Open AccessDiscovery of Microsecond Time Lags in Kilohertz QPO[CLC]s[/CLC]
Author(s) -
Brian Vaughan,
M. van der Klis,
Mariano Méndez,
J. van Paradijs,
R. Wijnands,
W. H. G. Lewin,
Frederick K. Lamb,
Dimitrios Psaltis,
E. Kuulkers,
T. Oosterbroek
Publication year - 1997
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/310740
Subject(s) - microsecond , physics , photon , coherence (philosophical gambling strategy) , astrophysics , photon energy , energy (signal processing) , optics , quantum mechanics
Using the Rossi X-ray Timing Explorer we have measured 27 microsecond timedelays in 830 Hz quasi-periodic oscillations (QPO) between 4-6 keV and 11-17keV in 4U 1608-52, with high-energy photons lagging low energy photons, andfound upper limits to the time delays of 45 microseconds between 2-6.5 keV and6.5-67 keV in 730 Hz QPO in 4U 0614+091 and 30 microseconds between 8.7-12.4keV and 12.4-67 keV in 870 Hz QPO in 4U 1636-53. We also find that the crosscoherence function between QPO at different energies is > 0.85 with 95%confidence in 4U 1608-52 and 4U 1636-53. If Compton upscattering of low-energyX-rays in a region with an optical depth of a few is responsible for thedelays, then the Compton upscattering region is between a few kilometers and afew tens of kilometers in size.Comment: 8 pages, 1 Postscript figure, LaTeX, to appear in Ap.J Letter
Accelerating Research
Robert Robinson Avenue,
Oxford Science Park, Oxford
OX4 4GP, United Kingdom
Address
John Eccles HouseRobert Robinson Avenue,
Oxford Science Park, Oxford
OX4 4GP, United Kingdom