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Optical/X-ray Variability in Swift 1753.5-0127

ATel #562; R. I. Hynes (LSU), F. Mullally (UT-Austin)
on 11 Jul 2005; 02:15 UT
Credential Certification: Robert Hynes (rih@phys.lsu.edu)

Subjects: Optical, X-ray, Binary, Black Hole, Transient

Further rapid optical photometry of Swift J1753.5-0127 (Palmer et al., ATEL #546) was obtained at McDonald Observatory on July 6th and 7th, simultaneously with RXTE public observations. Observational details were exactly as for the previous observation (Hynes & Mullally ATEL #554). Closer examination of the optical power spectrum reveals that the apparent red-noise is actually composed of two components. A high-frequency band-limited noise component is superimposed on a lower-frequency component with a steep flickering power-spectrum. The high-frequency noise correlates fairly well with X-ray variations on both nights, but the low-frequency component is absent in the X-ray data. The high-frequency optical response appears smeared by a few seconds relative to the X-rays consistent with an origin in reprocessing. Further simultaneous observations are urged to exploit this rare echo-mapping opportunity. Time resolutions of a second or better are recommended.