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The correlations and anticorrelations in QPO data

Journal article
Authors Marek A Abramowicz
D. Barret
M. Bursa
Jíri Horák
Wlodek Kluzniak
Paola Rebusco
G. Török
Published in Astronomische Nachrichten
Volume 326
Issue 9
Pages 864-866
ISSN 0004-6337
Publication year 2005
Published at Department of Physics (GU)
Pages 864-866
Language en
Subject categories Physical Sciences, Astronomy, Astrophysics and Cosmology


Double peak kHz QPO frequencies in neutron star sources varies in time by a factor of hundreds Hz while in microquasar sources the frequencies are fixed and located at the line ν2 - ν1 in the frequency-frequency plot. The crucial question in the theory of twin HFQPOs is whether or not those observed in neutron-star systems are essentially different from those observed in black holes. In black hole systems the twin HFQPOs are known to be in a 3:2 ratio for each source. At first sight, this seems not to be the case for neutron stars. For each individual neutron star, the upper and lower kHz QPO frequencies, ν2 and ν1, are linearly correlated, ν2 = ν1 + B, with the slope A < 1.5, i.e., the frequencies definitely are not in a 1.5 ratio. In this contribution we show that when considered jointly on a frequency-frequency plot, the data for the twin kHz QPO frequencies in several (as opposed to one) neutron stars uniquely pick out a certain preferred frequency ratio that is equal to 1.5 for the six sources examined so far.

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