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arXiv · astro-ph/9807303

Discovery of extended radio emission in the young cluster Wd1

J. S. Clark·R. P. Fender·L. B. F. M. Waters·S. M. Dougherty·J. Koornneef·I. A. Steele·A. van Blokland
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Abstract

We present 10 micron, ISO-SWS and Australia Telescope Compact Array observations of the region in the cluster Wd1 in Ara centred on the B[e] star Ara C. An ISO-SWS spectrum reveals emission from highly ionised species in the vicinity of the star, suggesting a secondary source of excitation in the region. We find strong radio emission at both 3.5cm and 6.3cm, with a total spatial extent of over 20 arcsec. The emission is found to be concentrated in two discrete structures, separated by 14''. The westerly source is resolved, with a spectral index indicative of thermal emission. The easterly source is clearly extended and nonthermal (synchrotron) in nature. Positionally, the B[e] star is found to coincide with the more compact radio source, while the southerly lobe of the extended source is coincident with Ara A, an M2 I star. Observation of the region at 10micron reveals strong emission with an almost identical spatial distribution to the radio emission. Ara C is found to have an extreme radio luminosity in comparison to prior radio observations of hot stars such as O and B supergiants and Wolf-Rayet stars, given the estimated distance to the cluster. An origin in a detatched shell of material around the central star is therefore suggested; however given the spatial extent of the emission, such a shell must be relatively young (10^3 yrs). The extended non thermal emission associated with the M star Ara A is unexpected; to the best of our knowledge this is a unique phenomenon. SAX (2-10keV) observations show no evidence of X-ray emission, which might be expected if a compact companion were present.

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J. S. Clark, R. P. Fender, L. B. F. M. Waters, S. M. Dougherty, J. Koornneef, I. A. Steele, A. van Blokland. 1998-07-29. Discovery of extended radio emission in the young cluster Wd1. https://doi.org/10.1046/j.1365-8711.1998.02038.x

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