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Astron. Astrophys. 362, L29-L32 (2000)

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1. Introduction

Massive stars that are the likely progenitors of core collapsed supernovae are expected to be spatially correlated with molecular clouds. IC 443 (G189.1+3.0) is one of the best space laboratories to study rich phenomena accompanying supernova interaction with a molecular cloud. This was established from observed shock-excited molecular line emission from OH, CO and H2 (e.g. Burton et al. 1988; van Dishoeck et al. 1993; Cesarsky et al. 1999). Observations of OH masers and CO clumps towards IC 443, W28 and W44 also provide convincing evidence of molecular cloud interaction in this case (Claussen et al 1997).

IC 443 was a target of X-ray observations with HEAO 1 (Petre et al. 1988), Ginga (Wang et al. 1992), ROSAT (Asaoka & Aschenbach 1994) and ASCA (Keohane et al. 1997, K97 hereafter). The soft X-ray 0.2-3.1 keV surface brightness map of IC 443 from the Einstein Observatory (Petre et al. 1988) shows bright features in the northeastern part of the remnant as well as bright soft emission from the source central part. The presence of nearly uniform X-ray emission from the central part of the remnant was clearly seen also by ROSAT (Asaoka & Aschenbach, 1994), and corresponds to the emission from hot (T[FORMULA] K), low density gas interior to the shock. ASCA GIS observations by K97 discovered the localized character of the hard X-ray emission. They concluded that most of the 2-10 keV GIS photons came from an isolated emitting feature and from the southeast elongated ridge of hard emission. Preite-Martinez et al. (1999) have reported a hard ([FORMULA] keV) component with BeppoSAX/PDS and two hot spots corresponding to the ASCA sources of K97 using the MECS.

The supernova remnants (SNRs) that are likely candidates to be [FORMULA]-ray sources in CGRO EGRET observations (Esposito et al. 1996) also show evidence for interaction with molecular gas. In the case of IC 443, the molecular line emission region is partially inside the EGRET [FORMULA]-ray detection circle.

Theoretical models of SNRs interacting with clouds were discussed recently by Sturner et al. (1997), Baring et al. (1999), Chevalier (1999). The non-thermal multi-wavelength spectrum of a SNR interacting with a molecular cloud was studied by Bykov et al. (2000). They showed that the propagation of a radiative shock wave within a molecular cloud lead to a substantial non-thermal emission both in hard X-rays and in [FORMULA]-ray. The complex structure of molecular cloud consisting of dense massive clumps embedded in the inter-clump medium could result in localized sources of hard X-ray emission correlated with both bright molecular emission and extended source of non-thermal radio and [FORMULA]-ray emission. In this Letter, we present the archive BeppoSAX observations of IC443 and, in particularly, we discuss the features detected in the MECS hard X-ray mosaiced map of the remnant.

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© European Southern Observatory (ESO) 2000

Online publication: October 24, 2000