PI: Bruce J. Hrivnak, Valparaiso University, email@example.com
Address: Dept. of Physics and Astronomy, Valparaiso, IN 46383, USA
CoI: Kevin Volk, Gemini Observatory
CoI: Sun Kwok, University of Calgary
Title: Mid-IR Imaging of Circumstellar Rings in the C-Rich PPN HD 56126
Abstract: Circumstellar arcs and rings have recently been discovered in visible light around 5 proto-planetary nebulae (PPNs) and 4 planetary nebulae (PNs); they are assumed to be remnants of the circumstellar envelopes of their AGB progenitors. These arcs and rings appear circular, implying that they are portions of spherical shells; on the other hand, most of these objects show a clearly bipolar morphology. The simultaneous presence of circular arcs and bipolar nebulosities provides strong constraints on how and when the shaping of PPNs and PNs occurs. We propose to obtain deep mid-infrared observations of a PPN that appears to be viewed nearly pole-on. HST visible observations have shown only a bright star and a faint diffuse nebulosity but not rings. By observing in the mid-infrared, we hope to detect the rings in direct thermal emission (not scattered light); the star will not contribute any significant emission. This would open the door for detailed studies of the properties of the dust in these rings (actually shells in 3-D) and how they form. A non-detection, though disappointing, would nevertheless set limits on these dust shells and would also allow us to set important constraints on the mass loss history, which we would model using a 2D dust, radiative-transfer code.
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