The Origin of Recombining Plasma and the Detection of the Fe-K Line in the Supernova Remnant W28

Abstract

Overionized recombining plasmas (RPs) have been discovered from a dozen of 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 understand the physical origin of RPs. We report on a spatially resolved X-ray spectroscopy of W28, which is one of the largest MM SNRs found in our Galaxy. Two observations with Suzaku XIS cover the center of W28 to the northeastern rim where the shock is interacting with molecular clouds. The X-ray spectra in the inner regions are well reproduced by a combination of two-RP model with different temperatures and ionization states, whereas that in 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 north- eastern rim also shows an excess emission of the Fe I Kα 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 W28.

arXiv comment9 page, 6 figures, 4 tables, accepted in PASJ on February 8, 2018

References in corpus (33)

• Monte-Carlo Simulator and Ancillary Response Generator of Suzaku XRT/XIS System for Spatially Extended Source Analysis
• Reproducibility of Non-X-ray Background for the X-ray Imaging Spectrometer aboard Suzaku
• Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W28 (G6.4-0.1) field
• Study of the X-Ray Background Spectrum and its Large-Scale Fluctuation with ASCA
• Polarization Observations of 1720 MHz OH Masers toward the Three Supernova Remnants W28, W44, and IC443
• ASCA X-Ray Spectroscopy of LMC Supernova Remnants and the Metal Abundances of the LMC
• Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)
• Discriminating the Progenitor Type of Supernova Remnants with Iron K-Shell Emission
• Shock Excited Maser Emission from the Supernova Remnant W28
• Molecular clouds in the Trifid nebula M20; Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars
• ASCA Observations of the Supernova Remnant IC 443: Thermal Structure and Detection of Overionized Plasma
• Gamma rays from molecular clouds illuminated by accumulated diffusive protons from supernova remnant W28
• Investigation of the large-scale neutral hydrogen near the supernova remnant W28
• The K-shell Line Distribution of Heavy Elements along the Galactic Plane Observed with Suzaku
• AGILE detection of GeV gamma-ray emission from the SNR W28
• ROSAT/Asca Observations of the Mixed-Morphology Supernova Remnant W28
• X-Ray Observations of the Supernova Remnant W28 with Suzaku --- I. Spectral Study of the Recombining Plasma
• Dense, Fe-rich Ejecta in Supernova Remnants DEM L238 and DEM L249: A New Class of Type Ia Supernova?
• Unveiling the spatial structure of the overionized plasma in the supernova remnant W49B
• Evidence for a neutral iron line generated by MeV protons from supernova remnants interacting with molecular clouds
• Numerical Simulations of Supernova Remnant Evolution in a Cloudy Interstellar Medium
• Evolution of Supernova Remnants Expanding out of the Dense Circumstellar Matter into the Rarefied Interstellar Medium
• Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission
• Suzaku View of the Supernova Remnant RCW 86: X-Ray Studies of Newly-Discovered Fe-Rich Ejecta
• Discovery of Recombining Plasma in the Supernova Remnant 3C 391
• An XMM-Newton study of the mixed-morphology supernova remnant W28 (G6.4-0.1)
• Progenitors of Recombining Supernova Remnants
• Suzaku spectra of a Type II Supernova Remnant Kes 79
• Toward the Understanding of the Physical Origin of Recombining Plasma in the Supernova Remnant IC 443
• N49: the first robust discovery of a recombining plasma in an extra galactic supernova remnant
• Localized Recombining Plasma in G166.0+4.3: A Supernova Remnant with an Unusual Morphology
• X-ray Spectroscopy of the Mixed Morphology Supernova Remnant W28 with XMM-Newton
• CTIO, ROSAT HRI and Chandra ACIS Observations of the Archetypical Mixed-Morphology Supernova Remnant W28 (G6.4-0.1)

Cited by in corpus (23)

• Evidence for Rapid Adiabatic Cooling as an Origin of the Recombining Plasma in the Supernova Remnant W49B Revealed by NuSTAR Observations
• Deep XMM-Newton Observations Reveal the Origin of Recombining Plasma in the Supernova Remnant W44
• ALMA CO Observations of the Mixed-Morphology Supernova Remnant W49B: Efficient Production of Recombining Plasma and Hadronic Gamma-rays via Shock-Cloud Interactions
• NuSTAR Detection of Nonthermal Bremsstrahlung from the Supernova Remnant W49B
• Study of the excess Fe XXV line emission in the central degrees of the Galactic centre using XMM-Newton data
• Spatially Resolved Chandra Spectroscopy of the Large Magellanic Cloud Supernova Remnant N132D
• Constraining the cosmic ray spectrum in the vicinity of the supernova remnant W28: from sub-GeV to multi-TeV energies
• ALMA observations of supernova remnant N49 in the LMC: I. Discovery of CO clumps associated with X-ray and radio continuum shells
• Discovery of a Wind-Blown Bubble Associated with the Supernova Remnant G346.6-0.2: A Hint for the Origin of Recombining Plasma
• Observational constraints on the maximum energies of accelerated particles in supernova remnants: low maximum energies and a large variety
• Uniform distribution of the extremely overionized plasma associated with the supernova remnant G359.1-0.5
• Interaction between Molecular Clouds and MeV-TeV Cosmic-ray Protons Escaped from Supernova Remnants
• Suzaku X-ray observations of the mixed-morphology supernova remnant CTB 1
• An XMM-Newton X-ray View of Supernova Remnant W49B: Revisiting its Recombining Plasmas and Progenitor Type
• Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties
• Spatially-Resolved Study of Recombining Plasma in W49B Using XMM-Newton
• Intrusion of MeV-TeV Cosmic-Rays into Molecular Clouds Studied by Ionization, the Neutral Iron Line, and Gamma-Rays
• Probing Cosmic Rays with Fe K$\alpha$ Line Structures Generated by Multiple Ionization Process
• Initial state of the recombining plasma in supernova remnant W 28
• Typing supernova remnant G352.7$-$0.1 using XMM-Newton X-ray observations
• On the formation of over-ionized plasma in evolved supernova remnants
• A Complete X-ray View of Supernova Remnant W28 with Einstein Probe: Spatial Distribution of Parameters and Origin of the Thermal-Composite Morphology
• Investigation of the Physical Origin of Overionized Recombining Plasma in the Supernova Remnant IC 443 with XMM-Newton