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Astron. Astrophys. 339, 601-609 (1998)

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A multi-frequency radio study of the supernova remnant HB9

Denis A. Leahy 1, Zhang Xizhen 2, Wu Xinji 3 and Lin Jiale 3

1 Department of Physics, University of Calgary, Calgary T2N 1N4, Canada (leahy@iras.ucalgary.ca)
2 Beijing Astronomical Observatory, CAS, Beijing 100101, China
3 Department of Geophysics, Peking University and Chinese Academy of Sciences- Peking University Joint Astrophysical Center, Beijing 100871, P.R. China

Received 17 April 1998 / Accepted 28 August 1998

Abstract

We present a new radio map of HB9 at 232 MHz made at the Beijing Astronomical Observatory. We also present previously unpublished maps at 151 MHz, from the new Cambridge Low-Frequency Synthesis Telescope Survey, and at 4750 MHz, from the Effelsberg Telescope. These radio maps are compared with previously published maps at 408, 1420, and 2695 MHz, thus providing the most complete frequency coverage for a spectral index study of a supernova remnant to date. Spectral index maps are constructed using the running T-T plot method. Several properties of spectral index behavior are determined. The mechanisms which can most naturally account for the observed behavior are: variable thermal electron density near the rim causing variable low frequency absorption and spectral flattening; and variable magnetic field near the rim and a curved electron spectrum causing variable high frequency steepening near the rim. A high spectral index region is likely associated with extended emission from 4C46.09.

Key words: shock waves – ISM: supernova remnants – ISM: individual objects: HB9, G160.9+2.6

Send offprint requests to: D. Leahy

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998
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