Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), using Hubble, Spitzer, ZTF, Keck, APO and GROWTH Visible & Infrared Imaging and Spectroscopy
Abstract
We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with HST/WFC3, Spitzer/IRAC, the GROWTH telescope network, visible spectroscopy from Keck/LRIS and archival ZTF observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2-1.8 km assuming a 0.08 albedo and a coma dominated by 100μ m-scale dust ejected at 1 m/s speeds with a 1'' jet pointing in the SW direction. LD2 experienced a total dust mass loss of 108 kg at a loss rate of 6 kg/s with Af/cross-section varying between 85 cm/125 km2 and 200 cm/310 km2 from 2019 April 9 to 2019 Nov 8. If the increase in Af/cross-section remained constant, it implies LD2's activity began 2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of 1027 mol/s /1026 mol/s from our 4.5 μm Spitzer observations, g-r = 0.590.03, r-i = 0.180.05, i-z = 0.010.07 from GROWTH observations, H2O gas production of 80 kg/s scaling from our estimated C2 production of QC27.5×1024 mol/s from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter family comets having close encounters with Jupiter within 0.5 Hill radius in the last 3 y, within 0.8 Hill radius in 9 y. Additionally, 78.8\% of our orbital clones are ejected from the Solar System within 1 × 106 years having a dynamical half-life of 3.4 × 105 years.