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UvA-DARE (Digital Academic Repository) Discovery of 7-13 HZ quasi-periodic oscillations in the new X-ray transient XTE J1806246 Wijnands, R.A.D.; van der Klis, M.B.M. Published in: The astronomer's telegram Link to publication Citation for published version (APA): Wijnands, R., & van der Klis, M. (1998). Discovery of 7-13 HZ quasi-periodic oscillations in the new X-ray transient XTE J1806-246. The astronomer's telegram, 17. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl) Download date: 17 Jun 2017 Discovery of 7-13 Hz quasi-periodic oscillations in the new X-ray transient XTE J1806-246 ATEL # 17; Rudy Wijnands & Michiel van der Klis (Astronomical Institute "Anton Pannekoek", University of Amsterdam) on 8 May 1998; 1:06 UT Password Certification: Rudy Wijnands ([email protected]) Subjects: X-ray, Binaries, Transients We have discovered quasi-periodic oscillations (QPO) with frequencies of 7-13 Hz (see the power density spectrum) in the recently discovered X-ray transient XTE J1806-246 (IAUC 6891 ) in data obtained on May 3 1998 21:03-22:31 UT with the proportional counter array (PCA) onboard the Rossi X-ray Timing Explorer. The total PCA count rate varied between approximately 7000 and 8000 counts/sec. The rms amplitude of the QPO in the 2-60 keV energy band varied between 2 and 6.5 % (rms) and the FWHM of the QPO peak varied between 2 and 9.5 Hz. Their is no clear correlation between X-ray count rate and the QPO parameters. In the X-ray colorcolor diagram a two-branched structure was traced out. The QPO parameters are well correlated with the position of the source on these branches. During earlier observations on 1998 April 27, 28 and 29 the count rates were between 5000 and 7000 counts/sec. The 7-13 Hz QPO was not detected during these observations. In the X-ray color-color diagram those observations are slightly displaced from the data obtained on May 3. The frequency of the QPOs and the behavior of the QPO parameters with respect to the position of the source on the two branches is similar to the behavior of the 5-7 Hz QPO usually found in the brightest low-mass X-ray binaries, the Z sources, which accrete matter from a companion star at close to the Eddington mass accretion rate. It is possible that XTE J1806-246 is similar to these systems. If so, then it would be the first discovery of a Z source in over more then twenty years. It would also be the first transient Z source known.