The origin and location of the 5 March 1979 gamma-ray burst

Abstract

Gamma-ray bursts (GRBs) have been controversial since their discovery, mainly because of the absence of counterparts at any other wavelength that would help identify the nature of the astrophysical object associated with them; this in turn could determine their distances and luminosities, providing some constraints on their physical parameters. The absence of identifiable counterparts, as well as certain spectral features attributed to red-shifted e⁺–e^– annihilation radiation, has led to the conclusion that they occur on isolated neutron stars and hence their luminosities should not be far in excess of ˜10³⁸ergs^–1, the Eddington luminosity for a solar mass object. On this assumption, the observed fluxes of 10^–5–10^–6 erg cm^–2 s^–1 gave distance estimates of the order of a few kpc, although their isotropic distribution may be in conflict with such an assumption. Perhaps the most controversial GRB is that of 5 March 1979, precisely because there is an accurate positional identification of this burst¹ with a known astronomical object, the supernova remnant N49 in the Large Magellanic Cloud (LMC). Such an association would fix the distance at 55 kpc, and with the observed flux (this is by far the brightest GRB observed to date), would require prodigious energy and luminosity from this GRB (l0⁴⁴erg and l0⁴⁴ergs^–1 respectively), casting doubt, on theoretical grounds, on its distance and its physical association with the LMC. However, some Kosmos 856 observations² may provide more direct evidence on energy released and hence give a decisive answer to this question.