Abstract
WE would like to confirm Weinreb, Barrett, Meeks and Henry's1 discovery of the hydroxyl (OH) radical in the interstellar medium at frequency 1667.36 Mc/s. Fig. 1. shows observations of the Sagittarius A source in the frequency range 1,667.672–1,667.210 Mc/s. These observations were made between December 2 and December 9, 1963, with the 33-ft. antenna at the Hat Creek Radio Astronomy Observatory of the University of California, Berkeley. We used a switched-frequency receiver in which the comparison channel was fixed at 1,669 Mc/s and the signal channel, of bandwidth 50 kc/s, was scanned over the spectrum at the rate of 0.93 Mc/s per hour. The output of the receiver was digitized. ‘Print-out’ occurred every 23.3 kc/s during the scan; this corresponds to an integration time of 90 sec per point. For the receiver used we found an excess system noise of 750° K. We may thus expect (and we find) a root mean square uncertainty of 0.7° K for a single readout. The mean error of a plotted point on the OH curve in Fig. 1 is ± 0.13° K. The plotted frequency profile represents the mean of 29 scans.
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Weinreb, S., Barrett, A. H., Meeks, M. L., and Henry, J. C., Nature, 200, 829 1963).
Penzias, A. A., Meeting of Amer. Astron. Soc., Washington, D.C., December 26–28, 1963. [See also, Nature, 201, 279 (1964).]
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WEAVER, H., WILLIAMS, D. OH Absorption Profile in the Direction of Sagittarius A. Nature 201, 380 (1964). https://doi.org/10.1038/201380a0
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DOI: https://doi.org/10.1038/201380a0
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