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Discovery of Recurring Soft to Hard State Transitions in LMC X-3

J. Wilms·M. A. Nowak·K. Pottschmidt·W. A. Heindl·J. B. Dove·M. C. Begelman
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Abstract

We present the analysis of an RXTE monitoring campaign of the canonical soft state black hole candidates LMC X-1 and LMC X-3. In contrast to LMC X-1, which does not exhibit any periodic spectral changes, we find that LMC X-3 exhibits stron spectral variability on time scales of days to weeks. For typical RXTE ASM count rates, the luminosity variations of LMC X-3 are due to changes of the phenomenological disk blackbody temperature. During episodes of especially low luminosity (ASM count rates < 0.6 counts/sec), kT strongly decreases and the power law significantly hardens to a photon index of ~1.8. These changes are consistent with state changes of LMC X-3 from the soft state to the canonical hard state of galactic black hole candidates. We argue that the long term variability of LMC X-3 might be due to a wind-driven limit cycle such as discussed by Shields et al. (1986)

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J. Wilms, M. A. Nowak, K. Pottschmidt, W. A. Heindl, J. B. Dove, M. C. Begelman. 2000-08-08. Discovery of Recurring Soft to Hard State Transitions in LMC X-3. https://doi.org/10.1046/j.1365-8711.2001.03983.x

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