Discovery of microsecond time lags in kilohertz QPOs

Using the Rossi X-Ray Timing Explorer, we have measured ~27 μs time delays in 830 Hz quasi-periodic oscillations (QPOs) between 4-6 and 11-17 keV in 4U 1608-52, with high-energy photons lagging low-energy photons, and found upper limits to the time delays of 45 μs between 2-6.5 and 6.5-67 keV in ~73...

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Detalles Bibliográficos
Autores principales: Vaughan, B. A., Klis, M. van der, Méndez, Mariano R., Paradijs, J. van, Wijnands, R., Lewin, W. H. G., Lamb, F. K., Psaltis, D., Kuulkers, E., Oosterbroek, T.
Formato: Articulo
Lenguaje:Español
Publicado: 1997
Materias:
Ciencias Astronómicas
Physics
Astronomy
Photon
Accretion disc
Time delays
Microsecond
Astrophysics
Spectral line
Optical depth (astrophysics)
Low energy photons
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/123089
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
Descripción
Sumario:Using the Rossi X-Ray Timing Explorer, we have measured ~27 μs time delays in 830 Hz quasi-periodic oscillations (QPOs) between 4-6 and 11-17 keV in 4U 1608-52, with high-energy photons lagging low-energy photons, and found upper limits to the time delays of 45 μs between 2-6.5 and 6.5-67 keV in ~730 Hz QPOs in 4U 0614+091 and 30 μs between 8.7-12.4 and 12.4-67 keV in ~870 Hz QPOs in 4U 1636-53. We also find that the cross-coherence function between QPOs at different energies is greater than 0.85 with 95% confidence in 4U 1608-52 and 4U 1636-53. If Compton upscattering of low-energy X-rays in a region with an optical depth of a few is responsible for the delays, then the Compton upscattering region is between a few kilometers and a few tens of kilometers in size.

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