Characterization of Asteroid 52768 (1998 OR2)

We report analysis of radar and photometric observations obtained in 2020 for the potentially hazardous asteroid 52768 (1998 OR2). OR2 is a H=15.8 mag near-Earth asteroid (NEA) that experienced its closest approach to Earth (16.4 Lunar distance) until 2079 on April 29th, 2020.

The radar observations were obtained between April 13 to 19, 2020, with the Arecibo S-Band (2.38 GHz, 12.6 cm, 1 MW) planetary radar system at the 305-m William E. Gordon Telescope in Arecibo, Puerto Rico. Radar delay-Doppler images with a resolution as fine as 7.5 meters/pixel revealed a diameter of approximately 2 km. We analyzed radar data using the Hickson et al. 2020 method to derive the polarimetric properties of the radar observations.

The photometric observations were obtained from the KASI Optical Wide-Field Patrol (OWL) network of 0.6 m telescopes from March to May 2020. Data were obtained in the BVRI set of the johnson-cousins filters and all the images were reduced and calibrated in their own band using the photometry pipeline. The photometric data allowed us to obtain the lightcurve of 1998 OR2 and confirm its rotation period of P=4.11 hours. Using the absolute photometry calibrated in the B, V, R, and I bands we were able to determine the broad band color indexes of OR2 and obtain a broad band spectrum that we compared to the Bus-Demeo taxonomic system to determine OR2's taxonomy. Analysis of the asteroid distance-corrected magnitude allowed us to construct its photometric phase curve. Our phase curve contains data from 41° to 77° phase angle and does not allow us to determine a value of the H magnitude due to the lack of low phase angle observations, but we derived the value of the G1, and G2 parameters in the H,G1,G2 system.