Contemporaneous Multi-Wavelength Observations of the Active Centaur P/2019 LD2

The discovery that the active Centaur P/2019 LD2 (ATLAS), hereafter LD2, will transition inward of Jupiter’s orbit in 2063 to become a bona-fide member of the Jupiter-Family Comet population [1,2] presents a unique opportunity. It will enable us to monitor a Centaur as its primary source of activity becomes water sublimation for likely the first time. The evidence that LD2 is a recently activated primordial body is presented by Sarid et al. [3]. These factors make LD2 a high priority target for characterization of its composition and activity patterns.

We present contemporaneous visible, near-infrared, and millimeter-wavelength observations of LD2 obtained in July 2020 from Gemini North, the NASA IRTF, and the Arizona Radio Observatory Submillimeter Telescope, as well as pre-covery data from the CTIO Blanco 4-m taken from the Dark Energy Survey archive. We will present spatial profiles and brightnesses at visible and near-infrared wavelengths, near-infrared reflectance spectra of the inner coma, and a sensitive upper limit on CO production [4]. The spatial profiles and pre-covery data are consistent with at least episodic activity since May 2018, and the reflectance spectrum shows evidence for water ice in the coma at the few percent level. We will also present the evidence for a nuclear size of under 1.2 km radius [5]. These observations are in broad agreement with dynamical analyses showing a pristine object that has not visited the inner Solar System previously [2]. LD2 presents an unparalleled opportunity to understand the transition cometary bodies experience as they evolve from the outer to inner solar system.

1. Kareta, et al. 2020, RNAAS, 4, 74.

2. Steckloff et al. 2020, submitted to ApJL, arXiv:2008.02943.

3. Sarid et al. 2020, “P/2019 LD2 in Transition: Dynamical and Thermal Context for an Evolving Active Centaur”, This Meeting.

4. Kareta et al., in preparation.

5. Schambeau et al. 2020, CBET 4821