Observations of supernova remnants and pulsar wind nebulae at gamma-ray energies

Abstract

International audienceIn the past few years, gamma-ray astronomy has entered a golden age thanks to two major breakthroughs: Cherenkov telescopes on the ground and the Large Area Telescope (LAT) onboard the Fermi satellite. The sample of supernova remnants (SNRs) detected at gamma-ray energies is now much larger: it goes from evolved supernova remnants interacting with molecular clouds up to young shell-type supernova remnants and historical supernova remnants. Studies of SNRs are of great interest, as these analyses are directly linked to the long standing issue of the origin of the Galactic cosmic rays. In this context, pulsar wind nebulae (PWNe) need also to be considered since they evolve in conjunction with SNRs. As a result, they frequently complicate interpretation of the gamma-ray emission seen from SNRs and they could also contribute directly to the local cosmic ray spectrum, particularly the leptonic component. This paper reviews the current results and thinking on SNRs and PWNe and their connection to cosmic ray production

Gamma-ray emission from binaries in context

“…When the pulsar is isolated, the pulsar wind propagates freely until it is contained by the interstellar medium or the ejecta from its parent supernova, forming a shock structure. These are called pulsar wind nebulae (PWN) [50,51]. In PSR B1259-63, the pulsar wind propagates in the much denser environment provided by the circumstellar disk and stellar wind.…”

“…Inversely, a strong pulsar wind pushes back the stellar wind all the way to the surface of the star (η 1 ⇒ R/d ≈ 1). Here, as in PWN [51], the shock is thought to channel a fraction of the pulsar wind energy to particles that then radiate gamma rays. The process may involve randomization of the particles initially frozen with the magnetic field in the pulsar wind, diffuse shock acceleration, or shock-driven reconnection.…”

Search for Extended Sources in the Galactic Plane Using Six Years of Fermi-Large Area Telescope Pass 8 Data above 10 GeV

“…Several surveys of the Galaxy have been undertaken at TeV γ-ray energies (e.g., Aharonian et al 2006a) by the current Instrument Atmospheric Cherenkov Telescopes (IACTs) revealing different classes of astrophysical sources such as supernova remnants (SNRs), pulsar wind nebulae (PWNe), and molecular clouds (MCs; see Hewitt & Lemoine-Goumard 2015, for a review on SNRs and PWNe). Many are observed as spatially extended with respect to the angular resolution of the instruments.…”

Supernova remnants in the very–high–energy gamma-ray domain: the role of the Cherenkov telescope array

“…The angular extension of the SNRs, the unknown level of the diffusion emission, and the high numbers of the sources leading to overlapping between sources may be a significant issue for identification. This effect is expected to be especially relevant in the inner regions of the Galaxy and for the fainter objects (Hewitt & Lemoine-Goumard 2015). According to the latest gamma-ray surveys, the most numerous Galactic sources are Pulsar Wind Nebulae (PWNe) and the overlapping of sources is expected (Donath et al 2016).…”