Kinetic theory of cosmic ray and gamma-ray production in supernova remnants expanding into wind bubbles
A kinetic model of particle acceleration in supernova remnants (SNRs) is - extended to study the cosmic ray (CR) and associated high-energy gamma - -ray production during SN shock propagation through the inhomogeneous - circumstellar medium of a progenitor star that emits a wind. The wind - forms a...
Saved in:
| Main Authors: | , |
|---|---|
| Format: | Article (Journal) |
| Language: | English |
| Published: |
May 2000
|
| In: |
Astronomy and astrophysics
Year: 2000, Volume: 357, Pages: 283-300 |
| ISSN: | 1432-0746 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: http://adsabs.harvard.edu/abs/2000A%26A...357..283B
|
| Author Notes: | E.G. Berezhko, H.J. Völk |
| Summary: | A kinetic model of particle acceleration in supernova remnants (SNRs) is - extended to study the cosmic ray (CR) and associated high-energy gamma - -ray production during SN shock propagation through the inhomogeneous - circumstellar medium of a progenitor star that emits a wind. The wind - forms a low-density bubble surrounded by a swept-up shell of - interstellar matter. gamma -rays are produced as a result of decay of - pions which in turn are the result of collisions of CRs with nuclei of - the thermal plasma. The time evolution of the SNRs is followed - numerically, taking into account the nonlinear backreaction of the - accelerated CRs. The model for SNRs includes injection of suprathermal - particles at the shock front and heating of the thermal plasma due to - dissipation of Alfvén waves in the precursor region. Examples - typical for SN type Ib and SN type II explosions are considered. Apart - from the confirmation of the known fact that acceleration is extremely - rapid and that the upper momentum cutoff is reached almost immediately - after the explosion due to the high wind magnetic field, it is also - shown that the CRs are accelerated with a high efficiency. Depending on - the circumstellar parameters, 20% to 40% of the SN explosion energy is - absorbed by CRs during the SNR evolution for a moderate injection rate, - when a fraction eta = 10-3 of the gas particles, swept up by - the supernova shock, is accelerated. The CR momentum spectrum, - ultimately produced in the SNRs, has a power law form N~ p-gamma - with an index gamma =2.0 to 2.1 in a wide energy range up to a - maximum energy, which is about 1014 eV, if the CR diffusion - coefficient is as small as the Bohm limiting value. It is to be expected - that the resulting CR chemical composition at high energies reflects - more the stellar wind composition, whereas at lower energies it - corresponds more to that of the average interstellar medium. The - expected pi 0-decay gamma -ray flux is however considerably - lower than in the case of a uniform interstellar medium; a relatively - high gamma -ray luminosity in the band epsilon gamma > 1 - TeV, detectable at distances of several kpc, is only expected in the - case of a relatively dense ISM with a number density above 10 - cm-3. Extremely high gamma -ray emission may be produced when - the SN shock propagates through the slow dense wind of a red supergiant, - the progenitor of a SN type II. In this case SNRs might be visible in - gamma -rays for several hundred years out to distances of tens of kpc. - For the case of a SN type Ib the expected pi 0-decay - gamma-ray TeV-energy flux during the whole SNR evolution remains lower - than 10-11 cm-2s-1 if the interstellar - number density is less than 0.3 cm-3. |
|---|---|
| Item Description: | Gesehen am 08.12.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |