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The Astronomical Journal
Article . 2000 . Peer-reviewed
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Water Maser Emission from Comets

Authors: Ashley P. Graham; Bryan J. Butler; Leonid Kogan; Patrick Palmer; Vladimir Strelnitski;

Water Maser Emission from Comets

Abstract

We used the Very Large Array in 1997 January, February, March, and April to observe comet Hale-Bopp in the 1.35 cm H2O line. No line was detected in any of the four observations, and upper limits to the H2O line emission are presented. These upper limits are typically around 60 mJy, which is much lower than the ~2.5 Jy flux density reported for this line in comet Bradfield (1974b) and jansky-level flux densities sporadically reported for a few other comets. This discrepancy is most likely due to a combination of questionable reliability of past reported detections and the possibility that masing in particular observational geometries is required for detection of the line. We concur with previous studies that indicated that this line could be detected only if it were masing. In the only masing scenario likely to yield a positive result, a line may be seen only if the masing region is observed along a jet against the radio continuum background of the nucleus. We estimate the probabilities of a detection in a random search for two typical positions of the origin of a jet on a rotating nucleus: (1) close to the pole and (2) close to the equator. Because the probabilities are very low (0.01) in either case, our negative result for comet Hale-Bopp (as well as previous negative results for other comets) cannot exclude the possibility of such masing jets. Carefully scheduled observations of future comets whose rotation and jet locations have been determined must be used to evaluate this possibility.

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
8
Average
Average
Average
gold