A 421-d activity cycle in the BeX recurrent transient A0538–66 from MACHO monitoring |
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| Authors: | C. Alcock,R. A. Allsman,D. R. Alves,T. S. Axelrod,A. C. Becker,D. P. Bennett,P. A. Charles,K. H. Cook,A. J. Drake,K. C. Freeman,M. Geha,K. Griest,M. J. Lehner,S. L. Marshall,K. E. McGowan,&dagger ,D. Minniti,C. A. Nelson,B. A. Peterson,P. Popowski,M. R. Pratt,P. J. Quinn,C. W. Stubbs,W. Sutherland,A.B. Tomaney,T. Vandehei, D. L. Welch |
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| Affiliation: | Lawrence Livermore National Laboratory, Livermore, CA 94550, USA;Center for Particle Astrophysics, University of California, Berkeley, CA 94720, USA;Supercomputing Facility, Australian National University, Canberra, ACT 0200, Australia;Space Telescope Science Institute, Baltimore, MD 21218, USA;Research School of Astronomy and Astrophysics, Canberra, Weston Creek, ACT 2611, Australia;Departments of Astronomy and Physics, University of Washington, Seattle, WA 98195, USA;Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA;Department of Astrophysics, Nuclear Physics Laboratory, Keble Road, Oxford OX1 3RH;Department of Astronomy and Astrophysics, UC Santa Cruz, Santa Cruz, CA 90064, USA;Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA;Department of Physics, University of Sheffield, Sheffield S3 7RH;Departmento de Astronomia, P. Universidad Catolica, Casilla 104, Santiago 22, Chile;Department of Physics, University of California, Berkeley, CA 94720, USA;Center for Space Research, MIT, Cambridge, MA 02139, USA;European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching, Germany;Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada |
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| Abstract: | We present a ∼5-yr optical light curve of the recurrent Be/X-ray transient A0538–66 obtained as a by-product of the MACHO Project. These data reveal both a long-term modulation at P =420.8±0.8 d and a short-term modulation at 16.6510±0.0022 d which, within errors, confirms the previously found orbital period. Furthermore, the orbital activity is only seen at certain phases of the 421-d cycle, suggesting that the long-term modulation is related to variations in the Be star envelope. |
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| Keywords: | binaries: close stars: individual: A0538–66 X-rays: stars |
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