{"paper":{"title":"Discovery of a second kHz QPO peak in 4U 1608-52","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"B.A. Vaughan (Caltech), D. Psaltis (Harvard/CfA), E. Kuulkers (University of Oxford), F. K. Lamb (University of Illinois), J. van Paradijs (University of Amsterdam), M. Mendez, M. van der Klis, W.H.G. Lewin (MIT), W. Zhang (NASA/GSFC)","submitted_at":"1997-12-05T17:53:49Z","abstract_excerpt":"Using a new technique to improve the sensitivity to weak Quasi-Periodic Oscillations (QPO) we discovered a new QPO peak at about 1100 Hz in the March 1996 outburst observations of 4U 1608-52, simultaneous with the ~ 600-900 Hz peak previously reported from these data. The frequency separation between the upper and the lower QPO peak varied significantly from $232.7 \\pm 11.5$ Hz on March 3, to $293.1 \\pm 6.6$ Hz on March 6. This is the first case of a variable kHz peak separation in an atoll source. We discuss to what extent this result could be accommodated in beat-frequency models such as pro"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/9712085","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/astro-ph/9712085/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}