Evidence of nonthermal X-ray emission and TeV gamma rays from supernova remnants (SNRs) have strengthened the hypothesis that primary Galactic cosmic-ray electrons are accelerated in SNRs. High-energy electrons lose energy via synchrotron and inverse Compton processes during propagation in the Galaxy. Because of these radiative losses, TeV electrons liberated from SNRs at distances larger than $1 kpc, or times older than $10 5 yr, cannot reach the solar system. We investigated the cosmic-ray electron spectrum observed in the solar system using an analytical method and considered several candidate sources among nearby SNRs that may contribute to the high-energy electron flux. In particular, we discuss the effects for the release time from SNRs after the explosion, as well as the deviation of a source spectrum from a simple power law. From this calculation, we found that some nearby sources, such as Vela, Cygnus Loop, or Monogem, could leave unique signatures in the form of identifiable structure in the energy spectrum of TeV electrons and show anisotropies toward the sources, depending on when the electrons were liberated from the remnant. This suggests that, in addition to providing information on the mechanisms of acceleration and propagation of cosmic rays, specific cosmic-ray sources can be identified through the precise electron observation in the TeV region.
Cosmic-ray electrons1 have been observed in the energy range from 12 to D100 GeV with a new balloon-borne payload, the Balloon-borne Electron Telescope with Scintillating Fibers (BETS). This is the Ðrst publication of the absolute energy spectrum of electrons measured with a highly granulated Ðber calorimeter. The calorimeter makes it possible to select electrons against the background protons by detailed observation of both the longitudinal and the lateral shower development. The performance of the detector was calibrated by the CERN-SPS accelerator beams : electrons from 5 to 100 GeV, protons from 60 to 250 GeV. The balloon observations were carried out twice, in 1997 and 1998, at the Sanriku Balloon Center (Institute of Space and Astronautical Science) in Japan. The observation time was D13 hr in all at an altitude above 34 km. A total of 1349 electron candidates were collected, and the 628 events with energies above 12.5 GeV, well above the geomagnetic rigidity cuto † of D10 GV, have been used to compose a di †erential absolute energy spectrum at the top of the atmosphere. The energy spectrum is described by a power-law index of 3.00^0.09, and the absolute di †erential intensity at 10 GeV is 0.199^0.015 m~2 s~1 sr~1 GeV~1. The overall shape of the energy spectrum in 10 D 100 GeV can be explained by a di †usion model, in which we assume an energy-dependent di †usion coefficient (PE0.3) for an injection spectrum, E~2.4.
The present analyses clearly indicate that OMBC is a distinct subgroup with long-term prognosis superior to MBC, with reasonable provability for clinical cure. Further prospective studies to better characterize OMBC are warranted to improve prognosis in MBC.
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