A Search for sub-TeV Gamma-rays from the Vela Pulsar Region with CANGAROO-III

(Astrophys. J., in press)

R. Enomoto, K. Tsuchiya, Y. Adachi, S. Kabuki, P.G. Edwards, A. Asahara, G.V. Bicknell, R.W. Clay, Y. Doi, S. Gunji, S. Hara, T. Hara, T. Hattori, Sei. Hayashi, Y. Higashi, R. Inoue, C. Itoh, F. Kajino, H. Katagiri, A. Kawachi, S. Kawasaki, T. Kifune, R. Kiuchi, K. Konno, L.T. Ksenofontov, H. Kubo, J. Kushida, Y. Matsubara, Y. Mizumoto, M. Mori, H. Muraishi, Y. Muraki, T. Naito, T. Nakamori, D. Nishida, K. Nishijima, M. Ohishi, J.R. Patterson, R.J. Protheroe, Y. Sakamoto, M. Sato, S. Suzuki, T. Suzuki, D.L. Swaby, T. Tanimori, H. Tanimura, G.J. Thornton, S. Watanabe, T. Yamaoka, M. Yamazaki, S. Yanagita, T. Yoshida, T. Yoshikoshi, M. Yuasa, Y. Yukawa

We made stereoscopic observations of the Vela Pulsar region with two of the 10m diameter CANGAROO-III imaging atmospheric Cherenkov telescopes in January and February, 2004, in a search for sub-TeV gamma-rays from the pulsar and surrounding regions. We describe the observations, provide a detailed account of the calibration methods, and introduce the improved and bias-free analysis techniques employed for CANGAROO-III data. No evidence of gamma-ray emission is found from either the pulsar position or the previously reported position offset by 0.13 degree, and the resulting upper limits are a factor of five less than the previously reported flux from observations with the CANGAROO-I 3.8m telescope. Following the recent report by the H.E.S.S. group of TeV gamma-ray emission from the Pulsar Wind Nebula, which is 0.5 degree south of the pulsar position, we examined this region and found supporting evidence for emission extended over ~0.6 degree.