Abstract
Abstract The observations of comet C/2020 T2 (Palomar) were carried out using the 3.4 mm wavelength microwave band before perihelion from January 22 to July 5, 2021 and after perihelion on July 13, 2021. During this period, the comet was located at a heliocentric distance of between rh=2.840 AU and 2.055 AU. The consecutive long-term monitoring of outgassing of C/2020 T2 was conducted with Purple Mountain Observatory (PMO) 13.7-m telescope and the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope in the atmospheric radio window. The hyperfine triplet components of hydrogen cyanide (HCN (1-0) F=0-1, F=2-1 and F=1-1) of the J=1-0 vibrational ground-state transitions, as the primary tracer of molecular gas, were unambiguously identified in this comet C/2020 T2. Combining all data, we derived the positive signal of line width corresponds to the coma expansion velocity vexp from ∼0.2 km s−1 to ∼0.4 km s−1. The mean gas molecular production rates of HCN were derived QHCN = (2.92 ± 0.51) × 1025 molecules s−1 at PMO 13.7-m, and QHCN = (6.26 ± 1.55) × 1025 molecules s−1 at IRAM 30-m, respectively. Overall, studying the gas composition of the Long-Period Comet revealed abundant information about the missing link between interstellar molecular clouds and the outer regions of a distant protoplanetary accretion disk, and the relationship between amorphous ice sublimation mechanism and heliocentric distance.
Published Version
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