Is SN 1987A Fading at IR Wavelengths?

The cryogenic Spitzer campaign to monitor the evolution of SNR 1987A has succeeding in revealing a steady change in the brightness of emission from silicate dust in equatorial ring (ER) of the SN progenitor. The change in brightness is well-correlated with the X-ray emission. However, the Spitzer IRAC and IRS data unexpectedly revealed at second hotter dust component. The spectra did not provide a distinct spectroscopic signature of this dust, but the time series of observations indicated that it may be evolving at a slightly different rate from the dominant silicate component. In this program we will use a total of 0.4 hr to obtain 3.6 and 4.5 micron photometry of SNR 1987A at two additional epochs. The initial warm observation has revealed a definite flattening of the light curve at these wavelengths. Presently, we lack sufficient information to identify the physical processes responsible for this trend. The requested observations will reveal the long-term behavior of the light curve which may even show the onset of a decline. The continued evolution of this hot dust component will provide important and unique information on the nature and fate of this dust component, and on the origin and morphology of the ER.