Photometry of 2006 RH₁₂₀: an asteroid temporary captured into a geocentric orbit

Abstract

Aims. From July 2006 to July 2007 a very small asteroid orbited the Earth within its Hill sphere. We used this opportunity to study its rotation and estimate its diameter and shape. Methods. Due to its faintness, 2006 RH 120 was observed photometrically with the new 10-m SALT telescope at the SAAO (South Africa). We obtained data on four nights: 11, 15, 16, and 17 March 2007 when the solar phase angle remained almost constant at 74• . The observations lasted about an hour each night and the object was exposed for 7−10 s through the "clear" filter. Results. From the lightcurves obtained on three nights we derived two solutions for a synodical period of rotation: P 1 = 1.375 ± 0.001 min and P 2 = 2.750 ± 0.002 min. The available data are not sufficient to choose between them. The absolute magnitude of the object was found to be H = 29.9 ± 0.3 mag (with the assumed slope parameter G = 0.25) and its effective diameter D = 2−7 m, depending on the geometric albedo p V (with the most typical near-Earth asteroids albedo p V = 0.18 its diameter would be D = 3.3 ± 0.4 m). The body has an elongated shape with the a/b ratio greater than 1.4. It probably originates in low-eccentricity Amor or Apollo orbits. There is still a possibility, which needs further investigation, that it is a typical near-Earth asteroid that survived the aerobraking in the Earth's atmosphere and returned to a heliocentric orbit similar to that of the Earth.

Photometric survey of the very small near-Earth asteroids with the SALT telescope

“…The Light Curve Data Base 1 (LCDB), described in Warner et al (2009) Recently new periods were reported for four very small NEAs by Birtwhistle (2009) (Kwiatkowski et al 2009), 13 fast-rotating NEAs (Paper I), and another 12 objects from the near-Earth asteroid population (this paper). We also revised the period of 2006 XY, which is already included in the LCDB, and which we discussed in Paper I.…”

“…The instruments and the methods of data reduction were described in Kwiatkowski et al (2009), which presents observations of an unusual asteroid 2006 RH 120 . A systematic presentation of the early results of the survey was presented in Kwiatkowski et al (2010) (hereafter Paper I) where we published the lightcurves of a sample of the fastest rotating asteroids (periods shorter than 1 h).…”

First EURONEAR NEA discoveries from La Palma using the INT★

“…The data were reduced using the same LIDAS package. The lightcurve was analysed by iteratively fitting a Fourier series using different trial periods (Kwiatkowski et al 2009). The best fit was obtained for two synodic periods: P 2 = 4.459 ± 0.003 min and P 3 = 8.917 ± 0.004 min which is quite common in case of noisy lightcurves.…”

Photometric survey of the very small near-Earth asteroids with the SALT telescope

“…The first object from our campaign has been presented in Kwiatkowski et al (2009). It was an unusual near-Earth asteroid 2006 RH 120 .…”