2018/02/08 by Hiromichi Okon, Hiroyuki Uchida, Takaaki Tanaka +2
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Emission spectrum #Ionization #Line (geometry) #Molecular cloud #Plasma #Spectral line #Supernova #Supernova remnant #astro-ph.HE
paper · pdf · doi:10.1093/pasj/psy022
9 page, 6 figures, 4 tables, accepted in PASJ on February 8, 2018
arxiv created 2018/02/08 · openalex created_date 2018/02/23 · openalex publication_date 2018/02/26 · arxiv updated 2018/04/04 · openalex updated_date 2026/08/05
Abstract Overionized recombining plasmas (RPs) have been discovered from a dozen mixed-morphology (MM) supernova remnants (SNRs). However, their formation process is still under debate. As pointed out by many previous studies, spatial variations of plasma temperature and ionization state provide clues to understanding the physical origin of RPs. We report on spatially resolved X-ray spectroscopy of W 28, which is one of the largest MM SNRs found in our Galaxy. Two observations with Suzaku XIS cover the center of W 28 to the northeastern rim where the shock is interacting with molecular clouds. The X-ray spectra in the inner regions are reproduced well by a combination of two RP models with different temperatures and ionization states, whereas that in the northeastern rim is explained with a single RP model. Our discovery of the RP in the northeastern rim suggests an effect of thermal conduction between the cloud and hot plasma, which may be the production process of the RP. The X-ray spectrum of the northeastern rim also shows an excess emission of the Fe i K α line. The most probable process to explain the line would be inner shell ionization of Fe in the molecular cloud by cosmic ray particles accelerated in W 28.