Título:
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Evidence of a decrease of kHz quasi-periodic oscillation peak separation towards low frequencies in 4U 1728-34 (GX 354-0)
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Autor/a:
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Migliari, Simone; Van der Klis, M.; Fender, R. P.
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Otros autores:
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Universitat de Barcelona |
Abstract:
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We have produced the colour-colour diagram of all the observations of 4U 1728-34 available in the Rossi X-ray Timing Explorer public archive (from 1996 to 2002) and found observations filling in a previously reported `gap' between the island and the banana X-ray states. We have made timing analysis of these gap observations and found, in one observation, two simultaneous kHz quasi-periodic oscillations (QPOs). The timing parameters of these kHz QPOs fit in the overall trend of the source. The `lower' kHz QPO has a centroid frequency of ~308 Hz. This is the lowest `lower' kHz QPO frequency ever observed in 4U 1728-34. The peak frequency separation between the `upper' and the `lower' kHz QPO is Δν= 274 +/- 11 Hz, significantly smaller than the constant value of Δν~ 350 Hz found when the `lower' kHz QPO frequency is between ~500 and 800 Hz. This is the first indication in this source for a significant decrease of kHz QPO peak separation towards low frequencies. We compare the result briefly to theoretical models for kHz QPO production. |
Materia(s):
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-Estels de neutrons -Estels -Astronomia de raigs X -Neutron stars -Stars -X-ray astronomy |
Derechos:
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(c) Migliari, Simone et al., 2003
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Tipo de documento:
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Artículo Artículo - Versión publicada |
Editor:
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Royal Astronomical Society
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