Probing Dust Evolution in the Equatorial Ring and Ejecta of SNR 1987A

In this program we propose to use a total of 0.4 hr to obtain 3.6 and 4.5 micron photometry of SNR 1987A at two additional epochs beyond day 9800 after the explosion. The emission in these two IRAC bands arises from a hot dust component residing in the equatorial ring (ER) with a distinctly different spectral shape and temperature from the dominant 180 K silicate dust component in the ER. The dust in the ER is collisionally-heated by the SN blast wave that also gives rise to the soft X-ray emission from the ER. The intensity in the IR emission is generally well correlated with that of the X-ray emission. However, the most recent X-ray observations have showed a difference in the evolution of their respective light curves. These differences could stem from a variety of causes, including the sputtering of the dust or changes in the morphology of the ER. Ongoing X-ray observations of the remnant are taking place. Supplementing these with IR observations is essential for determining the nature and the evolution of this hot dust component. Finally, the observations may reveal the appearance of a new emission component from the SN ejecta which is currently interacting with the reverse shock.