Publications (5)6.02 Total impact
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Article: Satellites of the Largest Kuiper Belt Objects
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ABSTRACT: We have searched the four brightest objects in the Kuiper Belt for the presence of satellites using the newly commissioned Keck Observatory Laser Guide Star Adaptive Optics system. Satellites are seen around three of the four objects: Pluto (whose satellite Charon is well-known and whose recently discovered smaller satellites are too faint to be detected), 2003 EL61 (where a second satellite is seen in addition to the previously known satellite), and 2003 UB313 (where a satellite is seen for the first time). The object 2005 FY9, the brightest Kuiper Belt object (KBO) after Pluto, does not have a satellite detectable within 04 with a brightness of more than 1% of the primary. The presence of satellites around three of the four brightest KBOs is inconsistent with the fraction of satellites in the Kuiper Belt at large at the 99.2% confidence level, suggesting a different formation mechanism for these largest KBO satellites. The two satellites of 2003 EL61, and the one satellite of 2003 UB313, with fractional brightnesses of 5% and 1.5%, and 2%, of their primaries, respectively, are significantly fainter relative to their primaries than other known KBO satellites, again pointing to possible differences in their origin.The Astrophysical Journal 12/2008; 639(1):L43. · 6.02 Impact Factor -
Article: Satellites of the largest Kuiper belt objects
[show abstract] [hide abstract]
ABSTRACT: We have searched the four brightest objects in the Kuiper belt for the presence of satellites using the newly commissioned Keck Observatory Laser Guide Star Adaptive Optics system. Satellites are seen around three of the four objects: Pluto (whose satellite Charon is well-known), 2003 EL61, and 2003 UB313. The object 2005 FY9, the brightest Kuiper belt object after Pluto, does not have a satellite detectable within 0.4 arcseconds with a brightness of more than 0.5% of the primary. The presence of satellites to 3 of the 4 brightest Kuiper belt objects is inconsistent with the fraction of satellites in the Kuiper belt at large at the 99.1% confidence level, suggesting a different formation mechanism for these largest KBO satellites. The satellites of 2003 EL61 and 2003 UB313, with fractional brightnesses of 5% and 2% of their primaries, respectively, are significantly fainter relative to their primaries than other known Kuiper belt object satellites, again pointing to possible differences in their origin.10/2005; -
Article: The First Laser Guide Star Adaptive Optics Observations of the Galactic Center: Sgr A*'s Infrared Color and the Extended Red Emission in its Vicinity
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ABSTRACT: (Abridged) We present the first Laser Guide Star Adaptive Optics (LGS-AO) observations of the Galactic center. LGS-AO has dramatically improved the quality, robustness, and versatility with which high angular resolution infrared images of the Galactic center can be obtained with the W. M. Keck II 10-meter telescope. Specifically, Strehl ratios of 0.7 and 0.3 at L'[3.8 micron] and K'[2.1 micron], respectively, are achieved in these LGS-AO images. During our observations, the infrared counterpart to the central supermassive black hole, Sgr A*-IR, showed significant infrared intensity variations, with observed L' magnitudes ranging from 12.6 to 14.5 mag. The faintest end of our L' detections, 1.3 mJy (dereddened), is the lowest level of emission yet observed for this source by a factor of 3. No significant variation in the location of SgrA*-IR is detected as a function of either wavelength or intensity. Near a peak in its intensity, we obtained the first measurement of SgrA*-IR's K'-L' color (3.0 +- 0.2 mag, observed), which corresponds to an intrinsic spectral index of -0.5 +- 0.3. This is significantly bluer than other recent infrared measurements. Because our measurement was taken at a time when Sgr A* was ~6 times brighter in the infrared than the other measurements, we posit that the spectral index of the emission arising from the vicinity of our Galaxy's central black hole may depend on the strength of the flare, with stronger flares giving rise to a higher fraction of high energy electrons in the emitting region.09/2005; -
Article: The Orbit of 617 Patroclus Binary Trojan System from Keck LGS AO observations
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ABSTRACT: We report the results from Laser Guide Star Adaptive Optics observations in 2004-2005 of 617 Patroclus using the NIRC2 camera at the W. M. Keck Observatory. An observing campaign which focuses on this only known binary Trojan asteroid, was initiated by our group. Both components of the system were detected at 5 different epochs between Nov. 2004 and May 2005 with an angular separation between 45 and 190 mas and a Dm ˜0.17. The orbital parameters were estimated independently using two algorithms, a Monte-Carlo technique (Hestroffer and Vachier, IAU-ACM, 2005), and a visual binary method (Descamps, Cel. Mech., 2005): a= 685±40 km, e = 0.02±0.02, P = 4.287±0.002 or P= 2.391±0.003 corresponding to a total mass of 1.4 x 1018 or 4.3 x 1018 ± 0.2 kg. Considering recent radiometric measurements by Fernandez et al., (AJ, 126, 2003), the radii of components would be R1= 60.9 km and R2=56.3 km (error ˜1.6 km and with η =0.94), leading to an averaged bulk density of 0.8 or 2.6 ±0.1 g/cm3. The factor of ˜2 uncertainty in the period will be removed using additional observations from CADC archive (in progress). In contrast to what was observed for a Kuiper-belt binary system (1998WW31 in Veillet et al., Nature, 2002), the low eccentricity is more common of main-belt binaries, indicating that dissipation effects must be considered. This work was partly supported by the National Science Foundation Science and Technology Center for Adaptive Optics and a KPAC NASA grant.07/2005; 37:637. -
Article: Satellites of the largest Kuiper Belt objects
[show abstract] [hide abstract]
ABSTRACT: We have searched the four brightest objects in the Kuiper Belt for the presence of satellites using the newly commissioned Keck Observatory Laser Guide Star Adaptive Optics system. Satellites are seen around three of the four objects: Pluto (whose satellite Charon is well-known and whose recently discovered smaller satellites are too faint to be detected), 2003 EL61 (where a second satellite is seen in addition to the previously known satellite), and 2003 UB313 (where a satellite is seen for the first time). The object 2005 FY9, the brightest Kuiper Belt object (KBO) after Pluto, does not have a satellite detectable within 0".4 with a brightness of more than 1% of the primary. The presence of satellites around three of the four brightest KBOs is inconsistent with the fraction of satellites in the Kuiper Belt at large at the 99.2% confidence level, suggesting a different formation mechanism for these largest KBO satellites. The two satellites of 2003 EL61, and the one satellite of 2003 UB313, with fractional brightnesses of 5% and 1.5%, and 2%, of their primaries, respectively, are significantly fainter relative to their primaries than other known KBO satellites, again pointing to possible differences in their origin.
