37th DPS Meeting, 4-9 September 2005
Session 56 TNOs and Centaurs
Poster, Thursday, September 8, 2005, 6:00-7:15pm, Music Recital Room

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[56.12] Photometric observations of a very bright TNO with an extraordinary lightcurve.

D. Rabinowitz, S. Tourtellotte (Yale University), M. Brown (Caltech), C. Trujillo (Gemini Observatory)

We have been monitoring bright Trans-Neptunian objects with the SMARTS 1.3m telescope at CTIO to determine colors, solar phase curves, and rotation periods[1]. Here we present the first photometric observations of K40506A[2], currently the brightest and perhaps largest TNO, recently found with the Palomar Quest camera during our ongoing search for such objects[3]. The average V-band magnitude is 17.5 and the mean absolute magnitude is 0.44, about 1.5 magnitudes fainter than absolute magnitude of Pluto. We measure a neutral reflectance at visible wavelengths and a linear phase curve with slope varying from 0.11 mag/deg in the B band to 0.15 mag/deg in the I band. Our observations also reveal an unambiguous, double-peaked rotational lightcurve with period of 3.9152 hours and peak to peak amplitude ~0.35 mag. Given the object's large size, this lightcurve is extraordinary. The double peaks in the lightcurve indicate an elongated object with large to small axis ratio of 1.4. We discuss the constraints these observations place on the body's size, strength, and density. [1] B. Schaefer, D. Rabinowitz, and S. Tourtellote, this proceedings. [2] K40506A is our own internal catalog name. [3] M. Brown, C. Trujillo, and D. Rabinowitz, 2004, Ap J 617. 546-649.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.