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Proposal Information for 2012B-0317


PI: Arlin Crotts, Columbia University, arlin@astro.columbia.edu
Address: Department of Astronomy, 550 West 120th St., New York, NY 10027, U.S.A.

Title: SN 1987A's Vacuum UV/Optical Light Echo Evolution

Abstract: We propose to continue a series of observations that for the past 24 years has yielded most of the results concerning the light echoes from SN 1987A, both on interstellar and circumstellar scales. These data are collected every month or two, primarily on the CTIO 0.9-meter (and occasionally Las Campanas 1-meter). We now propose to continue a series of new discoveries; among these we anticipate: 1) mapping of the detailed three-dimensional structure of a large supershell around a massive OB association near 30 Doradus, 2) a determination of where dense dust globules, perhaps the sites of incipient star formation, rest in relation to the large-scale shocks which likely produce them, 3) completion of the three-dimensional map of SN 1987A's circumstellar nebula, 4) help in using echoes from SN 1987A to establish a geometrically-determined distance to the SN and the LMC, and 5) in connection with Galex, a measurement of the vacuum-UV flux emitted by the SN explosion during its first hours, missed in 1987. These involve our demonstrated techniques in extracting echo signals from brighter, constant-flux environments. Of all of these observations, next semester's is most crucial, because Galax is making its last pointings (including bright-star fields like SN 1987A). The UV echo, primarily from shock breakout during the first hours of the SN, never observed elsewhere, has been observed by IUE, UIT and HST to ambiguous result. Galex will have the best combination of wide field and sensitivity to settle this issue. We need ground-based photometry to properly interpret UV data from this once-in-a-lifetime opportunity, and follow-up optical imaging like ours 80 days later is absolutely essential, since it characterizes the clouds at max light which reflect the initial UV pulse. NOTE: we did obtain an initial epoch of Glex SN 1987A echo imaging in 2011 December, and good followup imaging with SMARTS in early 2012. The Galex mission has not been teminated, and may re-observe the SN 1987A field in 2012. (See below.)


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