Discovery of a Bipolar Shell around G25.5+0.2.
Astrophysical Journal, 541 L67-L70.
We present new high-resolution and signal-to-noise ratio near-IR observations of the central object and nebula of G25.5+0.2, a heavily reddened luminous blue variable candidate. Imaging reveals that the nebula shows a striking bipolar morphology, reminiscent of the Homunculus of η Carinae. Two complete limb-brightened lobes are visible, with an apparent double-nested equatorial ring system. Two additional jet or paddle-like features also appear to be present in the equatorial plane of the nebula, apparently emanating from the central star, again in a manner reminiscent of the Homunculus. The H I and He I nebular emission line spectrum, which samples primarily the equatorial ejecta, suggests a peak projected expansion velocity for this material of ~180 km s-1, implying a kinematic age of ~2500 yr. The stellar spectrum is suggestive of very high temperatures for the central object, with no evidence of He I 2.058 μm or H I 2.166 μm emission. The only unambiguously identifiable emission lines of stellar origin were found to be C IV 2.079 μm and He II 2.189 μm, although a broad feature centered on ~2.115 μm possibly corresponds to blended C III, N III, and He I emission.
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