DPS 2001 meeting, November 2001
Session 37. Galilean and Other Outer Planet Satellite Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Friday, November 30, 2001, 9:00-10:30am, French Market Exhibit Hall

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[37.11] Deep Optical Searches for Faint Uranian and Neptunian Satellites

M. J. Holman (Harvard-Smithsonian Center for Astrophysics), J.J. Kavelaars (McMaster University), B. J. Gladman (Observatoire de la Cote d'Azur), J.-M. Petit (Observatoire de Besancon), D. Milisavljevic (McMaster University), P. D. Nicholson (Cornell University)

With irregular satellites of Jupiter (Sheppard et al. 2001), Saturn (Gladman et al. 2001), and Uranus (Gladman et al. 1998, 2000) discovered in recent years, our attention naturally turns to Neptune. During our successful 1999 search around Uranus , we conducted a similar search around Neptune covering about 8 square degrees, almost the entire stable region around the planet. This survey yielded no new neptunian satellites down to magnitude R~24. At the time, we interpreted the null result as supporting a violent destruction of the neptunian outer satellite system as Triton was captured (Goldreich et al. 1989, McKinnon et al. 1995). However, the distribution of sizes of the irregular satellites of the other giant planets suggest that the largest undiscovered neptunian satellites might be just beyond our previous survey's detection limit.

To test this, we conducted deep searches in July and August 2001 using the CTIO 4-m and CFHT 3.6-m telescopes with their wide-field mosaic cameras. By combining a long sequences of images, shifted at the planet's apparent rate of motion, we can detect objects significantly below the single exposure detection limit. Specifically, we searched the region within ~36 arcminutes of Neptune to a magnitude limit of R ~25.5. In addition, we conducted a similar survey of the region near Uranus. We report the detection of two candidate satellites of Neptune and four candidate satellites of Uranus. These are all in the magnitude range R~24.5-25.5. We emphasize that these are candidate detections; it is possible that these are foreground Centaur objects moving at nearly the neptunian or uranian rate and direction. Follow-up observations with the Palomar 5-m and Magellan 6.5-m telescopes have been attempted.

This work is supported in part by the NASA Planetary Astronomy program.

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