In this work, we have constructed a relation between the surface brightness (Σ) and diameter (D) of Galactic C-and S-type supernova remnants (SNRs). In order to calibrate the Σ-D dependence, we have carefully examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of the ambient medium) properties of the remnants and, taking into account also the distance values given in the literature, we have adopted distances for some of the SNRs * huseyin@pascal.sci.akdeniz.edu.tr † askin@gursey.gov.tr ‡ sezer@pascal.sci.akdeniz.edu.tr § physic@lan.ab.az 1 which have relatively more reliable distance values. These calibrator SNRs are all C-and S-type SNRs, i.e. F-type SNRs (and Stype SNR Cas A which has an exceptionally high surface brightness) are excluded. The Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: Σ(at 1 GHz)=8.4 −0.16 Wm −2 Hz −1 ster −1 (for Σ>3.7×10 −21 Wm −2 Hz −1 ster −1 and D<36.5 pc). We discussed the theoretical basis for the Σ-D dependence and particularly the reasons for the change in slope of the relation were stated. Added to this, we have shown the dependence between the radio luminosity and the diameter which seems to have a slope close to zero up to about D=36.5 pc. We have also adopted distance and diameter values for all of the observed Galactic SNRs by examining all the available distance values presented in the literature together with the distances found from our Σ-D relation.

We present here the results of the observation of CTB 37A obtained with the Xray Imaging Spectrometer onboard the Suzaku satellite. The X-ray spectrum of CTB 37A is well fitted by two components, a single-temperature ionization equilibrium component (VMEKAL) with solar abundances, an electron temperature of kT e ∼ 0.6 keV, absorbing column density of N H ∼ 3 × 10 22 cm −2 and a power-law component with photon index of Γ ∼ 1.6. The X-ray spectrum of CTB 37A is characterized by clearly detected K-shell emission lines of Mg, Si, S, and Ar. The plasma with solar abundances supports the idea that the X-ray emission originates from the shocked interstellar material. The ambient gas density, and age of the remnant are estimated to be ∼1f −1/2 cm −3 and ∼3×10 4 f 1/2 yr, respectively. The center-filling X-ray emission surrounded by a shell-like radio structure and other X-ray properties indicate that this remnant would be a new member of mixed-morphology supernova remnant class.

In this paper, we present the results from a Suzaku observation of the Galactic supernova remnant G272.2−3.2. The spectra of G272.2−3.2 are well fitted by a single‐temperature variable abundance non‐equilibrium ionization (VNEI) model with an electron temperature kTe∼ 0.77 keV, an ionization time‐scale τ∼ 6.5 × 1010 cm−3 s and an absorbing column density NH∼ 1.1 × 1022 cm−2. We have detected enhanced abundances of Si, S, Ca, Fe and Ni in the centre region, indicating that the X‐ray emission has an ejecta origin. We estimate that the electron density is ne∼ 0.48f−1/2 cm−3, the age is ∼4300f1/2 yr and the X‐ray total mass is Mx= 475f1/2 M⊙ by taking the distance to be d= 10 kpc. To understand the origin of the centrally peaked X‐ray emission of the remnant, we have studied the radial variations of the electron temperature and surface brightness. The relative abundances in the centre region suggest that G272.2−3.2 is the result of a Type Ia supernova explosion.

We present the results from the Suzaku X-ray Imaging Spectrometer observation of the mixed-morphology supernova remnant (SNR) HB9 (G160.9+2.6). We discovered recombining plasma (RP) in the western Suzaku observation region and the spectra here are well described by a model having collisional ionization equilibrium (CIE) and RP components. On the other hand, the X-ray spectra from the eastern Suzaku observation region are best reproduced by the CIE and non-equilibrium ionization model. We discuss possible scenarios to explain the origin of the RP emission based on the observational properties and concluded that the rarefaction scenario is a possible explanation for the existence of RP. In addition, the gamma-ray emission morphology and spectrum within the energy range of 0.2−300 GeV are investigated using ∼10 years of data from the Fermi Large Area Telescope (LAT). The gamma-ray morphology of HB9 is best described by the spatial template of radio continuum emission. The spectrum is well-fit to a log-parabola function and its detection significance was found to be ∼25σ. Moreover, a new gamma-ray point source located just outside the south-east region of the SNR's shell was detected with a significance of ∼6σ. We also investigated the archival H i and CO data and detected an expanding shell structure in the velocity range of −10.5 and +1.8 km s −1 that is coinciding with a region of gamma-ray enhancement at the southern rim of the HB9 shell.