O($^{\mathsf 1}$S) and O($^{\mathsf 1}$D) emission lines in the spectrum of 153P/2002 C1 (Ikeya-Zhang)

Abstract

High resolution spectroscopy observation of comet 153P/2002 C1 Ikeya-Zhang was performed on April 20, 2002 with the echelle spectrograph SARG on the 3.5 m Telescopio Nazionale Galileo in La Palma. The atomic O emission lines at 5577, 6360 and 6363 Å are clearly visible in the spectrum. We determined the intensity ratio of the green line to the sum of the red lines. In order to verify the hypothesis that water is the main parent species of these emissions, the result was compared with the value obtained from a coupled chemistry-transport model. The measured value for the green to red ratio, 0.12 ± 0.1, agrees quite well with the value obtained from the model. This led us to conclude that during the observation water was the parent species of atomic O lines.

Catalog of the emission lines in the visible spectrum of comet 153P/Ikeya-Zhang

“…Furthermore we have found some atomic lines to be oxygen, that we have used to determine the ratio between the green and red emission (Capria et al 2005), and the sodium D-lines, confirming their presence in this comet (Fig. 3).…”

“…The atomic oxygen emission lines were the subject of a dedicated paper (Capria et al 2005). The intensity ratio of the green to the red doublet was measured and the value found is compatible with the hypothesis that the lines originate mainly from the dissociation of the water molecule.…”

“…They suggested that the unidentified band at 5310 Å is correlated to the flux of H 2 O + . The visible spectrum that is the subject of this paper (see the following section) has already been used for the determination of the nuclear spin temperature of ammonia (Kawakita et al 2004) and of the ratio of atomic oxygen lines (Capria et al 2005), confirming the usefulness of the high resolution spectrum of a comet. 153P/Ikeya-Zhang is one of the few comets for which the nuclear spin temperature of ammonia has been estimated (Kawakita et al 2004) and is about 32 K. The result is similar to previous measurements in three other comets, C/2001 A2, C/1999 S4 and C/1995 O1: the nuclear spin temperatures of ammonia in these comets are around 30 K (Kawakita et al 2004).…”

The CO 2 abundance in Comets C/2012 K1 (PanSTARRS), C/2012 K5 (LINEAR), and 290P/Jäger as measured with Spitzer

“…These forbidden lines are fairly bright features in cometary spectra and can be readily observed in moderately bright comets (V=10) with medium aperture telescopes (2-3 meter class) (Capria et al, 2005;Cochran, 2008;Decock et al, 2013;McKay et al, 2015, and references therein). However, the photochemistry of O I release from CO 2 photodissociation, as well as from its other primary parents H 2 O and CO, is still poorly understood, and limits the usefulness of O I as a reliable proxy (McKay et al, 2013;Decock et al, 2013).…”

Prediction of Forbidden Ultraviolet and Visible Emissions in Comet 67p/Churyumov–gerasimenko

“…The direct de-excitation of O( 1 S) yields a 2972 Å emission line, which has been observed in the cometary spectrum only once (Festou & Feldman 1981). Since there are other oxygen-bearing species, such as CO 2 and CO, which can also produce these metastable states via dissociative excitation reactions, the observed green to red-doublet emission intensity ratio (hereafter referred as the G/R ratio) has been used to confirm the parent source of these emission lines (Cochran 1984(Cochran , 2008Morrison et al 1997;Cochran & Cochran 2001;Zhang et al 2001;Capria et al 2005Capria et al , 2008Capria et al , 2010Furusho et al 2006;McKay et al 2012McKay et al , 2013McKay et al , 2015Decock et al 2013). Based on O( 1 S) and O( 1 D) photorates calculated by Festou & Feldman (1981), the observed high G/R ratio values (>0.1) were ascribed to large CO 2 and CO volume mixing ratios in the coma (Furusho et al 2006;Capria et al 2010;McKay et al 2012;Decock et al 2013).…”