Dust environment of active asteroids P/2019 A4 (PANSTARRS) and P/2021 A5 (PANSTARRS)

ABSTRACT We report on the characterization of dust activity and dynamical evolution two faint active asteroids, P/2019 A4, P/2021 A5, observed with 10.4 m GTC using both imaging spectroscopy. Asteroid A4 is found to be linked an impulsive event occurring some ±10 d around perihelion, probably due a collision or rotational disruption. Its orbit stable over 100 Myr time-scales. Dust tail models reveal short-term burst producing (2.0 ± 0.7) × 106 kg for maximum particle radius rmax = 1 cm. The spectrum featureless, slightly redder than Sun. A5 was ∼50 after lasting ∼5 ∼60 d, ejecting (8 2) orbital simulations show that few percent clones are unstable 20–50 Thus, might implanted object from JFC region beyond. These facts point water-ice sublimation as activation mechanism. This also displays featureless spectrum, but bluer Nuclei sizes estimated in hundred meters range asteroids. Particle ejection speeds (≈0.2 s−1) consistent escape those small-sized objects.