Some parameters of selected NEAs Ireneusz Wlodarczyk1 Chorzow Astronomical Observatory, IAU 553, 41-500 Chorzow, Poland
[email protected] (Submitted on 01.06.2018. Accepted on 06.08.2018) Abstract. For studied 146 NEAs we computed non-gravitational parameter, A2, Lyapunov time, LT , secular frequency of perihelion and of ascending node and their relationships. In addition, we have extended the study of several of these parameters to all NEAs known so far. We computed their orbits based on all astrometric and radar observations available on December 29, 2017, and used a uniform selection and weighing method for observational material. It appeared that 102 NEAs have A2 < 0, from which about 70% −14 2 have a maximum value in the range (0,-1.0) 10 au/day . It gives of about 15.7% of all NEAs. On the other hand, the remaining 30% NEAs with positive A2 have maximum −14 2 value in the range (+2,+3) 10 au/day . A maximum value of LT is between 20 and 60 years. In this range we found 50 NEAs, i.e. of about 34%. Studied NEAs with the longest LT are mainly located between the space controlled by the perihelion of Mars and aphelion of the Earth. Here are NEAs which do not cross the orbit of planets. From all 17506 NEAs, we found secular frequencies close to secular precessions of the perihelion of Saturn, g6, for 368 NEAs and of Jupiter, g5, for 337 NEAs. Also, we detected secular frequencies close to the secular precession of the ascending node of Saturn, s6, for 275 NEAs.