Observations of O (1S) and O (1D) in Spectra of C/1999 S4 (LINEAR)

Cochran, A. L.; Cochran, William D.

doi:10.1006/icar.2001.6718

Cited by 38 publications

(46 citation statements)

References 41 publications

(52 reference statements)

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“…In addition, Cochran and Cochran (2001) showed that the production of the oxygen from CO in comet 1999 S4 (LINEAR) was inconsistent with UV observations showing a depletion of CO in its coma. Thus, we dismiss CO as a parent.…”

Section: Constraints From Our Spectramentioning

confidence: 94%

“…The ratios we find are listed in Table II. These ratios have been corrected for the relative response of the red and green orders of the spectrograph by use of observations of α Lyr (the green-to-red flux ratio needed to be increased by 30%, as per Cochran and Cochran 2001). Festou and Feldman (1981) showed that this will result in a flatter column density profile for the red lines than for the green line.…”

Section: Constraints From Our Spectramentioning

confidence: 99%

“…However, for some comets, the oxygen line is stronger than the C 2 bands and can be successfully deblended from the cometary C 2 and the telluric oxygen if the spectral resolution is sufficient. Some comets have been observed to have almost no C 2 , making detection of the green line simple (Cochran and Cochran 2001).…”

Section: Introductionmentioning

confidence: 99%

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Atomic oxygen in the comae of comets

Cochran

2008

Icarus

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We report on the detection of atomic oxygen lines in the spectra of 8 comets. These forbidden lines are a result of the photodissociation of the parent oxygen-bearing species directly into an excited state. We used high resolution spectra obtained at the McDonald Observatory 2.7m telescope to resolve the cometary oxygen lines from the telluric oxygen lines and from other cometary emissions. We find that the relative intensities of the two red lines (6300.304 and 6363.776Å) are consistent with theory. The green line (5577.339Å) has an intensity which is about 10% of the sum of the intensities of the two red lines. We show that collisional quenching may be important in the inner coma. If we assume the relative excitation rates of potential parents which have appeared in the literature, then H 2 O would be the parent of the cometary green oxygen line. However, those rates have been questioned. We measured the width of the three oxygen lines and find that the green line is wider than either of the two red lines. The finding of a wider line could imply a different parent for the green and red lines. However, the constancy of the green to red line flux ratio suggests the parent is the same for these lines but that the exciting photons have different energies.

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Section: Constraints From Our Spectramentioning

confidence: 94%

Section: Constraints From Our Spectramentioning

confidence: 99%

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Atomic oxygen in the comae of comets

Cochran

2008

Icarus

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“…In the optical region of cometary spectra, three forbidden O transitions are usually detectable, while they are not always separable from the corresponding telluric lines: the green line at 5577.339 Å ( 1 S-1 D) and the red doublet at 6300.304 Å and 6363.776 Å ( 1 D-3 P) (Feldman et al 2004;Cochran & Cochran 2001;Cochran 2008). In the spectra JMEC0039, taken on October 25, and JODF0017, taken on December 2, some of these emission lines are visible.…”

Section: Analysis Of the Atomic Oxygen Emission Linesmentioning

confidence: 99%

“…In the case of a red doublet, the ratio of the two line strengths should be the same as the ratio of their branching ratios, because they are both transitions from the (2p 4 ) 1 D state to the (2p 4 ) 3 P ground state. The green to red intensity ratio can be written as (Cochran & Cochran 2001)…”

Section: Analysis Of the Atomic Oxygen Emission Linesmentioning

confidence: 99%

High resolution observation of 17P/ Holmes during the outburst event in 2007

Capria

Cremonese

Sanctis

2010

A&A

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Aims. On October 24, 2007 the comet 17P/ Holmes underwent an outburst that was extraordinary in both duration and size. We attempted to determine the cause of the outburst by acquiring and analyzing high resolution spectra of the comet. Methods. On two nights, October 25 and December 2, we acquired four high resolution spectra in the visible range at the Telescopio Nazionale Galileo in La Palma. The oxygen lines intensity ratio was estimated for the observation performed on October 25, and computed for the observation performed on December 2. Results. Many emission lines were detected in the spectra, most of them attributable to C 2 , NH 2 , CN and CH. The atomic O green line and one of the red doublet lines were detected in a spectrum acquired on October 25. All the three atomic O lines were detected in a spectrum acquired on December 2. The value obtained for the first night, 0.1 ± 0.11, implies that the H 2 O molecule was the main parent of the emission lines, while the value obtained for the second night, 0.3 ± 0.1, implies that the main parent was CO or CO 2 instead than H 2 O. Conclusions. Our results imply that in the days around the outburst the water production was exceptionally high for that heliocentric distance. By December, however, the behavior of 17P/ Holmes had returned to that of a comet orbiting at 2.6 AU from the Sun, in which state the activity is probably sustained mostly by gases more volatile than water, such as CO and CO 2 .

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