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Title:
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The Island State of the Atoll Source 4U 1820-30
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Author:
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Altamirano, Diego; Van der Klis, M.; Méndez, M.; Migliari, Simone; Jonker, P. G.; Tiengo, A.; Zhang, W.
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Other authors:
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Universitat de Barcelona |
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Abstract:
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We study the rapid X-ray time variability in all public data available from the Rossi X-Ray Timing Explorer Proportional Counter Array on the atoll source 4U 1820-30 in the low-luminosity island state. A total of ~46 ks of data were used. We compare the frequencies of the variability components of 4U 1820-30 with those in other atoll sources. These frequencies were previously found to follow a universal scheme of correlations. We find that 4U 1820-30 shows correlations that are shifted by factors of 1.13 ± 0.01 and 1.21 ± 0.02 with respect to those in other atoll sources. These shifts are similar to, but smaller than, the shift factor of ~1.45 previously reported for some accreting millisecond pulsars. Therefore, 4U 1820-30 is the first atoll source that shows no significant pulsations but has a significant shift in the frequency correlations compared with the other three nonpulsating atoll sources. |
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Subject(s):
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-Estels binaris de raigs X
-Estels de neutrons
-Astronomia de raigs X
-X-ray binaries
-Neutron stars
-X-ray astronomy |
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Rights:
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(c) American Astronomical Society, 2005
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Document type:
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Article
Article - Published version |
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Published by:
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Institute of Physics (IOP)
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