Probable optical counterpart of a γ-ray burster

Abstract

I describe here 1.6 × 10⁷ s (over half a year) of optical monitoring of three γ-ray burst positions using the collection of archival plates at the Harvard College Observatory. The search has uncovered the probable optical counterpart for the 19 November 1978 γ-ray burster on a blue emulsion plate exposed in 1928. The optical flash observed on the 1928 plate has m_B ∼ 3, for an assumed duration of 1 s. Optical searches indicate that the absolute magnitude of the γ-ray burst system at quiescence is fainter than 13. A recurrence rate of ∼10^−7.5 s⁻¹ is found from the γ-ray and optical data. A recurrence rate this high rules out any model which uses a collision between a neutron star and an asteroid-like body as well as any model which requires accretion from the interstellar matter onto a neutron star.