Theoretical Overview on High-Energy Emission in

Microquasars

Valentí Bosch i Ramon

Universitat de BarcelonaDepartament d'Astronomia i

Meteorologia

Barcelona, 5-7-2006The 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:

Uphotons

: black body: disk/star

power-law: sync./cor. comp.

B (assumption ~ √ematter

)

nprotons

= f(dMw/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/ECdisk/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/ECdisk/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 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)

(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. 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 1915+105

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)

1E1740.7-2942 Cygnus X-1

(Gallo et al. 2005)(Mirabel et al. 1992)

(Heinz & Sunyaev 2002)

Protons and molecular cloudsProton / 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 ~ 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)