Issue |
A&A
Volume 436, Number 1, June II 2005
|
|
---|---|---|
Page(s) | 187 - 193 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20042431 | |
Published online | 20 May 2005 |
Radio spectral index variations of the SNR HB3
1
National Astronomical Observatories, CAS, Beijing 100012, PR China e-mail: tww@ns.bao.ac.cn
2
Department of Physics & Astronomy, University of Calgary, Calgary, Alberta T2N 1N4, Canada
Received:
24
November
2004
Accepted:
26
January
2005
We present images of the SNR HB3 at both 408 MHz and 1420 MHz from the
Canadian Galactic Plane Survey mainly based on data from the Synthesis Telescope
of the Dominion Radio Astrophysical Observatory. We reproduce the 100 m-Effelsberg
HB3 image at 2695 MHz at large scale, and find that there exists a background
emission gradient across the HB3 area. Based on our analysis of background emission
and the boundary between W3 and HB3, we
give HB3's flux density as Jy at 408 MHz and
Jy
at 1420 MHz, after subtracting flux from compact sources within HB3. The
integrated flux-density-based spectral index between 408 MHz and 1420 MHz is
. The averaged T–T plot
spectral index using all subareas is 0.36. Our measurement values are less than a
previously published value of 0.6. The 408–1420 MHz spectral index varies spatially
in HB3 in the range 0.1 to 0.7. We investigate the data used by previous authors,
and consider
more data at 232 MHz, 3650 MHz and 3900 MHz which are not included in previous
calculations. There is evidence for two spectral indices for HB3 in
the radio band, i.e., 0.63 (38–610 MHz) and 0.32 (408–3900 MHz). This is
consistent with the spatial variations: the low frequency data mainly reflects the
steeper indices and the high frequency data mainly reflects the flatter indices.
Key words: ISM: individual: HB3 / radio continuum: ISM / ISM: supernova remnants
© ESO, 2005
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