From: Jay Pasachoff [Jay.M.Pasachoff@williams.edu]
Sent: Tuesday, September 25, 2007 6:27 PM
To: Dunham, David
Subject: Re: [PLANOCCULT] Occultation of 8.9-mag. star by possible rings of Pluto this week
Is it Charon or is it rings. Anyway (a) we "did" Charon very well from at least 4 telescopes in Chile two years ago, and found no atmosphere; and (b) we have carefully examined our Pluto occultation data over the summer and have sensitive limits on rings, beyond what we reported at a DPS.

Gulbis, A. A. S., J. L. Elliot, M. J. Person, and E. R. Adams (MIT), B. A. Babcock (Williams), M. Emilio (Univ. Estadual de Ponta Grossa, Brazil),  J. W. Gangestad (Williams), S. D. Kern and E. A. Kramer (MIT), D. J. Osip (OCIW), J. M. Pasachoff and S. P. Souza (Williams College), and T. Tuvikene (Vrije Univ., Belgium), 2006, "Charon's radius and atmospheric constraints from the stellar occultation observations," Nature; Jan. 5, 2006, issue, 439, doi:10.1038/nature04276, pp. 48-51.

http://www.nature.com/nature/journal/v439/n7072/pdf/nature04276.pdf
http://www.nature.com/nature/journal/v439/n7072/full/nature04276.html 

Person, M. J., J. L. Elliot, A. A. S. Gulbis, J. M. Pasachoff, B. A. Babcock, S. P. Souza, and J. W. Gangestad 2006, "Charon's Radius and Density from the Combined Data Sets of the 2005 July 11 Occultation," Astron. J. 132, 1575-1580. 

Pasachoff, Jay M., B. A. Babcock, S. P. Souza, J. W. Gangestad, A. E. Jaskot, J. L. Elliot, A. A. S. Gulbis, M. J. Person, E. A. Kramer, E. R. Adams, C. A. Zuluaga, R. E. Pike, P. J. Francis, R. Lucas, A. S. Bosh, D. J. Ramm, J. G. Greenhill, A. B. Giles, and S. W. Dieters 2006, "A Search for Rings, Moons, or Debris in the Pluto System during the 2006 July 12 Occultation," Pasadena Division of Planetary Sciences meeting, October 2006, abstract 25.02 in Bull. Am. Astron. Soc. 38, #3, 523.