAST AGN (Blazars)?

- Paolo Coppi
- Yale University

- GLAST

- Suzaku, SWIFT,
- RXTE, Astro-SAT,
- EXIST?

- P. Coppi, Yale

## CGRO/EGRET and the “GeV” Blazars

## PKS 2155-304: multiwavelength coverage of flares ... 

- PKS 2155-304: multiwavelength coverage of flares ...

- Foschini et al. 2007 (astro-ph/07010868)

- SWIFT??

- Uh, oh....

## When (external) photon field dominates energy density, be careful 

- [~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!

## 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 get*
*too many X/soft *
*gamma-rays *
*if not careful! *

- Need simultaneous X-ray coverage!

##      Need X-rays!  

- Origin of alpha_x < 0.5 in EGRET blazars never resolved (and seenin more blazars than EGRET ones) – “slow cooling” interpretation has
- problems 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

- Acceleration to 1018 eV
- close to the gravitational
- radius  (1012 – 1013 cm)

- UHE neutrinos – detectable by AUGER ?
- Maybe UHE neutrons??

- g

- interaction with IR and mm
- photons (and B) fields
-      =>  E-M cascades

**no conflict with X-rays !**

**requires  10 kG **

- F. Aharonian

- N.B. For PIC, bulk of luminosity in neutrinos (good)
-         but neutrinos don’t cascade (in AGN) = bulk of luminosity at ~threshold
-         energy (bad for ICECUBE?)

- Sample calculation

##      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*

*unlikely*

-          *detectable  neutrinos from EGRET AGN  but not from TeV blazars

- F. Aharonian

## Blazar Emission Mechanisms: Idealized vs. Real Life

- “Zone of
- Avoidance” forpair jet  -- Dark Energy!

## Boettcher et al. 2001

- GeV Blazar Models & Complications...

- Blazejowski et al. 2000

- vs.

- 3C279

- Seed photons: IR from dust

- Beamed from behind, reduced efficiency?

- Which photon field(s) does jet interact with???

## Multiwavelength 

- IC         or 

- Multiwavelength
- observations
- very powerful/critical!
- E.g., if have synchrotron/IC
- model LIC/Lsyn=UB/Urad,
- constrain B if know Urad.
- Also, *correlated* IC/synch. spectra!

## Numerical simulations for 3C 279. Spada et al. 2001

## The “ Boring” TeV Blazars

## The potential advantage of TeV blazars... they are much simpler?

- Suzaku/
- EXIT

- HESS
- VERITAS
- MAGIC
- CANGAROO

- [N.B. Klein-Nishina effects important!]

- SSC model

- Internal,
- self-consistently
- generated
- photon field...
- Testable
- predictions!

- Coppi & Aharonian 1999

## TeV blazar (Mkn 501-like) case?

- [“flares”=varying
- electron acceleration
- luminosity]

## Christmas Tree/Internal Shock Model ... clearly not right for some objects

- Steady X-Ray
- Component??

- N.B. June 1997 data (after main flaring) included!

- Mrk 501 X-TeV
- correlation
- STABLE
- over 3+ months!

- Linear
- Axes!

- Key – 3 keV flux
- tracks TeV flux
- relatively poorly

## O.K. So you can explain individual spectrum, but 

-  Krawczysnki, Coppi, & Aharonian 2002

- O.K. So you can explain individual spectrum, but
- what about the variability data?

- Vary
- source
- luminosity

- Vary
- E_max...

## Oops!! -- 1ES1959 May-Aug 2002

- Krawczynski et al. 2004

**Multiple Emission**
**Components!**

## In case you still thought things 

- 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

*preliminary*

*preliminary*

- 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 2*
*timescales – 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)

## IR/O Absorption

- 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

- (big effect!)

- Fewer and fewer
- soft 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 above
- 2 keV equally well...

- Response to variations in electron
- acceleration luminosity.

- HARD spectrum

## concave up ...

- 1ES 1426?

- 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 = synchrotron
- GeV/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!

- 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... 

- 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!

- Mkn 501: absorption corrected spectrum

- EBL

- [Coppi&Aharonian 1999]

- [See also
- Dwek &
- Krennrich ]

## L. Costamante

## Next Few Years Promising for Bright TeV Blazars ...

- Krawczynski, 2004

## Model used for simulation (tcool) is slightly different at low energies compared

- Model used for simulation (tcool) is slightly different at low energies compared
- to fit model (high min).
- Both models give excellent fit to current data – but not tosimulated HESS
- data!

- 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 polarized
- Synchrotron
-  TeV+ electrons!

- Uchiyama et al. 2007

## Uchiyama et al. 2007

- Another quasar jet (1136) ...

## The X-ray/Radio correlation ...

- GX339 - Corbel et al. 2004

**AGN** !? - Maccarone et al. 2003

- Are “low” luminosity AGN interesting?  Yes....

## A “boring” object in the sky: the nearby elliptical galaxy M87

- Optical

## HST M87 Superluminal Motion

## M 87 – evidence for production of TeV -rays close to BH

- Distance:  ~16 Mpc
- central BH:   3109 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

**M87: light curve and variabiliy**

- X-ray emission:
- knot HST-1[Harris et al. (2005),ApJ, 640, 211]
- nucleus(D.Harris private communication)

- I>730 GeV [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-Znajek
- mechanism)

- But...

- [ Jet composition???]

## TeV gamma-rays from Galactic Center 

- 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 

- 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 structure
- formation 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