The Cygnus Loop was observed from the northeast to the southwest with XMM-Newton. We divided the observed region into two parts, the north path and the south path, and studied the X-ray spectra along two paths. The spectra can be well fitted either by a one-component non-equilibrium ionization (NEI) model or by a two-component NEI model. The rim regions can be well fitted by a one-component model with relatively low kT e whose metal abundances are subsolar (0.1-0.2). The major part of the paths requires a two-component model. Due to projection effects, we concluded that the low kT e (∼0.2 keV) component surrounds the high kT e (∼0.6 keV) component, with the latter having relatively high metal abundances (∼5 times solar). Since the Cygnus Loop is thought to originate in a cavity explosion, the low kT e component originates from the cavity wall while the high kT e component originates from the ejecta.The flux of the cavity wall component shows a large variation along our path. We found it to be very thin in the south-west region, suggesting a blowout along our line of sight. The metal distribution inside the ejecta shows non-uniformity, depending on the element. O, Ne and Mg are relatively more abundant in the outer region while Si, S and Fe are concentrated in the inner region, with all metals showing strong asymmetry. This observational evidence implies an asymmetric explosion of the progenitor star. The abundance of the ejecta also indicates the progenitor star to be about 15 M ⊙ .
We present the results of a spatially resolved spectral analysis from four Suzaku observations covering the northeastern rim of the Cygnus Loop. A two-kT e nonionization equilibrium (NEI) model fairly well represents our data, which confirms the NEI condition of the plasma there. The metal abundances are depleted relative to the solar values almost everywhere in our field of view. We find abundance inhomogeneities across the field: the northernmost region (Region A) has enhanced absolute abundances compared with other regions. In addition, the relative abundances of Mg/O and Fe/O in Region A are lower than the solar values, while those in the other regions are twice higher than the solar values. As far as we are concerned, neither a circumstellar medium, (nor) fragments of ejecta, nor abundance inhomogeneities of the local interstellar medium around the Cygnus Loop can explain the relatively enhanced abundance in Region A. This point is left as an open question for future work.1
We observed a linearly sliced area of the Cygnus Loop from the north-east to the south-west with Suzaku in seven pointings. After dividing the entire fields of view (FOV) into 119 cells, we extracted spectra from all of the cells and performed spectral analysis for them. We then applied both one-and two-component non-equilibrium ionization (NEI) models for all of the spectra, finding that almost all were significantly better fitted by the two-component NEI model rather than the one-component NEI model. Judging from the abundances, the high-kT e component must be the ejecta component, while the low-kT e component comes from the swept-up matter. Therefore, the ejecta turn out to be distributed inside a large area (at least our FOV) of the Cygnus Loop. We divided the entire FOV into northern and southern parts, and found that the ejecta distributions were asymmetric to the geometric center: the ejecta of Si, S, and Fe seem to be distributed more in the south than in the north of the Cygnus Loop by a factor of ∼2. The degree of ejecta-asymmetry is consistent with that expected by recent supernova explosion models.
In this paper we performed moderate-resolution spectroscopy on the data obtained with XMM-Newton of the northeastern limb of the Cygnus Loop. This observation was proposed as a higher resolution follow-up to that made by ASCA. We investigated the radial variation of the temperature, ionization timescale, elemental abundances, and hydrogen column density across our field of view. We confirmed that on average all the abundances are depleted. However, we could not confirm the jump structure found by Miyata et al. in the physical properties of the plasma at 0.9R S . We also detected what looks like a new line in our spectra which probably comes from C vi. Comparing our results for heavy element abundances with those from Suzaku, we found that they agree to within a factor of 2Y3. The heavy element ratios relative to O were relatively constant across the field of view and a comparison with models shows that the ISM in this part of the remnant was probably created by low-to intermediate-mass stars.
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