The origin of the X-ray-emitting plasma in the eastern edge of the Cygnus Loop

Zhou, Xin; Bocchino, F.; Miceli, M.; Orlando, S.; Chen, Yang

doi:10.1111/j.1365-2966.2010.16684.x

Cited by 11 publications

(10 citation statements)

References 33 publications

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“…As the X-ray emission is emitted from the shock-cloud interaction region, the hot plasma may consist of two density components: (1) the dense cloud material and (2) the tenuous inter-cloud medium. The denser cloud material heated by the transmitted shock is relatively colder, which is responsible for the 0.3 keV component, while the inter-cloud medium may give arise to the ∼0.6 keV component, as also seen in the shells of the Vela SNR (Bocchino et al 1999;Miceli et al 2006) and the Cygnus Loop (Zhou et al 2010). The ionization timescale (0.5-1.6 × 10 12 cm −3 s) of the hot inter-cloud gas can provide a rough estimation of its ionization age of 1-4 × 10 4 yr.…”

Section: Gas Properties Of the Ne Shellmentioning

confidence: 98%

ANXMM-NEWTONSTUDY OF THE MIXED-MORPHOLOGY SUPERNOVA REMNANT W28 (G6.4–0.1)

Zhou

Safi‐Harb

Chen

et al. 2014

ApJ

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We have performed an XMM-Newton imaging and spectroscopic study of supernova remnant (SNR) W28, a prototype mixed-morphology or thermal composite SNR believed to be interacting with a molecular cloud. The observed hot X-ray emitting plasma is characterized by low metal abundances, showing no evidence of ejecta. The X-rays arising from the deformed northeastern shell consist of a thermal component with a temperature of ∼0.3 keV plus a hard component of either thermal (temperature ∼0.6 keV) or non-thermal (photon index = 0.9-2.4) origin. The X-ray emission in the SNR interior is blobby and the corresponding spectra are best described as the emission from a cold (∼0.4 keV) plasma in non-equilibrium ionization with an ionization timescale of ∼4.3 × 10 11 cm −3 s plus a hot (∼0.8 keV) gas in collisional ionization equilibrium. Applying the two-temperature model to the smaller central regions, we find non-uniform interstellar absorption, temperature, and density distribution, which indicates that the remnant is evolving in a non-uniform environment with denser material in the east and north. The cloudlet evaporation mechanism can essentially explain the properties of the X-ray emission in the center, and thermal conduction may also play a role for length scales comparable to the remnant radius. A recombining plasma model with an electron temperature of ∼0.6 keV is also feasible for describing the hot central gas with the recombination age of the gas estimated at ∼2.9 × 10 4 yr.

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Section: Gas Properties Of the Ne Shellmentioning

confidence: 98%

ANXMM-NEWTONSTUDY OF THE MIXED-MORPHOLOGY SUPERNOVA REMNANT W28 (G6.4–0.1)

Zhou

Safi‐Harb

Chen

et al. 2014

ApJ

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“…Furthermore, according to the X‐ray studies, a dense‐gas wall is suggested to occur along the eastern edge (Levenson et al 1997; Levenson, Graham & Snowden 1999) and shock–cloud interaction is thought to be taking place there (e.g. Miyata & Tsunemi 2001; Zhou et al 2010). Such a molecular‐rich environment may act as a reasonable site for the hadronic origin of γ‐ray emission from shock‐accelerated CRs, as pointed out by Katagiri et al (2011).…”

Section: Application To Individual Snrsmentioning

confidence: 99%

γ-rays from molecular clouds illuminated by accumulated diffusive protons - II. Interacting supernova remnants

Li¹,

Chen²

2012

Monthly Notices of the Royal Astronomical Society

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Recent observations reveal that spectral breaks at ∼GeV are commonly present in Galactic γ‐ray supernova remnants (SNRs) interacting with molecular clouds and that most of them have a spectral (E2dF/dE) ‘platform’ extending from the break to lower energies. In Paper I, we developed an accumulative diffusion model by considering an accumulation of the diffusive protons escaping from the shock front throughout the history of the SNR expansion. In this paper, we improve the model by incorporating the finite volume of molecular clouds, demonstrate the model dependence on particle diffusion parameters and cloud size, and apply it to nine interacting SNRs (W28, W41, W44, W49B, W51C, Cygnus Loop, IC443, CTB 37A and G349.7+0.2). This refined model naturally explains the GeV spectral breaks and, in particular, the ‘platforms’, together with available TeV data. We find that the index of the diffusion coefficient δ is in the range 0.5–0.7, similar to the Galactic averaged value, and the diffusion coefficient for cosmic rays around the SNRs is essentially two orders of magnitude lower than the Galactic average (χ∼ 0.01), which is a good indication for the suppression of cosmic‐ray diffusion near SNRs.

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“…Allowing N H to vary causes it to trend toward unphysically low values with large errors in a handful of regions. Therefore, for all fits the column density of intervening material, N H , was set to 8 × 10 20 cm −2 consistent with other Cygnus Loop studies (McEntaffer & Cash 2008;Zhou et al 2010;Miyata & Tsunemi 2001). Other variables include the temperature of the plasma, kT , a normalization parameter which includes emission measure, norm, and the ionization timescale, τ .…”

Section: Spectral Extractions and Fittingmentioning

confidence: 99%

“…Similar to the above X-ray studies, they find inhomogeneous structure and explain their results with a reflection-shock model resulting from the interaction of the blast wave with a single cavity wall cloud. More recently, Zhou et al (2010) analyzed higher resolution XMM-Newton data. They find a low temperature exterior (kT ∼0.07-0.15 keV) with depleted abundances and high temperature interior (kT ∼0.24-0.46 keV).…”

Section: Introductionmentioning

confidence: 99%

CHANDRAIMAGING AND SPECTROSCOPY OF THE EASTERN XA REGION OF THE CYGNUS LOOP SUPERNOVA REMNANT

McEntaffer¹,

Brantseg²

2011

ApJ

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The XA region of the Cygnus Loop is a bright knot of X-ray emission on the eastern edge of the supernova remnant. The emission results from the interaction of the supernova blast wave with density enhancements at the edge of a precursor formed cavity. However, this interaction is complex given the irregular morphology of the cavity wall. To study the nature and origin of the X-ray emission we use high spatial resolution images from Chandra. We extract spectra from these images to analyze the physical conditions of the plasma. Our goal is to probe the density of various regions to form a picture of the cavity wall and characterize the interaction between this supernova and the local interstellar medium. We find that a series of regions along the edge of the X-ray emission appears to trace out the location of the cavity wall. The best fit plasma models result in two temperature component equilibrium models for each region. The low temperature components have densities that are an order of magnitude higher than the high temperature components. The high density plasma may exist in the cavity wall where it equilibrates rapidly and cools efficiently. The low density plasma is interior to the enhancement and heated further by a reverse shock from the wall. Calculations of shock velocities and timescales since shock heating are consistent with this interpretation. Furthermore, we find a bright knot of emission indicative of a discrete interaction of the blast wave with a high density cloud in the cavity wall with a size scale ∼0.1 pc. Aside from this, other extractions made interior to the X-ray edge are confused by line of sight projection of various components. Some of these regions show evidence of detecting the cavity wall but their location makes the interpretation difficult. In general, the softer plasmas are well fit at temperatures kT ∼0.11 keV, with harder plasmas at temperatures of kT ∼0.27 keV. All regions displayed consistent metal depletions most notably in N, O, and Ne at an average of 0.54, 0.55, and 0.36 times solar, respectively. arXiv:1103.5648v1 [astro-ph.HE]

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The origin of the X-ray-emitting plasma in the eastern edge of the Cygnus Loop

Cited by 11 publications

References 33 publications

ANXMM-NEWTONSTUDY OF THE MIXED-MORPHOLOGY SUPERNOVA REMNANT W28 (G6.4–0.1)

ANXMM-NEWTONSTUDY OF THE MIXED-MORPHOLOGY SUPERNOVA REMNANT W28 (G6.4–0.1)

γ-rays from molecular clouds illuminated by accumulated diffusive protons - II. Interacting supernova remnants

CHANDRAIMAGING AND SPECTROSCOPY OF THE EASTERN XA REGION OF THE CYGNUS LOOP SUPERNOVA REMNANT

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