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Paper: A Massive Protobinary System in the Hot Core W3(H2O)
Volume: 356, Revealing the Molecular Universe: One Antenna Is Never Enough
Page: 270
Authors: Chen, H.-R.; Welch, W.J.; Wilner, D.J.; Sutton, E.C.
Abstract: We used the BIMA array to observe the hot molecular core W3(H2O). Our continuum maps at wavelengths of 1.4mm and 2.8mm both achieve sub-arcsecond angular resolutions and show a double-peaked morphology. The angular separation of the two sources is 1″.19 corresponding to 2.43 × 103 AU at the source distance of 2.04 kpc. The flux densities of the two sources at λλ 1.4mm and 2.8mm have a spectral index of 3, translating to an opacity law of κv ∝ v. The small spectral indices suggest that grain growth has begun in the hot core. We have also observed 5 of the K-components of the methyl cyanide (CH3CN) J=12−11 transition. A radial velocity difference of 2.81 kms−1 is found for the gas in the two continuum peaks. Interpreting these two sources as binary components in orbit about one another, we find a minimum mass of 22 MSolar for the system. Power-law density distributions close to the free-fall value, r−1.5, are found for both components, suggesting continuing accretion. The derived luminosities suggest the two sources have equivalent zero-age main sequence (ZAMS) spectral type B0.5 - B0. A velocity gradient previously detected may be explained by unresolved binary rotation with a small velocity difference.
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