Discovery of a kHz QPO in 2S 0918-549

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dc.creatorJonker, Peter G.
dc.creatorvan der Klis, Michiel
dc.creatorHoman, Jeroen
dc.creatorMendez, Mariano
dc.creatorvan Paradijs, Jan
dc.creatorBelloni, Tomaso
dc.creatorKouveliotou, Chryssa
dc.creatorLewin, Walter
dc.creatorFord, Eric C.
dc.date2001-01-10
dc.date.accessioned2026-07-07T01:57:19Z
dc.date.available2026-07-07T01:57:19Z
dc.descriptionWe report the discovery of a kilohertz quasi-periodic oscillation (kHz QPO) in the low-mass X-ray binary (LMXB) 2S 0918-549. The kHz QPO has a frequency of 1156+-9 Hz, a FWHM of 70+-20 Hz, and a fractional rms amplitude of 18%+-2%. We also detected for the first time a type I X-ray burst in this source. The compact object must therefore be a neutron star. Finally, we were able to classify the source as an atoll source exhibiting the full complement of spectral/timing states of this class (island and banana). From the peak burst flux an upper limit on the persistent luminosity can be derived of 0.5% of the Eddington luminosity, making 2S 0918-549 one of the least luminous LMXBs showing a kHz QPO. We compare the fractional rms amplitudes of the upper kHz QPO across the ensemble of LMXBs. We find a strong anticorrelation with luminosity. In LMXBs with luminosities ~100 times lower than those of Z-sources, the fractional rms amplitude is a factor ~10 larger.
dc.descriptionAccepted for publication in ApJ, uses emulateapj, 7 pages, 4 figures (figure 4 is in color)
dc.identifierhttps://arxiv.org/abs/astro-ph/0101150
dc.identifierhttp://arxiv.org/abs/astro-ph/0101150
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/2342
dc.subjectAstrophysics
dc.titleDiscovery of a kHz QPO in 2S 0918-549
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