Initial Characterization of Active Transitioning Centaur, P/2019 LD<sub>2</sub> (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy
Bryce T. Bolin, Yanga R. Fernandez, Carey M. Lisse, Timothy R. Holt, Zhong-Yi Lin, Josiah N. Purdum, Kunal P. Deshmukh, James M. Bauer, Eric C. Bellm, Dennis Bodewits, Kevin B. Burdge, Sean J. Carey, Chris M. Copperwheat, George Helou, Anna Y. Q. Ho, Jonathan Horner, Jan van Roestel, Varun Bhalerao, Chan-Kao Chang, Christine Chen, Chen-Yen Hsu, Wing-Huen Ip, Mansi M. Kasliwal, Frank J. Masci, Chow-Choong Ngeow, Robert Quimby, Rick Burruss, Michael Coughlin, Richard Dekany, Alexandre Delacroix, Andrew Drake, Dmitry A. Duev, Matthew Graham, David Hale, Thomas Kupfer, Russ R. Laher, Ashish Mahabal, Przemyslaw J. Mróz, James D. Neill, Reed Riddle, Hector Rodriguez, Roger M. Smith, Maayane T. Soumagnac, Richard Walters, Lin Yan, Jeffry Zolkower
Abstract
Abstract We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD 2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD 2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μ m-scale dust ejected at ∼1 m s −1 speeds with a ∼1′ jet pointing in the southwest direction. LD 2 experienced a total dust mass loss of ∼10 8 kg at a loss rate of ∼6 kg s −1 with Af ρ /cross section varying between ∼85 cm/125 km 2 and ∼200 cm/310 km 2 from 2019 April 9 to 2019 November 8. If the increase in Af ρ /cross section remained constant, it implies LD 2 's activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H 2 O sublimation. We measure CO/CO 2 gas production of ≲10 27 mol s −1 /≲10 26 mol s −1 from our 4.5 μ m Spitzer observations; g – r = 0.59 ± 0.03, r – i = 0.18 ± 0.05, and i – z = 0.01 ± 0.07 from GROWTH observations; and H 2 O gas production of ≲80 kg s −1 scaling from our estimated C 2 production of mol s −1 from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD 2 is similar to Jupiter-family comets having close encounters with Jupiter within ∼0.5 Hill radius in the last ∼3 y and within 0.8 Hill radius in ∼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 × 10 6 yr, having a dynamical half-life of 3.4 × 10 5 yr.