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The applications of the MHD Alfvén wave oscillation model for kHz quasi‐periodic oscillations
Author(s) -
Zhang C.M.,
Yin H.X.,
Zhao Y.H.,
Chang H.K.,
Song L.M.
Publication year - 2007
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200610750
Subject(s) - physics , oscillation (cell signaling) , neutron star , astrophysics , magnetohydrodynamics , radius , accretion (finance) , magnetic field , genetics , computer security , quantum mechanics , computer science , biology
In this paper, we improve the previous work on the MHD Alfvén wave oscillation model for the neutron star (NS) kHz quasi‐periodic oscillations (QPOs), and compare the model with the updated twin kHz QPO data. For the 17 NS X‐ray sources with the simultaneously detected twin kHz QPO frequencies, the stellar mass M and radius R constraints are given by means of the derived parameter A in the model, which is associated with the averaged mass density of the star as 〈 ρ 〉 = 3 M /(4π R 3 ) ≃ 2.4 × 10 14 ( A /0.7) 2 g/cm 3 , and we also compare the M ‐ R constraints with the stellar equations of state. Moreover, we also discuss the theoretical maximum kHz QPO frequency and maximum twin peak separation, and some expectations on SAX J1808.4–3658 are mentioned, such as its highest kHz QPO frequency ∼ 870 Hz, which is about 1.4–1.5 times less than those of the other known kHz QPO sources. The estimated magnetic fields for both Z sources (about Eddington accretion rate $ {\dot M}_{\rm Edd} $ ) and Atoll sources (∼ 1% $ {\dot M}_{\rm Edd} $ ) are approximately ∼10 9 G and ∼10 8 G, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)