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

Outline ● Introduction ● Microquasar jet “hot”regions ● Physical processes behind emission ● Discussion

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

(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 (e.g.Bosch-Ramon et al. 2005b) (e.g. Corbel et al. 2002) (Tavani et al. 1998) (Aharonian et al. 2005, Albert et al. 2006) (e.g. Mirabel & Rodríguez 1999; Fender et al. 2001)

(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

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

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

●...be convected away in the jet ●...radiate interacting with:  U photons : black body: disk/star power-law: sync./cor. comp.  B (assumption ~ √ e matter )  n protons = f(dM w /dt,v rel,R orb ) | f(dM jet /dt,R jet ) | n cloud ●...can lose energy via adiabatic losses ●...could escape the jet (fast diffusion/convection) (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/EC disk/cor (KN) ➢ (e.g. Markoff et al. 2001) (e.g. Romero et al. 2002; Bosch-Ramon & Paredes 2004) (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/EC disk/cor (KN) ➢ - > Jet proton/proton collisions (  ) ➢ -> Jet proton/disk photon collisions (  )  Cascading (e.g. Levinson & Waxman 2001; Aharonian et al. 2005) Jet base (physical processes)

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

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

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

Jet middle scales  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. Atoyan & Aharonian 1999) (e.g. Van der Laan 1966) (e.g. Bosch-Ramon et al. 2006) (physical processes)

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

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

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

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

(physical processes) Jet termination region  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. Heinz & Sunyaev 2002; Bosch-Ramon et al. 2005) (e.g. Bosch-Ramon PhD thesis)

1E Cygnus X-1 (Gallo et al. 2005) (Mirabel et al. 1992)

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

(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 (Bosch-Ramon et al. 2005b) (e.g. Corbel et al. 2002) (Tavani et al. 1998) (Aharonian et al. 2005, Albert et al. 2006) (e.g. Mirabel & Rodríguez 1999; Fender et al. 2001)

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?)

(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 ~ km 3 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)