Dust environment of active asteroids P/2019 A4 (PANSTARRS) and P/2021 A5 (PANSTARRS). Issue 2 (30th June 2021)

• Record Type: Journal Article
• Authors: Moreno, Fernando; Licandro, Javier; Cabrera-Lavers, Antonio; Morate, David; Guirado, Daniel
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 506:Issue 2(2021)
• Page Start: 1733
• Page End: 1740
• Publication Date: 2021-06-30
• Subjects: Minor planets -- asteroids: individual: P/2019 A4P/2021 A5; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1841
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We report on the characterization of the dust activity and dynamical evolution of two faint active asteroids, P/2019 A4, and P/2021 A5, observed with the 10.4 m GTC using both imaging and spectroscopy. Asteroid P/2019 A4 activity is found to be linked to an impulsive event occurring some ±10 d around perihelion, probably due to a collision or a rotational disruption. Its orbit is stable over 100 Myr time-scales. Dust tail models reveal a short-term burst producing (2.0 ± 0.7) × 10 6 kg of dust for maximum particle radius r max = 1 cm. The spectrum of P/2019 A4 is featureless, and slightly redder than the Sun. P/2021 A5 was active ∼50 d after perihelion, lasting ∼5 to ∼60 d, and ejecting (8 ± 2) × 10 6 kg of dust for r max = 1 cm. The orbital simulations show that a few percent of dynamical clones of P/2021 A5 are unstable on 20–50 Myr time-scales. Thus, P/2021 A5 might be an implanted object from the JFC region or beyond. These facts point to water-ice sublimation as the activation mechanism. This object also displays a featureless spectrum, but slightly bluer than the Sun. Nuclei sizes are estimated in the few hundred meters range for both asteroids. Particle ejection speeds (≈0.2 m s −1 ) are consistent with escape speeds from those small-sized objects.