No QPO time lags from Sco X-1 as seen with EXOSAT: a comparison with Cyg X-2

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dc.creatorDieters, Stefan W.
dc.creatorVaughan, Brian A.
dc.creatorKuulkers, Erik
dc.creatorLamb, Frederick K.
dc.creatorvan der Klis, Michiel
dc.date1999-11-16
dc.date.accessioned2026-07-07T02:34:28Z
dc.date.available2026-07-07T02:34:28Z
dc.descriptionWe have measured the phase-delay and rms amplitude spectra of CygX-2 and ScoX-1. Using EXOSAT data from the normal branch of CygX-2 we confirm earlier (Ginga) results, showing that at an energy near 6keV there is both a minimum in the QPO rms amplitude spectrum and a 150 degree phase jump in the quasi-periodic oscillations (QPO) phase-delay spectrum. Surprisingly, using EXOSAT and Ginga data, we find no evidence for a phase jump of this kind in the phase-delay spectrum of ScoX-1 on either the normal or flaring branch. Upper limits (90% confidence) of 42 degrees can be set on any phase jump in the energy range 2-10keV on the normal branch, and 88 degrees on the flaring branch. The QPO rms amplitude spectrum of ScoX-1 increases steeply with energy on both the normal and flaring branches. These results suggest that the X-ray spectrum pivots about an energy of <~2keV or >~10keV or that normal branch QPO of ScoX-1 does not have a pivoting spectrum. We discuss the implications of these results in terms of the radiation-hydrodynamic model for normal branch QPO.
dc.description9 pages, 4 figures. Accepted Astron and Astrophysics
dc.identifierhttps://arxiv.org/abs/astro-ph/9911287
dc.identifierhttp://arxiv.org/abs/astro-ph/9911287
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/15252
dc.subjectAstrophysics
dc.titleNo QPO time lags from Sco X-1 as seen with EXOSAT: a comparison with Cyg X-2
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