X-ray emission from charge exchange in the Cygnus Loop SNR

Uchida

et al. 2022

ApJ

Recent high-resolution X-ray spectroscopy revealed the possible presence of charge exchange (CX) X-ray emission in supernova remnants (SNRs). Although CX is expected to take place at the outermost edges of SNR shells, no significant measurement has been reported so far due to the lack of nearby SNR samples. Here we present an X-ray study of SNR G296.1−0.5, which has a complicated multiple-shell structure, with the Reflection Grating Spectrometer on board XMM-Newton. We select two shells in different regions and find that in both regions the O vii line shows a high forbidden-to-resonance (f/r) ratio that cannot be reproduced by a simple thermal model. Our spectral analysis suggests a presence of CX and the result is also supported by our new radio observation, where we discover evidence of molecular clouds associated with these shells. Assuming G296.1−0.5 has a spherical shock, we estimate that CX is dominant in a thin layer with a thickness of 0.2%–0.3% of the shock radius. The result is consistent with a previous theoretical expectation and we therefore conclude that CX occurs in G296.1−0.5.

Section: Future Workmentioning

confidence: 93%

Charge Exchange X-Ray Emission Detected in Multiple Shells of Supernova Remnant G296.1–0.5

Uchida

et al. 2022

ApJ

“…If we assume our result can be applied to other nearby SNRs, it is possible to identify regions where CX is dominantly occurring. As pointed out in several studies (Katsuda et al 2012;Roberts & Wang 2015;Uchida et al 2019), the Cygnus Loop is one of the plausible candidates for detecting CX. Given that the Cygnus Loop has a spherical shell with an apparent diameter of 3 • , we expect that a pure CX emission can be detected in a thickness of ∼ 15 from the shock front.…”

Section: Future Workmentioning

confidence: 93%

Charge Exchange X-ray Emission Detected in Multiple Shells of Supernova Remnant G296.1-0.5

Tanaka,

Uchida,

Tanaka

et al. 2022

Preprint

Recent high-resolution X-ray spectroscopy revealed possible presence of charge exchange (CX) X-ray emission in supernova remnants (SNRs). Although CX is expected to take place at outermost edges of SNR shells, no significant measurement has been reported so far due to the lack of nearby SNR samples. Here we present an X-ray study of SNR G296.1−0.5, which has a complicated multiple-shell structure, with the Reflection Grating Spectrometer (RGS) onboard XMM-Newton. We select two shells in different regions and find that in both regions O VII line shows a high forbidden-to-resonance (f /r) ratio that cannot be reproduced by a simple thermal model. Our spectral analysis suggests a presence of CX and the result is also supported by our new radio observation, where we discover evidence of molecular clouds associated with these shells. Assuming G296.1−0.5 has a spherical shock, we estimate that CX is dominant in a thin layer with a thickness of 0.2-0.3% of the shock radius. The result is consistent with a previous theoretical expectation and we therefore conclude that CX occurs in G296.1−0.5.

“…Heliospheric CX, varying on the timescale of days to weeks, is particularly difficult to identify and subtract in observations. Astrophysically, there are hints of CX in objects such as clusters of galaxies (Aharonian et al ; Walker et al ), starbust galaxies (Tsuru et al ), and supernova remnants (Roberts & Wang ). CX is thus relevant to our current observations from, e.g., XMM‐Newton and Chandra , as well as from future missions such as XRISM and Athena .…”

Section: Charge Exchange Observationsmentioning

confidence: 99%

Charge exchange, from the sky to the laboratory: A method to determine state‐selective cross‐sections for improved modeling

2020

Charge exchange (CX) is a semi‐resonant recombination process that can lead to spectral line emission in the X‐ray band. It occurs in nearly any environment where hot plasma and cold gas interact: in the solar system, in comets and planetary atmospheres, and likely astrophysically, in, for example, supernova remnants and galaxy clusters. It also contributes to the soft X‐ray background. Accurate spectral modeling of CX is thus critical to properly interpreting our astrophysical observations, but the commonly used CX models in popular spectral fitting packages often rely on scaling equations and may not accurately describe observations or laboratory measurements. This paper introduces a method that can be applied to high‐resolution CX spectra to directly extract state‐selective CX cross‐sections for electron capture, a key parameter for properly simulating the resulting CX spectrum.