Optical Variability of the LMC Supersoft Source RX J0513.9-6951

Publication information:

K. A. Southwell, M. Livio, P. A. Charles, W. Sutherland, C. Alcock, R. A. Allsman, D. Alves, T. S. Axelrod, D. P. Bennett, K. H. Cook, K. C. Freeman, K. Griest, J. Guern, M. J. Lehner, S. L. Marshall, B. A. Peterson, M. R. Pratt, P. J. Quinn, A. W. Rodgers, C. W. Stubbs, and D. L. Welch. 1996. “Optical Variability of the LMC Supersoft Source RX J0513.9-6951”. In Supersoft X-Ray Sources, 472:Pp. 165. doi:10.1007/BFb0102261

Abstract

We present optical spectroscopy and photometry of the LMC supersoft source (SSS) RX J0513.9-6951. Through the exceptional monitoring capabilities of the MACHO project, we show the optical history of this object for a≈3 year period. Recurring low states, in which the optical brightness drops by up to a magnitude, are observed at quasi-regular intervals. Analysis of the high state data reveals a small modulation with a semi-amplitude of ≈0.02 magnitudes at P=0^d.76278±0^d.00005. By considering all the available data, including optical photometry, spectroscopy and X-ray observations, we suggest a theoretical model to explain the fundamental variations exhibited by this source.