Download Discovery of 7-13 HZ quasi-periodic oscillations in the new X

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.