Abstract
We are developing the Gamma-Ray Astro-Imager with Nuclear Emulsion project, designed for 10 MeV–100 GeV cosmic
γ
-ray observations with a high angular resolution (5′/0.°08 at 1–2 GeV) and a ...polarization-sensitive large-aperture (∼10 m
2
) emulsion telescope for repeated long-duration balloon flights. In 2018, a balloon-borne experiment was carried out in Australia with a 0.38 m
2
sensitive area and a flight duration of 17.4 hr, including 6.7 hr of Vela observations. Significant improvements compared with the 2015 balloon-borne experiment were achieved by a factor of 5, including both an increase in effective area × time and a reduction in the background contribution. We aimed to demonstrate the telescope’s overall performance based on detection and imaging of a known
γ
-ray source, the Vela pulsar. A robust detection of the Vela pulsar was achieved with a 68% containment radius of 0.°42, at a significance of 6
σ
, at energies above 80 MeV. The resulting angular profile is consistent with that of a pointlike source. We achieved the current best imaging performance of the Vela pulsar using an emulsion
γ
-ray telescope with the highest angular resolution of any
γ
-ray telescope to date.
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