Suzaku Observations of Ejecta-Dominated Galactic Supernova Remnant G346.6-0.2

arXiv:1103.2912v1 [astro-ph.HE] 15 Mar 2011 Mon. Not. R. Astron. Soc. 000, 1–?? (2002) Printed 15 November 2018 (MN LATEX style file v2.2) Suzaku Observations of Ejecta-Dominated Galactic Supernova Remnant G346.6-0.2 A. Sezer,1,2⋆F. G¨ok,3 M. Hudaverdi,1 M. Kimura4 and E.N. Ercan2⋆† 1T ¨UB˙ITAK Space Technologies Research Institute, ODTU Campus, Ankara, 06531, Turkey 2Bo˜gazic. i University, Faculty of Art and Sciences, Department of Physics, ˙Istanbul, 34342, Turkey 3Akdeniz University, Faculty of Sciences, Department of Physics, Antalya, 07058, Turkey 4Osaka University, Department of Earth and Space Science, Graduate School of Science, Machikaneyama 1-1, Toyonaka, Osaka, 560-0043, Japan ABSTRACT We present here the results of the X-ray analysis of Galactic supernova remnant G346.6-0.2 observed with Suzaku. K-shell emission lines of Mg, Si, S, Ca and Fe are detected clearly for the first time. Strong emission lines of Si and S imply that X-ray emission nature of G346.6-0.2 is ejecta-dominated. The ejecta-dominated emission is well fitted with a combined model consisting of thermal plasma in non-equilibrium ionization and a non-thermal component, which can be regarded as synchrotron emis- sion with a photon index of Γ ∼0.6. Absorbing column density of NH ∼2.1 × 1022 cm−2 is obtained from the best-fitting implying a high-density medium, high electron temperature of kTe ∼1.2 keV, and ionization timescale of net ∼2.9 × 1011 cm−3s indicating that this remnant may be far from full ionization equilibrium. The rela- tive abundances from the ejecta show that the remnant originates from a Type Ia supernova explosion. Key words: ISM: supernova remnants−ISM: individual(G346.6-0.2)−X-rays: ISM 1 INTRODUCTION A supernova remnant (SNR) consists of expelled material called “ejecta” from the explosion and a swept-up interstel- lar matter. The X-ray emission results from the interactions of ejecta and swept-up matter. From the X-ray emission of SNRs we may obtain valuable information about the phys- ical properties of the ejecta, swept-up plasma, elemental abundances and the history of the explosion. Shock wave may be the blast wave associated with the stellar explosion and/or the reverse shock wave, which propagates inwards from the decelerated blast wave and raises the tempera- ture of the stellar ejecta. The young SNRs are bright in X-rays and dominated by the emission from ejecta. Thus they provide fruitful information about the elements syn- thesized by the supernova (SN) explosions. Therefore, the observation of the young SNRs is the best method to in- vestigate the abundances of the elements synthesized by ⋆E-mail: aytap.sezer@uzay.tubitak.gov.tr (AS); gok@akdeniz.edu.tr (FG); murat.hudaverdi@uzay.tubitak.gov.tr (MH); mkimura@ess.sci.osaka-u.ac.jp (MK); ercan@boun.edu.tr (ENE). † This file has been amended to highlight the proper use of LATEX 2ε code with the class file. These changes are for illustrative purposes and do not reflect the original paper by A. Sezer. the SNe (see e.g. SN1006 (Koyama et al. 1995), RCW86 (Bamba, Koyama & Tomida 2000), Tycho (Warren et al. 2005) for the best studied ejecta-dominated SNRs in the X-ray band). G346.6-0.2 (RA(2000) = 17h10m19s, Dec. (2000) = −40◦11′) is a shell-type SNR located in the Galactic plane. It was discovered by Clark, Caswell & Green (1975) in radio band having an angular size of 8 arcmin (Whiteoak & Green 1996). In X-ray band, on the other hand, G346.6-0.2 was first observed by ASCA during its Galactic plane survey (Yamauchi et al. 2008). It is shown that the size of the X-ray emission from G346.6-0.2 is less extended than its reported radio structure. Five OH(1720 MHz) masers were detected toward this SNR and they are all located along the southern edge of the remnant (Koralesky et al. 1998). We are studying the X-ray emissions from the ejecta- dominated SNRs. For this purpose we have chosen several small size Galactic SNRs, one of which is G346.6-0.2. De- tailed properties of G346.6-0.2 remained unknown so far be- cause of very limited photon statistics in the ASCA (AGPS) data. Suzaku is the most recent X-ray astronomical satellite (see Mitsuda et al. (2007)) having a large collecting area and low background. Therefore, it is the best instrument for ob- serving dim and diffuse sources. We propose here to study G346.6-0.2 to understand the origin of its thermal and non- 2 A. Sezer, F. G¨ok, M. Hudaverdi, M. Kimura and E.N. Ercan thermal X-ray emission which will help us to distinguish its SN explosion type. By using the archival data of Suzaku, we were able to produce higher quality image and the spectra of the remnant, which lead to the results in this study. In Section 2, we describe the observation log and the data reduction methods. We present the image analysis in Section 2.1 and the spectral analysis in Section 2.2. We discuss our results and the origin of the thermal and non- thermal emission in Section 3. 2 OBSERVATION AND DATA REDUCTION Suzaku satellite has two s

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