A Close Binary Star Resolved from Occultation by 87 Sylvia

• Published in: Publications of the Astronomical Society of the Pacific Vol. 121; no. 878; pp. 359 - 364
• Main Authors: Lin, Chi-Long, Zhang, Zhi-Wei, Chen, W. P., King, Sun-Kun, Lin, Hung-Chin, Wang, J.-H., Mondal, S., Alcock, C., Axelrod, T., Bianco, F. B., Byun, Y.-I., Coehlo, N. K., Cook, K. H., Dave, R., de Pater, I., Descamps, P., Lehner, M. J., Kim, D.-W., Lee, T., Lissauer, J. J., Marshall, S. L., Porrata, R., Protopapas, P., Rice, J. A., Schwamb, M. E., Wang, S.-Y., Wen, C.-Y.
• Format: Journal Article
• Language: English
• Published: Chicago, IL University of Chicago Press 01.04.2009
• Subjects: Asteroids; Astronomical objects; Astronomy; Coordinate systems; Earth, ocean, space; Ellipses; Exact sciences and technology; Imaging; Light curves; Occultation; Position angle; Sampling rates; Telescopes; Occultations; Close binary stars
• ISSN: 0004-6280; 1538-3873
• DOI: 10.1086/598968

The star BD +29 1748 was resolved to be a close binary from its occultation by the asteroid 87 Sylvia on 2006 December 18 UT. Four telescopes were used to observe this event at two sites separated by some 80 km. Two flux drops were observed at one site, whereas only one flux drop was detected at the other. From the long-term variation of Sylvia, we inferred the probable shape of the shadow during the occultation, and this in turn constrains the binary parameters: the two components of BD +29 1748 have a projected separation of 0.̋097–0.̋140 on the sky with a position angle 104°–110°. The asteroid was clearly resolved, with a size scale ranging from 130 to 290 km as projected onto the occultation direction, consistent with the size dimensions 385 × 265 × 230     km , measured by direct adaptive optics imaging. No occultation was detected for either of the two known moonlets of 87 Sylvia.