Showing papers on "Stellar-wind bubble published in 2020"

A radio continuum and polarization study of the pulsar wind nebula CTB 87 (G74.9+1.2)

Abstract: We present radio continuum and linear polarisation observations of the pulsar wind nebula CTB87 (G74.9+1.2) with the Effelsberg 100-m radio telescope between 4.75 and 32 GHz. An analysis of these new data including archived low-frequency observations at 1420 MHz and 408 MHz from the Canadian Galactic Plane Survey shows that CTB87 consists of two distinct emission components: a compact kidney-shaped component, 14 pc x 8.5 pc (7.8' x 4.8') in size and a larger diffuse, spherical and centrally peaked component of about 30 pc (17') in diameter. The kidney-shaped component with a much steeper radio continuum spectrum is highly linearly polarised and likely represents a relic pulsar wind nebula. The diffuse component represents the undisturbed part of the PWN expanding inside a cavity or stellar wind bubble. The previously reported spectral break above 10 GHz is likely the result of missing large-scale emission and insufficient sensitivity of the high-frequency radio continuum observations. The simulation of the system's evolution yields an age of about 18,000 years as the result of a type II supernova explosion with an ejecta mass of about 12 solar masses and an explosion energy of about 7 x 10^50 erg. We also found evidence for a radio shell in our polarisation data which represents the blast wave that entered the molecular cloud complex at a radius of about 13 pc.

Studies of TeV Gamma-Ray Sources in the Hydrogen-Alpha Optical Line

Abstract: The first way humanity explored our Milky Way Galaxy and the Universe was through optical light observations. That led us to explore the cosmos using different electromagnetic wavebands such X-rays, gamma-rays, and radio wavelengths. Since then multi-wavelength studies of sources have started to explain their physical properties. The links between the TeV (1012 eV) gamma-ray emission of HESS J1825-137 and an optical supernova remnant (SNR) G18.7-2.2 is helping us to understand the interstellar medium (ISM) in multiple different wavebands (Voisin et al., 2016). G18.7-2.2 is observed in optical H𝛼, and has a spectral intensity ratio of ionised sulphur to H𝛼 [S II] / H𝛼 indicating that it is a SNR. There is a need to look for similar counterparts in H𝛼 towards TeV gamma-ray surveys that have some interesting features. We use the archival data from optical H𝛼 survey, as well as the HESS galactic plane survey (HGPS), looking for attributes that may link the two emission channels. Moreover, other radio and X-ray surveys are used with some HESS candidates to provide more evidence in different electromagnetic wavelengths. A model is used to calculate the SNR radius as a function of age and density, where this age has been inferred from the energetic pulsars which have been left behind in the formation of the SNR. Additionally, a stellar wind bubble (SWB) model is used to estimate the radius of the stellar wind shock produced by the SNR progenitor star. In this work, There are some TeV sources that have no features in the H𝛼. However, there are many notable candidates that have been investigated in this study. We found that HESS J1356-645. HESS J1912+101 and HESS J1804-216 have an arcs in the optical H𝛼 line which indicates a plausible relationship. HESS J1303-631 and HESS J1640-465 have an interesting H𝛼 emission morphology that may be related to the stellar wind bubble created by the progenitor star. Finally, we present the unique H𝛼 jet structure and the bow shock morphology in the region of HESS J1826-148 which may be linked to a powerful microquasar in the galactic plane.