J/ApJ/728/9ivo://CDS.VizieR/J/ApJ/728/9doi:10.26093/cds/vizier.17280009CDSBarret D.Bachetti M.Miller M.C.2017-06-19T07:58:17Z2012-10-16T15:30:13ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frx-ray-binary-starsWe investigate the quality factor and root mean square (rms) amplitude of the lower kilohertz quasi-periodic brightness variations (kHz QPOs) from XTE J1701-462, a unique X-ray source which was observed in both the so-called Z and atoll states. Correcting for the frequency drift of the QPO, we show that, as in all sources for which such a correction can be applied, the quality factor and rms amplitude drops sharply above a critical frequency. For XTE J1701-462, this frequency is estimated to be ~800Hz, where the quality factor reaches a maximum of ~200 (e.g., a value consistent with the one observed from more classical systems, such as 4U 1636-536). Such a drop has been interpreted as the signature of the innermost stable circular orbit, and that interpretation is consistent with the observations we report here. The kHz QPOs in the Z state are much less coherent and lower amplitude than they are in the atoll state. We argue that the change of the QPO properties between the two source states is related to the change of the scale height of the accretion disk; a prediction of the toy model proposed by Barret et al. As a by-product of our analysis, we also increased the significance of the upper kHz QPO detected in the atoll phase up to 4.8{sigma} (single trial significance) and show that the frequency separation (266.5+/-13.1Hz) is comparable with the one measured from simultaneous twin QPOs in the Z phase.2011ApJ...728....9Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/728/9CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2012)J/A+A/522/A68 : Variable sources detected by INTEGRAL (Telezhinsky+, 2010)J/A+A/469/807 : Catalogue of Galactic low-mass X-ray binaries (Liu+, 2007)J/A+A/467/585 : Sources detected by ISGRI (Bodaghee+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/728/9https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/728/9http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/728/9https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/728/9https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/728/9http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/728/9GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/728/9/table2QPO frequency datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsDate of PDS segment start (1)stime.epochnullableStartStarting date of PDS segment (2)stime.epochlongStopStoping date of PDS segment (2)stime.epochlongFreqQPO frequency estimated for PDS segmentHzem.freqfloat