Activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with OSIRIS at the 10.4 m GTC

Context. The existence of comets with heliocentric orbital periods close to that of Jupiter (i.e., co-orbitals) has been known for some time. Comet 295P/LINEAR (2002 AR2 ) is a well-known quasi-satellite of Jupiter. However, their orbits are not long-term stable, and they may eventually experience flybys with Jupiter at very close range, close enough to trigger tidal disruptions like the one suffered by comet Shoemaker-Levy 9 in 1992.Aims. Our aim was to study the observed activity and the dynamical evolution of the Jupiter transient co-orbital comet P/2019 LD2 (ATLAS) and its dynamical evolution.Methods. We present results of an observational study of P/2019 LD2 carried out with the 10.4 m Gran Telescopio Canarias (GTC) that includes image analyses using a Monte Carlo dust tail fitting code to characterize its level of cometary activity, and spectroscopic studies to search for gas emission. We also present N -body simulations to explore its past, present, and future orbital evolution.Results. Images of P/2019 LD2 obtained on May 16, 2020, show a conspicuous coma and tail, but the spectrum obtained on May 17, 2020, does not exhibit any evidence of CN, C2 , or C3 emission. The comet brightness in a 2.6′′ aperture diameter is r ′ = 19.34 ± 0.02 mag, with colors (g ′− r ′) = 0.78 ± 0.03, (r ′− i ′) = 0.31 ± 0.03, and (i ′− z ′) = 0.26 ± 0.03. The temporal dependence of the dust loss rate of P/2019 LD2 can be parameterized by a Gaussian function having a full width at half maximum of 350 days, with a maximum dust mass loss rate of 60 kg s−1 reached on August 15, 2019. The total dust loss rate from the beginning of activity until the GTC observation date (May 16, 2020) is estimated at 1.9 × 109 kg. Comet P/2019 LD2 is now an ephemeral co-orbital of Jupiter, following what looks like a short arc of a quasi-satellite cycle that started in 2017 and will end in 2028. On January 23, 2063, it will experience a very close encounter with Jupiter at perhaps 0.016 au; its probability of escaping the solar system during the next 0.5 Myr is estimated to be 0.53 ± 0.03.Conclusions. Photometry and tail model results show that P/2019 LD2 is a kilometer-sized object, in the size range of the Jupiter-family comets, with a typical comet-like activity most likely linked to sublimation of crystalline water ice and clathrates. Its origin is still an open question. Our numerical studies give a probability of this comet having been captured from interstellar space during the last 0.5 Myr of 0.49 ± 0.02 (average and standard deviation), 0.67 ± 0.06 during the last 1 Myr, 0.83 ± 0.06 over 3 Myr, and 0.91 ± 0.09 during the last 5 Myr.