Possible indirect method for the detection of $gamma$-ray flashes from supernovae

Journal Article · Fri Oct 19 04:00:00 EDT 1973 · Nature (London), v. 245, no. 5425, pp. 366-367

DOI:https://doi.org/10.1038/245366a0· OSTI ID:4400619

Porter, N A

Reference is made to the electron-photon cascade calculations of Messel and Crawford (Electron- Photon Shower Distribution Function (Pergamon Press, Oxford, 1970)) which it is stated conttain a feature that has not attracted much attention. Although the secondary electrons reach maximum numbers and die away in a fashion broadly consistent with previous calculations, very low energy gamma rays persist in relatively large numbers to great depths of absorber. If these findings are correct a burst of high energy gamma rays striking the top of the atmosphere may be observable with a gamma -ray detector of feasible size and efficiency at sea level, and because of the very slow attenuation such a system may be more effective at sea level than at mountain or balloon altitude. Estimates of the gamma -ray flash from a supernova have been made and are discussed. A supernova in the Virgo cluster is estimated to produce a burst of 3 x 10/sup 4/ to 3 x 10/sup 5/ 2-MeV gamma rays per square meter at sea level and this would be easily detectable, although it could be confused with an extensive air shower. In another estimate, using a modified theory, however, the expected flux is reduced to about 10/sup -7/ erg/cm/sup 2/ in about 10 ms. Yet another estimate for ultra highenergy gamma rays oredicted 10/sup 44/ ergs of ~10/sup 12/ eV photons from a ty pe 1 supernova. For a distance of 10 Mpc this would produce 10/sup -8/ ergs/ cm/sup 2/ at the top of the atmosphere, which fails in detectabillty by about two orders of magnitude. Energy fluxes of 10/sup -5/ to 4 x 10/sup -4/ e observations of low energy gamma -ray bursts, that may come from supernova explosions. The findings may be applicable to searches for gamma rays from phenomena other than supernovae. An experimental test of the theory is desirable; this would be difficult in air, but in light solids, or Cu or Pb, where similar predictions are made, it would seem relatively easy at accelerator energies. The method may be feasible at mountain altitudes, though larger cosmic- ray backgrounds will complicate matters. The method appears suitable only for signal durations less than about 10 ms. (UK)

• Research Organization: University Coll., Dublin
• NSA Number: NSA-29-005821
• OSTI ID: 4400619
• Journal Information: Nature (London), v. 245, no. 5425, pp. 366-367, Journal Name: Nature (London), v. 245, no. 5425, pp. 366-367; ISSN NATUA
• Country of Publication: United Kingdom
• Language: English

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