Large Aperture Oi6300 A Observations of Comet Hyakutake: Implications for the Photochemistry of OH and OiProduction in Comet Hale‐Bopp

Abstract

In previous work (Morgenthaler et al. and Glinski et al.), we proposed a revision to the standard OH photochemistry of van Dishoeck & Dalgarno in order to explain the anomalously bright [O i] 6300 8 emission observed by several instruments in comet C/1995 O1 (Hale-Bopp). In order to test the validity of revisions to the OH photochemistry, we present wide-field Fabry-Pérot [O i] 6300 8 observations of comet C/1996 B2 (Hyakutake) and review similar observations recorded for 1P/ Halley and 1989 c1 (Austin). Conventional long-slit spectroscopic observations of several comets in [O i] are also reviewed. The bulk of the evidence suggests that the OH photochemical rates of van Dishoeck & Dalgarno are, on the whole, correct and that the bright [O i] emission observed in Hale-Bopp, particularly at cometocentric distances beyond $3 ; 10 4 km, was unique to that comet, or possibly any comet with such a large production rate.

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

“…We determined H 2 O production rates from our [O I]6300Å line observations by employing algorithms based on those used in Morgenthaler et al (2007) and …”

High Resolution Spectroscopic Campaigns to Support Spacecraft Observations of Comets with Small Telescopes

“…Moreover, since a metastable atom emits only one time, the integrated flux measures the steady state mass of the parent species in the coma. This combination of factors makes it straightforward to invert the wide field brightness to production rate (Q) provided the branching ratios of the parents are understood (Schultz et al 1992;MageeSauer et al 1989;Oliversen et al 2002;Morgenthaler et al 2001Morgenthaler et al , 2007. The major difficulty is that both O 1 D and C 1 D require high resolving power to separate the cometary emissions from nearby molecular bands (NH 2 and OH) and from telluric emission and/or absorption features.…”

“…The accuracy of the inversion is dependent on an understanding of the photochemical branching ratios leading to H from H 2 O and on the importance of collisions within the photochemical scale length (Combi et al 2000). Ground based observations of OH (Harris et al 2002a, b), O 1 D (Morgenthaler et al 2001, Morgenthaler et al 2007, and Ha (Morgenthaler et al 2002a, b) all reveal a complex environment with implications for estimates of Q H2O . Modeling of the radial distribution of OH showed significant evidence of thermalization of photochemical The spectrum shows both the comet and geocoronal lines and demonstrates the significance of using high resolving power and the Doppler shift of the comet to obtain a clean signal (from .…”

Oxygen emission lines in the high resolution spectra of 9P/Tempel 1 following the Deep Impact event

“…If it can be assumed that water is the main source of these lines, the O column density can be used to deduce the H 2 O production rate (see, for example, Morgenthaler et al 2001;Morgenthaler et al 2007). Moreover, since the lifetime of the 1 D state at 1 AU is ∼110 s, much shorter than the corresponding lifetime of a water molecule (∼8 × 10 4 s at 1 AU) (Crovisier 1994), the red emission lines are a good tracer of the distribution of water molecules in the cometary coma, because they cannot travel far without decaying.…”

“…One or more of these oxygen lines have been detected in several comets (see for example Fink & Johnson 1984;MageeSauer et al 1990;Schultz et al 1993;Morrison et al 1997;Cochran 1984;Cochran & Cochran 2001;Zhang et al 2001;Morgenthaler et al 2001;Capria et al 2005;Morgenthaler et al 2007), but their unambiguous detection, especially that of the green line at 5577 Å, is a non-trivial task. Firstly, the high spectral resolution is necessary to distinguish the three lines from usually strong telluric O emission lines.…”