Future Observations of Galactic Compact Sources

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Future Observations of Galactic Compact Sources
Philip Kaaret, Reshmi Mukherjee, Martin Pohl, Ken
Ragan, Brenda Dingus, Jamie Holder, John Finley,
Rene Ong, Stephan LeBohec

• Supernova remnants and acceleration of cosmic
  rays
• Particle acceleration by black holes and neutron
  stars
• Unidentified GeV/TeV sources
• Search for new Galactic sources

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Cosmic Rays

• The origin of cosmic rays is one of the oldest
  and most challenging problems in astroparticle
  physics
• There is clear evidence for acceleration of
  electrons to 10 TeV in supernova remnants,
  pulsar wind nebulae, and black hole jets.
• Evidence for acceleration of hadronic cosmic
  rays is ambiguous at best. Not clear if SNR are
  dominant source or if PWN, black hole jets, or OB
  winds are important.
• Ability to distinguish TeV photons produced by
  hadronic vs leptonic cosmic rays is key.
  Hadronically produced emission should correlate
  with target material.

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IC 443
Near IR image of IC 443 Red at South is 2.12 ?m
H2 molecular line excited by the supernova
shock. Blue is mainly Fe II. Need to resolve
remnant on physical scale of target material.
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SN 1006
X-Ray (2-4.5 keV) and radio images of SN 1006.
Nonthermal X-ray emission gives evidence for
acceleration of electrons to 10-100 TeV. Mapping
of TeV photons from inverse-Compton scattering
would determine the magnetic field and the
maximum electron energy. Should also constrain
diffusion and lifetime of the electrons.
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Cosmic Ray Acceleration

• Key goal is to unambiguously disentangle TeV
  emission from electronic versus hadronic cosmic
  rays, imaging appears to be best method.
• Observe SNR (production sites?) and giant
  molecular clouds (passive targets) to map
  distribution.
• Non-detection of hadronically produced ?-rays
  would require either a very steep source
  spectrum, inconsistent with that needed to
  produce the local spectrum, or a greatly reduced
  cosmic-ray intensity, inconsistent with the
  energy budget for cosmic rays.
• Either possibilities would lead to serious
  revisions in our understanding of the origin of
  cosmic rays.

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Particle Acceleration by Black Holes

• Jets are ubiquitous in accreting Galactic black
  holes and likely play a major, yet poorly
  understood, role in the overall accretion
  process.
• X-ray observations provide clear evidence for
  acceleration of electrons to 10-100 TeV.
• Detection of TeV photons constrain the highest
  energy particles and place strong constraints on
  the acceleration mechanism.

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XTE J1550-564
? 0.66 0.01
Radio and X-ray from a single population of
electrons. Maximum energy ?e gt 2 x107
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Microquasar Detected at TeV
LS 5039
1.4 Crab (gt100 GeV)
Slide by Wei Cui
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TeV emission from LS 5039

• TeV photons may arise from inverse-Compton
  scattering of electrons on photons from the O6.5V
  companion star or interactions of protons
  accelerated in the jet with the stellar wind.
• The luminosity in the TeV band indicates an
  extremely powerful outflow. For 1 acceleration
  efficiency, the jet kinetic power must be 10?
  the X-ray luminosity.
• This result has major implications for our
  understanding of accretion flows near black holes.

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TeV emission from microquasars

• LS 5039 has a high mass companion star and a
  continuous jet.
• Additional systems should be studied and their
  energy spectra accurately measured.
• More of microquasars have low mass companion
  stars and intermittent jets. Need all-sky
  coverage or frequent monitoring.

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Particle Acceleration by Neutron Stars

• TeV observations of pulsar wind nebula will help
  determine the precise mechanism by which the
  pulsar spin-down energy is dissipated, the
  maximum particle energy, the particle injection
  rate, and the strength of the nebular magnetic
  field.
• PWN are, probably, the most common TeV source.
• High angular resolution measurements of several
  nebula and statistics on a large set of nebula
  are needed.
• HESS detection of PSR B1259-63 provides a
  different probe of particle acceleration by
  young, rotation-powered pulsars.

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Unidentified Gamma-Ray Sources

• EGRET produced a large set of unID sources, HESS
  has found several, GLAST will like find many (the
  majority of its sources)
• Possible sources
• Dark Accelerators
• Gamma-Ray Burst Remnants
• Completely new objects

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Unidentified Gamma-Ray Sources

• Requirements
• High angular resolution
• Source location accuracy to lt 1, prefer better
• Extension of energy band to overlap with GLAST
• High count rate for pulsation searches

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Search for New Gamma-Ray Sources

• Flux sensitivity of 10-14 erg/cm2/s corresponds
  to luminosity of 1032 erg/s at 10 kpc, 1031 erg/s
  at 3 kpc.
• This is comparable to the quiescent X-ray
  luminosity of black hole and neutron star
  binaries, the expected TeV luminosity of
  individual giant molecular clouds, luminosity of
  isolated pulsars.
• A survey with such sensitivity could lead to the
  detection of hundreds of new Galactic sources.
• Wide field of view is needed.

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Testing Lorentz Symmetry

• TeV measurements of the spectrum of the Crab
  nebula constrain vacuum Cherenkov radiation
  (Jacobsen et al. 2001).
• The absence of energy dependent time delays in
  the GeV band from pulsars constraint Lorentz
  violations (Kaaret 1999).

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Goals for Future Observations

• Cosmic rays good angular resolution (1-6),
  high photon counting rate.
• Jets good sensitivity (lt 1 Crab in few hours),
  all-sky coverage would be a plus.
• Unidentified sources good angular resolution,
  position centroids to lt 1, lowest possible
  energy threshold.
• New sources, flux sensitivity of 10-14 erg/cm2/s
  and field of view gt 5º.