Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties. (arXiv:2006.03382v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Suzuki_H/0/1/0/all/0/1">Hiromasa Suzuki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bamba_A/0/1/0/all/0/1">Aya Bamba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yamazaki_R/0/1/0/all/0/1">Ryo Yamazaki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ohira_Y/0/1/0/all/0/1">Yutaka Ohira</a>
In this decade, GeV/TeV gamma-ray observations of several supernova remnants
(SNRs) have implied that accelerated particles are escaping from their
acceleration sites. However, when and how they escape from the SNR vicinities
are yet to be understood. Recent studies have suggested that the particle
escape might develop with thermal plasma ages of the SNRs. In this paper, we
present a systematic study on time evolution of particle escape using thermal
X-ray properties and gamma-ray spectra.
We used 38 SNRs which associate with GeV/TeV gamma-ray emissions. We
conducted spectral fittings on the gamma-ray spectra using exponential cutoff
power law and broken power law models to estimate the exponential cutoff or the
break energies, both of which are indicators of particle escape. The plots of
the gamma-ray cutoff/break energies over the plasma ages show similar
tendencies to those predicted by simple theories of the particle escape under
conditions in which a shock is interacting with thin interstellar medium or
clouds. The particle escape timescale is estimated as $sim$100 kyr from
decreasing trends of the total energy of the confined protons with the plasma
age. The large dispersions of the cutoff/break energies of the data may suggest
an intrinsic variety of particle escape environments. This might be the cause
of the complicated Galactic cosmic-ray spectral shape measured on Earth.
In this decade, GeV/TeV gamma-ray observations of several supernova remnants
(SNRs) have implied that accelerated particles are escaping from their
acceleration sites. However, when and how they escape from the SNR vicinities
are yet to be understood. Recent studies have suggested that the particle
escape might develop with thermal plasma ages of the SNRs. In this paper, we
present a systematic study on time evolution of particle escape using thermal
X-ray properties and gamma-ray spectra.
We used 38 SNRs which associate with GeV/TeV gamma-ray emissions. We
conducted spectral fittings on the gamma-ray spectra using exponential cutoff
power law and broken power law models to estimate the exponential cutoff or the
break energies, both of which are indicators of particle escape. The plots of
the gamma-ray cutoff/break energies over the plasma ages show similar
tendencies to those predicted by simple theories of the particle escape under
conditions in which a shock is interacting with thin interstellar medium or
clouds. The particle escape timescale is estimated as $sim$100 kyr from
decreasing trends of the total energy of the confined protons with the plasma
age. The large dispersions of the cutoff/break energies of the data may suggest
an intrinsic variety of particle escape environments. This might be the cause
of the complicated Galactic cosmic-ray spectral shape measured on Earth.
http://arxiv.org/icons/sfx.gif
