An XMM-Newton study of the mixed-morphology supernova remnant W28 (G6.4–0.1)
- School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)
- Department of Physics and Astronomy, University of Manitoba, Winnipeg R3T 2N2 (Canada)
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{sup 11} cm{sup –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{sup 4} yr.
- OSTI ID:
- 22365340
- Journal Information:
- Astrophysical Journal, Vol. 791, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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