M. Conjat, F. Colas, R. Montaigut, R. Behrend, M. Devogele, B. Carry, D. Vernet, and J.-P. Rivet.
We report that photometric observations taken with a 0.40-m telescope at Nice Observatory, a 1.0-m telescope at the Pic du Midi Observatory, and a 1.0-m telescope at Calern Observatory during Dec. 2016-Mar. 2017 reveal that minor planet (6100) is a binary system with an orbital period of 18.46 ± 0.02 hr. The primary shows a period of 4.3018 ± 0.0011 hr with light-curve amplitudes of 0.11 mag at solar phase 4° and 0.22 mag at solar phase 25°, suggesting a nearly spheroidal shape. Mutual eclipse/occultation events that are 0.15 to 0.27 magnitude deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.38..
M. Marsset, B. Carry, B. Yang, F. Marchis, P. Vernazza, C. Dumas, J. Berthier & F. Vachier
We report the discovery of a second satellite around minor planet (107) Camilla. This known binary system was observed on five epochs between 2015 May 29 and 2016 July 30 UT with the SPHERE instrument at the ESO 8-m Very Large Telescope UT3 on Cerro Paranal. On 2015 May 29.215 UT, the YJH band (0.97- to 1.66-micron) IFU spectral cubes returned the following position for the second companion: separation 0.18 ± 0.01 arcsec (projected separation 340 km) and p.a. 320 ± 2°, and a non-sidereal motion similar to that of (107): in terms of (R.A.)(cos Decl.), -0.40 arcsec/min; and in Decl., +0.09 arcsec/min. On 2016 July 12.218 UT, the new satellite was found at separation 0.30 ± 0.01 arcsec and p.a. 67 ± 1°, and on 2016 July 30.073, it was at separation 0.31 ± 0.01 arcsec and p.a. 70 ± 1°. The new satellite could not be detected during observations carried out with the same instruments on 2016 July 2 and 28. Based on the three detections, the mean YJH-band magnitude contrast between (107) and its new companion is 9.0 ± 0.3. The already known satellite of (107), discovered in 2001 (cf. IAUC 7599), is detected on the five epochs with a separation varying from 0.25 to 0.59 arcsec. Minor planet (107) becomes the sixth triple system discovered and imaged in the main asteroid belt after (87) Sylvia (IAUC 8582), (45) Eugenia (IAUC 8817), (216) Kleopatra (IAUC 8980), (93) Minerva (IAUC 9069), and (130) Elektra (CBET 4036).
F. Vachier, J. Berthier, B. Carry, S. Messner, D. Dunham, J. Dunham, P. D. Maley, C. McPartlin, S. Preston & B. Timerson
F. Vachier, J. Berthier, and B. Carry, Mecanique Celeste et de Calcul des Ephemerides (IMCCE); and colleagues associated with the International Occultation Timing Association (S. Messner, D. Dunham, J. Dunham, P. D. Maley, C. McPartlin, S. Preston, and B. Timerson) report the successful observation of the stellar occultation of TYC 1822-00535-1 (mag 10.0) by the triple-minor-planet system (93) Minerva on Sept. 6.33784 UTC. Nine positive chords of the occultation by the primary, lasting between 8.08 and 16.80 s, have been reported, which confirms the value of the equivalent diameter of 154 ± 6 km determined by Marchis et al. (2013, Icarus 224, 178). One observation by Messner appears to be a brief, 0.6-s stellar occultation by one moonlet of the system, perhaps due to the inner satellite II (Gorgoneion), which would imply that the satellite's size is about 6.5 km across the chord, and thus that it is either larger than the estimated 3.2 ± 0.9 km (Marchis et al.) or significantly elongated. The derived relative apparent position of the moonlet is 0.128" west and 0.106" south of the primary on 2014 Sept. 6.33767. Additional observations of the Minerva system are strongly encouraged. Additional details, including information on a forthcoming occultation of the (93) system on 2014 Nov. 8 (with predicted paths across China, South Korea, and Japan) appear on CBET 3985.
W. J. Merline, P. M. Tamblyn, B. D. Warner, P. Pravec, J. P. Tamblyn, C. Neyman, A. Conrad, W. M. Owen, B. Carry, J. D. Drummond, C. R. Chapman, B. Enke, W. Grundy, C. Veillet, S. Porter, C. Arcidiacono, J. C. Christou, D. D. Durda, A. W. Harris, H. A. Weaver, C. Dumas, D. Terrell & P. D. Maley
W. J. Merline, Southwest Research Institute (together with P. M. Tamblyn, B. D. Warner, P. Pravec, J. P. Tamblyn, C. Neyman, A. R. Conrad, W. M. Owen, B. Carry, J. D. Drummond, C. R. Chapman, B. L. Enke, W. M. Grundy, C. Veillet, S. B. Porter, C. Arcidiacono, J. C. Christou, D. D. Durda, A. W. Harris, H. A. Weaver, C. Dumas, D. Terrell, and P. Maley) reports the discovery, using the Keck II telescope (+ NIRC2 Laser-Guide-Star adaptive-optics system), of a second satellite of the Hungaria-type minor planet (2577) Litva. On 2012 June 22.3 UT, the satellite was found at p.a. 89 deg and separation 0.229" (projected separation 230 km). At that time, (2577) was 1.39 AU from the earth at magnitude V = 16.6. The satellite has been imaged in the K_p, H, and J bands. It was also detected on 2012 June 27, Aug. 11, and Aug. 16. Failure to detect it on 2012 July 15 is now seen to be due to being in conjunction with the primary. Follow-up observations were made at the Keck II telescope on 2013 Aug. 25 and 26 by Merline, Tamblyn, Conrad, and Tamblyn. Additional detections were made at the Large Binocular Telescope by Veillet and Arcidiacono on Oct. 12 and at the Keck II telescope by Grundy and Porter on Oct. 25, giving a total baseline of 490 days. The best-fit orbit analysis indicates that the third component has a semi-major axis of 378 km and an orbital period of 214 days; a period of half this length cannot be ruled out. Either orbit would be among the longest periods known for main-belt multiple systems and would be the most loosely bound. It resembles other wide binary systems discovered by this same group (cf. Durda et al. 2010, Proc. Lunar and Planet. Sci. Conf. 41, 2558; Jacobson et al., Ap.J., submitted). The third component is about 2.6 mag fainter than the combined brightness of the close inner pair. Using H magnitudes to scale the size of (2577) from other E-type objects of better-known size, the diameter of (2577) is estimated to be about 4 km, implying a size for the new satellite of 1.2 km. The first satellite of (2577) was inferred by Warner et al. (CBET 1715) in 2009 via lightcurve analysis; their estimate of the size ratio was 0.35, meaning that the second component would be 1.4 km diameter, based on the 4-km assumption for (2577), above. This close inner pair is unresolvable in the imaging data reported above. Warner et al. (2009, Minor Planet Bull. 36, 165) suggested that a residual 5.7-hr lightcurve period may be due to rotation by a third body -- an idea bolstered by Pravec et al. (2012, Icarus 218, 125), who found that this period was still evident even when the secondary object was in eclipse. To the authors' knowledge, S/2012 (2577) 1 is the only satellite to have been predicted prior to being found by targeted imaging. Additional information is provided on CBET 3765.
W. J. Merline, J. D. Drummond, P. Tamblyn, B. Carry, C. Neyman, A. Conrad, C. Chapman, J. C. Christou, C. Dumas, & B. L. Enke
We report on resolved imaging of 2005 YU_55 during its close passage by the earth on Nov. 9 in the near-infrared bands H and K_p using the Keck II telescope (+ NIRC2/AO adaptive-optics system). At the start of the observations (about 8 hr after closest approach at 7h15m UT, when Delta = 0.00332 AU with solar phase angle 44 deg), 2005 YU_55 was at magnitude V = 11.1, with an angular size (of the approximately 88-percent illuminated disk) of about 0.12 arcsec. The images span 2.8 hr, until 10h03m UT (Delta = 0.00407 AU; phase 36 deg). These data were used to derive dimensions under assumptions of a smooth triaxial ellipsoid, having principal-axis rotation with spin period 18 hr (from the JPL Small-Body Database). There is the usual 2-pole degeneracy, although the rapidly changing geometry afforded a preference for prograde rotation. The preliminary solution has triaxial diameters of 337 x 324 x 267 m, with estimated uncertainties of 15 m in each dimension; pole towards R.A. = 282 deg, Decl. = +64 deg (equinox 2000.0; uncertainty radius about 6 deg), or ecliptic lambda = 339 deg, beta = +84 deg. The spherical-equivalent diameter is then 308 m ± 9 m. The retrograde pole is toward R.A. = 34 deg, Decl. = -24 deg (uncertainty radius 15 deg), or ecliptic lambda = 22 deg, beta = -35 deg, with dimensions 328 x 312 x 245 m (uncertainties of 15, 15, 30 m) and a spherical-equivalent diameter of 293 ± 14 m. Deviations from the ellipsoidal shape are evident. Solutions are also obtained by allowing a shorter spin period, but a shorter period is not being asserted here. No satellites typical of near-earth objects were evident in this initial analysis (here covering magnitude differences < 3 and orbit radius > 3 radii) of 2005 YU_55.
W. J. Merline, P. Tamblyn, J. D. Drummond, J. C. Christou, A. Conrad, B. Carry, C. Chapman, C. Dumas, D. D. Durda, W. M. Owen & B. L. Enke
We report the discovery on Nov. 24.4 UT of a satellite of minor planet (317) Roxane from Kp-band imaging using the 8-m Gemini-North telescope (+ Altair/NIRI adaptive optics system). On Nov. 24.39992 UT, the satellite was at separation 0.27 (projected separation 245 km) and position angle 76 deg. The satellite was imaged in Kp-, H-, and J-bands and was tracked for more than 26 hours. The brightness difference in Kp-band is about 2.7 mag, giving an estimated diameter (primary diameter assumed of 19 km) of the satellite of 5 km. This binary has characteristics very similar to the other wide binaries previously reported by our group (see IAUCs 7827, 8075, 8232, 8293, 8297), all being consistent with the EEB formation mechanism of Durda et al. (2004 Icarus 170, 243). Among binaries that can be resolved by imaging, this appears to be the first E-type. Given the recent detection of dual lightcurve periods in (1509) Esclangona (CBET 2020), it is possible that separate spin periods could be extracted from lightcurve data on (317).
W. J. Merline, A. Conrad, W. M. Keck Observatory, J. D. Drummond, P. Tamblyn, C. Dumas, B. Carry, R. D. Campbell, R. W. Goodrich, C. Chapman, & W. M. Owen
We report the first-ever visible or near-infrared imaging of any binary near-Earth asteroid. On 2008 Aug. 9 UT, we acquired images of clearly-separated components of binary NEA (35107) 1991 VH, which was first suspected as a binary by Pravec et al. (IAUC 6607) based on interpretation of lightcurve observations. Over a span of about one hour, we obtained J-, H-, and Kp-band images using the 10-m Keck II Telescope (+ NIRC2/AO adaptive optics system) on Mauna Kea. On Aug. 9.236, the satellite was at separation 0.08 arcsec (projected separation 3.1 km) and position angle 105 deg. The brightness ratio in Kp-band was approximately 2.0 mag. This is the smallest angular and physical separations yet detected for a binary asteroid using adaptive optics. The observed separation and size ratio are consistent with the parameters derived by Pravec et al.
A. Conrad, W. M. Keck Observatory, W. J. Merline, J. D. Drummond, P. Tamblyn, C. Dumas, B. Carry, R. D. Campbell, R. W. Goodrich, W. M. Owen & C. Chapman
We report the discovery on Mar. 28.5 UT of a satellite of minor planet (41) Daphne from more than 100 J-, H-, K-, and K'-band images with the 10-m Keck II telescope (+ NIRC2/AO adaptive-optics system) on Mauna Kea. On Mar. 28.5032, the satellite was at separation 0.56 arcsec (projected separation 443 km) and position angle 277 deg. The satellite was observed to be moving with the primary, as they traveled 80 arcsec across the background sky over the 3 hours. The significant (0.3 arcsec) orbital motion of the satellite observed during this time implies an orbital period near 1.6 days. The H-band brightness ratio is estimated at about 10 mag, giving an estimated diameter of the satellite of < 2 km; if so, this system has the most extreme size ratio known (cf. EMP 2008, p. 256).