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Session 109 - Novae & Cataclysmic Variables.
Display session, Saturday, January 10
Exhibit Hall,
We present optical (UBVRI) and infrared (JHKL'M) photometry of Nova Centauri 1991 (=V868 Cen) covering the period April, 1991, to June, 1992. The infrared evolution of V868 Cen is unlike any previously observed nova. During our earliest observations, the spectral energy distribution (SED) of the optical (UBVRI) and infrared fluxes of V868 Cen can be modeled by two blackbodies: a hot component (9,000 K), and a cooler component (3,000 K). The cooler component is the dominant source of the optical and infrared luminosity. This peculiar SED suggests a scenario where the hot component is due to scattered light leaking from the cool pseudo-photosphere. As V868 Cen rose to infrared maximum, the dominant blackbody source cooled to 1,000 K, indicating the formation of an extensive dust shell. During the remainder of our observations, this single SED is able to explain the infrared photometry! The dust shell in V868 Cen did not cool, even though its luminosity declined by a factor of 100. Throughout the entire monitoring period, V868 Cen exhibited a strong M-band excess. We attribute this excess to emission from the CO fundamental at 4.65 \mum. K-band spectroscopy in 1991 June revealed CO overtone emission, confirming this hypothesis.
