2001/06/30 by Deepto Chakrabarty, Lee Homer, P. A. Charles +3 · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #High-pressure geophysics and materials #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/323877
7 pages (including figs). Revised, accepted for publication in ApJ
arxiv created 2001/08/06 · openalex publication_date 2001/12/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We have detected large-amplitude 0.3-1.2 mHz quasi-periodic oscillations (QPOs) from the low-mass X-ray binary pulsar 4U 1626-67/KZ TrA, using UV photometry from the Hubble Space Telescope and ground-based optical photometry. These 1 mHz QPOs, which have coherence (ν/Δν) ≈ 8, are entirely distinct from the 130 mHz pulsar spin frequency, a previously known 48 mHz QPO, and the 42 minute binary period (independently confirmed here). Unlike the 48 and 130 mHz oscillations, which are present in both the optical/UV and the X-ray emission, the 1 mHz QPOs are not detected in simultaneous observations with the Rossi X-Ray Timing Explorer . The rms amplitude of the mHz QPO decreases from 15% in the far-UV to 3% in the optical, while the upper limit on a corresponding X-ray QPO is as low as 0.8%. We suggest that the mHz oscillations are due to warping of the inner accretion disk. We also report the detection of coherent upper and lower sidebands of the 130 mHz optical pulsations, with unequal amplitude and a spacing of 1.93 mHz around the main pulsation. The origin of these sidebands remains unclear.