We have investigated the X-ray emission from the shock-heated plasma of the Galactic supernova remnant Kesteven 69 with
A series of multiwavelength observations has been devoted for investigating Galactic supernova remnant (SNR) Kesteven 69 (Kes 69). Millimeter band observations of CO and HCO+ lines towards Kes 69 provided strong evidence for the association between Kes 69 and the molecular cloud (Zhou et al. 2009). An extended OH (1,720 MHz) emission region further indicates the presence of shocked molecular gas in Kes 69 (Hewitt et al. 2009). With HI observation, the kinematic distance for Kes 69 has been determined for a range from 5.5 kpc to 11.2 kpc (Tian & Leahy 2008).
In X-ray regime, it has an irregular morphology as observed by
While the aforementioned studies are focused on the point source population detected in the field of Kes 69, in this paper we report a detailed analysis of diffuse emission with
[Fig. 1.] X-ray color image of a 25′×25′ FoV toward the supernova remnant Kes 69 with MOS1/2 and PN data merged (red: 0.3？1 keV, green: 1 ？ 2 keV, blue: 2 ？ 12 keV). Radio contours as observed by Very Large Array (VLA) at 1.4 GHz are overlaid for comparison. The X-ray emission is well correlated with the radio shell on south edge. The bright source as highlighted by the white box is XGPS-I J183251-100106/2XMM J183251.4-100106 which is found to be a serendipitous magnetic CV detected in this field (Hui et al. 2012a).
Kes 69 was observed on 2009 October 8-9 with the European Photon Imaging Camera (EPIC) on board
[Fig. 2.] (Left panel) Adaptively smoothed image with all EPIC data merged. All the resolved point sources have been subtracted from the data in accordance with the point spread function width at their off-axis angles and peak energies. The extracted region for X-ray spectrum of the remnant emission is illustrated by the green ellipse. (Right panel) Energy spectrum of Kes 69 remnant emission as observed with MOS1 (black symbols), MOS2 (red symbols) and PN (green symbols).
which were potentially contaminated by bad pixels, effective exposures were found to be 55.9 ks, 56.6 ks, and 41.3 ks for MOS1, MOS2, and PN, respectively.
The X-ray color image of the field around Kes 69 is shown in Fig. 1. With source detection performed on all EPIC data in the energy range of 0.3-12 keV, we have revealed a population of point sources in this field. Since we concerned only diffuse emission from the SNR, all these resolved point sources were subsequently subtracted in accordance with the point spread function width at their off-axis angles and peak energies. In the left panel of Fig. 2, the adaptively smoothed “cheese” image after point source subtraction is shown. The energy spectra of the SNR were then extracted from individual camera within the elliptical region as illustrated in the left panel of Fig. 2. Response files were computed by using XMMSAS. The energy spectra as seen by individual camera are shown in the right panel of Fig. 2. In order to obtain a tight constraint on the emission properties, we fitted the data obtained from all three cameras simultaneously.
For the spectral fitting, we used XSPEC (version 12.6.0) with
Following Hui et al. (2012b), we discuss the properties of Kes 69. Assuming the shocked densities of hydrogen
[Fig. 3.] Confidence contours for CIE plasma model fitted to the X-ray spectrum of diffuse emission of Kes 69. (left panel: plasma temperature vs. model normalization; right panel: plasma temperature vs. column density). The χ2 values for the minimum and each contour are given at the top of each plot.