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Paper: High-Dispersion Spectroscopy of a Be/X-Ray Binary A0535+26/V725 Tau
Volume: 404, The Eighth Pacific Rim Conference on Stellar Astrophysics: A Tribute to Kam Ching Leung
Page: 154
Authors: Moritani, Y.; Nogami, D.; Okazaki, A.T.; Imada, A.; Kambe, E.; AS Honda,
Abstract: Classical Be stars (Be stars) are main sequence or non-supergiant B-type stars which have shown Balmer lines in emission at least once. Rapid rotation, which is characteristic of Be stars, is believed to play an important role in forming a circumstellar envelope (called Be-disc). How the disc is formed and disappeared, however, is still disputable. We carried out ‘continuous’ high-dispersion spectroscopic observations of a Be/X-Ray binary A0535+262/V725 Tau at OAO with the 188 cm telescope and HIDES, aiming at spectral variabilities caused by the tidal interaction between the Be disc and the neutron star which depends on the orbital phase. In 2005, we observed from 24th November to 3rd December (corresponding to the orbital phase 0.68 – 0.79), detecting no variability in the emission line profile of the Be disc near apastron. Our observations were also performed from 6th to 14th November 2007 (corresponding to the orbital phase 0.09 - 0.16) and 2nd and 31st January 2008 (0.50 and 0.86, respectively) at OAO, and in December 2007 at GAO. Observed line profiles of H-alpha only slightly changed in the autumn 2007, which implies that Be disc did not vary even after the periastron. The four-year spectroscopic observations give a suggestion that Be disc has an axi-asymmetric structure.
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