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Area of Science:

  • Astrophysics
  • High-energy astrophysics
  • Black hole physics

Background:

  • Microquasars are binary systems with a black hole and companion star, studied for relativistic particle jets.
  • Previous observations of V4641 Sagittarii did not detect gamma-ray emission.
  • SS 433, a similar microquasar, shows electron acceleration in its jet far from the black hole.

Purpose of the Study:

  • To investigate TeV gamma-ray emission from the microquasar V4641 Sagittarii.
  • To understand particle acceleration mechanisms in microquasar jets.
  • To assess the contribution of microquasars to galactic cosmic rays.

Main Methods:

  • Detection of TeV gamma-ray emission using advanced telescopes.
  • Spectral analysis of the gamma-ray emission.
  • Comparison of V4641 Sagittarii's emission with other microquasars like SS 433.

Main Results:

  • Detection of TeV gamma-ray emission from V4641 Sagittarii.
  • Localization of particle acceleration in the jet at distances comparable to SS 433.
  • Observation of an exceptionally hard TeV gamma-ray spectrum, extending above 200 TeV.
  • The hard spectrum challenges electron acceleration models and suggests potential proton acceleration.

Conclusions:

  • V4641 Sagittarii exhibits particle acceleration in its large-scale jets, similar to SS 433.
  • The observed gamma-ray spectrum implies either a highly constrained electron acceleration or significant proton acceleration.
  • Microquasar jets may be more prevalent sources of galactic cosmic rays than previously thought.