Astron. Astrophys. 319, 655-663 (1997)

New radio and soft X-ray observations of the supernova remnant G 18.95-1.1

E. Fürst ¹, W. Reich ¹ and B. Aschenbach <sup>2

1</sup> Max-Planck-Institut für Radioastronomie,  Auf dem Hügel 69,  D-53121 Bonn, Germany
² Max-Planck-Institut für extraterrestrische Physik,  Postfach 1603,  D-85740 Garching, Germany

Received 8 March 1996 / Accepted 9 August 1996

Abstract

New observations of the Galactic supernova remnant (SNR) G 18.95-1.1 have been obtained in soft X-rays and at 10.55 GHz. The X-ray emission was observed with the ROSAT satellite using its position proportional counter (PSPC). The data are best fitted by a single-component, thermal spectrum with a temperature of and an interstellar absorption equivalent to . No significant variation of and across the source was detected. The upper limit of any power law emission is about 1% of the total observed X-ray flux density of . The new 10.55 GHz observations made with the Effelsberg 100-m telescope confirm the previous radio spectral index of = -0.28 () for the integrated flux densities. The integrated radio polarization at 10.55 GHz is about , peak values reach . The magnetic field direction is aligned to the arc structures. Two components contribute to the radio as well as to the X-ray emission: A large-scale centrally peaked diffuse emission, comprising about of the emission at 10.55 GHz and about at X-rays, and small scale structures. The radial dependence of the column emissivity of the diffuse emission is very similar at radio waves and in the X-ray domain suggesting that , where is the magnetic field component perpendicular to the line of sight. It requires a fast decrease of towards the boundary of the source and the formation of a circumferential magnetic field. The radial dependence of the X-ray emission is in good agreement with models of White & Long (1991) for a SNR evolution in a cloudy interstellar medium, if the cloud evaporation time is very large compared with the age of the SNR. The models lead to a rather low ambient density of a few , indicating that G 18.95-1.1 is expanding in a previously created stellar wind bubble.

Key words: Supernova remnants ISM: G 18.95-1.1 X-rays: ISM radio continuum: ISM

Send offprint requests to: E. Fürst

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Contents

• 1. Introduction
• 2. New observations of G 18.95-1.1
  • 2.1. X-ray observations
  • 2.2. Radio observations at 10.55 GHz
• 3. Analysis
  • 3.1. The X-ray data
  • 3.2. The radio data
  • 3.3. Comparison of radio with X-ray data
• 4. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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