High-energy Phenomena in Supernova Remnants

講演日:2022.09.20 (Tue)

  • 宇宙


Paul Yeung (University of Tokyo), Hiromasa Suzuki (Konan University)


Multiwavelength studies of G298.6-0.0: Possibly one of the oldest GeV supernova remnants

Paul Yeung (University of Tokyo)

Hadronic Gamma-ray sources associated with supernova remnants (SNRs) can serve as stopwatches for the escape of cosmic rays from SNRs, which gradually develops from highest-energy particles to lowest-energy particles with time. In this work, we analyze the 13.7 yr Fermi-LAT data to investigate the Gamma-ray feature in/around the SNR G298.6-0.0 region. With Gamma-ray spatial analyses, we detect three point-like components. Among them, Src-NE is at the eastern SNR shell, and Src-NW is adjacent to the western edge of this SNR. Src-NE and Src-NW demonstrate spectral breaks at energies around/below 1.8 GeV, suggesting an old SNR age of >10 kyr. We also look into the X-ray emission from the G298.6-0.0 region, with the Chandra-ACIS data. We detected an extended keV source having a centrally filled structure inside the radio shell. The X-ray spectra are well fit by a model which assumes a collisional ionisation equilibrium of the thermal plasma, further supporting an old SNR age. Based on our analyses of the NANTEN CO- and ATCA-Parkes HI-line data, we determined a kinematic distance of ~10.1 kpc from us to G298.6-0.0. This distance entails a large physical radius of the SNR of ~15.5 pc, which is an additional evidence for an old age of >10 kyr. Besides, the CO data cube enables us to three-dimensionally locate the molecular clouds which are potentially interacting with SNR G298.6-0.0 and could account for the hadronic Gamma-rays detected at Src-NE or Src-NW. Furthermore, the multiwavelength observational properties unanimously imply that the SNR--MC interaction occurs mainly in the northeast direction.


Investigation of cosmic-ray acceleration physics in supernova remnants through X-ray and gamma-ray observations

Hiromasa Suzuki (Konan University)

Supernova remnants (SNRs) are thought to be the most plausible sources of Galactic cosmic rays. One of the principal questions is whether they are accelerating particles up to the maximum energy of Galactic cosmic rays (∼PeV). We performed a systematic study of gamma-ray-emitting SNRs. Our purpose is to measure the evolution of maximum particle energies with the current best statistics and age estimates. We modeled their gamma-ray spectra to constrain the particle-acceleration parameters. The maximum energies were found to be well below PeV for most sources. The time dependence of the maximum energy could not be explained with the simplest acceleration condition (Bohm limit) and require shock–ISM (interstellar medium) interaction, which is naturally expected. The average maximum energy during lifetime was found to reach ∼PeV only if the age at the maximum is less than 10 yr. The maximum energies during lifetime are suggested to have a variety of 1-2 orders of magnitude from object to object, which will be due to the dependence on environments.
I will also talk about our detector response study of the X-ray CMOS sensor “XRPIX", which is planned be onboard future X-ray satellites.