A Theoretical Model to Explain TeV Gamma-ray and X-ray Correlation in Blazars

Transcription

1 A Theoretical Model to Explain TeV Gamma-ray and X-ray Correlation in Blazars Nissim Fraija In collaboration with: Magda Gonzalez Instituto de Astronomia - UNAM TAUP 2015, XIV International Conference Turin Italy, September 07 11, 2015

2 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

3 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

4 Mrk421 Ø Correlations Whipple and HEGRA Fossati et al. 08 X-ray and TeV are highly correlated. (flaring activity 2001). Mrk421 Mrk421 X-ray and TeV are correlated during the flare (flaring activity April/13). Maraschi et al. 99 Fraija et al. 15 X-ray and TeV are well correlated on timescale of hours (flaring activity April/98).

5 Ø Disconnections 1ES (Orphan Flares) Mrk421 Krawczynski et al. 04 flaring activity in May/2008 Acciari et al. 11 flaring activity in June-July/ 2002 Mrk421? Krawczynski et al. 04 Fraija et al. 15 Flaring activity in August/2012

6 Is there a correlation between X-ray and TeV γ-ray emission???? (hourly, daily, monthly, etc.) If so, what is the origin?? How could the orphan flares be explained???

7 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

8 Ø Theoretical Model Sketch of the basic model Observer and/or Protons (Np) We consider a spherical emitting region: - Moving at relativistic speed with bulk Lorentz factor Γ. - with a uniform particle densities (Ne and/or Np). - with radius (rd). - Endowed with a magnetic field B. Leptonic model Just 4 parameters (B, Γ, rd and Ne(β) ) Material from the accretion disk is accreted to the BH and after is launched in the jet. Dermer et al. 03 Hadronic model Additionally Np (5 parameters) (we will use natural unities c=h=1 and prime quantities are in the comoving frame)

9 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

10 Ø Synchrotron radiation By considering that a fraction of total energy is given To accelerate electrons minimum e - Lorentz factor To generate and/or amplify magnetic field Cooling Time scale cut-off e - Lorentz factor Compton parameter Acceleration time scale t 0 acc = r 2 m e U 1 B q e e Maximum e - Lorentz factor Photon energy released Break synchrotron energies

11 electron distribution Flux conservation β=(α+2)/2 Electron Synchrotron spectrum Milagro and Veritas (Low state) Power index: β = 2.3 Synchrotron emission v F v (kev cm -2 s -1 ) Values: Γ=20 rd=5 x cm B = 1 Gauss Ne = 10 2 cm Energy (ev)

12 Ø Compton scattering Synchrotron self- Compton relation 1e-10 Break Compton scattering energies v Fv (erg cm -2 s -1 ) SSC emission Values: Γ=20 rd=5 x cm B = 1 Gauss Ne = 10 2 cm -3 Compton parameter Compton scattering spectrum Y = 2.06 x 10-5 N o /B o 2 B=B o Gauss Ne= N o cm 3 erg/cm 3 =Gauss 2 1e+07 1e+08 1e+09 1e+10 1e+11 1e+12 1e+13 1e+1 Energy (ev)

13 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

14 Ø Pγ interactions The target photon density Charged and neutral pion production channels Photo pion cooling time, cross section Photo pion efficency Proton distribution Photo pion spectrum:

15 Ø µ -, e ± and proton synchrotron radiation comparison Photon energy where muon Lorentz factor lifetime Aharonian 2000, Mannheim 1993 Break synchrotron energies Muons are accelerated by a power law distribution Synchrotron spectrum of muons and secondary pairs

16 Ø Summing up: the hadronic spectrum Total Photo pion µ - synchrotron e ± synchrotron Proton synchrotron Values: Γ=10 rd=5 x cm B = 10 Gauss Abdo et al

17 Ø Models Leptonic Hadronic Electron synchrotron spectrum First peak 0.5 kev X-ray Primary electron synchrotron spectrum First peak 0.5 kev X-ray Compton scattering spectrum Second peak 200 GeV TeV γ-ray Photo pion + Muon, secondary e± and proton synchrotron spectrum Second peak 200 GeV TeV γ-ray There is correlation X-ray TeV γ-ray There is NOT correlation X-ray TeV γ-ray Orphan flares could be explain!! Botcher 2004 Fraija 2014

18 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

19 Ø Data sets IACTs: MAGIC, H.E.S.S., Whipple/VERITAS, CAT, HEGRA 14 years E > 400 GeV Mean=0.73 Crab (distribution) Resconi et al # observations 1 Tluczykont et al Acciari et al RXTE/ASM >14 years 2-10 kev Mean=0.5 counts/s (distribution) 0.1 very low low high Veritas flux states F VHE,400 GeV (Crab)

20 high low very low Patricelli et al 2015

21 Ø Considerations in our model Values of parameters =2.3 r d = cm = 10 Acciari et al. 2011, 2014 Abdo et al Values N e and B are computed fitting data VHE gamma-ray fluxes was normalized to the Crab flux, as measured by VERITAS 1 Crab = erg/cm 2 /s Unities of X-ray flux were changed (with the online WebPIMMS tool) erg/cm 2 /s! CPS Brum and Rademarkers Column density fixed to the Galactic value in the direction of Mrk 421: 1.61 x cm -2 Kalberla et al 2005

22 Ø Comparison Unique correlation B ' 0.8 G Magnetic field Electron density 0.01 apple B (G) apple apple N e (cm 3 ) apple Parameter space As fluxes increase the set of parameters decreases. As fluxes decrease B decreases Theoretical model equivalence low very low high equal low very low high Experimental data orphan flares

23 This model could be generalized to other blazars 1ES Mrk501 Krawczynski et al 2004 Gliozzi et al 2006 PKS Abramowski et al 2006

24 OUTLINE Ø Observations: TeV and X-ray correlations and disconnections Ø Theoretical model: - Generalities - Lepton model - Hadronic model Ø Application to Mrk 421 Ø Conclusions

25 Ø Conclusions ü Mrk421 shows a correlation between TeV γ-ray and X-ray emissions independent of time scales and instruments, although it seems to break at the highest γ-ray fluxes. ü The overall correlation can be interpreted as SSC scenario with a single value of magnetic field B ' 0.8 G ü The outliers and orphan flares might be described within SSC framework for a set of values of N e and B different from the ones characterizing the overall correlation. ü We have developed a theoretical model that can explain the correlation between TeV γ-ray and X-ray emissions of Mrk 421. Although the hadronic model can describe the SED, it can not explain the correlation.

26 Back up

27 Both leptonic and hadronic models describe well the SED