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Charles Franklin Prosser, Jr. was born in San Diego on August 26, 1963. He graduated from Lincoln High School in Gahanna, Ohio in 1981 and received a BS in physics and astronomy (cum laude, and with election to Phi Beta Kappa) from Ohio State University. While at OSU, he worked with Arne Slettebak and attended summer programs at NRAO and NCAR, working respectively with C. P. O'Dea and D. Mihalas. He subsequently attended the University of California, Santa Cruz (joining AAS in 1989) and earned a PhD in astronomy in 1991. His thesis was entitled "Low-Mass Membership of the Open Clusters Alpha Persei and IC 4665." While at UCSC, Charles worked primarily with Burton Jones and Robert Kraft (his official thesis advisor), and he maintained collaborations with them through out his too-brief career. Charles was killed in an automobile accident on August 16, 1998, in Tucson, Arizona.
Following his graduate education, Prosser moved to the Smithsonian Astrophysical Observatory, where he worked as a research assistant, primarily funded via a NASA Long-Term Space Astrophysics grant to John Stauffer. The main goal of that grant was a multi-wavelength observational study of the nearest open clusters in order to develop more complete and more selective membership lists and to use the data to constrain evolutionary models of low mass stars. Charles wrote or co-authored some 30 papers in that area over the six years he was at SAO, including membership studies; time-series photometric monitoring to determine rotation periods for spotted stars; and the analysis of ROSAT X-ray imaging data to prove coronal activity of the cluster members. He was the world's expert on the alpha Persei cluster, having identified most of the known members from his proper motion studies or from deep, CCD imaging surveys. From analysis of HST WF/PC images of the Trapezium cluster in Orion, Charles also provided the best available membership study for that cluster.
From SAO, Charles moved to Kitt Peak National Observatory, where he began work with Abhijit Saha on the analysis of HST data for RR Lyrae stars. He was also continuing his research on coronal activity in low-mass members of open clusters, using new ROSAT HRI data in collaborations with M. Giampapa and G. Micela. Investigation of rotation periods in Alpha Persei, with K. Grankin, was also under way.
Charles worked harder and put in longer hours than all but a few present-day professional astronomers. He could usually be found at the office seven days a week, among the first to arrive and the last to leave. Charles enjoyed harvesting astronomical data both from long observing runs on mountain tops and from rarely-read observatory publications. He was conservative in both his personal and his professional life; he very much preferred simply to state the results of his observations and to make as few extravagant interpretations of those observations as possible.
One of his major contributions to astronomy does not show on a list of publications, because it is not in the form of a journal article. While at SAO, Charles created a database of membership in 10 of the nearest open clusters, including a compilation of the existing photometry, spectroscopy, and X-ray activity, along with J2000 coordinates and a comprehensive reference list. The best known clusters in the database, which he made freely available over the Internet, are Alpha Persei, the Pleiades and Hyades, Praesepe and Coma. Following Charles' death, I moved the database back to SAO, where I will attempt to maintain it in his honor. It can be found at http://cfa-www.harvard.edu/~stauffer/opencl/index.html.
Charles was survived by his parents, Charles Franklin Prosser, Sr. and Lucy Hogan Prosser, of Suwanee, Georgia, his sister Evelyn, and other relatives. His scientific papers will be offered by the family to NOAO. Charles was buried in Monterville, West Virginia on August 22, 1998. He will be remembered as a kind, dedicated, and highly moral colleague, whose greatest desire was to be allowed to work 12 hours a day in the field to which he devoted himself entirely.
Photo (available in PDF version) courtesy of Charles F. Prosser, Sr.
Obituary written by: John Stauffer (Smithsonian Astrophysical Observatory)
BAAS Citation: BAAS, 1998, 30, 1462
SAO/NASA ADS Bibcode: 1998BAAS...30.1462S