The changing rotational excitation of C_3 in comet 9P/Tempel 1 during Deep Impact

Abstract

The 4050Å band of C${}_3$ was observed with Keck/HIRES echelle spectrometer during the {\em Deep Impact} encounter. We perform a 2-dimensional analysis of the exposures in order to study the spatial, spectral, and temporal changes in the emission spectrum of C${}_3$. The rotational population distribution changes after impact, beginning with an excitation temperature of $\sim$45\,K at impact and increasing for 2\,hr up to a maximum of 61$\pm$5\,K. From 2 to 4 hours after impact, the excitation temperature decreases to the pre-impact value. We measured the quiescent production rate of C${}_3$ before the encounter to be 1.0 $\times 10^{23}$ s${}^{-1}$, while 2 hours after impact we recorded a peak production rate of 1.7 $\times 10^{23}$ s${}^{-1}$. Whereas the excitation temperature returned to the pre-impact value during the observations, the production rate remained elevated, decreasing slowly, until the end of the 4\,hr observations. These results are interpreted in terms of changing gas densities in the coma and short-term changes in the primary chemical production mechanism for C${}_3$.

Accepted for publication in ApSS

References in corpus (6)

• Deep Impact : High Resolution Optical Spectroscopy with the ESO VLT and the Keck 1 telescope
• Observations of rotationally resolved C3 in translucent sight lines
• Carbon Monoxide in Comet 9P/Tempel 1 before and after the Deep Impact Encounter
• Observations of Comet 9P/Tempel 1 with the Keck 1 HIRES Instrument During Deep Impact
• Placing the Deep Impact Mission into Context: Two Decades of Observations of 9P/Tempel 1 from McDonald Observatory
• The temporal changes in the emission spectrum of Comet 9P/Tempel 1 after Deep Impact