Temperature, brightness and spectral index of the Cygnus radio loop

 

V. Borka Jovanovic¹ and D. Urosevic²

 

¹ Atomic Physics Laboratory (040), Vinca Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia (vborka@vinca.rs)

² Department of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia (dejanu@matf.bg.ac.rs).

 

Received 2010 October 18
Accepted 2011 February 10

 

RESUMEN

Se presenta el brillo estimado del remanente de supernova del Velo del Cisne en 2720, 1420, 820, 408 y 34.5 MHz. Mediante el método que hemos desarrollado anteriormente para anillos grandes, utilizamos las observaciones de radioemisión en el continuo para calcular las temperaturas de brillo medias y los brillos superficiales del Velo del Cisne en las frecuencias mencionadas. Estimamos el espectro de las temperaturas medias versus frecuencia entre las cinco frecuencias y obtenemos el índice espectral del Velo del Cisne. Nuestros resultados muestran que el Velo evoluciona en un medio de baja densidad, y que la energía inicial de la explosión de supernova fue relativamente baja. Confirmamos el origen no–térmico de la radiación del anillo del Cisne y mostramos que nuestro método es aplicable a la mayoría de los remanentes de supernova.

 

ABSTRACT

The estimated brightness of the Cygnus loop supernova remnant (SNR) at 2720, 1420, 820, 408 and 34.5 MHz is presented. The observations of the continuum radio emission are used to calculate the mean brightness temperatures and surface brightnesses of this loop at the five frequencies in a wide spectral range, using the method we have previously developed for large radio loops. The spectrum for mean temperatures versus frequency between the five frequencies is estimated and the spectral index of the Cygnus loop is obtained. Also, from our results it can be concluded that the Cygnus loop evolves in a low density environment and that the initial energy of the supernova explosion was relatively low. The results obtained confirm the non–thermal origin of the Cygnus radio loop and show that our method is applicable to almost all remnants.

Key Words: ISM: supernova remnants — radiation mechanisms: non–thermal — radio continuum: general — surveys.

 

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ACKNOWLEDGMENTS

The authors aregrateful to the referee whose suggestions substantially improved the paper. This research is supported by the Ministry of Science of the Republic of Serbia through project No. 176005.

 

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