Time lags of the kilohertz quasi-periodic oscillations in the low-mass X-ray binaries 4U 1608-52 and 4U 1636-53
| Autor: | Marcio G. B. de Avellar, Maria Clara Restrepo Mendez, Jorge Ernesto Horvath, Andrea Sanna |
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| Přispěvatelé: | Kapteyn Astronomical Institute, Astronomy |
| Předmět: |
Astrophysics::High Energy Astrophysical Phenomena
X-rays: individual: 4U 1608-52 ATOLL SOURCE STATES HARD FOS: Physical sciences RAIOS X Astrophysics ACCRETING NEUTRON-STARS stars: neutron X-rays: binaries H II regions COHERENCE Stars: Pre-main sequence Group delay and phase delay ISM: Jets and outflows Physics High Energy Astrophysical Phenomena (astro-ph.HE) X-rays: individual: 4U 1636-53 CYGNUS X-1 X-ray Astronomy and Astrophysics Light curve Neutron star VARIABILITY Stars: Mass loss Space and Planetary Science DISCOVERY COMPTONIZATION GRS 1915+105 Linear correlation Quasi periodic Low Mass Astrophysics - High Energy Astrophysical Phenomena SOFT LAGS Coherence (physics) |
| Zdroj: | NASA Astrophysics Data System Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual) Universidade de São Paulo (USP) instacron:USP Revista Mexicana de Astronomia y Astrofisica Conference Series, 109-109 STARTPAGE=109;ENDPAGE=109;TITLE=Revista Mexicana de Astronomia y Astrofisica Conference Series Revista mexicana de astronomia y astrofisica, 44, 109-109. UNIV NACIONAL AUTONOMA MEXICO, INST DE ASTRONOMIA ResearcherID Monthly Notices of the Royal Astronomical Society, 433(4), 3453-3463. Oxford University Press Scopus-Elsevier University of Groningen |
| ISSN: | 0185-1101 0035-8711 |
| Popis: | We studied the energy and frequency dependence of the Fourier time lags and intrinsic coherence of the kilohertz quasi-periodic oscillations (kHz QPOs) in the neutron-star low-mass X-ray binaries 4U 1608-52 and 4U 1636-53, using a large data set obtained with the Rossi X-ray Timing Explorer. We confirmed that, in both sources, the time lags of the lower kHz QPO are soft and their magnitude increases with energy. We also found that: (i) In 4U 1636-53, the soft lags of the lower kHz QPO remain constant at similar to 30 mu s in the QPO frequency range 500-850 Hz, and decrease to similar to 10 mu s when the QPO frequency increases further. In 4U 1608-52, the soft lags of the lower kHz QPO remain constant at 40 mu s up to 800 Hz, the highest frequency reached by this QPO in our data. (ii) In both sources, the time lags of the upper kHz QPO are hard, independent of energy or frequency and inconsistent with the soft lags of the lower kHz QPO. (iii) In both sources the intrinsic coherence of the lower kHz QPO remains constant at similar to 0.6 between 5 and 12 keV, and drops to zero above that energy. The intrinsic coherence of the upper kHz QPO is consistent with being zero across the full energy range. (iv) In 4U 1636-53, the intrinsic coherence of the lower kHz QPO increases from similar to 0 at similar to 600 Hz to similar to 1, and it decreases to similar to 0.5 at 920 Hz; in 4U 1608-52, the intrinsic coherence is consistent with the same trend. (v) In both sources the intrinsic coherence of the upper kHz QPO is consistent with zero over the full frequency range of the QPO, except in 4U 1636-53 between 700 and 900 Hz where the intrinsic coherence marginally increases. We discuss our results in the context of scenarios in which the soft lags are either due to reflection off the accretion disc or up-/down-scattering in a hot medium close to the neutron star. We finally explore the connection between, on one hand the time lags and the intrinsic coherence of the kHz QPOs, and on the other the QPOs' amplitude and quality factor in these two sources. |
| Databáze: | OpenAIRE |
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