A disbelief in 'cygnets.' (subatomic particles radiating from Cygnus X-3)

A disbelief in "cygnets'

Is there some strange radiation coming from the celestial object Cygnus X-3 or isn't there? Some months ago a group of physicists working with a particle detector in the Soudan iron mine north of Duluth, Minn., reported observations of such radiation. It seemed to involve some hitherto unknown, very energetic subatomic particle, to which they have given the provisional name "cygnet' (SN:10/12/85, p.231). Negative results from other detectors presented at this meeting seemed to lead many physicists to dismiss the idea, but Marvin Marshak of the University of Minnesota at Minneapolis, one of the leaders of the Soudan group, not only insisted on the accuracy of the Cyg X-3 observations but also presented a claim for similar radiation from four other objects of the same class as Cyg X-3.

Cyg X-3 is a binary star that is a strong emitter of X-rays. What appeared in the Soudan detector were muons, which seemed to be produced by some

invisible, highly energetic particles coming from the direction of Cyg X-3. The Soudan detector and the others under discussion--all intended to look for radioactive decay of the proton--are mostly calorimeters, large arrays consisting of iron plates separated by narrow spaces filled with gas. The plates serve to slow any radiation that may enter the detector or appear spontaneously within it, and the gas serves as a medium to record the paths of the radiation. As proton decay is expected to be extremely rare, these detectors are located deep underground to shield them from background radiation.

In those positions, however, the detectors can also detect radiation coming from beyond the earth if it is energetic enough to penetrate to their depth, and the lack of background will make it show up bright and clear. That is what the Soudan group says happened with Cyg X-3 and why the scientists were able to trace the paths of the cygnets back to Cyg X-3. Now they claim similar radiation from four more binary X-ray sources: Hercules X-1, Scorpio X-1, 4U0115 63 and 1E2259 586.

Last autumn scientists running a detector called NUSEX, located in a tunnel under Mont Blanc on the French-Swiss border, reported an apparent confirmation of the original Cyg X-3 detection. While no one from NUSEX spoke at the Berkeley meeting, detractors were well represented. Chief among them was the group operating the Frejus detector. Frejus is also in a tunnel under the Alps, this one between Mostane, France, and Bartolovecchio, Italy. Luciano Moscoso of the Centre d'Etudes Nucleaires at Saclay, France, reported that Frejus should have seen cygnets but has not. So far it might be called a borderline case, but there are two further negatives. Robert C. Svoboda of the University of California at Irvine reported that the IMB detector, which is in a salt mine under Lake Erie near Cleveland, should have seen cygnets and didn't. Daniel J. Cutler of the University of Utah in Salt Lake City reported that a detector located in the Mayflower mine in Utah also should have seen cygnets and didn't.

These detectors are all at different depths under different geologies and of different dimensions and slightly different composition. They are hard to compare with each other. Marshak alleges some of them shouldn't have seen cygnets. Furthermore, he says, Cyg X-3 turns on and off; its last outburst recorded at Soudan occurred in October 1985. Some of these detectors were not looking then, he avers.

Moscoso and Frejus representative Claude Longuemare of the University of Paris South at Orsay replied that Frejus was up and looking in October. Marshak responded that at that time Cyg X-3 should have been directly overhead, and the cygnets would have gone through the detector vertically and undetected. Not so, Moscoso and Longuemare insisted, but Marshak remains adamant. It is difficult, after all, to prove the nonexistence of something by negative evidence.