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D. Rabinowitz (Yale University), Quasar Equatorial Survey Team
Asteroid 2000 EB 173 is currently the brightest known TNO with opposition magnitude R<19.2, and presumably the largest known Plutino with absolute magnitude H=4.9 (1/4 the size of Pluto assuming low albedo 0.04). We discovered the object in a one-night search (2000 March 15 UT) covering 66.8 degrees using the 1-m Schmidt at Llano del Hato, Venezuela. Our collaboration, known as the Quasar Equatorial Survey Team [1] (QUEST), has designed and constructed for this telescope a 8k x 8k array of CCDs[2] which we use in drift-scanning mode to scan areas 2.36 deg wide in Dec and up to 165 deg wide in RA through a sequence of 4 broad-band filters. Normally, we cover the same area on a nightly basis to find quasars, supernovae, and other variable objects. To find TNOs, we limited the search to an area 28.3 deg wide in RA centered at RA = 13.249 h, Dec = -1.1 deg, which we scanned twice with a 4 hour separation. Later, we used software to subtract a reference image of the same area recorded on previous nights and to thereby isolate candidate images of TNOs. From detections of main-belt asteroids identified in the same manner, we measure our 50% detection limit at R=20.0 ± 0.2. Our observation of one TNO brighter than this limit favors the magnitude-frequency reported by Jewitt et al.[3] over the relatively steep distribution reported by Gladman et al.[4], and points to a continuous distribution up to Pluto-sized objects. Our BVRI photometry[5] in February, March and June reveals a stellar seeing profile and a steep red reflectance spectrum typical of fainter TNOs, except for a possible absorption in the I band. There is no apparent variability greater than 10% in the February and March observations, but the June observations are fainter by \approx0.3 magnitudes. This requires either an unusually steep phase curve post opposition, or else peculiar variability.
[1] Schaefer, B. et al., AJ 524, L103 (1999); [2] Snyder, J. SPIE 3355, 635 (1998); [3] Jewitt, D., Luu, J., and Trujillo, C. AJ 115, 2125-2135 (1998); [4] Gladman, B. et al., AJ 116, 2042-2054 (1998); [5] IAUC 7459 (2000).
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The author(s) of this abstract have provided an email address for comments about the abstract: david.rabinowitz@yale.edu