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Restrictions on the injection energy of positrons annihilating near the GC

Restrictions on the injection energy of positrons annihilating near the GC. D.O. Chernyshov , K.S. Cheng, V.A. Dogiel , C.M. Ko , W.H. IP. Annihilation: line VS continuum. Newborn fast positrons should annihilate in flight: - continuum emission > 1 MeV. COMPTEL:

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Restrictions on the injection energy of positrons annihilating near the GC

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  1. Restrictions on the injection energy of positrons annihilating near the GC D.O. Chernyshov, K.S. Cheng, V.A. Dogiel, C.M. Ko, W.H. IP Otranto, Italy, 2009

  2. Annihilation: line VS continuum Newborn fast positrons should annihilate in flight: - continuum emission > 1 MeV • COMPTEL: • No signs of narrow diffuse source • IA is lower than COMPTEL errors • 1-3 MeV: 2x10-4 cm-2s-1 • 3-10 MeV: 9x10-5 cm-2s-1 • 10-30 MeV: 3x10-5 cm-2s-1 Otranto, Italy, 2009

  3. Limitations from the COMPTEL data Beacom and Yuksel, 2006: • Neutral medium • No magnetic field • Stationary source Limitation at 3 MeV • Sizun et al., 2006: • Ionized medium • No magnetic field • Stationary source Limitation at 10 MeV Otranto, Italy, 2009

  4. No room for models with the positron energy injection higher than ~10 MeV Are there conditions in the GC which may extend a class of models explaining the origin of the 511 keV annihilation emission from the bulge? Otranto, Italy, 2009

  5. Magnetic field strengh in the GC • Though there is no consensus on the field strength in the GC, some quantitative estimations yields field strengths of the order of mG perpendicular to the Galactic plane(seereviews Mezger 1996 and Morris 2006). • This changes significantly the evolution of the positron spectrum in comparison with the cases analyzed by Beacom and Yuksel, 2006 or Sizun et al. 2006). Otranto, Italy, 2009

  6. Influence of magnetic field Injection at 30 MeV Otranto, Italy, 2009

  7. Limitations of positron injection energy from the COMPTEL data For H > 0.4 mG the injection energy of positrons is unlimited ionized neutral Otranto, Italy, 2009

  8. Synchrotron flux • In mG Magnetic fields 300 MeV electrons emit a radio flux at ~400 MHz. • If the injection rate of positrons is constant then the radioflux from the GC is of the order of 109 Jy that is much higher than follows from observations. Observations (LaRosa, 2005): diffuse emission near the GC at 330 MHz does not exceed observations: 10 kJy. Then nonstationary injection of positrons as assumed by (Cheng et al., 2006, 2007). 330 MHz Otranto, Italy, 2009

  9. Estimations of fluxes Suppose activity of the source ceased T years ago: Synchrotron radio at 330 MHz In-flight gamma at 10-30 MeV Otranto, Italy, 2009

  10. Limitations from radio and gamma 3x105 yr 2x105 yr 105 yr 5x104 yr stationary In principle, the positron injection energy is higher than 40 MeV if the magnetic field strength H>0.4 mG Otranto, Italy, 2009

  11. Conclusions • For sporadic positron injection their energy can be very high if H > 1 mG • Other galaxies? Otranto, Italy, 2009

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