2004/01/27 by C. Cappa, C. E. Cappa, W. M. Goss +1 · 8 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/383286
21 pages, Latex, 21 postscript figures, to be published in The Astronomical Journal, May 2004
arxiv created 2004/01/27 · openalex publication_date 2004/05/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We report the results of a survey of radio continuum emission of Galactic Wolf-Rayet (WR) stars north of δ = -46°. The observations were obtained at 8.46 GHz (3.6 cm) using the Very Large Array, with an angular resolution of ∼6'' × 9'' and typical rms noise of ∼0.04 mJy beam -1 . Our survey of 34 WR stars resulted in 15 definite and five probable detections, 13 of these for the first time at radio wavelengths. All detections are unresolved (θ ≲ 5''). Time variations in flux are confirmed in the cases of WR 98a, 104, 105, and 125. WR 79a and WR 89 are also variable in flux, and we suspect they are also nonthermal emitters. Thus, of our sample 20%–30% of the detected stars are nonthermal emitters. Average mass-loss rate determinations obtained excluding definite and suspected nonthermal cases give similar values for WN (all subtypes) and WC5–7 stars [ (WN) = (4 ± 3) × 10 -5 M ⊙ yr -1 and (WC5–7) = (4 ± 2) × 10 -5 M ⊙ yr -1 ], while a lower value was obtained for WC8–9 stars [ (WC8–9) = (2 ± 1) × 10 -5 M ⊙ yr -1 ]. Uncertainties in stellar distances largely contribute to the observed scatter in mass-loss rates. Upper limits to the mass-loss rates were obtained in cases of undetected sources and for sources that probably show additional nonthermal emission.