A population of isolated hard X-ray sources near the supernova remnant Kes 69

Abstract

Recent X-ray observations of the supernova remnant (SNR) IC 443 interacting with molecular clouds detected a new population of hard X-ray sources related to the remnant itself, which has been proposed to be fast ejecta fragments propagating within the dense environment. Encouraged by these studies, we obtained a deep XMM-Newton observation of the SNR Kes 69, which also shows signs of a shock-cloud interaction. We report on the detection of 18 hard X-ray sources in the field of Kes 69, which is a number sognificantly higher than expected for the Galactic source population in the field. The sources are spatially correlated with CO emission from the cloud in the remnant environment. The spectra of 3 of the 18 sources can be described as hard power-laws with photon indices smaller than two plus line emission associated with K-shell transitions. We discuss the two most promising scenarios for the interpretation of the sources, namely fast ejecta fragments (as in IC 443) and cataclysmic variables. While most of the observational evidence is consistent with the former interpretation, we cannot rule out the latter.

Evidence for a Neutral Iron Line Generated by MeV Protons from Supernova Remnants Interacting with Molecular Clouds

“…In the soft X-ray band (0.5-2.0 keV), we see clear emission associated with the SNRs, while in the hard X-ray band of 5.0-8.0 keV, no structure accompanied with the soft band is found. Thus, all these SNRs are soft Xray sources with electron temperature of 0.8 keV, which are confirmed in Sawada & Koyama (2012), Bocchino et al (2012), Bamba et al (2016), and Uchida et al (2012) for W28, Kes 69, Kes 78, and W44, respectively. Kes 67 is also a soft X-ray source with an electron temperature of ∼ 0.4 keV .…”

“…The point source in the south-west of W28 is reported by Pannuti et al (2017); the object, CXOU J175857.55-233400.3, is likely a cataclysmic variable or a quiescent lowmass X-ray binary. Two point-like sources located in the north and the west of Kes 69 are reported by Bocchino et al (2012). However no further information on these sources is available.…”

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

“…The observed hard spectra and enhanced abundances suggest that these may be fast-moving knots of ejecta traveling into dense molecular material and producing Kα emission accompanied by nonthermal bremsstrahlung (NTB) emission from shock-accelerated electrons (Bykov 2002). Knots with similar spectral properties are observed in Kes 69 and are coincident with CO emission from a nearby MC (Bocchino et al 2012), reinforcing this interpretation. Discrete X-ray knots directly along the SNR/MC interaction region in 3C 391 are also observed (Chen et al 2004), but while the inferred density for these knots is high, consistent with structures being driven into clouds, the abundances do not show strong evidence for metal enhancements.…”

Exploring the Diffuse X-ray Emission of Supernova Remnant Kesteven 69 with XMM-Newton

“…This has motivated a dedicated XMMNewton observation of Kes 69 (Obs ID: 0605480101 PI: Miceli). For searching the evidence of fast ejecta propagating in a dense environment, a recent study has revealed 18 hard X-ray point sources in the field of Kes 69 with this XMMNewton observation (Bocchino et al 2012). Investigations of their source nature suggest these hard X-ray sources can possibly be fast ejecta fragments or cataclysmic variables (CVs).…”