F. P. Velichko

Physical model of near-Earth asteroid 6489 Golevka (1991 JX) from optical and infrared observations

In 1995 asteroid 6489 Golevka (1991 JX) had a close encounter with the Earth at a distance of 0.034 AU, providing a good opportunity for a detailed study of a small Solar System object. In this paper we report the results of an extensive international obs

Photometry of seventeen asteroids

Abstract Results of photoelectric observations from Kharkov Astronomical Observatory (Ukraine) are reported. These observations were made between 1985 and 1991. We also include observations of 4 Vesta made in 1981 at Torun Astronomical Observatory (Poland). Most of the lightcurves are in the V band. The first published observations for Asteroids 151, 206, 550, and 705 are reported. We determine or revise synodic periods for four asteroids: 104, 206, 241, and 550. The phase curves are obtained for three asteroids: 44, 104, and 550.

Photometry and models of selected main belt asteroids. III. 283 Emma, 665 Sabine, and 690 Wratislavia

Photometric observations of 283 Emma (1998, 2000, 2001, 2004), 665 Sabine (1998, 1999, 2001, 2004, 2005), and 690 Wratislavia (1998, 2000, 2004, 2005-2006) carried out on 44 nights at two observatories are presented. Using all available lightcurves, the spin vectors, senses of rotation, and shape models for these three asteroids have been determined.

Eclipsing events in the binary system of the asteroid 90 Antiope

CCD observations of the binary asteroid 90 Antiope were carried out at four observatories (Borowiec, Pic du Midi, Kharkiv, and Chateau Renard) on 26 nights from October 2001 through February 2002. The results show a two-component lightcurve with each showing the same period of 16.505 ± 0.002 hours. The first component (with the amplitude of 0.10 mag) is associated with the rotation of two non-spherical bodies of the system; the second one, showing two sharp minima (with the amplitude in the range 0.05-0.12 mag, depending linearly on the phase angle) is due to eclipses in the binary system. The lightcurve suggests a synchronous rotation. The orientation of the systems orbit has been determined from the analysis of both the amplitudes and the duration of the eclipses. Some predictions of the possibility of observations of the eclipsing events during future oppositions have also been made.

Photometry and models of selected main belt asteroids IX. Introducing interactive service for asteroid models (ISAM)

Context. The shapes and spin states of asteroids observed with photometric techniques can be reconstructed using the lightcurve inversion method. The resultant models can then be confirmed or exploited further by other techniques, such as adaptive optics, radar, thermal infrared, stellar occultations, or space probe imaging. Aims. During our ongoing work to increase the set of asteroids with known spin and shape parameters, there appeared a need for displaying the model plane-of-sky orientations for specific epochs to compare models from different techniques. It would also be instructive to be able to track how the complex lightcurves are produced by various asteroid shapes. Methods. Basing our analysis on an extensive photometric observational dataset, we obtained eight asteroid models with the convex lightcurve inversion method. To enable comparison of the photometric models with those from other observing/modelling techniques, we created an on-line service where we allow the inversion models to be orientated interactively. Results. Our sample of objects is quite representative, containing both relatively fast and slow rotators with highly and lowly inclined spin axes. With this work, we increase the sample of asteroid spin and shape models based on disk-integrated photometry to over 200. Three of the shape models obtained here are confirmed by the stellar occultation data; this also allowed independent determinations of their sizes to be made. Conclusions. The ISAM service can be widely exploited for past and future asteroid observations with various, complementary techniques and for asteroid dimension determination.

Do Slivan states exist in the Flora family? - I. Photometric survey of the Flora region

Context. Recent studies have uncovered evidence that the statistical properties of asteroids’ physical parameters are a fundamental source of information on the physics of their collisions and evolution. The analysis of the spin rates and spin vector distributions helps us to understand the role of various known and new effects. The alignment of spin vectors and the correlation of spin rates are for the first time observed for ten members of the Koronis family. These unexpected non-random orientations of the spin axes and correlations of the spin rates, now known as Slivan states are interpreted in terms of a YORP effect and spin-orbit resonances. Aims. To study non-gravitational-effects, there appears to be a need for new observational campaigns devoted to determining the physical parameters of the asteroid families. Methods. We analysed the photometric observations of the asteroids, which are the most efficient method of studying asteroid physical parameters. Results. We report the results of a ten-year long observational survey of the light variations of objects in the Flora region. We present 544 individual lightcurves of 55 objects obtained at various observing geometries. These lightcurves yield new or refined synodic periods for 32 asteroids and confirm period determinations for 23 objects in our sample. To improve the statistics of the Flora family objects, we add to our dataset 91 objects with reliably determined periods. The distribution of rotation rates for the Flora family is nonMaxwellian at a confidence level of 94% and different from those of the Koronis and the Hungaria families. It seems to be consistent with the long-term influence of the YORP effect, although it is also indicative of a younger age for the Flora family compared to both the Koronis and the Hungaria families. Conclusions. Our new data is a foundation for the spin vector and shape determinations that will be the objectives of the second paper of the series. We search for spin vector and spin periods correlations in order to determine whether Slivan states exist in the Flora family.

Photometry and models of selected main belt asteroids V. 73 Klytia, 377 Campania, and 378 Holmia

We present photometric observations of three asteroids: 73 Klytia, 377 Campania, and 378 Holmia, together with their spin and shape models. The models were constructed with the lightcurve inversion method, using all available lightcurves of these objects. In the case of Campania, the long persisting doubts about its rotational period have been resolved. Various authors state periods between 8.48 and 16 h, while the period we determined is 11.664401 ± 0.000010 h.

Photometric observations and modelling of the asteroid 85 Io in conjunction with data from an occultation event during the 1995–96 apparition

Abstract The asteroid 85 Io has been observed using CCD and photoelectric photometry on 18 nights during its 1995–96 and 1997 apparitions. We present the observed lightcurves, determined colour indices and modelling of the asteroid spin vector and shape. The colour indices (U-B = 0.35±0.02, B-V = 0.66±0.02, V-R = 0.34±0.02, R-I = 0.36±0.02) are as expected for a C-type asteroid. The allowed spin vector solutions have the pole co-ordinates λ0 = 285±4°, β0 = −52±9° or λ0 = 108±10°, β0 = −46±10° and λ0 = 290±10°, β0 = −16±10° with a retrograde sense of rotation and a sidereal period Psid = 0d.286463±0d.000001. During the 1995–96 apparition the International Occultation Time Association (IOTA) observed an occultation event by 85 Io. The observations and modelling presented here were analysed together with the occultation data to develop improved constraints on the size of the asteroid. The derived value of 164 km is about 5% larger than the IRAS diameter.

Kharkiv study of near-Earth asteroids

The regular CCD observations of near-Earth asteroids (NEAs) in the Institute of Astronomy of Kharkiv National University were initiated in 1995 within the framework of asteroid hazard problem in collaboration with the DLR, Institute of Planetary Research (Berlin). The main aim of the study is a determination of rotation periods and shapes of NEAs as well as astrometry of newly discovered objects. We also carry out the absolute photometry of NEAs in BV RI bands in order to put constraints on surface properties and to estimate their diameters. The observations are carried out with 0.7-m telescope of the Institute of Astronomy (Kharkiv) and with 1-m telescope of the Crimean Astrophysical Observatory (Simeiz) in the standard Johnson-Cousins photometric system. Some observations were made as an optical support of radar observation of NEAs. We present the results of photometric observations of 21 NEAs obtained in 2004-2006 which include asteroid rotation properties, diameters and shapes.

Photometry of two Mars-crossing asteroids 2078 Nanking and 2204 Lyyli

Abstract Photoelectric observations of two Mars-crossing asteroids 2078 Nanking and 2204 Lyyli were carried out during 1992 and 1993 oppositions, respectively. The observed lightcurve amplitude for Nanking is 0.79±0.03 mag and it is 0.43±0.03 mag for Lyyli. The obtained Nanking rotation period is 6.50±0.04 h.