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Theoretical Overview on High-Energy Emission in Microquasars

Theoretical Overview on High-Energy Emission in Microquasars. Barcelona, 5-7-2006 The Multimessenger Approach to Unidentified Gamma-Ray Sources. Valentí Bosch i Ramon. Universitat de Barcelona Departament d'Astronomia i Meteorologia. Outline. Introduction Microquasar jet “hot” regions

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Theoretical Overview on High-Energy Emission in Microquasars

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  1. Theoretical Overview on High-Energy Emission in Microquasars Barcelona, 5-7-2006 The Multimessenger Approach to Unidentified Gamma-Ray Sources Valentí Bosch i Ramon Universitat de BarcelonaDepartament d'Astronomia i Meteorologia

  2. Outline • Introduction • Microquasar jet “hot” regions • Physical processes behind emission • Discussion

  3. Introduction • We infer from observations that microquasars are: • accelerators of particles up to TeV energies • emitters producing non-thermal radiation in the whole spectral range

  4. (introduction) • From observations: • Variable VHE gammas are generated in microquasars • Variable HE gammas are generated as well • X-rays are generated from the jet termination region • Variable non-thermal X-rays are generated • Non-thermal radio emission is generated in the jet at all scales (Aharonian et al. 2005, Albert et al. 2006) (Tavani et al. 1998) (e.g. Corbel et al. 2002) (e.g.Bosch-Ramon et al. 2005b) (e.g. Mirabel & Rodríguez 1999; Fender et al. 2001)

  5. (introduction) • We infer from observations that microquasars are: • accelerators of particles up to TeV energies • emitters producing non-thermal radiation in the whole spectral range • Gamma-rays are related to regions with: • particle acceleration and (relatively) strong magnetic, photon and matter fields • Microquasar jets provide such conditions, presenting (at least) radio to X-ray emission. Thus: • these jets could produce/be studied through gamma-rays

  6. Microquasar jet “hot” regions • Outside the jet • The Jet termination region • Jet middle scales • Jet binary system scales • Jet base Figure from Chaty's PhD thesis

  7. Physical processes behind emission • Particles can be accelerated and... Outside the jet • Particles escape from the jet The Jet termination region • Shock acceleration (e.g. Drury 1983) Jet middle scales • Shock acceleration, shear acceleration (e.g. Drury 1983, Rieger talk) Jet binary system scales • Shock acceleration, shear acceleration (e.g. Drury 1983, Rieger talk) Jet base • Converter mechanism, plasma instabilities (?) (e.g. Derishev et al. 2003; Zenitani & Hoshino 2001)

  8. (physical processes) • ...be convected away in the jet • ...radiate interacting with: • Uphotons: black body: disk/star power-law: sync./cor. comp. • B (assumption ~√ematter) • nprotons= f(dMw/dt,vrel,Rorb) | f(dMjet/dt,Rjet) | ncloud • ...can lose energy via adiabatic losses • ...could escape the jet (fast diffusion/convection)

  9. (physical processes) Jet base • Variability (accretion disk) • Evolution: radiative cooling • min? -> Monoenergetic particle sync./IC low energy spectrum • max controlled by cooling • - > Sync. soft X-ray emission • - > gamma-ray SSC/ECdisk/cor (KN) (e.g. Markoff et al. 2001) (e.g. Romero et al. 2002; Bosch-Ramon & Paredes 2004)

  10. Jet base (physical processes) • Variability (accretion disk) • Evolution: radiative cooling • min? -> Monoenergetic particle sync./IC low energy spectrum • max controlled by cooling • - > Sync. soft X-ray emission • - > gamma-ray SSC/ECdisk/cor (KN) • - > Jet proton/proton collisions () • -> Jet proton/disk photon collisions () • Cascading (e.g. Levinson & Waxman 2001; Aharonian et al. 2005)

  11. Jet base leptonic emission Corona IC is deeply in the Klein Nishina regime. Jet base (ext.) opacities (ext.) cascading is unavoidable Internal pair creation may lead to internal cascading as well

  12. Binary system scales (physical processes) • Variability (orbital) • Evolution: radiation and convection • Optically thick flat radio emission • max controlled by cooling/size • - > Sync. hard X-ray emission • - > gamma-ray ECstar (Thomson/KN) (e.g. Cui et al. 2005) (e.g. Bosch-Ramon et al. 2006; Paredes et al. 2006) (Paredes et al. 2000; Kaufman Bernadó et al. 2002; Bosch-Ramon & Paredes 2004; Dermer & Böttcher 2006)

  13. Binary system scales (physical processes) • Variability (orbital) • Evolution: radiation and convection • Optically thick flat radio emission • max controlled by cooling/size • - > Sync. hard X-ray emission • - > gamma-ray ECstar (Thomson/KN) • - > Jet proton/wind ion interaction () • Cascading (e.g. Romero et al. 2003; Romero & Orellana 2005) Concerning secondaries, see the poster by Bordas et al. (e.g. Aharonian et al. 2005; Bednarek 2006; Romero's talk)

  14. (Aharonian et al. 2005) Hadronic emission Powerful jets Strong wind ion/jet hadron mixing (Romero et al. 2003) Leptonic emission LS 5039 (Paredes et al. 2006)

  15. Jet middle scales (physical processes) • Variability (star mass loss rate) • Evolution: convection/adiabatic losses • Uncooled optically thin radio emission • max controlled by size , adiabatic losses (?) • - > Sync. IR/opt. emission • - > IC? (e.g. Van der Laan 1966) (e.g. Bosch-Ramon et al. 2006) (e.g. Atoyan & Aharonian 1999)

  16. Radio emission from LS 5039 Partially dominated by jet middle scales (adapted from Paredes et al. 2006) Broadband emission from GRS 1915+105 Powerful blob (Atoyan & Aharonian 1999)

  17. Outside the jet (physical processes) • Variability (orbital) • Evolution: diffusion and convection • Uncooled/cooled optically thin radio emission • Jet particles escape • -> X-ray sync. • - > gamma-ray IC

  18. Outside the jet (physical processes) • Variability (orbital) • Evolution: diffusion and convection • Uncooled/cooled optically thin radio emission • Jet particles escape • -> X-ray sync. • - > gamma-ray IC • - > Jet proton/wind ion interaction () • Cascading (e.g. Aharonian et al. 2005, Bednarek 2005) (e.g. Bednarek 2006)

  19. Escaped particles can radiate significantly via synchrotron and IC emission within the binary system Cascading can create significant amounts of pairs within the binary system emitting IC (Bednarek 2006)

  20. Jet termination region (physical processes) • Variability (>years) • Evolution: diffusion, convection, adiabatic losses • Uncooled/cooled optically thin radio emission • max controlled by size, convection, adiabatic losses (e.g. Bosch-Ramon PhD thesis) (e.g. Heinz & Sunyaev 2002)

  21. Jet termination region (physical processes) • Variability (>years) • Evolution: diffusion, convection, adiabatic losses • Uncooled/cooled optically thin radio emission • max controlled by size, convection, adiabatic losses • -> X-ray sync. • - > gamma-ray IC • - > Jet proton/ISM nuclei interaction () (e.g. Wang et al. 2003; Bosch-Ramon PhD thesis) (e.g. Bosch-Ramon PhD thesis) (e.g. Heinz & Sunyaev 2002; Bosch-Ramon et al. 2005)

  22. Cygnus X-1 1E1740.7-2942 (Mirabel et al. 1992) (Gallo et al. 2005)

  23. Protons and molecular clouds Proton / Electron halos (Heinz & Sunyaev 2002)

  24. (introduction) From observations: Variable VHE gammas are generated in microquasars Variable HE gammas are generated as well X-rays are generated from the jet termination region Variable non-thermal X-rays are generated Non-thermal radio emission is generated at small and large scales (Aharonian et al. 2005, Albert et al. 2006) (Tavani et al. 1998) (e.g. Corbel et al. 2002) (Bosch-Ramon et al. 2005b) (e.g. Mirabel & Rodríguez 1999; Fender et al. 2001)

  25. Discussion From observations: Variable VHE gammas are generated in microquasars Variable HE gammas are generated as well X-rays are generated from the jet termination region Variable non-thermal X-rays are generated Non-thermal radio emission is generated at small and large scales • From theory: • Hadronic vs. leptonic jet origin: Jet base < VHE gammas < middle scales • Hadronic vs. leptonic jet origin: HE gammas < middle scales • It is likely synchrotron emission from a strong blob/ISM shock • It could be synchrotron emission: X-rays ≤ binary system scales • It is synchrotron emission from compact and extended jets (min, ISM interaction?)

  26. (discussion) • At large scales, hadronic radiation could be significant (e.g. for CR p/e ratio, dense targets...) • Neutrinos produced at different scales may be detectable for ~ km3 detectors. • New high quality data call for more accurate modeling (e.g. cascading, particle acceleration, magnetic field, confinement) • Multimessenger studies can lead to a deeper understanding of jet physics (e.g. jet content and energetics, leptonic vs. hadronic acceleration)

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