Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp: Implications for the photochemistry of OH

Jeffrey P. Morgenthaler, Walter M Harris, Frank Scherb, Christopher M. Anderson, Ronald J. Oliversen, Nathaniel E. Doane, Michael R. Combi, Maximus L. Marconi, William H. Smyth

Research output: Contribution to journalArticle

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Abstract

Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 Å) with the 150 mm dual-etalon Fabry-Pérot spectrometer that comprises the Wisconsin Hα Mapper and a 50 mm dual-etalon Fabry-Pérot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable Q(1D) production rate of (2.3-5.9) × 1030 s-1. Applying the standard H2O and OH photodissociation branching ratios found in Huebner, Keady, & Lyon and van Dishoeck & Dalgarno, we derive a water production rate, Q(H2O), of (2.6-6.1) × 1031 s-1, which disagrees with Q(H2O) ≈ 1 × 1031 s-1 determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 Å observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) ≈ 1 × 1031 s-1. Using our [O I] 6300 Å data, which cover spatial scales ranging from 2,000 to 1 × 106 km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O(1D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant Q(1D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O(1D) emission. Since even less O(1D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O(1D) is likely coming from photodissociating OH. Using the experimental OH photodissociation cross section of Nee & Lee at Lyα as a guide in modifying the theoretical OH cross sections of van Dishoeck & Dalgarno, we can account for ≈60% of the observed O(1D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

Original languageEnglish (US)
Pages (from-to)451-461
Number of pages11
JournalAstrophysical Journal
Volume563
Issue number1 PART 1
DOIs
StatePublished - Dec 10 2001
Externally publishedYes

Fingerprint

Hale-Bopp comet
Hale-Bopp
photochemistry
photochemical reactions
photodissociation
comet
photometry
apertures
coma
spectrometer
cross section
trucks
oxygen
telescopes
spectrometers
Hydra
electron sources
cross sections
spectrographs
electron

Keywords

  • Comets: individual (hale-bopp 1995 O1, hyakutake (C/1996 B2))
  • Instrumentation : spectrographs
  • Molecular processes

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Morgenthaler, J. P., Harris, W. M., Scherb, F., Anderson, C. M., Oliversen, R. J., Doane, N. E., ... Smyth, W. H. (2001). Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp: Implications for the photochemistry of OH. Astrophysical Journal, 563(1 PART 1), 451-461. https://doi.org/10.1086/323773

Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp : Implications for the photochemistry of OH. / Morgenthaler, Jeffrey P.; Harris, Walter M; Scherb, Frank; Anderson, Christopher M.; Oliversen, Ronald J.; Doane, Nathaniel E.; Combi, Michael R.; Marconi, Maximus L.; Smyth, William H.

In: Astrophysical Journal, Vol. 563, No. 1 PART 1, 10.12.2001, p. 451-461.

Research output: Contribution to journalArticle

Morgenthaler, JP, Harris, WM, Scherb, F, Anderson, CM, Oliversen, RJ, Doane, NE, Combi, MR, Marconi, ML & Smyth, WH 2001, 'Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp: Implications for the photochemistry of OH', Astrophysical Journal, vol. 563, no. 1 PART 1, pp. 451-461. https://doi.org/10.1086/323773
Morgenthaler JP, Harris WM, Scherb F, Anderson CM, Oliversen RJ, Doane NE et al. Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp: Implications for the photochemistry of OH. Astrophysical Journal. 2001 Dec 10;563(1 PART 1):451-461. https://doi.org/10.1086/323773
Morgenthaler, Jeffrey P. ; Harris, Walter M ; Scherb, Frank ; Anderson, Christopher M. ; Oliversen, Ronald J. ; Doane, Nathaniel E. ; Combi, Michael R. ; Marconi, Maximus L. ; Smyth, William H. / Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp : Implications for the photochemistry of OH. In: Astrophysical Journal. 2001 ; Vol. 563, No. 1 PART 1. pp. 451-461.
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abstract = "Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 {\AA}) with the 150 mm dual-etalon Fabry-P{\'e}rot spectrometer that comprises the Wisconsin Hα Mapper and a 50 mm dual-etalon Fabry-P{\'e}rot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable Q(1D) production rate of (2.3-5.9) × 1030 s-1. Applying the standard H2O and OH photodissociation branching ratios found in Huebner, Keady, & Lyon and van Dishoeck & Dalgarno, we derive a water production rate, Q(H2O), of (2.6-6.1) × 1031 s-1, which disagrees with Q(H2O) ≈ 1 × 1031 s-1 determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 {\AA} observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) ≈ 1 × 1031 s-1. Using our [O I] 6300 {\AA} data, which cover spatial scales ranging from 2,000 to 1 × 106 km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O(1D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant Q(1D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30{\%} of the observed excess O(1D) emission. Since even less O(1D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O(1D) is likely coming from photodissociating OH. Using the experimental OH photodissociation cross section of Nee & Lee at Lyα as a guide in modifying the theoretical OH cross sections of van Dishoeck & Dalgarno, we can account for ≈60{\%} of the observed O(1D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.",
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T1 - Large-aperture [O I] 6300 Å photometry of comet Hale-Bopp

T2 - Implications for the photochemistry of OH

AU - Morgenthaler, Jeffrey P.

AU - Harris, Walter M

AU - Scherb, Frank

AU - Anderson, Christopher M.

AU - Oliversen, Ronald J.

AU - Doane, Nathaniel E.

AU - Combi, Michael R.

AU - Marconi, Maximus L.

AU - Smyth, William H.

PY - 2001/12/10

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N2 - Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 Å) with the 150 mm dual-etalon Fabry-Pérot spectrometer that comprises the Wisconsin Hα Mapper and a 50 mm dual-etalon Fabry-Pérot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable Q(1D) production rate of (2.3-5.9) × 1030 s-1. Applying the standard H2O and OH photodissociation branching ratios found in Huebner, Keady, & Lyon and van Dishoeck & Dalgarno, we derive a water production rate, Q(H2O), of (2.6-6.1) × 1031 s-1, which disagrees with Q(H2O) ≈ 1 × 1031 s-1 determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 Å observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) ≈ 1 × 1031 s-1. Using our [O I] 6300 Å data, which cover spatial scales ranging from 2,000 to 1 × 106 km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O(1D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant Q(1D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O(1D) emission. Since even less O(1D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O(1D) is likely coming from photodissociating OH. Using the experimental OH photodissociation cross section of Nee & Lee at Lyα as a guide in modifying the theoretical OH cross sections of van Dishoeck & Dalgarno, we can account for ≈60% of the observed O(1D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

AB - Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 Å) with the 150 mm dual-etalon Fabry-Pérot spectrometer that comprises the Wisconsin Hα Mapper and a 50 mm dual-etalon Fabry-Pérot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable Q(1D) production rate of (2.3-5.9) × 1030 s-1. Applying the standard H2O and OH photodissociation branching ratios found in Huebner, Keady, & Lyon and van Dishoeck & Dalgarno, we derive a water production rate, Q(H2O), of (2.6-6.1) × 1031 s-1, which disagrees with Q(H2O) ≈ 1 × 1031 s-1 determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 Å observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) ≈ 1 × 1031 s-1. Using our [O I] 6300 Å data, which cover spatial scales ranging from 2,000 to 1 × 106 km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O(1D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant Q(1D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O(1D) emission. Since even less O(1D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O(1D) is likely coming from photodissociating OH. Using the experimental OH photodissociation cross section of Nee & Lee at Lyα as a guide in modifying the theoretical OH cross sections of van Dishoeck & Dalgarno, we can account for ≈60% of the observed O(1D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

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KW - Instrumentation : spectrographs

KW - Molecular processes

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