4015 Wilson-Harrington, 2201 Oljato, and 3200 Phaethon: Search for CN Emission

Abstract

There is evidence that 2201 Oljato and 3200 Phaethon may be inactive cometary remnants. Comet P/Wilson-Harrington (1949 III) was discovered to be the same object as asteroid 4015 1979 VA. With this knowledge, we made measurements of these near-Earth objects (NEOs) to search for the CN (Δv=0) band emission at 3880 —the most easily observed volatile species signature in comets. No CN emission feature was detected within 3-sigma for any of these NEOs. A Haser model was used to determine the production rate of CN (QCN) corresponding to 3-sigma upper limits on the CN band flux. CN production rates were <4 × 1022mol·sec−1for 4015 Wilson-Harrington, <1 × 1023mol·sec−1for 2201 Oljato, and <1 × 1023mol·sec−1for 3200 Phaethon. These production rates are lower (by as much as an order of magnitude) than those observed in low production rate comets. We have lowered the upper limits onQCNfor 2201 Oljato from its previous value by an order of magnitude. The active surface area required to produce the derived upper limit onQCN, <0.02% for 4015 Wilson-Harrington and <0.01% for 3200 Phaethon, is lower than those derived for most active comets. However, 2201 Oljato's active area, <0.4%, is within the lower end of the active comet range.