Physical Characterization of Main-belt Comet (248370) 2005 QN₁₇₃

Abstract We report results from new and archival observations of the newly discovered active asteroid (248370) 2005 QN 173 (also now designated Comet 433P), which has been determined to be a likely main-belt comet based on subsequent discovery that it is recurrently near perihelion. From data analysis, we estimate g ? -, $r^{\prime} r $i^{\prime} i $z^{\prime} z -band absolute magnitudes for nucleus H g = 16.62 ± 0.13, r 16.12 0.10, i 16.05 0.11, z 15.93 0.08, corresponding colors -r^{\prime} =0.50\pm 0.16$?> ? = 0.50 ± 0.16 , -i^{\prime} =0.07\pm 0.15$?> 0.07 0.15 -z^{\prime} =0.12\pm 0.14$?> 0.12 0.14 ; an equivalent V magnitude 16.32 0.08; radius n 1.6 0.2 km (using albedo p 0.054 0.012). Meanwhile, find mean near-nucleus coma when 248370 =0.47\pm 0.03$?> 0.47 0.03 =0.10\pm 0.04$?> 0.10 0.04 =0.05\pm 0.05$?> 0.05 similar dust tail colors, suggesting no significant gas present. approximate ratios between scattering cross sections (within 5000 nucleus) A d / 0.7 0.3 2016 July 22 1.8 < 2.9 in 2021 August. During observation period, declined intrinsic brightness by ?0.35 mag (or ?25%) 37 days, while surface remained effectively constant over same period. Constraints derived sunward extent width as measured perpendicular orbit plane suggest terminal velocities ejected grains are extremely slow (?1 m s ?1 1 ? particles), observed emission may aided rapid rotation lowering effective escape velocity.