Long-lasting activity of asteroid (248370) 2005 QN173

Abstract

We present the results of observations of asteroid (248370) QN173 obtained during July 2021 – January 2022 with three telescopes. Our analysis revealed the presence of the dust tail for about half of a year. The direct images of the asteroid were obtained with broad-band filters. No emissions were revealed in the spectra, and the spectrum of the asteroid closely matched that of a C-type asteroid. Created color and linear polarization variations along the tail were analyzed. The asteroid demonstrated a redder color compared to the Sun. Dramatic changes in dust productivity obtained in different filters were not detected. The g − r color changes from 0.2m to 0.7m over the coma, and the linear polarization degree varies from about 1.2% to 0.2% and from −0.2% to −1.5% at the phase angle of 23.2○ and 8.16○. The total dust mass ejected until the latest observation on October 10 is 4.2 × 107 kg, with a maximum rate of 2.6 kg s−1 based on the Monte Carlo modeling of the dust tail. The estimated asteroid size is 1.3 km. It is shown that large particles are concentrated around the nucleus, whereas smaller ones dominate in the tail. The evolution of (248370) QN173 orbit and the orbits of the sample of the 464 short-periodic comets were followed. Ten of them approached the asteroid’s orbit. These objects are not genetically related, despite the very close distance of their orbits for a relatively long time.