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Jeffrey P. Morgenthaler, Walter M. Harris (U. Washington), Michael R. Combi (U. Michigan)

Large Aperture [O I] 6300 Å Observations of Comet Hyakutake: Implications for the Photochemistry of OH and [O I] Production in Comet Hale-Bopp. Jeffrey P. Morgenthaler, Walter M. Harris (U. Washington), Michael R. Combi (U. Michigan). Emission line from a metastable state of oxygen

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Jeffrey P. Morgenthaler, Walter M. Harris (U. Washington), Michael R. Combi (U. Michigan)

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  1. Large Aperture [O I] 6300 Å Observations of Comet Hyakutake: Implications for the Photochemistry of OH and [O I] Production in Comet Hale-Bopp Jeffrey P. Morgenthaler, Walter M. Harris (U. Washington), Michael R. Combi (U. Michigan)

  2. Emission line from a metastable state of oxygen O(1D) difficult to get to with photon excitation Product of electron excitation or molecular dissociation 110 s lifetime What is [O I] 6300 Å?

  3. Hale-Bopp had “too much” [O I] • By a factor of 3—4 • Assuming standard H2O and OH photochemistry • 4 instruments on 3 telescopes • Morgenthaler et al., Ap.J., 2001 asked: is photochemistry correct? • OH in particular

  4. Likely Answer • Glinski et al. (2004): Hale-Bopp coma dense enough for gas phase chemistry: O + OH → O2 + H • Simple coma model with 14 concentric shells • Complex chemical model with 55 reactions • O2 efficient at producing [O I] • OH → [O I] branching ratio still needed to be raised to match Hale-Bopp data

  5. Do [O I] observations of other comets support any change in OH branching ratios? • Uwe Fink [O I] profiles of many comets consistent with standard H2O and OH photochemistry • Fink et al. do not cleanly separate airglow and NH2 • Sensitivity of long-slit spectrometers to extended sources is low compared to wide-field Fabry-Pérots • OH does dominates [O I] >104 km • Fink sensitivity to [O I] from OH may be too low to address this issue

  6. Fabry-Pérot Observations • Solar minimum comets: • Hale-Bopp (Morgenthaler et al. 2001) • “Too much” [O I] • Halley (Magee-Sauer et al. 1988, 1990), Hyakutake (this work) • Highly variable production rates • Solar max comet: Austin • Good agreement with standard photochemistry (Schultz et al. 1993)

  7. Comet Austin [O I] Profile (Schultz et al. 1993)

  8. Hyakutake (2006 March 23)

  9. Hyakutake (2006 March 23)

  10. Hyakutake (2006 March 23)

  11. Hyakutake (2006 March 23) • Time-varying Haser model based on Combi et al. (2005) Q(H2O) values • Glinski et al. (2004) modified OH → [O I] branching ratio (BR3G) not compatible • Model fits data best with standard photochemistry • Let’s stick with standard H2O and OH photochemistry

  12. Halley measured profiles steeper than model

  13. Halley measured profiles steeper than model • Hyakutake model based on actual Q(H2O) values (Combi et al. 2005) fits well • Halley time-varying model based on Q(C2) values (Schleicher et al. 1990) • CN and NH2 profiles match C2 well (Combi et al. 1993) • Does H2O have a different inner coma or outgassing or behavior than CN, NH2, and C2?

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