Contemporaneous Multi-Wavelength and Precovery Observations of Active Centaur P/2019 LD2 (ATLAS

The discovery of Gateway Centaur P/2019 LD2 (ATLAS) (Sarid et al., 2019) provides the first opportunity to observe the orbital migration of a Solar System small body from a Centaur orbit to a Jupiter Family Comet (JFC) some four decades from now (Kareta et al., 2020, Hsieh et al., 2020.) The Gateway transition region is beyond where water ice can power cometary activity, so coma production there is as poorly understood as in all Centaurs. We present contemporaneous multi-wavelength observations of LD2 from 2020 July 2-4: Gemini North visible imaging, NASA IRTF near-infrared spectroscopy, and ARO Sub-Millimeter Telescope millimeter-wavelength spectroscopy. Precovery DECam images limit the nucleus's effective radius to $\sim$ 1.2 km or less and Catalina Sky Survey archival data show only smooth changes in brightness. The observed colors of LD2's coma are $g' - r' = 0.70 \pm 0.07$ and $r' - i' = 0.26 \pm 0.07$ with a dust production rate of $\sim 10-20$ kg/s. We used LD2's coma morphology to estimate the dust coma's outflow velocity between $ v \sim 0.6-3.3$ m/s. We do not detect CO towards LD2, giving a 2020 Jul 2-3 production rate upper limit of $Q(CO) < $ 3.8 x 10$^{27}$ mol s$^{-1}$ (3-$\sigma$). The near-infrared spectra show evidence for water ice at the 1-10\% level depending on grain size. Spatial profiles and archival data support the idea of ongoing consistent activity. The evidence supports the hypothesis that LD2 is a typical small Centaur that will become a typical JFC, and thus LD2 is critical to understanding the transition between these two populations. Finally, we discuss strategies for taking advantage of the windfall of cometary science from a community-wide, long baseline monitoring effort of P/2019 LD2.