Detection of the Activity of 468861 (2013 LU28)

Abstract The perihelion of long-period comets places them near the Sun so they may exhibit activity. Before 2013 LU28 reached its perihelion, we performed a continuous observation to detect possible activity. Using the Lijiang 2.4 m telescope with a Johnson R filter, we measured the brightness of 2013 LU28 from 2024 January 3 to April 13. The instrumental magnitudes were subsequently transformed into the Pan-STARRS r system. Due to the noticeable descending trend in the absolute magnitude, we verified the cometary activity and constrained some photometric properties of 2013 LU28. Consequently, the increased cross-sectional area had a rate of 42.8 km 2 day −1 , and the corresponding mass-loss rate was 2.64 kg s −1 with the assumption of a dust-particle size <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mi>a</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mspace width="0.25em"/> <mml:mo>=</mml:mo> <mml:mspace width="0.25em"/> <mml:mn>10</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> and the density ρ = 400 kg m −3 . We estimated the nucleus radius as 0.11 ≲ r n ≲ 0.21 km for CO sublimation and 0.20 ≲ r n ≲ 0.71 km for CO 2 sublimation and the grain size of 2013 LU28 was a c ≃ 117.95 μ m for CO and a c ≃ 7.57 μ m for CO 2 . The long-term observations provided in this paper will offer significant value for investigating the mechanisms driving the activity of 2013 LU28.