14 research outputs found

    All-Sky Video Orbits of Lyrids 2009

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    We report observational results of the Lyrid meteor shower observed by the double station all-sky video system in the night of April 21/22, 2009 at the Astronomical and Geophysical Observatory of the Comenius University in Modra and Arboretum, Tes\'arske Mly\v{n}any, Slovakia. This observation was the first test of the double stations and orbit determination method within the frame of the new Slovak Video Meteor Network (SVMN). We present the whole set of 17 observed orbits of Lyrids as well as the five most precise orbits in detail form. The comparison with the known datasets, precise photographic IAU MDC and SonotaCo video orbits, demonstrate quite good consistency and similar quality.Comment: 4 pages, 3 figures, 2 table

    Spin rates of V-type asteroids

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    Context. Basaltic V-type asteroids play a crucial role in studies of Solar System evolution and planetesimal formation. Comprehensive studies of their physical, dynamical, and statistical properties provide insight into these processes. Thanks to wide surveys, currently there are numerous known V-type and putative V-type asteroids, allowing a detailed statistical analysis. Aims. Our main goal is to analyze I corrected for US language conventions in this paper the currently available large sample of V-type spin rates, to find signatures of the non-gravitational Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect among the different V-type populations, and to estimate the spin barrier and critical density for V-type asteroids. Our intention is to increase the pool of information about the intriguing V-types. Methods. We collected rotational periods from the literature for spectrally confirmed V-types, putative V-types, and Vesta family members. Through spectroscopic observations we confirmed their taxonomic type and verified the high confirmation rates of the putative V-types. We combined the collected periods with periods estimated in this manuscript and produced rotational frequency distributions. We determined the spin barrier in the frequency–light curve amplitude space for V-type asteroids. Results. We analyzed rotational periods of 536 asteroids in our sample. As expected, due to the small size of the objects analyzed, the frequency distributions for the Vesta family and the V-types outside the family are inconsistent with a Maxwellian shape. The Vesta family shows an excess of slow-rotators. V-types outside the family show an excess of both slow and fast rotators. Interestingly, we found that the population of V-types outside the Vesta family shows a significant excess of fast rotators compared to the Vesta family. The estimated critical density for V-type asteroids exceeds ρc = 2.0 g cm−3, which surpasses the previous estimates. Conclusions. We demonstrated that V-type asteroids have been influenced by the thermal radiation YORP effect and that their critical spin rate is higher than for C-type asteroids. The population of V-types outside the Vesta family shows a significant excess of fast rotators compared to the Vesta family. We hypothesize that the objects that evolved from the Vesta family though the Yarkovsky drift are also more susceptible to the YORP effect. Objects for which YORP has not yet had enough time to act and those that are more YORP resistant will be left in the family, which explains the relatively small proportion of fast rotators being left. The YORP timescale must thus be similar to the migration timescale for those objects

    Physical modeling of triple near-Earth asteroid (153591) 2001 SN 263 from radar and optical light curve observations

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    We report radar observations (2380-MHz, 13-cm) by the Arecibo Observatory and optical light curves observed from eight different observatories and collected at the Ondrejov Observatory of the triple near-Earth asteroid system (153591) 2001 SN263. The radar observations were obtained over the course of ten nights spanning February 12-26, 2008 and the light curve observations were made throughout January 12 - March 31, 2008. Both data sets include observations during the object's close approach of 0.06558 AU on February 20th, 2008. The delay-Doppler images revealed the asteroid to be comprised of three components, making it the first known triple near-Earth asteroid. Only one other object, (136617) 1994 CC is a confirmed triple near-Earth asteroid.We present physical models of the three components of the asteroid system. We constrain the primary's pole direction to an ecliptic longitude and latitude of (309 °, - 80 °) ± 15 ° . We find that the primary rotates with a period 3.4256 ± 0.0002 h and that the larger satellite has a rotation period of 13.43 ± 0.01 h , considerably shorter than its orbital period of approximately 6 days. We find that the rotation period of the smaller satellite is consistent with a tidally locked state and therefore rotates with a period of 0.686 ± 0.002 days (Fang et al. [2011]. Astron. J. 141, 154-168). The primary, the larger satellite, and the smaller satellite have equivalent diameters of 2.5 ± 0.3 km , 0.77 ± 0.12 km , 0.43 ± 0.14 km and densities of 1.1 ± 0.2 g /cm3, 1.0 ± 0.4 g /cm3, 2.3 ± 1.3 g /cm3 , respectively

    Photometric survey of binary near-Earth asteroids

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    International audiencePhotometric data on 17 binary near-Earth asteroids (15 of them are certain detections, two are probables) were analysed and characteristic properties of the near-Earth asteroid (NEA) binary population were inferred. We have found that binary systems with a secondary-to-primary mean diameter ratio D/D=>0.18 concentrate among NEAs smaller than 2 km in diameter; the abundance of such binaries decreases significantly among larger NEAs. Secondaries show an upper size limit of D=0.5-1 km. Systems with D/D20 h. The specific total angular momentum of most of the binary systems is similar to within ±20% and close to the angular momentum of a sphere with the same total mass and density, rotating at the disruption limit; this suggests that the binaries were created by mechanism(s) related to rotation near the critical limit and that they neither gained nor lost significant amounts of angular momentum during or since formation. A comparison with six small asynchronous binaries detected in the main belt of asteroids suggests that the population extends beyond the region of terrestrial planets, but with characteristics shifted to larger sizes and longer periods. The estimated mean proportion of binaries with D/D=>0.18 among NEAs larger than 0.3 km is 15±4%. Among fastest rotating NEAs larger than 0.3 km with periods between 2.2 and 2.8 h, the mean proportion of such binaries is (66 10-12)%
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