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      https://www.ias.ac.in/article/fulltext/joaa/003/02/0207-0216

    • Keywords

       

      supernova remnants; spectral break; free-free absorption

    • Abstract

       

      We have observed the extended supernova remnants HB 9 (G 160.5 + 2.8) and IC 443 (G 189.1 + 2.9) at 34.5 MHz with a resolution of 26 arcmin × 40 arcmin. A map of HB 9 is presented. The integrated flux density of HB 9 at 34.5 MHz is 750 ± 150 Jy. The spectral index in the frequency range from 34.5 MHz to 2700 MHz is found to be constant (- 0.58 ± 0.06) without any spectral break such as was reported earlier by Willis (1973). There is no significant variation of the spectral index across the remnant. The integrated flux density of IC 443 at 34.5 MHz is 440 ± 88 Jy. The spectral index in the frequency range from 20 MHz to 10700 MHz is - 0.36 ± 0.04. The reduction in flux at very low frequencies (10 MHz) is attributable to free-free absorption in the interstellar medium and/or in the H II region S 249.

    • Author Affiliations

       

      K. S. Dwarakanath1 2 R. K. Shevgaonkar1 2 Ch. V. Sastry1 2

      1. Raman Research Institute, Bangalore - 560080
      2. Indian Institute of Astrophysics, Bangalore - 560034
    • Dates

       
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