SIMBAD references

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 O(¹D) production rate of (2.3-5.9)x10³⁰ 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, QH₂O, of (2.6-6.1)x10³¹ s^–1, which disagrees with QH₂O~1x10³¹ 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 multiobject spectrographs yield Q(H₂O)~1x10³¹ s^–1. Using our [O I] 6300 Å data, which cover spatial scales ranging from 2,000 to 1x10⁶ 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 O(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.