Hung-Hsiang Liang (NTHU); Jeng-Lun Chiu (NTHU); Chien-Ying Yang (NTHU); Che-Yen Chu (NTHU); Yi-Chi Chang (NTHU); Hsiang-Kuang Chang (NTHU); Steven E. Boggs (UCSD, UCB); the COSI Collaboration (UCB, LBNL, NTHU, AS, NCU, IRAP)
The Compton Spectrometer and Imager (COSI) is a balloon-borne soft gamma ray telescope aiming at studying the images, spectra, and the polarization characteristics of astrophysical sources in the MeV band. The most recent flight was a 47-day mission carried by a super-pressure balloon which was launched from Wanaka, New Zealand, in May 2016. The Vela pulsar is one of the brightest high-energy gamma-ray source in the sky. Though it has been well studied throughout the electromagnetic band, there were only couple observations in the MeV band, most showing flux upper limit. The spectral behaviour at ~1 MeV is still ambiguous, and COSI (sensitive between 0.2 and 5 MeV) is going to provide more hints to the spectral properties at ~1 MeV to determine the physical mechanism from its continuum. Here, we will present the preliminary result for the detection of the Vela Pulsar by COSI.